Geometry setup problems! and Settings
Discussion
Steve,
Iam running 7,5x17 (offset = 25) with 215/40 ZR 17 / front axle and 8,5 x 18 (offset = 30) with 235/40 ZR 18/ rear axle.
To my understanding, there is no difference regarding the suspension between the 4.x Griffith and the newer ones, if you have the single upper wishbone at the front axle and an anti roll bar in the back. Am I wrong.
Jochen
Iam running 7,5x17 (offset = 25) with 215/40 ZR 17 / front axle and 8,5 x 18 (offset = 30) with 235/40 ZR 18/ rear axle.
To my understanding, there is no difference regarding the suspension between the 4.x Griffith and the newer ones, if you have the single upper wishbone at the front axle and an anti roll bar in the back. Am I wrong.
Jochen
wheels are unlikely to be the issue, you have had these wheels for years without problems!
also the rear toe in is unlikely to give the problems you have. if they are the same they should be ok. tyre wear would be the only issue (minor)
problem has to be at the front...and should be ok to trace. having said all this, the wheel size will affect the rake (angle of the car front to rear) and even the camber, slightly.
but again, as the wheels havn't changed...
which wishbones did you fit? are they the standard grey ones, or the black round ones which are adjustable. i have these and if they are not adjusted squarely, the camber will change. that is to say, that if the front is out and the back in... the camber will increase.
also the rear toe in is unlikely to give the problems you have. if they are the same they should be ok. tyre wear would be the only issue (minor)
problem has to be at the front...and should be ok to trace. having said all this, the wheel size will affect the rake (angle of the car front to rear) and even the camber, slightly.
but again, as the wheels havn't changed...
which wishbones did you fit? are they the standard grey ones, or the black round ones which are adjustable. i have these and if they are not adjusted squarely, the camber will change. that is to say, that if the front is out and the back in... the camber will increase.
I ordered the standard factory wishbones from peninsula, which are more or less grey. Got from Dave the factory alignment figures for the "spider wheel" upgrade, which are in terms of size etc. more like mine. Toe in is standard, camber a bit more up to 1°25 and caster up to 5°00 which is nearly what I have done to my car. So it should be o.k. Today I talked to a guy which is in the racing business (Formel Renault). Hope that he will drive my car sometime to figure out what hopefully helps.
cheers
Jochen
cheers
Jochen
Looking at your figures, I think that experimenting with a bit more (front) toe in should sort it out.
I've just upgraded to the same size wheels/tyres as you & the car is more stable in a straight line than it was on the standard ones.
Edited to say:
My tyres are slightly different to yours - 225/45F & 245/40R. Goodyear GSD3's
You don't say what type of tyre you have, might be the biggest influence?
>> Edited by Leadfoot on Saturday 17th April 14:09
I've just upgraded to the same size wheels/tyres as you & the car is more stable in a straight line than it was on the standard ones.
Edited to say:
My tyres are slightly different to yours - 225/45F & 245/40R. Goodyear GSD3's
You don't say what type of tyre you have, might be the biggest influence?
>> Edited by Leadfoot on Saturday 17th April 14:09
Sorry I haven’t been paying much attention to this thread Jochen, and in any case it sounds as if your Renault man is sorting it out which would be your best bet in which case you can ignore the following ... 
Reading back through the thread, I'm still having trouble picturing how the car is behaving and feeling, which is key to understanding and fixing the problem. For example:
Does the problem happen at slow speed (say under 100 kM/H) or only at high speed?
Do you feel the load on the steering wheel changing?
Do you have to actually move the steering to keep the car tracking in a state line, if so roughly how much and how often?
Does this correspond to changes in the road surface, or to wind gusts?
Does the problem only show up in a dead straight line, or do you also feel the car is unstable when you are on sweeping bends, or when you make a ‘lane change’ manoeuvre?
I'm trying to guess how the car feels and behaves and under what conditions, which is difficult without driving it, so these questions may be on completely the wrong track, but the more you can describe it the better chance we have of understanding the problem.
There's nothing obviously wrong with the geometry figures you gave. Personally I would be inclined to run a touch more camber and toe-in all round but I am used to a more aggressive track setup, your values look like a good conservative road setup.
I understand that the wheels are a non-standard size. What tyre pressures are you running? Does the problem occur when the tyres are hot, or cold, or all the time?
