Geometry setup problems! and Settings
Discussion
During wintertime I have done a full suspension upgrade to my Griff (4.3/93). Polybushes shore 95, set of nitrons and an anti rollbar at the back. Now I have been at a garage to have a full geometry setup. Got the car back today and had the first ride. In corners the car is just great, but on the straight line I need both hands at the steering wheel, because the car tries to jump from one side to the other. It´s more than nervy. I am not sure that the local garage has used the right figures. So if someone can send me the official geometry setup data, it would be just great. Any other idea is welcome. I am just disappointed right now.
jochen
jochen
i meant to give you these details before but it slipped my memory,
heres what I have from TVR regarding my 92 Griff dated 10/12/92.
Camber in Degrees (front)-0.75 +- 0.25
Toe In....................0/10 minutes total
Tyre Pressures(SO2)........20psi cold.
Camber in Degrees (rear)-0.75 +- 0.25
Toe In....................20/30 minutes total
Tyre Pressures.............22psi cold.
hope this helps.
h
heres what I have from TVR regarding my 92 Griff dated 10/12/92.
Camber in Degrees (front)-0.75 +- 0.25
Toe In....................0/10 minutes total
Tyre Pressures(SO2)........20psi cold.
Camber in Degrees (rear)-0.75 +- 0.25
Toe In....................20/30 minutes total
Tyre Pressures.............22psi cold.
hope this helps.
h
you can run much more camber at the front without substantial "pointyness"
mine ran -2.0 degrees and was fine on nitrons/polys (front). 15" rims.
now with 16" rims, i need more camber. will probably go to 2.5 maybe 3.0 if it can standing it without tramlining everywhere.
so if there is more camber don't be too worried.
it might sound silly, but if it went to a non tvr specialist, check pressures. they tend to put them on 30lb, and that WILL make it twitchy on nitrons.
also check damper settings. i run mine on 17 all the time...but that is very high for road. for the road you should start at 8 each side and work up a couple at a time. clockwise is up...getting harder (slower).
hope this helps.
mine ran -2.0 degrees and was fine on nitrons/polys (front). 15" rims.
now with 16" rims, i need more camber. will probably go to 2.5 maybe 3.0 if it can standing it without tramlining everywhere.
so if there is more camber don't be too worried.
it might sound silly, but if it went to a non tvr specialist, check pressures. they tend to put them on 30lb, and that WILL make it twitchy on nitrons.
also check damper settings. i run mine on 17 all the time...but that is very high for road. for the road you should start at 8 each side and work up a couple at a time. clockwise is up...getting harder (slower).
hope this helps.
i would agree .. 2 degrees on the front should be great.
the lower the sidewall AR the less tolerant it will be to camber variation.
why do you think you need more camber? .. have you measured the cornering forces at different camber levels, and taken tyre temp readings .. the only real way to gauge it.
also adding lots of front camber and very low ride height giving more camber gain in compression will harm yyour braking performance through les tyre grip as the inner edge rapidly overheats..
there's more to lap times that good corner speeds..
the lower the sidewall AR the less tolerant it will be to camber variation.
why do you think you need more camber? .. have you measured the cornering forces at different camber levels, and taken tyre temp readings .. the only real way to gauge it.
also adding lots of front camber and very low ride height giving more camber gain in compression will harm yyour braking performance through les tyre grip as the inner edge rapidly overheats..
there's more to lap times that good corner speeds..
well, firstly i'd defer to BOTH of you who certainly know your stuff.
i found that i immediately had developed mid corner wash out after the griff had the 16" spider conversion.
It had been running very well on this set up with the standard estoril wheels.
tyres are of course an important factor. i had been running bridgie SO3's and am now on toyo's. however i have got So2's on a a second set i use for trackdays and have found little difference.
temperature's also in there. both set up runs were over the winter (nov-feb) so dificult to get alot of heat into the tyres. a touch of understeer is preferable but i found not too controlable (the amount, not the handling). temp spread on the tyres was suprisingly good.
not running the car as low as i used to (4"front 5"rear). the proxies are more bulbus on the sidewall than brigies and with the different offset on the spiders, the wheels foul the chassis on hard cornering. so now running 4.5" front to 5.5" rear. i find that 1" gives a good balance for improved front end grip without getting too tail happy. not sure what standard is on that!
have been talking to jochen, griff430, on line and am of the same opinion as you joospeed, that he may be running too much. he also has a new (standard) anti roll bar in the back which will also be making the front more pointy.
i now think that for Griff 430, 2 degrees is possibly too much, 1 degree may be more suitable with 18s. depending on tyres, he may not be getting any movement in the sidewalls on the road and would be very skittish.
i'm sure we'd both be grateful of any input.
mines fine on the road and very quick on the track too
would like a touch less understeer tho if poss. but hey! that only for perfection
cheers
>> Edited by Guillotine on Monday 12th April 17:53
i found that i immediately had developed mid corner wash out after the griff had the 16" spider conversion.
