USAC Ford Focus Midget
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Chassis Set-up & Tuning

USAC Ford Focus

Pavement Midget

Quick Tuning Guide

Version 2009.1

Copyright 2009 Ron Sutton’s Winner’s Circle, Inc.

USAC Focus Midget Racers are hereby granted permission to use this information for their personal racing use.  Any attempts to sell, rent, charge for, or use this information commercially in any way, will constitute copyright infringement.

 

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Tuning Fundamentals & Concepts

 

Traction/Grip:

Force applied to a tire adds grip to that tire.

Weight transfer from tire(s) to tire(s) is the force we have to work with.

Tire sidewall design, rim width & PSI dictate optimum contact patch.

Most chassis tuning is to control the degree of weight transfer to achieve the traction goal.

Goal: To have optimum grip on all tires and simply disengage the LR (to a degree) to turn well … then re-engage the LR (to a degree) for maximum forward bite on exit.

 

Weight Transfer:

Most chassis tuning is to control the degree of weight transfer (WT) to achieve the traction goal.

If braking happens before initial turn-in = Initial WT is from rear to front.

Then upon turn-in, then WT is from left to right.     Entry = WT from LR to RF

If initial turn-in happens before braking = Initial WT is from left to right.

Then upon braking, then WT is from rear to front.    Entry = WT from LR to RF

WT from LR to RF is critical to making the car turn.

If there is not enough WT from LR to RF, the car won’t want to turn on entry and/or middle.

Upon release of the brakes, WT back onto the rear wheels.  Middle = Left to right side WT.

As Driver unwinds steering = Initially WT is from right side to left side.

As Driver picks up the throttle, then WT from front to rear.  Exit = WT from RF to LR

Engaging the LR to a degree on exit is critical to forward bite off the turn.

 

Roll Angle:

Roll angle is the degree the car “rolls” over from side-to-side in cornering.

Optimum roll angle produces tire temp splits in the 30-35 degree range.

Optimum roll angle works the left & right side tires closer to even providing a long run set-up & optimum cornering traction. It takes 4 laps for the tires to “come in.”

Too much roll angle works the right side tires too much & the left side tires too little providing a short run set-up, “knife edgy” to drive, tires heat up quicker & go away quicker.

Too little roll angle produces less than optimum grip.  Car feels “skatey” … like “on top of the track” = right side tires are not gripping enough.

 

Tire Durometer Hardness:

Check to be sure each set of tires is “matched” in durometer hardness, to prevent uneven handling when changing to a different set of tires.

Harder RR and/or Softer RF = Loose      Softer RR and/or Harder RF = Push

Focus "B" right rear & MG7 RF will both durometer at approximately 50 when new & hot.

Focus "A" right rear will durometer at approximately 54 when new & hot.

 

Tires:

Tires are the single most important component to traction and speed.

You can tune a worn out tire to get around the track … but you can’t make it fast.

The RF tire is most fragile.  If pushing too long, tire will go away permanently.

Most racers run the harder MG-7 RF.  The softer MG-6 RF is too fragile.

The new RR “Focus-B” tire is softer and wears quicker than the original RR Focus tire.

The LF & LR are super soft and can be ran multiple races.

You can put 40-50 PSI in a tire and let it sit for days to stretch it.

You can run cold water over a hot/warm tire to help lock it into a certain diameter.

 

Tire Temps & Splits:

Higher temps in the middle of a tire means the PSI is inflated past optimum contact patch.

Lower temps in the middle of a tire means the PSI is less than needed for optimum contact.

30-35 degree tire temp splits front & rear is desired for correct roll angle.

Front tire temp splits larger than the rear tire temp splits = Tight/Push.  If driver if easing up on the entry, it will hide this.

Rear tire temp splits larger than the front tire temp splits = Loose.  If driver if easing up on the throttle on exit, it will hide this.

Both tire temp splits smaller than normal = Roll angle is too little and/or car is under driven.

Both tire temp splits larger than normal = Roll angle is too much and/or car is over driven.

Overall high tire temps mean the track is hot and/or the Driver is over driving the car.

Overall low tire temps mean the track is cold and/or the Driver is under driving the car.

Optimum temp Averages for each tire:     LF = 135      RF = 165     LR = 165     RR = 195

Tip: Excessive tire PSI growth is sign that tire is over worked or sliding.

 

Stagger:

More stagger makes the car turn better throughout the entire turn.  It may affect the entry less (depending on to what degree the LR is engaged).

Less stagger tightens the car up throughout the entire turn.  It may affect the entry less (depending on to what degree the LR is engaged).

Too much stagger = Loose   Too little stagger = Tight/Push

 

Tire Pressure / Spring Rate VS Stagger:

Increasing tire pressure increases the spring rate at that corner. 

Contact patch is the highest priority.

Tire spring rate has more affect on handling than small changes in stagger.

Window for setting tire PSI:      LF = 11-13        RF = 15-17       LR = 6-14        RR = 12-16

 

Fine tuning with Tire Pressure:

More right side PSI decreases roll angle / Less right side PSI increases roll angle.

More front PSI tightens car mostly on entry & middle … slightly on exit.

Less front PSI frees/loosens car mostly on entry & middle … slightly on exit.

More rear PSI frees/loosens car mostly on middle & exit … slightly on entry.

Less rear PSI tightens car mostly on middle & exit … slightly on entry.

Less RF PSI frees/loosens car on entry & middle, but increases roll angle.

More RF PSI tightens car on entry & middle and decreases roll angle.

Less RR PSI increases roll angle, working RR tire more & LR less. Hikes LF on exit.

