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SLM SETUP INFO, HELP, AND ADJUSTMENTS
This car weighs 2800 lbs and has about 550 hp
The most important thing when doing a setup is balance
Ride Heights: How far the frame is off the ground.
Tire Pressure: How Much air is in the tire.
Stagger: How much diameter difference in the tires. Example; left front 86 inches and the right front 88 inches gives a 2 inch front stagger.
Ballast: How much lead you put in the car - placement of the lead is huge.
Cross: The weight resting on RF and the LR tires added together then divided by the total vehicle weight.
Left Percentage: LF Weight + LR Weight ÷ Total Weight = Left Side %
Nose Weight: LF Weight + RF Weight ÷ Total Weight = Nose %
Rear Percentage: LR Weight + RR Weight ÷ Total Weight = Rear %
Cross Percentage: LR Weight + RF Weight ÷ Total Weight = Cross %
Rear Bite: Subtract the weight on the RR tire from the LR
Nose Weight: see above.
Left Bar End Clearance: How much load is on the sway bar. Negative number here means preload on the sway bar. More preload generally tightens you up upon corner entry. A detached sway bar should allow some play in the left front suspension before the bar is loaded, perhaps better left detached for bumpy tracks. Rule of thumb increasing the end clearance to free it up on entry, decrease to tighten it on entry. I saw this on OSRacing.net and found it comical, "If your End Clearance is a negative value, it makes no sense to have the left end detached, since it’s constantly loading the sway bar"
Arm Preload: see above.
ARM Diameter: A bigger diameter should tighten the car up. Most impact is at the middle of the turn while in rotation.
ARB Length: Longer arm should free it up on entry and exit.
Toe: How much the front tires point in or out from the centerline of the car (towards each other or away). + means the tire is pointing towards the other tire. - means the tire is pointing away from the other tire.
Camber: The vertical lean of the tires. If the LF top of the tire leans away from the engine this is positive camber. If the top RF leans towards the engine this is negative camber.
Caster: Positive caster - the upper ball joint is behind the lower ball joint. Negative caster - the upper ball joint is ahead of the lower ball joint. Less caster for smaller tighter tracks. Less caster on the LF than the RF will cause the car to pull more to the left and create a quicker turn in. Less banking the more caster split like LF +2.0 RF +6.0 for example, less split for higher banked tracks.
Track Bar: The simple explanation, it changes the position of the rear axle in relation to the car's centerline. Raise both ends of the trackbar, will raise the rear roll center, which makes you looser. LR range 6.25 to 14.5 middle of that range is 10.5 - the RR range is 5.75 to 13.25 middle of that range is 9.5
Shocks: Taking the number from a 10 to 11 will make the shock stiffer and harder to compress. With rebound going from a 10 to 11 the slower it will release.
Where do I start adjusting?
You can start where you like, this is the methodical approach we use to adjust the SLM. Before getting too far set the gear, fuel, caster, and camber.
Gear - Set this to your driving preference and track, hit the rev limiter before the end of the straight and let it sing a couple times to help with braking or, have it go all the way into the turn with no chip is really up to you and how you get into the turn.
Caster - Tighter turns on a short track you will probably want about a LF start at 2 and a RF start at 6 then adjust so the feels like it wants to turn into the corner
Fuel - Take enough so you don't have to pit if not needed to complete the race
Camber - Adjust this to maximize the contact patch as indicated by a pretty even tire temp across the inside/middle/outside of the tire. We aim for less than a 20 degree spread
Stagger 2" front and rear
ARB Length - We start with a base of 12"
ARB Diameter - We start with a 1.5
Left end attached - We start with this unattached
Left Bar Clearance - We keep this at zero while dialing things in, you will need to keep resetting it over the setup phase
LR Spring - start with 250lbs
RR Spring - start with 300 lbs
LF Spring - depending on track size but start with 3500
RF Spring - depending on track size but start with 3500
Corner Springs - 100 each side
Track Bar - 11
Cross - we will adjust this when we do the longer runs
Trailing Arm Mounts - middle
Ride Heights - we will adjust this, keep them at the stock heights for now
Packer Shims - add until the ride height changes then back off to the original ride height
Preload - keep at zero
Toe - negative 1 on each side
Car does this here on the track, what might help?