It had been running very well on this set up with the standard estoril wheels.
tyres are of course an important factor. i had been running bridgie SO3's and am now on toyo's. however i have got So2's on a a second set i use for trackdays and have found little difference.
temperature's also in there. both set up runs were over the winter (nov-feb) so dificult to get alot of heat into the tyres. a touch of understeer is preferable but i found not too controlable (the amount, not the handling). temp spread on the tyres was suprisingly good.
not running the car as low as i used to (4"front 5"rear). the proxies are more bulbus on the sidewall than brigies and with the different offset on the spiders, the wheels foul the chassis on hard cornering. so now running 4.5" front to 5.5" rear. i find that 1" gives a good balance for improved front end grip without getting too tail happy. not sure what standard is on that!
have been talking to jochen, griff430, on line and am of the same opinion as you joospeed, that he may be running too much. he also has a new (standard) anti roll bar in the back which will also be making the front more pointy.
i now think that for Griff 430, 2 degrees is possibly too much, 1 degree may be more suitable with 18s. depending on tyres, he may not be getting any movement in the sidewalls on the road and would be very skittish.
i'm sure we'd both be grateful of any input.
mines fine on the road and very quick on the track too
would like a touch less understeer tho if poss. but hey! that only for perfection cheers
>> Edited by Guillotine on Monday 12th April 17:53
The problem is that there is NO perfect setting for all conditions. Camber is usually dialed in to compensate for body roll to make sure that the tyre contact is good. The downside is that when the car is not rolling so much it reduces the tyre contact which means in less than optimum conditions i.e. cold/damp/wet the available grip is greatly reduced. Tyre wear is also an issue as is braking. So the slower speed handling is compromised in respect to the higher speed stuff. The car will be great in the dry but worse in the wet.
Other factors come into play and this also includes how stable the sidewalls are. Ideally they shouldn't move and be stiff enough to be consistent. THis is due to their construction and tyre pressure. Compromises come into play here as well as a higher tyre pressure that stiffens the sidewall will lift the edges and reduce the tyre contact patch and with large amounts of camber this makes the problem even worse. Less contact, less grip, more understeer. If the pressure is reduced then this can be solved but the sidewall stiffness may not be strong enough and the tyre can distort and roll off the rim. End result is lack of contact again. There is a sweet spot somewhere in the middle and this will vary depending on tyre make/size etc.
I solve this problem by fitting the tyres onto extra wide rims so that the tyre sidewall is effectively braced. YOu can then run lower pressures without distortion. Can't easily do this on a Griff because of clearance issues.
If there is not enough heat in them then they won't grip and so you will not be able to push as hard and get the body roll to match the camber. A bit of a chicken and egg but unless the tyres are getting upto 50-60 C you won't really be able to work out what is happening.
The other point is corner weighting and the effect of fuel tanks and passengers. Tower View have just got a set od CW scales and I borrowed them to set up the 520. Takes some time but I found that simple changes to ride heights radically moved the balance about. The cross directional balance in my case was about 70KG out. This will also have a big effect on the car's balance.
In summary, there are no real right and wrong values but the more extreme the settings are, the more compromised the handling will be. It may be fine on high speed corners with plenty of grip on hot days but lousy in anything else. It is easy to get carried away and say add more camber to compensate for body roll when the solution is to stop the body roll in the first place.
To work out waht is happening, get some video /still pictures of the car cornering and look at what is happening to the car, how vertical the tyres are and the contact patch. This will tell you an awful lot about what is happening in the car and where the focus should be.
Other factors come into play and this also includes how stable the sidewalls are. Ideally they shouldn't move and be stiff enough to be consistent. THis is due to their construction and tyre pressure. Compromises come into play here as well as a higher tyre pressure that stiffens the sidewall will lift the edges and reduce the tyre contact patch and with large amounts of camber this makes the problem even worse. Less contact, less grip, more understeer. If the pressure is reduced then this can be solved but the sidewall stiffness may not be strong enough and the tyre can distort and roll off the rim. End result is lack of contact again. There is a sweet spot somewhere in the middle and this will vary depending on tyre make/size etc.