More RR PSI decreases roll angle, making car more drivable (less knife-edgy) and frees/loosens middle & exit.

Less LR PSI decreases dynamic cross = disengaging LR some / loosening car on exit. 

More LR PSI increases dynamic cross = engaging LR some / tightening car on exit. 

More LF PSI works both front tires more = better turning in the middle. Also decreases dynamic cross weight, freeing/loosening the car up in the middle.

Less LF PSI works both front tires less = tightening the car in the middle. Also increases dynamic cross weight, tightening the car up in the middle.

 

Stagger & Spring SPlit:

Stagger & spring split have to be matched for optimum performance.

The race car will not like a big spring split without stagger to offset it … nor will excessive stagger work without the spring split to offset it.

Too much stagger or too little spring split = Car is loose middle & exit.

Too little stagger or too much spring split = Car is tight/pushy middle & exit

 

Springs:

Stiffer right side springs decrease roll angle / Softer right side springs increase roll angle.

Stiffer front springs tightens car on entry & middle (slightly on exit).

Softer front springs frees/loosens car on entry & middle (slightly on exit).

Stiffer RF spring tightens car entry/middle (slightly on exit). Decreases front roll angle.

Softer RF spring frees/loosens car entry/middle (slightly on exit). Increases front roll angle.

Stiffer LF spring engages LF tire more = better turning in the entry & middle. Increases roll angle &  decreases dynamic cross weight, freeing/loosening the car up entry & middle. 

Softer LF spring engages LF tire less = gives car more rear grip in the entry & middle. Decreases roll angle & increases dynamic cross weight, tightening the car up entry & middle. 

*  Don’t rely on LF to help much with exit.  With so much WT off the LF to the RR, the LF tire often hikes on exit, having little effect or at a minimum is floating on the asphalt with little grip.

Stiffer rear springs frees/loosens car on middle & exit (slightly on entry).

Softer rear springs tightens car on middle & exit (slightly on entry).

Stiffer RR spring decreases rear roll angle, making car more drivable (less knife-edgy) and frees/loosens middle & exit (slightly on entry).

Softer RR spring increases rear roll angle, works RR tire more & LR less. Hikes LF on exit.

Stiffer LR spring increases dynamic cross weight = engaging LR more / tightening car middle & exit.  Too stiff can cause car to be loose on entry. (Stiffen RF spring to fix)

Softer LR spring decreases dynamic cross weight = disengaging LR more / loosening car middle & exit.  Too soft can cause car to be tight/pushy on entry.  (Soften RF spring to fix)

Remember: Springs reach a certain compression with force and stay there as long as the same force is there.  Shocks continue to travel as long as the same force is there.

 

Spring Goals:

Flatter tracks require stiffer right side springs to counteract the increased roll rate.

High banked tracks use softer right side springs to achieve optimum roll rate.

Faster turns require stiffer right side springs to counteract the increased roll rate.

Slower turns require softer right side springs to achieve optimum roll rate.

Rookies need softer springs in the beginning, so they can feel the car, then stiffen as they drive harder.

 

Shock Valving / Rebound Adjustments:

Stiffer left side valving decreases roll angle.

Stiffer front valving frees/loosens car on exit … on the throttle.

Softer front valving tightens car on exit … on the throttle.

Stiffer rear valving tightens car on entry & middle.

Softer rear valving frees/loosens car on entry & middle.

Softer LR valving frees/loosens car on entry & middle.

Stiffer LR valving tightens car on entry & middle.

Softer LF valving increases roll angle, works right side more in middle & LR less on exit.

Stiffer LF valving decreases roll angle, working left side tires more in middle.  Doesn’t effect the exit much with so much WT off the LF to the RR.

Softer RF valving engages LR more & tightens car on exit … on the throttle.

Stiffer RF valving engages LR less & frees/loosens car on exit … on the throttle 

Softer RR valving works both front tires more, frees/loosens car up entry & middle.

Stiffer RR valving works both front tires less, tightens car up entry & middle. (Tightens exit too in extreme cases of “tie down rebound valving”)

 

Shocks or Spring ?

If you have maxed out a shock (either direction) you probably need to change a spring on the opposite corner, or end, of the car.  Examples:

If both front shocks end up full soft, you need softer springs on the rear of the car.

If both front shocks end up full stiff, you need stiffer springs on the rear of the car.

If both rear shocks end up full soft, you need softer springs on the front of the car.

If both rear shocks end up full stiff, you need stiffer springs on the front of the car.

If the LF shock ends up full soft, you need softer spring on the RR of the car.

If the LF shock ends up full stiff, you need stiffer spring on the RR of the car.

Etc.

Remember: Springs reach a certain compression with force and stay there as long as the same force is there.  Shocks continue to travel as long as the same force is there.

 

Rear Anti-Roll Bar:

A bigger ARB decreases roll angle, and engages the LR tire more. This produces more LR tire grip tightening the entry & middle the most … and exit to a lesser degree.

A smaller ARB increases roll angle, and disengages the LR tire more. This produces less LR tire grip freeing/loosening the entry & middle the most … and exit to a lesser degree.

ARB spring rate conversions:  .400” = 7.5#                  .450” = 12#           .500” = 18#

 

Shocks, Springs, ARB & Tire Pressure:

Spring rate & tire spring rate add up to equal overall spring rate for each corner.

On the right rear corner, the ARB also adds into the equation.

But remember, tire spring “action” is instantaneous, where springs are “slowed or dampened in their action” by the shock valving.

 

Static vs Dynamic:

“Static” is what the car is at rest, on the scales.

“Dynamic” is what the car is doing while in motion, on the track.

