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Suspension


cyberfella

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I think this info belongs right here in the technical section. It'll help people diagnose their own suspension shortcomings when it comes to handling of their car when being drive by them, with their own driving style, so they can make more informed choices when modifying.

 

Firstly, I don't profess to be an expert. That said, I have spent an entire day with Mike Whiddett and Frederic Aasbo talking suspension tuning in between their runs on the track. A treat I doubt I'll ever equal. Their comments reassured me that my own knowledge is solid and my findings tuning 450 different cars on Gran Turismo 5 Driving Simulator over the last 3 years for both racing and drift were indeed correct. They could not be seen to officially comment due to their affiliation with a rival racing game brand - EA Games/Speedhunters.

 

My advice would be to get a PS3 with GT5 then get GT6 in December when it's released (it has an improved suspension model developed with KW Suspension). You will spend a lot less money learning about suspension and have a lot of harmless fun in the process. When you think you've got it dialled, get online and see if your settings actually work when the heat is on - they'll almost certainly be too aggressive and you'll back things off a bit. Then apply your knowledge to your real car in the confidence that it's right for YOU. Test it on a track, not on a road. A normal person would run out of bottle long before their suspension lets go if their setup is right but why risk it? Unlike GT5, death is real, there's no restart button.

 

Don't spend real money and crash real cars learning about geometry when such a good simulator is available for so little money. GT6 is destined to be a PS3 title, not PS4 too, which is great.

 

Advanced Suspension Setup, Toe? Camber? Castor? Rake? Spring Rates? Uhh?? Learn here!

 

Front spring rate increase:

More under steer; increase in proportional weight transfer to the front when rear wheel rate is not increased; reduces front traction when rear rate is not changed.

Usable adjustment: 150-600 lbs/in

Symptoms of too much adjustment: terminal under steer; front of car hops in corners; excessive wheel spin on inside front tire on FF cars.

 

Front spring rate decrease:

Less under steer; decreases proportional weight transfer to the front when rear wheel rate is not increased; increases front traction when rear rate is not changed.

Usable adjustment: 150-600 lbs/in

Symptoms of to much adjustment: Too much over steer; over steer then under steer if spring is so soft that the car bottoms out on lean, car bottoms out excessively with a jolting ride.

 

Rear spring rate increase:

More over steer; increase in proportional weight transfer to the rear when front wheel rate is not increased; increases rear traction when front rate is not changed.

Usable range: 100-600 lbs/in

Symptoms of too much adjustment: too much over steer; sidestep hop in corners; twitchy; pretty scary.

 

Rear spring rate decrease:

Less over steer: decreases proportional weight transfer to the rear when front wheel rate is not changed; increases rear traction when front rate is not changed

Usable range: 100-600 lbs/in

Symptoms of too much adjustment: car under steers; if way to soft car under steers then over steers as car bottoms out on lean; car bottoms out excessively with a jolting ride.

 

Front anti-roll bar stiffer: more under steer

Usable range: none to 1.25 inches in diameter

Symptoms of to much adjustment: terminal under steer; lifts inside front tire off the ground witch can cause massive wheel spin on FF cars; also not good for most effective tire usage as inside tire is now doing nothing.

 

Front anti-roll bar softer: less under steer

Usable range: none to 1.25 inches in diameter

Symptoms of to much adjustment: overstate scary; more like fun

 

Rear anti-roll bar stiffer: more over steer

Usable range: none to 1 inch in diameter

Symptoms of too much adjustment: Big-time over steer. Can cause inside rear tire to lift off the ground.

 

Rear anti-roll bar softer: less over steer

Usable range: none to 1 inch in diameter

Symptoms of to much adjustment: under steer; slow and boring

 

Front tire pressure higher: less under steer by reducing slip angels on most tires

Usable adjustment: up to 55psi hot

Symptoms of too much adjustment: no traction- tire crowned so more under steer; adds wheel spin in FF cars; jarring ride; center of tire wears out

 

Front tire pressure lower: more under steer by increasing slip angles on most tires

Usable adjustment: not less then 20psi

Symptoms of too much adjustment: edges of tire wear quickly because tire is folding over; feels mushy; tires chunk because low pressure means heat build up.