I solve this problem by fitting the tyres onto extra wide rims so that the tyre sidewall is effectively braced. YOu can then run lower pressures without distortion. Can't easily do this on a Griff because of clearance issues.
If there is not enough heat in them then they won't grip and so you will not be able to push as hard and get the body roll to match the camber. A bit of a chicken and egg but unless the tyres are getting upto 50-60 C you won't really be able to work out what is happening.
The other point is corner weighting and the effect of fuel tanks and passengers. Tower View have just got a set od CW scales and I borrowed them to set up the 520. Takes some time but I found that simple changes to ride heights radically moved the balance about. The cross directional balance in my case was about 70KG out. This will also have a big effect on the car's balance.
In summary, there are no real right and wrong values but the more extreme the settings are, the more compromised the handling will be. It may be fine on high speed corners with plenty of grip on hot days but lousy in anything else. It is easy to get carried away and say add more camber to compensate for body roll when the solution is to stop the body roll in the first place.
To work out waht is happening, get some video /still pictures of the car cornering and look at what is happening to the car, how vertical the tyres are and the contact patch. This will tell you an awful lot about what is happening in the car and where the focus should be.
usefull stuff steve.
Griff 430
info from peninsula...
feeling is that you may have altered the caster when replacing the bushes. on your car the upper wishbones are the split type (two halves).
there should be a packing plate (shim) at the FRONT of the bushes where the halves are bolted together at the ball joint, which sets the CASTER! if this plate(s) is missed or put at the back of the wishbone it will give exactly your symptoms.
check it out.
cheers
Griff 430
info from peninsula...
feeling is that you may have altered the caster when replacing the bushes. on your car the upper wishbones are the split type (two halves).
there should be a packing plate (shim) at the FRONT of the bushes where the halves are bolted together at the ball joint, which sets the CASTER! if this plate(s) is missed or put at the back of the wishbone it will give exactly your symptoms.
check it out.
cheers
gulliotine
thank you very much for your info. I have moved up from the two piece wishbones to the new one piece wishbones which you find in all new modells. But it might be, that I still made a mistake by bringing all together. In the parts catalog, they are talking of a thick spacer (which i have installed) and two small spacer (which I have, but never installed since I couldn`t manage to get between ball joint and whisbone).
But more important to me is that I need to know what the right CASTER figure is, so that I can try to add these shims at the right place.
Do you have any hints regarding that.
Jochen
thank you very much for your info. I have moved up from the two piece wishbones to the new one piece wishbones which you find in all new modells. But it might be, that I still made a mistake by bringing all together. In the parts catalog, they are talking of a thick spacer (which i have installed) and two small spacer (which I have, but never installed since I couldn`t manage to get between ball joint and whisbone).
But more important to me is that I need to know what the right CASTER figure is, so that I can try to add these shims at the right place.
Do you have any hints regarding that.
Jochen
maybe we're getting somewhere.
the spacer(s) should be at the front to drop the caster back. are they at the front?
just had a quick look at mine, its difficult to see without taking the wheel off - big discs!, but i could only see one big spacer at the front.
not sure what the caster angle should be, have to speeak to peninsula tomorrow so will get the angle.
joospeed or steve may be able to provide this info directly.
cheers
andy
the spacer(s) should be at the front to drop the caster back. are they at the front?
just had a quick look at mine, its difficult to see without taking the wheel off - big discs!, but i could only see one big spacer at the front.
not sure what the caster angle should be, have to speeak to peninsula tomorrow so will get the angle.
joospeed or steve may be able to provide this info directly.
cheers
andy
andy,
I have double checked the place of the big spacer again and it´s pointing to the front of the car. So it should be o.k.
Might be that I get a better insight, when I have the exact factory figures for the caster.
Here are my setup figures after it has been set up:
FRONT
CASTER
left 4°48
right 4°48
CAMBER
left -1°06
right -1°06
TOE IN
left 0°06
right 0°06
BACK
CAMBER
left -1°24
right -1°24
TOE IN
left 0°18
right 0°18
If someone sees anything ín here which points out my problem, please let me know.
cheers jochen
I have double checked the place of the big spacer again and it´s pointing to the front of the car. So it should be o.k.
Might be that I get a better insight, when I have the exact factory figures for the caster.