Stiffer LR & RF springs = more dynamic cross weight, regardless of scale readings.


Static Cross Weight/Wedge:

More cross weight tightens the car throughout the turn, although it may affect the entry less.*

Less cross weight loosens the car throughout the turn, although it may affect the entry less.*

 

Dynamic Cross Weight/Wedge:

A combination of LR & RF springs stiffer than the LF & RR springs create dynamic cross weight/wedge.  The stiffer the combination of the LR & RF springs are, in relation to the LF & RR springs … the more dynamic cross weight the car has. 

Of the LR/RF combination, if the RF spring is too stiff, the car will be tight on entry and middle … and have good grip on exit.

Of the LR/RF combination, if the LR spring is too stiff, the car will be free/loose on entry & middle … and have good grip on exit.

If the LR spring is way to stiff, the car will be tight/pushy on exit.

More dynamic cross weight tightens car throughout the turn.  It will affect the entry less if the car has so much WT from the LR to the RF that it is unhooking the LR.

Less cross weight loosens the car throughout the turn. It will affect the entry less if the car has so much WT from the LR to the RF that it is unhooking the LR.

 

Ride Heights:

Raising the whole car evenly, increases roll angle, working the right side tires more & left side tires less. This is the correct adjustment with low grip tires and/or track surface.

Lowering the whole car evenly, decreases roll angle, working the tires more evenly. This is the correct adjustment with good grip tires and track surface.

Raising the front or lowering the rear … transfers weight off the front and onto the rear of the car … tightening the car everywhere on the track.

Raising the rear or lowering the front … transfers weight off the rear and onto the front of the car … freeing/loosening the car everywhere on the track.

 “Rocking the Car” is when you raise one end and lower the opposite end in equal amounts to maintain the same ride height at the motorplate. The above affects apply.

Reminder: Reset the panhard bar heights … unless you want them changed with ride height.

 

Front End Geometry

Always optimize the front end geometry to get the car to turn well.

Optimum settings:     Toe-out = 1/8” to 3/16”     Caster = 4-12°  varies with turn radius

If the car is not turning well, always double check the front end geometry.

Do not adjust front end geometry past optimum settings to get the car to turn better.

If the car is not turning well with optimum front end geometry, unhook the LR or total rear.

 

Front Panhard Bar:

Affects the front roll angle of the car onto the RF tire, mostly at “turn in” on entry of corner. Continues affecting the front roll angle through the middle of the turn … and slightly on exit until steering is unwound.

Lowering the front panhard bar, transfers more weight … from the LR tire onto the RF tire upon entry … creating increased turn-in.  Too low = free/loose on corner entry & middle.

Raising the front panhard bar, transfers less weight … from the LR tire onto the RF tire upon entry … creating decreased turn-in.  Too high = tight/pushy on corner entry & middle.

 

Rear Panhard Bar:

Affects the rear roll angle of the car onto the RR tire, mostly in the middle of corner before throttle. Continues affecting the rear roll angle through the exit, until steering is unwound.

Lowering the rear panhard bar, transfers more weight onto the RR tire … tightening the car in the middle of the turn, before throttle.  Too low = Tight/pushy in middle of corner.

Raising the rear panhard bar, transfers less weight onto the RR tire … freeing/loosening the car in the middle of the turn, before throttle.  Too high = Loose in middle of corner.

 

Brake Bias:

Too much front brake bias makes the car tight/pushy on entry.

Too much rear brake bias makes the car loose on entry.

The optimum brake bias is to run as much rear brake force as allowable … without causing the rear to become loose on entry under hard braking.

Higher speed corners, momentum tracks & Driver lines with braking while turning … need more front brake bias.

Slower speed corners, paperclip tracks & Driver lines with straighter braking … can use more rear brake bias.

As the track grips up, the Driver needs to adjust the brake bias to the rear in small steps.

Power/Response:

More power/better response = More weight transfer front to rear on exit (unless tire spins).

More power/better response can lead to push on exit, if rear tires have full traction.

Less power/weak response = Less weight transfer from front to rear on exit.

Less power/weak response can lead to looser or free condition on exit.

 

Gearing:

The 1 or 2 digit number on the gear box is NOT the ratio.  It is a Winters reference number.  Examples:  24 gear set = 4.93-1 ratio         8 gear set = 5.29-1 ratio         12 set = 5.77-1 ratio

 The bigger the ratio number, the lower the gear … meaning it will accelerate quicker but top out at less speed. 

The smaller the ratio number, the higher the gear … meaning it will accelerate slower but top out at more speed.

Lower gear (bigger ratio #) = More weight transfer from front to rear on exit (unless tire spins).

Lower gear can lead to a tight/pushy condition if rear tires have full traction.

Higher gear/smaller # = Less weight transfer from front to rear on exit.

Higher gear can lead to a looser or free condition on exit.

Paperclip style tracks with tight corners and dragstrip style straights benefit from a lower gear (bigger #).  Even though the gear is taking the engine past its optimum powerband, the extra gear ratio helps accelerate off the turn and then helps the engine act as a brake on entry.

Longer, momentum style tracks with higher speed corners, benefit from a higher gear (smaller #) to keep the engine near the optimum power band.

Find the gear needed for the track early and stay with it so you can tune to the gear. 

 

Tuning Goals - Entry:

Goal = Great grip on entry without being tight/pushy.

You want the driver to have confidence to drive the car hard into the corner.

Grip = confidence.  Free or loose is never fast … on entry.

 

Tuning Goals - Middle:

Goal = This varies depending on the type of track.