Stupid loose (loose everywhere)
Stiffer front springs
Softer rear springs
More sway bar
Lower the track bars
Less rear stagger
Drives like a dump truck (tight everywhere)
Soften the front springs
Stiffer rear springs
Less sway bar
Raise the track bars
More rear stagger
Entry (never start a race until the entry--cut is right)
Loose:
Softer LF front spring - or less spring split - or stiffer front springs
More rear spring split soften LR first
Adjust brake bias toward the front
Lower the track bars
Less stagger
More toe out
More positive caster
Not moving the ballast forward so that is off the table, and not using the sway bar or shocks yet
Good - go to cut
Tight
More caster split
Raise left track bar
Stiffer LF spring
Cut (never start a race until the entry--cut is right)
Loose:
Stiffen 1 front spring at a time starting with LF
Softer rear springs LR first
Adjust brake bias toward the front
Lower the track bars
Less stagger
More toe out
More positive caster
Not moving the ballast forward so that is off the table, and not using the sway bar or shocks yet
Good - go to middle
Tight
Middle
Loose
Good - go to acceleration
Tight
Acceleration
Loose
Good - go to exit
Tight
Exit
Loose
Good - turn several laps and get tire data
Tight
Never use shocks during a setup build to solve issues: Using shocks for poor handling problems will be like chasing a ghost. Use the 9/9 setting on all four corners to build your set, then make changes one corner at a time near the end and feel the results. Make the car easier for the driver comfort which will produce faster more consistent laps.
Wont stay low and sliding up into the next groove: Bars could be too High - only if all else fails, as a last resort, move the ballast forward
Loose on entry: The makings for a long day and poor finish. Nearly always push in the middle
Push in the middle: probably loose on exit
Beware: If you keep going softer on a front spring to fix a push - look at somewhere else - you could push worse
Beware: If you keep going softer on a rear spring to fix loose - look at somewhere else - you could make it worse
RIDE HEIGHTs
Front:
Lowering the front will shift weight to front, helping front grip which should give oversteer.
Raising the front will shift weight to the rear helping grip of the rear tires which should make understeer.
Rear:
Lowering the rear of the car will shift weight and grip to the rear creating understeer.
Raising rear will shift weight and grip to the front creating oversteer.
SHOCK COMPRESSION:
FRONT
The stiffer the front shocks, (higher the number) the tighter the car will be when braking.
The softer the front shocks, (lower the number) the looser the car will be when braking.
REAR
The stiffer the rear shocks, (higher the number) the looser the car will be under acceleration.
The softer the rear shocks, (lower the number) the tighter the car will be under acceleration.
SHOCK REBOUND:
FRONT
The stiffer the front shocks, (higher the number) the tighter the car will be under acceleration.
The softer the front shocks, (lower the number) the looser the car will be under acceleration.
REAR
The stiffer the rear shocks, (higher the number) the looser the car will be under braking.
The softer the rear shocks, (lower the number) the tighter the car will be under braking.
Shock break down by the corner:
RF (Right Front)
Higher compression will tighten the chassis entering a corner.
Lower compression will loosen the chassis entering a corner.
Higher rebound will tighten the chassis accelerating out of a corner.
Lower rebound will loosen the chassis accelerating out of a corner.
Overall stiffer RF shock will tighten chassis, weaker will loosen it.
RR (Right Rear)
Higher compression will loosen the chassis accelerating out of a corner.
Lower compression will tighten the chassis accelerating out of a corner.
Higher rebound will loosen the chassis entering a corner.
Lower rebound will tighten the chassis entering a corner.
Overall stiffer RR shock will loosen chassis, weaker will tighten it.
LF (Left Front)
Higher compression will tighten the chassis entering a corner.
Lower compression will loosen the chassis entering a corner.
Higher rebound will tighten the chassis accelerating out of a corner.
Lower rebound will loosen the chassis accelerating out of a corner.
Overall stiffer LF shock will loosen chassis, weaker will tighten it.
LR (Left Rear)
Higher compression will loosen the chassis accelerating out of a corner.
Lower compression will tighten the chassis accelerating out of a corner.
Higher rebound will loosen the chassis entering a corner.
Lower rebound will tighten the chassis entering a corner.
Overall stiffer LR shock will tighten chassis, weaker will loosen it.
Shock change notes:
The stiffer the shock, the less grip that tire will have.
Stiffer rebound on the left shocks will help the car turn in by slowing weight transfer to the right.
Stiffer compression on the right shocks will help the car turn in by also slowing weight transfer to the right.
Softer rebound on the front shocks will loosen the chassis exiting the corner.
Softer compression on the rear shocks will tighten the chassis exiting the corner.
Doing just the opposite mentioned above, on either compression or rebound will produce just the opposite results.
Asymmetrical changes seem to have a greater influence than individual shock changes.
loosen it up:
Changes to the rear springs. Stiffer RR or softer LR or both will loosen it.
Tighten it up:
Changes to the rear springs. Softer RR or stiffer LR or both will tighten it.
Spring to shock ratio:
When using a softer spring package, try the shocks at a high-compression low rebound initial setting. Stiffer springs try a low-compression high-rebound setting.
If using a higher the ride height, start the setup with a softer spring package.
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