BMW understeer
Discussion
Can anyone give me some advice on the best method to dial out understeer on my E36 M3 trackcar. Its running AST 3 way adjustable suspension, on michelin slicks running 28psi.
I think if I lower the front ride height and increase the front tyre pressure that will help, but is there anything else I could do??? And yes, I know BeeEmms are designed to under steer but its a PIA on the track.
I think if I lower the front ride height and increase the front tyre pressure that will help, but is there anything else I could do??? And yes, I know BeeEmms are designed to under steer but its a PIA on the track.
Edited by hazy on Wednesday 12th November 11:49
I think you are going the wrong way.
You will increase understeer by increasing the front tyre pressures.
What you should be doing is softening the front suspension and stiffening the rear . I would suggest tyre pressures kept the same front and back while you work with suspension mods first and leave the tyre pressure changes till last.
Try the suspension settings on their medium setting to begin with and then start stiffening the front and softening the rear one notch at a time until you feel the balance has improved. Other than that you need to alter the front tracking to give some toe out this will help initiate the turn.
If none of those help then a change in driving style may help.
You will increase understeer by increasing the front tyre pressures.
What you should be doing is softening the front suspension and stiffening the rear . I would suggest tyre pressures kept the same front and back while you work with suspension mods first and leave the tyre pressure changes till last.
Try the suspension settings on their medium setting to begin with and then start stiffening the front and softening the rear one notch at a time until you feel the balance has improved. Other than that you need to alter the front tracking to give some toe out this will help initiate the turn.
If none of those help then a change in driving style may help.
E26??? Or do you mean E36 of E46???
You need to know where your 3 way dampers are set as regards to bump and rebound.I would leave the high speed bump alone for now. You need to reduce the front bump to allow(increase) weight transfer to the front wheels under braking then increase front rebound to keep it there under acceleration. At the rear you need to make sure you dont have lots of rebound damping as this will reduce (the speed of the) weight transfer to the front wheels and no bump damping as this will transfer all the weight to the rear wheels under acceleration (very quickly).Increasing rear bump should also help but go to far and you will induce oversteer
Tyre pressures need to be checked hot to high front pressures will cause more under steer. Adding rake in the car, higher at the rear and lower at the front will also improve understeer by moving more weight over the front wheels.
Edited to keep lanan happy
Trying to keep it simple and understandable !!
Dampers help control weight transfer they don't change it
You need to know where your 3 way dampers are set as regards to bump and rebound.I would leave the high speed bump alone for now. You need to reduce the front bump to allow(increase) weight transfer to the front wheels under braking then increase front rebound to keep it there under acceleration. At the rear you need to make sure you dont have lots of rebound damping as this will reduce (the speed of the) weight transfer to the front wheels and no bump damping as this will transfer all the weight to the rear wheels under acceleration (very quickly).Increasing rear bump should also help but go to far and you will induce oversteer
Tyre pressures need to be checked hot to high front pressures will cause more under steer. Adding rake in the car, higher at the rear and lower at the front will also improve understeer by moving more weight over the front wheels. Edited to keep lanan happy
Trying to keep it simple and understandable !! Dampers help control weight transfer they don't change it
Edited by ngr on Sunday 9th November 21:53
I think mark and ngr made some good points, I can't speak from personal experience, but I do have an interest in vehicle dynamics.
If you have anti roll bars fitted front and rear, you could try softening the front a little, this will often produce a bit more turn-in. Mark mentioned toe out at the front, this will work but can have the side effect of making the car unstable in a straight line.
Before you try anything though, I think it's important to get some setup advice from a professional. Some changes, even small ones can make cars dangerously undriveable. Not only that but you will save you a lot of time and money too. (Having seen the cars on your profile, I'm sure you know all this, I just thought I would mention it anyway for the benefit of others too)
One PH'er I know is a racecar engineer is JohnFelstead, he might be able to help you. You might also try BMW themselves, they may be able to give you some settings from their original touring cars.
Good luck.
If you have anti roll bars fitted front and rear, you could try softening the front a little, this will often produce a bit more turn-in. Mark mentioned toe out at the front, this will work but can have the side effect of making the car unstable in a straight line.
Before you try anything though, I think it's important to get some setup advice from a professional. Some changes, even small ones can make cars dangerously undriveable. Not only that but you will save you a lot of time and money too. (Having seen the cars on your profile, I'm sure you know all this, I just thought I would mention it anyway for the benefit of others too
)One PH'er I know is a racecar engineer is JohnFelstead, he might be able to help you. You might also try BMW themselves, they may be able to give you some settings from their original touring cars.