Short tracks, especially paperclip tracks, reward a driver that “turns down” in the middle of the turn and drives off the exit “straighter.”  Not all turns are like this.

Any corner that the Driver needs to use steering input to “turn down” in the middle of the corner, needs the car to rotate on its axis, but only with steering input. Goal = Free.

Don’t confuse free with loose.  Free means the rear end glides around, as the driver wants it, when the driver “turns down.” Loose means the car rotates on its own, without steering input and/or rotates more than the driver wants.

Be careful if you have “good grip” in the middle on tight corners.  If it has too much grip the car will be tight, and the Driver will not be able to “turn it” where they want.

Any high speed corner that the driver does not “turn down” in the middle, does not need to be free.  Goal = Good grip.

 

Tuning Goals - Exit:

Goal = Great grip on exit without being tight/pushy.

The challenge is finding that fine line of great grip without being tight or pushy on exit.

Being slightly free is better than being tight or pushy on exit.  Free is when the car rotates into a state of yaw on the exit, but the driver can stay in the throttle and steer through it without loosing time.

Being loose is better than being pushy on exit … because the driver can modulate the exit with the throttle. Loose is when the car rotates into a high state of yaw on the exit, and the driver can not stay in the throttle without having the car sideways and losing time.

Remember, great grip is the goal, but when in doubt, err or free/loose side.

 

Tuning throughout Race Day:

The ultimate goal is to have a race car that:

Has great grip on entry.

Turns well in the middle. (Rotates freely if needed.)

Has great grip on exit.

 

The big challenge is … the track typically tightens up as more rubber is laid down, and tightens up more as evening comes and the track surface cools.  The trick is guesstimating how much that is going to happen.

Another challenge is the line between great grip and a tight or push condition is very fine.

When in doubt, err or the free side for middle & exit.  A good Driver can drive a free or loose race car with the throttle.  It is hard to drive a car fast that is pushing.

The first goal should be to get a car that is balanced … meaning it has similar grip on entry and exit … and still turns in the middle.

If you have the car with good grip on entry & exit … do not loosen that up … just free up the middle throughout the day/night … so the car will turn.  Stagger & rear panhard bar are the common tools to free up the middle (before throttle).

If the car is a little free on entry & exit early in the day (and turns in the middle) … you could almost let the track come to you.  Just be sure to make adjustments to keep the car turning in the middle … as the track tightens up.

 

Tuning for Qualifying:

If you have 8 laps to qualify, simply run your long run set up.  Laps 4-8 will be fast, and this acts as another test session.

If you have 2 laps to qualify, and a good long run set-up on the car that takes 4 laps to come in, you need to make a small adjustment to get the tires to come in quicker.

 

If the car is typically loose everywhere on the first 2-3 laps, then:

Add ¼ to ½ turn of cross weight … or

Soften up the front shocks & stiffen the rear shocks (1-2 clicks) … or

Reduce the stagger ¼”

Remember to keep the middle free with rear panhard bar adjustment.

 

If the car is typically tight/pushy everywhere on the first 2-3 laps, then:

Take out ¼ to ½ turn of cross weight … or

Stiffen up the front shocks & soften the rear shocks (1-2 clicks) … or

Increase the stagger ¼”

Remember to keep the middle free with rear panhard bar adjustment.

If the car is just loose or pushy in one part of the track when the tires are cool, fix that part.

 

Tuning for Heat Races:

If the car is typically loose everywhere on the first 2-3 laps, then:

Soften up the RF shock & stiffen the LR shock (1-2 clicks) … or

Reduce the stagger ¼”

Remember to keep the middle free with rear panhard bar adjustment.

 

If the car is typically tight/pushy everywhere on the first 2-3 laps, then:

Stiffen up the RF shock & soften the LR shock (1-2 clicks) … or

Increase the stagger ¼”

Remember to keep the middle free with rear panhard bar adjustment.

If the car is just loose or pushy in one part of the track when the tires are cool, fix that part.

 

Tuning for the Main Event:

If you have the car with good grip on entry … do not loosen that up … just free up the middle & exit… so the car will turn in the middle.  Adding stagger, reducing X in the rear only & raising the rear panhard bar are the common tools to do this.

An old trick:  Run regular air in the RR & LF tires on long races.  The additional tire growth will increase stagger, decrease cross weight, raise the rear panhard bar, and lower the front panhard bar … over the long run … insuring the car continues to turn well, as the track tightens up.

 

Winning Tuning Philosophies:

Test things on test days.  Go with what you know on race day.

On test days, to see the effects of a change, change just one thing.

On race day, make combination changes to dial the car in.  You don’t have enough time or runs to try one thing at a time on race day.

If you’re completely out to lunch on race day … and you don’t know for sure what to do … try something big one direction or the other.  You have a 50/50 chance of making progress.  Besides, if you’re 10th, what do you have to lose.

If the car is perfect now, it won’t be next session.  Tune it.

 

Tuning for Learning Drivers:

The biggest challenge a tuner can have is a Driver that is learning. They are constantly changing their driving.  Patience, communication and recognizing progress are all key.

In the early phases of a new driver learning a car or track, they typically have the brake & gas points off.  This will change the set-up needs of the car from optimum.

If the driver is lifting on the throttle and braking too late, you will need stiffer front springs than optimum to prevent the car from being loose in.  The challenge with the stiffer springs is the car will be tend to be tight/pushy in the middle, once they get off the brakes.

If the Driver is lifting on the throttle and braking too early, you will need softer front springs than optimum to prevent the car from being tight or pushy on entry & middle. The challenge with the softer springs will be too much roll angle and a knife-edgey race car. And, if they ever try to go deep … the car will be loose on entry and middle.