What spring rates are you running now? What damper settings? What ride heights?
You already mentioned that you have added a new anti-roll bar, what rate is it (either the bar rate, or the equivalent rate at the wheel)? I assume you used the normal inboard mounts on the lower wishbone (roughly 2.6:1 on the wishbone from what I remember?).
All these factors will impact the balance and stability of the car and may mean that the standard factory geometry is no longer appropriate. I don’t know whether the car was running with the factory geometry before the recent suspension changes so it may be you already had non-standard settings (by accident or by design) which happened to suit those wheels, and your preferences as a driver, better than the factory settings.
Sorry this post seems to be nothing but questions so I’ll have a stab in the dark and suggest a couple of things that haven’t been mentioned so far.
Make sure the ride height hasn’t changed by more than half an inch or so from standard. In particular, make sure the front is still 1” – 1.5” lower than the rear. If you lose the nose-down rake this can have a significant effect on the aerodynamic lift, which can show up as high speed instability. Raising and lowering the ride height will immediately change the camber settings so these will need to be corrected if you change the ride height, but due to the unequal length wishbones it will also change the amount of camber correction in roll which also has a big impact on steady-state stability. The standard ride height is safe, raising or lowering either end can introduce problems.
Second suggestion, make sure the rear dampers are not set too firm, in fact if I were you I’d soften the whole lot back to the minimum setting to minimise the transient effect of the dampers in pitch and roll. This is likely to be rather too soft for permanent use (although not unreasonably soft, you should have no trouble driving the car like this in normal use) but will ensure that you haven’t accidentally biased the handling through incorrect damper settings.
Finally, only ever change one thing at a time and allow a while for the effect of each change to be clear before you make any other changes. If you change lots of things at once it is very easy to end up going round in circles!
Hope this helps,
Peter Humphries (and a green V8S)
Reading back through the thread, I'm still having trouble picturing how the car is behaving and feeling, which is key to understanding and fixing the problem. For example:
Does the problem happen at slow speed (say under 100 kM/H) or only at high speed?
Do you feel the load on the steering wheel changing?
Do you have to actually move the steering to keep the car tracking in a state line, if so roughly how much and how often?
Does this correspond to changes in the road surface, or to wind gusts?
Does the problem only show up in a dead straight line, or do you also feel the car is unstable when you are on sweeping bends, or when you make a ‘lane change’ manoeuvre?
I'm trying to guess how the car feels and behaves and under what conditions, which is difficult without driving it, so these questions may be on completely the wrong track, but the more you can describe it the better chance we have of understanding the problem.
There's nothing obviously wrong with the geometry figures you gave. Personally I would be inclined to run a touch more camber and toe-in all round but I am used to a more aggressive track setup, your values look like a good conservative road setup.
I understand that the wheels are a non-standard size. What tyre pressures are you running? Does the problem occur when the tyres are hot, or cold, or all the time?
What spring rates are you running now? What damper settings? What ride heights?
You already mentioned that you have added a new anti-roll bar, what rate is it (either the bar rate, or the equivalent rate at the wheel)? I assume you used the normal inboard mounts on the lower wishbone (roughly 2.6:1 on the wishbone from what I remember?).
All these factors will impact the balance and stability of the car and may mean that the standard factory geometry is no longer appropriate. I don’t know whether the car was running with the factory geometry before the recent suspension changes so it may be you already had non-standard settings (by accident or by design) which happened to suit those wheels, and your preferences as a driver, better than the factory settings.
Sorry this post seems to be nothing but questions so I’ll have a stab in the dark and suggest a couple of things that haven’t been mentioned so far.
Make sure the ride height hasn’t changed by more than half an inch or so from standard. In particular, make sure the front is still 1” – 1.5” lower than the rear. If you lose the nose-down rake this can have a significant effect on the aerodynamic lift, which can show up as high speed instability. Raising and lowering the ride height will immediately change the camber settings so these will need to be corrected if you change the ride height, but due to the unequal length wishbones it will also change the amount of camber correction in roll which also has a big impact on steady-state stability. The standard ride height is safe, raising or lowering either end can introduce problems.
