FWD race set-up
Discussion
Hi,
I've started helping a friend who races a FWD saloon, he bought the car mid-season and doesn't feel he's got to grips with it (we both come from a RWD background).
The car:-
800kg, 205 section slicks, front and rear anti roll bars, 600 lb springs front and rear, 2.5 deg front camber, 7 deg castor, parallel toe front and rear, front and rear shocks are a bit of an unknown (strut inserts at the front). Tyres 28F 24R.
The observation is that is generally not very responsive, turn-in being a little vague. Being light, the rears take a few laps to warm up so it oversteers on cold tyres but not so much when up to temperature. It sounds to me like it's a 'feel' thing.
Thoughts would be:
A few mm of toe out to help the turn in?
A little stiffer all round? (seems a little low on springs perhaps?)
Look into the dampers over the winter
Any thoughts please? Also, does anyone know the sort of set up touring cars run?
Thanks for reading!
I've started helping a friend who races a FWD saloon, he bought the car mid-season and doesn't feel he's got to grips with it (we both come from a RWD background).
The car:-
800kg, 205 section slicks, front and rear anti roll bars, 600 lb springs front and rear, 2.5 deg front camber, 7 deg castor, parallel toe front and rear, front and rear shocks are a bit of an unknown (strut inserts at the front). Tyres 28F 24R.
The observation is that is generally not very responsive, turn-in being a little vague. Being light, the rears take a few laps to warm up so it oversteers on cold tyres but not so much when up to temperature. It sounds to me like it's a 'feel' thing.
Thoughts would be:
A few mm of toe out to help the turn in?
A little stiffer all round? (seems a little low on springs perhaps?)
Look into the dampers over the winter
Any thoughts please? Also, does anyone know the sort of set up touring cars run?
Thanks for reading!
captain jack said:
Hi, thanks for commenting! It's running 205 wide Dunlop radials (15" diameter).
I would definitely look at running more toe. Tyre temperatures are key, try measuring them at 3 points across the width of the tyre. If your cambers are right there should be a 10-15 degree spread across the tyre, with the inner being the hottest. I would aim for 75-80 degrees at the hottest point on the front tyres.I would advise some toe out on the rear (you will always have to work at getting temp in the rears when you first go out) More info on the car would be helpful, can you adjust ARB? is it a rear beam setup? If the driver is coming from RWD, then it could be just the difference in characteristics of the car? I'm no expert, but feel free to message me if you want to discuss.
Adam
Adam
On slicks the car will always be oversteery when cold, typically in touring cars the car will be sent out for a couple of laps to warm up the front tyres, then they will be swapped front to rear or diagonally although obviously this isn't really an option if you're not being run by a team.
NGTC setups are pretty irrelevant as they're odd, but a 1200kg S2000 class touring car will typically run 90-120N/mm springs (which may be a little high if the car doesn't have a proper cage to stiffen it up), zero bump steer all round (perhaps a touch of roll oversteer on the back if it has severe understeer), 1-3mm of toe out per side on the rear depending on driver taste, loads of castor, and with a typical McPherson strut setup you'll be balancing roll centre with camber gain (high roll centre = more camber gain) on the front depending on how soft or stiff you need to run it and then adjusting the rear around that to achieve the behaviour you want.
If it's feeling a bit vague on turn in then try putting a bit more low speed compression in the front, then rebound. If it takes away the vagueness but it still understeers on entry then you're too stiff on springs. Don't underestimate the importance of damping, once you get to a point where the car feels about right in terms of balance and pace but is a bit ragged and difficult to drive on the limit then it's well worth going to a decent damper guy to rate your shocks and make some suggestions for changes.
Tyre pressures are also very important, worth getting some opinions from the tyre supplier if possible on what you should be running and then making an effort to get them right when hot.
Generally the target with FWD is to maximise what you can get out of the front then loosen the rear to help it turn. This doesn't need to be done entirely with bars and stiffness, and if the car is feeling snappy then try softening it a bit and running a lot of camber on the back. It'll loosen the car initially to help it turn, but will take a set as it rolls onto it.