If the Driver is picking the throttle up too early on exit (in, or before, the middle) no set-up will work well … as the car is driving off the back wheels before the car is pointed the right way to exit.  The car may be tight/pushy, then snap loose as speed rises.

If the Driver is picking the throttle up too late on exit, just about any exit set-up will work.

The biggest challenge in tuning for a learning driver, is their inconsistency as they experiment.  No set-up will be right for the various brake & gas points.

Another challenge will be tuning for the driver changing lines.  Higher lines need less stagger.  Tighter lines needs more stagger.  Big radius entries need less rear brake and more RR spring.  “Straight-in” entries need more rear brake, and stiffer front springs.  Big radius exits need more stagger and side bite.  Straighter exits need less stagger, or stiffer LR springs. Coach the driver to find a line early and stick with it … and to run the same lines in racing as you practice and set-up for.

Try to tune to the driver’s needs for their current skills.  Educate them on the right ways, and change the set-up as their driving changes. This could be every session, when a new driver is learning a new track.

 

Trouble Shooting:

If you are making significant changes and seeing minor or no affect, you may have a problem.  Check these areas:

Suspension bind

Torque tube bind

Shock dead

Spring dead

Cracked / broken chassis

Axle(s) not square

 

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Free/Loose upon Entry ONLY

Driving Adjustments

Possible Cause                                            Correction

Driver braking too hard on entry ?                 Driver brake softer

Driver braking too late ?                               Driver brake earlier

Driver turn-in too late & too hard?                Driver adjust turn-in point earlier & gentler

Driver running too low on entry ?                  Driver adjust line to run higher entry into turns

Cockpit Adjustments

Is there too much rear brake ?                       Driver adjust brake bias toward the front brakes

Too much weight transfer                             Tighten up rebound valving on left rear shock

Chassis Adjustments

RF tire pressure too low?                             Increase PSI in RF tire

Both front tire pressures too low ?                Increase PSI in both front tires

Left rear shock rebound too soft         ?        Tighten the rebound valving on the LR shock

Both rear shocks rebound too soft ?             Tighten the rebound valving on both rear shocks

Roll Center too low ?                                    Raise front panhard bar

Right front spring too soft ?                          Change to a stiffer rate of right front spring

Both front springs too soft ?                         Change to a stiffer rate front springs

Needs a more Cross Weight                         Add Cross Weight on all 4 corners

LR spring overloading RF spring                  Change to softer LR spring

Car getting over onto RF too much               Diagonally Rock the Chassis

Trouble Shooting

Is the right rear tire crowned ?                       Reduce tire pressure in right rear tire

Rear suspension binding up                          Find problem and free up rear suspension

 

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Free/Loose at Middle of Turn ONLY

(Before Throttle is Applied)

Driving Adjustments

 

Possible Cause & Correction

 

Driver braking too little ?  Driver brake longer or harder to slow car more.

Driver running too low on entry & turning car too much in the middle?  Driver adjust entry and/or exit lines to widen turning radius in middle.

Driver turning too tight, or too much, in middle ?  Driver adjust line to run higher entry into turns to widen turning radius in middle

Car unhooking LR too much?  Driver trail brake in middle

Cockpit Adjustments

Not engaging LR enough                              Increase cross weight with weight jacker

Chassis Adjustments

Rear roll center too high                               Lower rear panhard bar sliding mount

Front roll center too low                               Raise front panhard bar sliding mount

Combination                                                Lower rear & raise front panhard bar mounts

Anti-roll bars too soft                                   Change to a stiffer anti-roll bar

Needs more cross (only in middle)                Soften LF Spring Rate

Trouble Shooting

If out of panhard bar adjustment                   Consider stiffer LR springs or more cross weight,

                                                                   and stiffen the front shocks to reduce exit push

Turning radius less than expected                 Reduce the stagger (but prepare to loosen the exit)

Both left side shocks rebound too stiff         Soften the rebound valving on both left shocks

Suspension binding up                                 Find the problem and free up rear suspension

 

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Loose on Exit - ONLY

(As Throttle is Applied)

Driving Adjustments

 

 

Possible Cause & Correction

Is driver getting on throttle earlier than traction is available? If true, try to fix car, not driver

 

Does driver have correct brake & throttle points?    If, no fix driver.

Cockpit Adjustments

Not engaging LR enough                              Soften rebound valving right front shock

Not engaging LR enough                              Increase cross weight with weight jacker

Chassis Adjustments

Right front shock rebound too stiff               Soften the rebound valving on right front shock

Both front shocks rebound too stiff              Soften the rebound valving on both front shocks

Is there too much rear stagger ?                     Decrease stagger with tire pressures

                                                                   (Remember to account for spring rate change)

Left rear tire not gripping enough                  Increase cross weight with spring adjusters

Not enough dynamic cross weight                Stiffen the left rear spring

Right rear shock rebound too soft                Stiffen the rebound valving on the RR shock

Trouble Shooting

Is the right rear tire is too crowned ?             Reduce tire pressure in right rear tire

Are birdcages out of time ?                           Reset birdcage timing

 

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Free/Loose at Both Entry & Middle  (Exit is Good)

Driving Adjustments

Possible Cause & Correction

Driver braking too late & too hard?               Driver brake earlier & softer

Driver turn-in too late & too hard?                Driver adjust turn-in point earlier & gentler

Driver running too low on entry ?                  Driver adjust line to run higher entry into turns

Driver running too tight of a radius ?             Driver adjust line for a wider radius

Driver running outside rubber groove?          Driver adjust line to find rubber groove

Cockpit Adjustments

Not engaging LR enough                              Stiffen the rebound valving on the LR shock

                                                                   & Increase cross weight with weight jacker

Chassis Adjustments

Anti-roll bar too soft                                    Change to a stiffer anti-roll bar

Panhard combination                                   Raise front panhard & Lower rear panhard

RF spring too soft                                       More PSI in RF tire

Front springs too soft                                  More PSI in both front tires

RF spring too soft                                       Stiffer rate of RF spring

Car getting over onto RF too much               Diagonally Rock the Chassis

Combination Solution for small changes:  Stiffen rebound valving on LR shock or both rear shocks for entry … and lower rear panhard bar for middle.