Second suggestion, make sure the rear dampers are not set too firm, in fact if I were you I’d soften the whole lot back to the minimum setting to minimise the transient effect of the dampers in pitch and roll. This is likely to be rather too soft for permanent use (although not unreasonably soft, you should have no trouble driving the car like this in normal use) but will ensure that you haven’t accidentally biased the handling through incorrect damper settings.
Finally, only ever change one thing at a time and allow a while for the effect of each change to be clear before you make any other changes. If you change lots of things at once it is very easy to end up going round in circles!
Hope this helps,
Peter Humphries (and a green V8S)
Peter,
thanks for your long reply. Today I tried to give a litte more toe at the front (turned the steering link a quarter on both sides) but no major differences.
But first I will try to give answers to your questions as good as I can.
It even happens, when I drive our really bad street in front of our house along. And that is at 20mph. The whole car moves from left to right when I am running above some pumps. Sometime it feels like the back axles tries to steer in a different direction.
The max speed I have tried is arround 70-90mph. I have the autobahn directly at my door (1 mile) but I haven´t had the courage to go faster than 90 miles.
By the way, the new nitrons are set to 7 clicks from minus at the front and 8 clicks at the back. I think its a good starting point. I have´nt checked the springs right now. They came as a set from Peninsula (the front spring should be slightly uprated - but no exact figures).
But as I said, you just need to go between 20to 60 miles and you will feed scared.
To get the car back in line, you have to move the steering wheel. How often is depending on the road. As more pumpy as more I have to steer. Sometimes I need more than my lane to get the car back.
If the street is absolutely flat, than it´s quite o.k., but you feel, that the car is still absolut nervy. When I had these situations on the autobahn at arround 80-90 mph my head shakes left and right so hard jumps the car left and right.
I tried tyres pressure from 20 up to 28 at the front and at the back. Right now I am running 22 at the front and 24 at the back. My feeling is, as less pressure as worth is the behavior. The ride hide was lowered with the new dampers about 1 inch all arround. After that they did the setup.
The anti roll bar is a 22mm one. That´s all I have regarding this.
Sometimes the feeling is, as if the rear axle would be loose and steer a different direction than me. Sound stupid, I know. But that you can feel this at speeds like 20 mph wonders me. So I have checked all screws at the back axle 10 times now, even had a look at the mountings of the differential. But couldn´t find anything.
If I wouldn´t have seen that the car was on a laser setup system, I would bet, that there is something absolutely wrong.
cheers jochen
thanks for your long reply. Today I tried to give a litte more toe at the front (turned the steering link a quarter on both sides) but no major differences.
But first I will try to give answers to your questions as good as I can.
It even happens, when I drive our really bad street in front of our house along. And that is at 20mph. The whole car moves from left to right when I am running above some pumps. Sometime it feels like the back axles tries to steer in a different direction.
The max speed I have tried is arround 70-90mph. I have the autobahn directly at my door (1 mile) but I haven´t had the courage to go faster than 90 miles.
By the way, the new nitrons are set to 7 clicks from minus at the front and 8 clicks at the back. I think its a good starting point. I have´nt checked the springs right now. They came as a set from Peninsula (the front spring should be slightly uprated - but no exact figures).
But as I said, you just need to go between 20to 60 miles and you will feed scared.
To get the car back in line, you have to move the steering wheel. How often is depending on the road. As more pumpy as more I have to steer. Sometimes I need more than my lane to get the car back.
If the street is absolutely flat, than it´s quite o.k., but you feel, that the car is still absolut nervy. When I had these situations on the autobahn at arround 80-90 mph my head shakes left and right so hard jumps the car left and right.
I tried tyres pressure from 20 up to 28 at the front and at the back. Right now I am running 22 at the front and 24 at the back. My feeling is, as less pressure as worth is the behavior. The ride hide was lowered with the new dampers about 1 inch all arround. After that they did the setup.
The anti roll bar is a 22mm one. That´s all I have regarding this.
Sometimes the feeling is, as if the rear axle would be loose and steer a different direction than me. Sound stupid, I know. But that you can feel this at speeds like 20 mph wonders me. So I have checked all screws at the back axle 10 times now, even had a look at the mountings of the differential. But couldn´t find anything.
If I wouldn´t have seen that the car was on a laser setup system, I would bet, that there is something absolutely wrong.
cheers jochen
That sounds very scary, I don’t think I’d be brave enough to drive a car like that at 90 mph! Perhaps you could get symptoms like that if the geometry was massively wrong but I think you’ve already ruled that out, and it seems to me that you’re probably looking for a mechanical fault.