Good luck.
mark69sheer said:
Try the suspension settings on their medium setting to begin with and then start stiffening the front and softening the rear one notch at a time until you feel the balance has improved. Other than that you need to alter the front tracking to give some toe out this will help initiate the turn.
Do this ^^^^^, but after this.....What are your corner weights like? Do you get more understeer turning one way than the other? How much weight (as a %) is carried across the front axle?
I'd advocate getting the car properly corner-weighted first (mainly adjusting ride height but possibly with different spring rates at one end) before tweaking the suspension. At the end of the day, your car may be telling you it's unbalanced.
However, if you're not worried about absolute times and just want a driveable track car I'd drop the front ride height by a cm, take it out on the track, raise it by a cm, take it out, raise it by another cm, take it out and see if you notice any difference. Leave it at what setting you feel is best for you.
lanan said:
Hazy.
You need to be more specific regarding the understeer.
Is it
Slow speed - High speed
Turn in - mid corner - Exit
Under braking - Under power
How you currently drive to negate the problem.
Also. Damper valving does not change weight transfer
the understeer is at medium to high speed on turn in after braking, if I drag the brake slightly during turn in that helps, but on some bends thats not always possible eg cascades at oulton, only requires a dab of brake before turning in, if I dragged the brake it would result in a loss of too much corner speed.You need to be more specific regarding the understeer.
Is it
Slow speed - High speed
Turn in - mid corner - Exit
Under braking - Under power
How you currently drive to negate the problem.
Also. Damper valving does not change weight transfer
I took the rear up by 1cm last week at Cadwell and it did seem to improve things a tad, I am a little reluctant to start messing too much with the high and low speed damping too much as I dont understand vehicle setup well enough to make major changes.
There is an anti-roll type bar which bolts directly to the dampers, is this a "sway" bar???? I have heard they help, along with raising front tyre pressures, but I dont see that at all myself???
Thanks for the help and advice so far.
Hazy, with all due respect an E36 M3 is the orginal slow in fast out car and your comment about... loosing to much corner speed.... would strongly suggest thats where a major part of your problem may lie.
Driving an E36/E46 M3 is all about going in hard on the brakes until the front grips over the rear then drive it out again BUT if it understeers past the apex brake earlier next time. It will always feel too slow just before mid corner but thats because its a big, heavy frankly soft chassied car and all that mass has to take a set before you power up again. But once its set, your outa there!
The other thing you must be absolutely positive about before changing the set up is that you have absolutely no power on at all when the car is still understeering after turn in
. If you have, it will just continue understeering and it is frankly amazing how many people miss this, I'm not saying you are but many do!
Sorry if I'm teaching you suck eggs but its often over looked in persuit of easy blame it on the car we are all guilty off from time to time.
Driving an E36/E46 M3 is all about going in hard on the brakes until the front grips over the rear then drive it out again BUT if it understeers past the apex brake earlier next time. It will always feel too slow just before mid corner but thats because its a big, heavy frankly soft chassied car and all that mass has to take a set before you power up again. But once its set, your outa there!
The other thing you must be absolutely positive about before changing the set up is that you have absolutely no power on at all when the car is still understeering after turn in
. If you have, it will just continue understeering and it is frankly amazing how many people miss this, I'm not saying you are but many do!Sorry if I'm teaching you suck eggs but its often over looked in persuit of easy blame it on the car we are all guilty off from time to time.
hazy said:
the understeer is at medium to high speed on turn in after braking, if I drag the brake slightly during turn in that helps, but on some bends thats not always possible eg cascades at oulton, only requires a dab of brake before turning in, if I dragged the brake it would result in a loss of too much corner speed.
I took the rear up by 1cm last week at Cadwell and it did seem to improve things a tad, I am a little reluctant to start messing too much with the high and low speed damping too much as I dont understand vehicle setup well enough to make major changes.
There is an anti-roll type bar which bolts directly to the dampers, is this a "sway" bar???? I have heard they help, along with raising front tyre pressures, but I dont see that at all myself???
Thanks for the help and advice so far.
i would think that softening the front arb (sway bar) or reducing the front tyre pressures 1-2 psi would help improve the understeer, possibly at the expense of response tho, which may make turn in a bit worse if that's your problem.I took the rear up by 1cm last week at Cadwell and it did seem to improve things a tad, I am a little reluctant to start messing too much with the high and low speed damping too much as I dont understand vehicle setup well enough to make major changes.
There is an anti-roll type bar which bolts directly to the dampers, is this a "sway" bar???? I have heard they help, along with raising front tyre pressures, but I dont see that at all myself???
Thanks for the help and advice so far.
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