Trouble Shooting

Is the right rear tire is too crowned ?             Reduce tire pressure in right rear tire

Is the right rear tire worn out ?                      Replace right rear tire

Front CG too low                                        Raise front ride height with spring adjustment

Rear CG too high                                         Lower rear ride height with spring adjustment

Ride Height Combination                              Lower rear ride height & raise front ride height

Suspension binding up                                 Find problem and free up rear suspension

 

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Loose Starts at Middle of Turn / Before Throttle is Applied

And … Continues When Throttle is Applied

Driving Adjustments

 Possible Cause & Correction

Driver over driving car for current set-up? Brake more to slow car in middle & roll throttle on slower on exit.

Does driver have correct brake & throttle points?    If, no fix driver.

Car could be way too loose in middle … and is still loose when it’s time to pick up the throttle? Fix the middle … and the exit may take care of itself

Cockpit Adjustments

                                                                   Increase cross weight with weight jacker

                                                                   Soften rebound valving right front shock

Chassis Adjustments

Is there too much rear stagger ?                    Decrease stagger with tire pressures

Left rear tire not engaged enough                  Increase cross weight with spring adjusters

Left rear tire not engaged enough                  Stiffer rate of left rear spring

RR not engaged enough                               Softer RR spring (Careful of increased roll angle)

 

Combination solution for small changes:  Soften the rebound valving on right front shock or

both front shocks for exit & lower rear panhard bar sliding mount for middle.

 

Front roll center too low                               Raise front panhard bar sliding mount

Combination panhard                                   Lower rear & raise front panhard bar mounts

Trouble Shooting

Is the right rear tire is too crowned ?             Reduce tire pressure in right rear tire

Is roll angle too much, disengaging LR          Stiffer rate of RR spring

 

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Too Free/Loose Everywhere: Entry – Middle – Exit

Driving Adjustments

Possible Cause & Correction

Driver running too tight of a radius ?             Driver adjust line for a wider radius

Driver running outside rubber groove?          Driver adjust line to find rubber groove

Driver running too low in turns ?                   Driver adjust line to run higher in turns

Driver overdriving car for current set-up        Brake earlier, longer and roll throttle on slower

Cockpit Adjustments

Stiffen rebound valving on left rear shock & soften rebound valving on right front shock & increase cross weight with weight jacker ã

Chassis Adjustments

Too much rear stagger                                 Decrease stagger with tire pressures

Left rear tire not engaged enough                  Increase cross weight with spring adjusters

Left rear tire not engaged enough                  Stiffen the left rear & right front spring

Anti-roll bars too soft                                   Change to a stiffer anti-roll bar

Too little roll angle, RR not loaded               Softer RR spring (just don’t hike the LF on exit)

Front CG too low                                        Raise front ride height with spring adjustment

Rear CG too high                                         Lower rear ride height with spring adjustment

Ride Height Combination                              Lower rear ride height & raise front ride height

Small combination solution: Stiffen rebound on rear shocks (for entry) & soften rebound on front shocks (for exit) & lower the rear panhard bar (for middle).

Trouble Shooting

Is roll angle too much, unloading LR             Stiffer rate of RR spring

Is rear roll rate too high?                               Increase rate of both rear springs

Rear tires too crowned with PSI?                  Reduce tire pressure

Is the right rear tire worn out ?                      Replace right rear tire

Left side shocks rebound WAY too stiff       Soften the rebound valving on both left shocks

Left side shocks rebound WAY too soft       Stiffen the rebound valving on both left shocks

Suspension binding up                                 Find problem and free up rear suspension

 

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Tight/Push on Entry ONLY

Driving Adjustments

Possible Cause & Correction

Driver lifting & braking too early                   Carry throttle deeper & brake later

Turning radius too tight                                Go wide and turn in early & gentle

                                                                   Try running outside the rubber traction groove

Cockpit Adjustments

Is there too much front brake ?                     Adjust brake bias toward the rear brakes

                                                                   Soften up rebound valving on left rear shock

Chassis Adjustments

Right front tire PSI too high                          Decrease right front tire PSI

Both front tire PSI too high                          Decrease both front tires PSI

Left rear shock rebound too tight                  Soften the rebound valving on the LR shock

Both left shocks rebound too tight                Soften the rebound valving on both rear shocks

Right front spring is too stiff                         Change to a softer rate of right front spring

Both front springs are too stiff                      Change to softer rate front springs

Roll center way too high                               Lower the front panhard bar

Trouble Shooting

Not enough toe-out (or toed in)                    Correct the toe out to 1/8” to 3/16” out

Too much toe out                                        Correct the toe out to 1/8” to 3/16” out

Wearing tire too much on one side                Correct the camber 

Is the right front tire crowning ?                    Lower the tire pressure in the right front tire

 

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Push at Middle of Turn – ONLY

(Before Throttle is Applied)

Driving Adjustments

 

Possible Cause & Correction

Is the Rookie Driver making the mistake of lifting too early, braking too early and getting on the throttle too early (before middle of turn & before steering unwind)?  If yes, Driver needs to carry throttle deeper, brake later and pick up throttle just after steering unwind.