A worn ball joint in the front suspension would allow the upright to move relative to the wishbones which throws the steering right out. That could cause exactly the sort of symptoms you’re getting, although I haven’t come across such severe symptoms before. One other reason this seems particularly worth investigating is that you have changed the front dampers recently. It is all too easy to over-extend the front suspension when you do this, in which case the ball joints act as your droop limits and could be damaged by being forced to flex further than they were designed to. One way to check for a damaged ball joint is to crouch down beside the front wheel, put your hands over the top of the tyre and your feet on the bottom rim and hang your weight off the side off the wheel. By bouncing your weight gently up and down you can feel whether there is any play in the ball joint. This isn’t a conclusive test but is easy to do and is a good first step.
If that isn’t it I would go on to look for play anywhere else in the steering or suspension, including the wheel bearings. Basically time to get the car in the air and go under it with a big pry bar. This is something that your friendly local MOT test station or equivalent might be able to help you with.
Hope this helps,
Peter Humphries (and a green V8S)
A worn ball joint in the front suspension would allow the upright to move relative to the wishbones which throws the steering right out. That could cause exactly the sort of symptoms you’re getting, although I haven’t come across such severe symptoms before. One other reason this seems particularly worth investigating is that you have changed the front dampers recently. It is all too easy to over-extend the front suspension when you do this, in which case the ball joints act as your droop limits and could be damaged by being forced to flex further than they were designed to. One way to check for a damaged ball joint is to crouch down beside the front wheel, put your hands over the top of the tyre and your feet on the bottom rim and hang your weight off the side off the wheel. By bouncing your weight gently up and down you can feel whether there is any play in the ball joint. This isn’t a conclusive test but is easy to do and is a good first step.
If that isn’t it I would go on to look for play anywhere else in the steering or suspension, including the wheel bearings. Basically time to get the car in the air and go under it with a big pry bar. This is something that your friendly local MOT test station or equivalent might be able to help you with.
Hope this helps,
Peter Humphries (and a green V8S)
When I renewed the suspension during wintertime, I did more or less erverything. New bushes, new steering UJ´s, new upper and lower ball joints, new one piece upper wishbones and the right lower wishbone at the rear, since I destroyed this while I tried to press the bushes out. Got this new, but I don´t know if there has been a desing change between my car (93) and the wishbone I got new. It didn´t look so. First I thougt somesthing is loose, but after checking everything again and even not hearing any rattling by driving arcross pumps, it seems to me not.
Jochen
Jochen
This is FAR too complicated for me,,,,,
I simply want to know what figures do I give to my local ATS outlet, so the man can set the geometry - or 4 wheel tracking, as he calls it - for Bluey , 94 Griff 500, please.
Numbers required to fit on a small piece of paper please,
Tyres will be new SP9000s all round, fitted at same time, 205/55 15s and 235/50 16s
Thanks in anticipation
Bluey is the name of our Griff 500, shadowfax being the name of my first TVR, the white 400SE.
235/50 16 ZR is the tyre size identified in the handbook that came with the car. They put 245/45s as standard later on in the production. Bought car with 245/45s on S02s all round. Either size is ok with insurance as TVR produced cars in both sizes. Mine had - just incase you missed that
- 235/50 rears.
235/50 16 ZR is the tyre size identified in the handbook that came with the car. They put 245/45s as standard later on in the production. Bought car with 245/45s on S02s all round. Either size is ok with insurance as TVR produced cars in both sizes. Mine had - just incase you missed that
- 235/50 rears.
shadowfax said:
Bluey is the name of our Griff 500, shadowfax being the name of my first TVR, the white 400SE.
235/50 16 ZR is the tyre size identified in the handbook that came with the car. They put 245/45s as standard later on in the production. Bought car with 245/45s on S02s all round. Either size is ok with insurance as TVR produced cars in both sizes. Mine had - just incase you missed that
Cheers, I didn't know most of that. I knew that the early cars had 225/50/16 rear and the later ones 245/45/16 with early chimps having 225/55/16r and later ones 245/45/16r but didn't know that the larger rolling dia was fitted to the Griffs.
Gassing Station | Griffith | Top of Page | What's New | My Stuff