NGTC setups are pretty irrelevant as they're odd, but a 1200kg S2000 class touring car will typically run 90-120N/mm springs (which may be a little high if the car doesn't have a proper cage to stiffen it up), zero bump steer all round (perhaps a touch of roll oversteer on the back if it has severe understeer), 1-3mm of toe out per side on the rear depending on driver taste, loads of castor, and with a typical McPherson strut setup you'll be balancing roll centre with camber gain (high roll centre = more camber gain) on the front depending on how soft or stiff you need to run it and then adjusting the rear around that to achieve the behaviour you want.
If it's feeling a bit vague on turn in then try putting a bit more low speed compression in the front, then rebound. If it takes away the vagueness but it still understeers on entry then you're too stiff on springs. Don't underestimate the importance of damping, once you get to a point where the car feels about right in terms of balance and pace but is a bit ragged and difficult to drive on the limit then it's well worth going to a decent damper guy to rate your shocks and make some suggestions for changes.
Tyre pressures are also very important, worth getting some opinions from the tyre supplier if possible on what you should be running and then making an effort to get them right when hot.
Generally the target with FWD is to maximise what you can get out of the front then loosen the rear to help it turn. This doesn't need to be done entirely with bars and stiffness, and if the car is feeling snappy then try softening it a bit and running a lot of camber on the back. It'll loosen the car initially to help it turn, but will take a set as it rolls onto it.
Edited by The Wookie on Tuesday 27th January 17:20
Dear all,
Thank you very much for your feedback and thoughts on this, very much appreciated. Certainly there has been some common themes that we will be trying on a couple of pre-season testing sessions. It'll be a few weeks off yet but I will feedback our findings/thoughts when we have tried the changes you have suggested!
What would you suggest for front toe? My current thought is 1-2mm each side to help turn in?
Thanks again!
Thank you very much for your feedback and thoughts on this, very much appreciated. Certainly there has been some common themes that we will be trying on a couple of pre-season testing sessions. It'll be a few weeks off yet but I will feedback our findings/thoughts when we have tried the changes you have suggested!
What would you suggest for front toe? My current thought is 1-2mm each side to help turn in?
Thanks again!
Edited by captain jack on Sunday 1st February 15:07
In or out ?
I reread this , and I couldn't find whether you mean in or out at the front . I ran a FWD pig in hill climbs and ran zero toe front -1.5 degree camber , 1/16" (1.5mm?) toe out rear and -1.0 camber at rear .
How many laps do your sessions/races run ? My Street hp tires would overheat at track days , circuit qualifying and the road race tires would take forever to warm at hill climbs.
Regards,Ed Flanagan
I reread this , and I couldn't find whether you mean in or out at the front . I ran a FWD pig in hill climbs and ran zero toe front -1.5 degree camber , 1/16" (1.5mm?) toe out rear and -1.0 camber at rear .
How many laps do your sessions/races run ? My Street hp tires would overheat at track days , circuit qualifying and the road race tires would take forever to warm at hill climbs.
Regards,Ed Flanagan
I previously ran a FWD 750kg car, not massive amounts of power and running toyo not slicks. However we ran what seems like a pretty different setup to you. Front springs were 350lb/in while the rears were 800lb/in, we also ran 2mm of toe in. We also wired the rear spring platforms to reduce droop and allow it to lift the inside rear easily. We were also quite heavy on the front camber (4-5deg) as the car effectively rotated diagonally leaning onto the outside front tyre.
This setup allowed for sharp turn in and a lovely balance through the corner, if you got it right you could turn the car in, straight back on the power and have almost neutral steering all the way through carrying plenty of speed. Understeer was never really an issue and at the same time the car wasnt wild on the rear and oversteering with very little provocation.
Of course this might not be ideal for your car but it worked for us.
This setup allowed for sharp turn in and a lovely balance through the corner, if you got it right you could turn the car in, straight back on the power and have almost neutral steering all the way through carrying plenty of speed. Understeer was never really an issue and at the same time the car wasnt wild on the rear and oversteering with very little provocation.
Of course this might not be ideal for your car but it worked for us.
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