Possible Cause & Correction

Driver has slowed car too much                    Driver brake softer or less, for more corner speed

Driver running too tight of a radius ?             Driver adjust line for a wider radius

Driver running too low in turns ?                   Driver adjust line to run higher in turns

Driver applying throttle too early                   Driver quit it !  Change brake & gas points.

Cockpit Adjustments

Not Ideal: Decrease cross weight w/weight jacker

 

Chassis Adjustments

Rear roll center too low                                Raise rear panhard bar sliding mount

Front roll center too high                              Lower front panhard bar sliding mount

Combination                                                Raise rear panhard bar & lower front panhard bar

Anti-roll bars too stiff                                   Change to a softer anti-roll bar (or remove)

Needs less cross (only in middle)                  Stiffen LF Spring Rate

Front tires not working enough                     Add Caster and/or Camber

Front axle needs leading                               Re-square front axle with 1/8” lead on right side

Trouble Shooting

Turning radius less than expected                 Reduce the stagger (but prepare to loosen the exit)

Front axle out of square (lead on left)            Re-square front axle

Rear axle out of square                                 Re-square rear axle & front axle with 1/8” lead

Suspension binding up                                 Find problem and free up rear suspension

Torque tube binding up under load               Adjust panhard bar rod end to free up under load

 

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Tight/Push Starts at Middle of Turn / Before Throttle is Applied

And … Continues When Throttle is Applied

Driving Adjustments

Possible Cause & Correction

Driver has slowed car too much                    Driver brake softer or less, for more corner speed

Driver applying throttle too early                   Driver quit it !  Change brake & gas points.

Driver running incorrect line ?                       Driver adjust line to offset oval

Cockpit Adjustments

Decrease cross weight w/weight jacker – AND - Stiffen RF shock rebound valving

Chassis Adjustments

Not enough rear stagger                                Increase stagger with tire pressures

Left rear tire engaged too much                     Decrease cross weight with spring adjusters

Left rear tire engaged too much                     Softer LR spring

Working RR too much                                 Stiffer RR spring

Sometimes the push starts before the throttle is picked up … and continues on exit. Simply fix the push in the middle and the Exit may take care of itself

Rear roll center too low                                Raise rear panhard bar sliding mount

Left rear tire engaged too much                     Stiffer LF spring

Left rear tire engaged too much                     Softer LR spring

Combination                                                Raise rear panhard bar & lower front panhard bar

Anti-roll bars too stiff                                   Change to a softer anti-roll bar

Many times the push starts before the  throttle is picked up … and gets WORSE as the throttle is applied. Combination solution: Fix the push in the middle with the tips above –AND- use the tips below.                  

Right/both front shocks rebound too soft     Stiffen rebound valving on right/both front shocks

Trouble Shooting

Is the Right Front Tire DEAD?                     Replace the right front tire

Is the right front tire crowning ?                    Lower the tire pressure in the right front tire

 

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Tight/Push on Exit

(As Throttle is Applied)

Driving Adjustments

Is push ONLY on exit?  Does driver changing the line to exit turn straighter, fix the problem?  Is the car good everywhere else?  If yes to all 3 questions … fix driver, not car. If not, fix car.

 

Possible Cause & Correction

Is Driver picking up throttle too early? Pick up throttle later

Entry too low / Exit too high                         Higher entry into turn sets up straighter, lower exit

Cockpit Adjustments

Stiffen rebound valving on right front shock

Chassis Adjustments

Right front shock rebound too soft               Stiffen rebound valving on right front shock

Both front shocks rebound too soft              Stiffen rebound valving on both front shocks

 

(With all 3 of the following tips, be prepared to adjust for looser entry or middle)

Left rear tire engaged too much                     Decrease cross weight with spring adjusters

Left rear tire engaged too much                     Softer LR spring

If LF hiking, RR spring may be too soft        Change to a stiffer rate of right rear spring

Trouble Shooting

RR shock has too much “tie-down”             Soften rebound valving on right rear shock

LR shock has too much “tie-down”              Soften rebound valving on left rear shock

Both shocks have too much “tie-down”        Soften rebound valving on both rear shocks

 

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Tight/Push on BOTH Entry & Middle  (Exit is Good)

Driving Adjustments

Is the Rookie Driver making the mistake of lifting too early, braking too early and getting on the throttle too early (before middle of turn & before steering unwind)?  If yes, Driver needs to carry throttle deeper, brake later and pick up throttle just after steering unwind.

Possible Cause & Correction

Driver braking too early & too much             Carry throttle deeper & brake LATER & LESS

Turning radius too tight                                Go wide and turn in early & gentle

                                                                   Try running outside the rubber traction groove

Cockpit Adjustments

Soften the rebound valving on the LR shock

Adjust brake bias to rear

Chassis Adjustments

Front roll center too high                              Lower front panhard bar sliding mount

Panhard combination                                    Lower front panhard & raise rear panhard

Right front tire PSI is too high                      Decrease PSI in RF tire

Both front tire PSI is too high                       Decrease PSI in both front tires

Anti-roll bars too stiff                                   Change to a softer anti-roll bar

Right front spring is too stiff                         Change to a softer right front spring

 

Small combination solution: Soften the rebound valving on both rear shocks (for entry) & raise the rear panhard bar sliding mount (for middle).