 

Rear tire pressure higher: less over steer by reducing slip angles on most tires

Usable range: up to 45psi hot

Symptoms of too much adjustment: no traction—tire is crowned so more over steer; bad wheel spin on FR cars; jarring ride; center of tire wears out.

 

Rear tire pressure lower: more over steer by incresing slip angles on most tires.

Usable range: not less then 20psi

Symptoms of too much adjustment: edges of tire wear quickly because tire is folding over; feels mushy; tires chunk because low pressure means heat build up

 

More negative camber front: less under steer because of better lateral traction as tread is flatter on the ground under side load.

Usable range: up to 3.5 degrees negative

Symptoms of too much adjustment: poor braking; car is road crown sensitive; twitchy; front tires wear on inside edge

 

More negative camber rear: less over steer because of better lateral traction as tread is flatter on the ground under side load. More rear grip

Usable range: up to 2.5 degrees negative

Symptoms of too much adjustment: more over steer; car feels twitchy in back; tires wear out on inside edge; less breakaway warning when limit is exceeded.

 

Ride height to low (typical beginner mistake): car is twitchy with unpredictable dynamics. Bump steer make you life miserable.

Usable range: usually 1.5-2.0 inches lower then stock unless car has been modified to go lower.

Symptoms of too much adjustment: everything that could possibly go wrong: sudden over/under steer; twitchy due to bump steer; very harsh ride; premature tire wear.

 

Toe in – front: car is stable going straight. Turn in is average

Usable range: 0-1/8th inch

Symptoms of too much adjustment: car has slow twitchiness under braking; feels odd; kills outside edge of tires

 

Toe out – front: Car turns in well; works pretty well on FF car as they tend to toe-in under load.

Usable range: 0-1/4 inch

Symptoms of too much adjustment: Car is really twitchy under braking; car wanders on straight road; kills inside edge of tire

 

Toe in – rear: car is less likely to over steer when the throttle is lifted

Usable range: 0-1/8th inch

Symptoms of too much adjustment: weird, slow, rocking movement in back; feels slow but still unstable; wears outside edge of tires.

 

Toe out – rear: Helps car rotate useful in low speed and slalom courses; very common on FF pro rally cars.

Usable range: 0-1/8th inch

Symptoms of too much adjustment: not to good for street driving; causes lift throttle over steer; makes violent side to side rocking motions in the rear; tie wears on inside more.

 

Positive front caster: helps stability; suspension will get more negative camber when turning; reducing positive caster reduces steering effort. (Negative caster is not usable)

Usable range: 4-9 degrees positive

Symptoms of too much adjustment: can increase under steer especially in cars with wide low-profile tires. Can increase steering effort.

 

Single adjustable shock stiffer: Better turn in; better transient response; causes slower onset of over/under steer by slowing weight transfer depending on what end of the car is adjusted.

Symptoms of too much adjustment: suspension becomes unresponsive; ride gets harsh; car skips over bumps, loosing traction; Causes a big delay in weight transfer resulting in strange handling like under steer then late corner stage over steer.

 

Single adjustable shock softer: slower transient response; quicker onset of over/under steer

Symptoms of too much adjustment: car oscillates due to under dampened spring motion, like a boat. Car gets twitchy in turns. Feels unstable.

 

PARAMETER TO INCREASE UNDERSTEER TO INCREASE OVERSTEER

Front Tire Pressure Lower Higher

Rear Tire Pressure Higher Lower

 

Front Tire Width Smaller Larger

Rear Tire Width Larger Smaller

 

Front Camber More Positive More Negative

Rear Camber More Negative More Positive

 

Front Springs Stiffer Softer

Rear Springs Softer Stiffer

 

Front Sway Bar Stiffer Softer

Rear Sway Bar Softer Stiffer

 

Have fun tuning your suspension. Use Toe and Camber to your advantage! Even Tire pressure helps.

Edited by cyberfella
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