Here are my setup figures after it has been set up:
FRONT
CASTER
left 4°48
right 4°48
CAMBER
left -1°06
right -1°06
TOE IN
left 0°06
right 0°06
BACK
CAMBER
left -1°24
right -1°24
TOE IN
left 0°18
right 0°18
If someone sees anything ín here which points out my problem, please let me know.
cheers jochen
sorry i'm late, bin at work.
front
castor = 3.5 degrees neg
(up to 5 degrees for Power steering only)
toe in 20min
camber 3/4 degree neg
rear
toe in 20 min
camber 3/4 degree neg
factory spec. you're a bit out. set to these above and see how you get on
>> Edited by Guillotine on Thursday 15th April 18:53
front
castor = 3.5 degrees neg
(up to 5 degrees for Power steering only)
toe in 20min
camber 3/4 degree neg
rear
toe in 20 min
camber 3/4 degree neg
factory spec. you're a bit out. set to these above and see how you get on
>> Edited by Guillotine on Thursday 15th April 18:53
andy,
thanks for all your informations. During weekend I will "play" arround a bit to see what happens. I got the advice from a local garage to try first the "toe in" at the front. If that doesn´t help, I will contact a guy that is responsible for suspension stuff for all BMW M modells. He should know about how to set up a car.
Talking to the head of the motorsports devision of Bilstein dampers, he mentioned, that it might have something to do with my wheels, since they have a different ET (don´t know the english expression for ET) than the originals.
I will keep you posted if anything has changed. First of all thank you very much for your help.
Cheers Jochen
thanks for all your informations. During weekend I will "play" arround a bit to see what happens. I got the advice from a local garage to try first the "toe in" at the front. If that doesn´t help, I will contact a guy that is responsible for suspension stuff for all BMW M modells. He should know about how to set up a car.
Talking to the head of the motorsports devision of Bilstein dampers, he mentioned, that it might have something to do with my wheels, since they have a different ET (don´t know the english expression for ET) than the originals.
I will keep you posted if anything has changed. First of all thank you very much for your help.
Cheers Jochen
WOW .. that must've taken about 10 days to get those figures, they're the most symetrical figures this side of F1! How did they manage to get them absolutely perfect both sides? .. amazing! I suspect the truth is somewhat different if you measure the car ..
griffith430 said:
andy,
I have double checked the place of the big spacer again and it´s pointing to the front of the car. So it should be o.k.
Might be that I get a better insight, when I have the exact factory figures for the caster.
Here are my setup figures after it has been set up:
FRONT
CASTER
left 4°48
right 4°48
CAMBER
left -1°06
right -1°06
TOE IN
left 0°06
right 0°06
BACK
CAMBER
left -1°24
right -1°24
TOE IN
left 0°18
right 0°18
If someone sees anything ín here which points out my problem, please let me know.
cheers jochen
Julian,
I have been beside the setup system which was a laser system. Might be that the systems has shown figures, which in reality are not right, but what I could see and have on paper are the figures that I have stated before. Might be that the guy did a great job.
Nevertheless, the behavior of the car is still bad.
The only figure which is out of range is the toe in at the back, which is in total 36 minutes at my car.
Reason - we couldn´t open the screw at one of the whisbones, therefore he could,´t adjust the toe on one side. So he decided to put them both the same.
Hope, that this is not the reason of my problem.
Jochen
I have been beside the setup system which was a laser system. Might be that the systems has shown figures, which in reality are not right, but what I could see and have on paper are the figures that I have stated before. Might be that the guy did a great job.
Nevertheless, the behavior of the car is still bad.
The only figure which is out of range is the toe in at the back, which is in total 36 minutes at my car.
Reason - we couldn´t open the screw at one of the whisbones, therefore he could,´t adjust the toe on one side. So he decided to put them both the same.
Hope, that this is not the reason of my problem.
Jochen
Jochen... what size wheels are you running?
Are the the standard 15/16inch wheels that the suspension was designed for or something more esoteric? My experience of the 4.x cars is that the suspension is very twitchy and bumpy at the best of times with the sidewalls providing most of the complience. If you have bigger whgeels with lower profile tyres, it could be that this is making this characteristic worse. It may even be worth dropping the tyre pressures to see if it improves things.
Are the the standard 15/16inch wheels that the suspension was designed for or something more esoteric? My experience of the 4.x cars is that the suspension is very twitchy and bumpy at the best of times with the sidewalls providing most of the complience. If you have bigger whgeels with lower profile tyres, it could be that this is making this characteristic worse. It may even be worth dropping the tyre pressures to see if it improves things.
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