Trouble Shooting

Not enough toe-out (or toed in)                 Correct the toe out to 1/8”- 3/16” out

Is the Right Front Tire DEAD?                     Replace the right front tire

Is the right front tire crowning ?                    Lower the tire pressure in the right front tire

Wearing tire too much on one side                Correct the camber

 

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Push Everywhere: Entry – Middle – Exit

Driving Adjustments

Carry throttle deeper & brake later … and brake very little. 

Cockpit Adjustments

 

Do ALL 3: Decrease cross weight with weight jacker, soften up rebound valving on left rear shock & tighten up rebound valving on right front shock

 

Chassis Adjustments

Possible Cause & Correction

Not enough rear stagger                                Increase stagger with tire pressures

LR tire engaged too much                             Decrease cross weight on all 4 spring adjusters

Too much dynamic cross weight                  Softer left rear and right front springs

Front CG too high                                       Lower front ride height with spring adjustment

Rear CG too low                                         Raise rear ride height with spring adjustment

Rock the Car                                               Raise rear ride height & Lower front ride height

Anti-roll bar WAY too stiff                           Change to a softer anti-roll bar

Trouble Shooting

Is the Right Front Tire DEAD?                   Replace the right front tire

Not enough toe-out (or toed in)                  Correct the toe out to 1/8”- 3/16” out

Front tire PSI out of sight                           Lower front tire PSI into normal range

Wearing tire too much on one side             Correct the camber

 

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Free/Loose on Entry & Tight/Push on Exit

 

Driving Adjustments

Possible Cause                                            Correction

Braking too late and/or hard on entry ?          Driver adjust braking point earlier and/or softer

Driver line is incorrect ?                                Driver adjust line for gentle entry turn in

Cockpit Adjustments

Is there too much rear brake ?                       Driver adjust brake bias toward the front brakes

Tighten up rebound valving on left rear shock

Chassis Adjustments

Left rear shock rebound too soft                   Tighten the rebound valving on the LR shock

Both rear shocks rebound too soft                Tighten the rebound valving on both rear shocks

Right front spring is too soft                         Change to a stiffer rate of right front spring

Both front springs are too soft                      Change to a stiffer rate front springs

LR spring overloading RF spring                  Change to softer LR spring

Car getting over onto RF too much               Diagonally Rock the Chassis

 

 3. The track grip is increasing to the point that weight transfer and roll rate are outside their happy window. If it is a “small problem” … the answer is shock valving.  If you are at a new track that is bigger & faster and the problem is BIG … the solution is springs.

If problem is minor                                       Stiffen rebound valving on all 4 shocks

If problem is major                                       Stiffen springs on all 4 corners (maybe not LR)

  

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Tight/Push on Entry & Free/Loose on Exit

Typical problem:  Car is pushing into the turn, then front finally hooks up after

A) The driver slows the car enough and/or

B) The front tires finally get grip.

This causes the back of the car to step out quickly … and the car is now loose from the middle off. We call this “Snap Loose.” Fix the push on entry… and the loose middle-off condition should go away.

 

Driving Adjustments

Possible Cause & Correction

Driver lifting & braking too early                   Carry throttle deeper & brake later

Turning radius too tight                                Go wide and turn in early & gentle

                                                                   Drive outside the rubber traction groove on entry

Cockpit Adjustments

Is there too much front brake ?                     Adjust brake bias toward the rear brakes

                                                                   Soften up rebound valving on left rear shock

Chassis Adjustments

Left rear shock rebound too tight                  Soften the rebound valving on the LR shock

Front roll center too high                              Lower front panhard bar sliding mount

Front tire PSI too high                                  Less PSI in front tires

Anti-roll bars too stiff                                   Change to a softer anti-roll bar

Right front spring is too stiff                         Change to a softer right front spring

Trouble Shooting

Is the right front tire crowning ?                    Lower the tire pressure in the right front tire

Wearing tire too much on one side                Correct the camber

Not enough toe-out (or toed in)                    Correct the toe out to 1/8”- 3/16” out

Too much toe out                                        Correct the toe out to 1/8”- 3/16” out

  

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Top 20 Tips to Remember

The goal is have car balanced without hiking the left front, or overworking the right front.

Unequal roll angles (front & back) causes the negative effects of “Averaging.”

Close left to right tire temps are our guide to a well balanced, drivable race car.

Stagger helps steering, and makes the car turn left easier.  Too much = loose.

Cross weight helps rear traction.  Too much = push.

Decreasing stagger increases cross weight.  Increasing stagger decreases cross weight.

Changing “Static Cross Weight” is done with the spring adjusters.

Changing “Dynamic Cross Weight” is done by changing the springs (rate).

Stiffer LF and/or RR springs decrease cross weight dynamically. Softer LF and/or RR springs increase cross weight dynamically.

Shocks are fine tune adjustment of front to rear weight transfer … and side to side transfer.

Disengaging the LR tire (to a degree) is the key to getting the car to turn on entry & middle.  Disengage LR tire too much = loose.  Disengage LR tire too little = tight/push.

Engaging the LR tire (to a degree) on corner exit is the key to forward bite. Engage LR tire too little = loose.  Engage LR tire too much = tight/push.

Stiffer anti-roll bars make the car run flatter while keeping LR tire engaged, providing grip.  Stiffer RR springs makes the car run flatter but decreases RR tire grip.

Chassis tilt adds left side weight, but low overall is best.

Tires-tires-tires !  (Fresh, clean, correct durometer, out of sun).

Tire coefficient of friction is best when driven at 102%.

Tire pressures affect contact patch.

Tire pressures affect sidewall spring rate.

Therefore stagger affects contact patch.

Therefore stagger affects spring rate.

 

Best wishes in your Focus Midget racing !

 

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