understeer/oversteer
Discussion
Been putting it off for ages but finally got round to investigating the terrible understeer the V8S acquired a the end of last year. Found quite a few factors that couldn't have been helping but the main one was twice as much neggy camber on the rear as I was expecting, and the dampers wound right off can't have helped. No wonder the inside shoulders have been wearing so much more than normal. Taken some of the camber off and a quick test round the MK handling was promising but I think I'll need to shim the hubs a little for the last bit. Really should have done this way back when I got the trailing arms rebuilt but one thing after another got in the way ... anyway in case you were curious, -4 deg camber and no dampers are the way to go if you are after understeer!
quote:
Been putting it off for ages but finally got round to investigating the terrible understeer the V8S acquired a the end of last year. Found quite a few factors that couldn't have been helping but the main one was twice as much neggy camber on the rear as I was expecting, and the dampers wound right off can't have helped. No wonder the inside shoulders have been wearing so much more than normal. Taken some of the camber off and a quick test round the MK handling was promising but I think I'll need to shim the hubs a little for the last bit. Really should have done this way back when I got the trailing arms rebuilt but one thing after another got in the way ... anyway in case you were curious, -4 deg camber and no dampers are the way to go if you are after understeer!
Peter and all the other suspension Gurus,
I need your advice on a similar suspension geometrics issue:
I checked camber front an rear, and before checking toe-in, camber should be settled first.
Now, the bible and Petrol Teds Post "Tracking Setting" ex. November 20th 2001, do not show the same values for the setting. Could it be that one is for the early V6 models and one for the newer V8s chassis? Below are the values for camber I measured on my S3c:
Front Left: -1,53°
Front Right: -098°
Rear Left: -1.34°
Rear Right: -0.49°
Petrol Ted's Range:
Front: -0.5° ...+0.5°
Rear: -1.25° ... -0.75°
Range out of the Bible:
Front: +0.75° ... +1.25°
Rear: +1° ... +1.50°
Questions:
1) Do I have to set camber front and rear? What range then?
2) How do I physically adjust camber:
a) at the front
b) at the back
3) How does one set toe at the rear?
Thanks for your hints
Patrick
Some of those numbers are obviously wrong because camber is always, always negative. It may be some of the figures were for toe-in.
I don't know what camber the factory specified, but I would expect it to be somewhere in the range -0.75 deg to -1.25 deg on all four corners. Quarter of a degree here or there isn't all that critical so you might get slightly different numbers from different sources.
Similarly I don't have the factory figures for toe-in to hand but I believe they are given in the bible, and I would expect them to be somewhere between 0 and 1 mm toe-in all round.
As you know, when you lower the ride height you inherently add camber (and slight toe-in, at the rear) and when you add camber you need to add toe-in (roughly quarter of a degree toe-in per degree -ve camber works for me). Generally, more camber gives more kick-back and worse tramlining on the road but improves lateral grip under very heavy cornering on the track. If you are aiming for mainly track use you might consider up to 2 degrees -ve camber but you will definitely notice the difference in normal driving.
Hope this helps,
Peter Humphries (and a green V8S)
I don't know what camber the factory specified, but I would expect it to be somewhere in the range -0.75 deg to -1.25 deg on all four corners. Quarter of a degree here or there isn't all that critical so you might get slightly different numbers from different sources.
Similarly I don't have the factory figures for toe-in to hand but I believe they are given in the bible, and I would expect them to be somewhere between 0 and 1 mm toe-in all round.
As you know, when you lower the ride height you inherently add camber (and slight toe-in, at the rear) and when you add camber you need to add toe-in (roughly quarter of a degree toe-in per degree -ve camber works for me). Generally, more camber gives more kick-back and worse tramlining on the road but improves lateral grip under very heavy cornering on the track. If you are aiming for mainly track use you might consider up to 2 degrees -ve camber but you will definitely notice the difference in normal driving.
Hope this helps,
Peter Humphries (and a green V8S)
quote:
What technique/instruments do you use to measure camber/toe? Know of any cheap cunning ways to do this? I struggled to get accurate data when I was a student building a racecar.
Technique I use is set the car on completely level ground using a spirit level and spacers under each wheel, then use a plumb line to measure the angle of each wheel. I've set up a small frame 600mm high with a steel ruler sticking out sideways top and bottom. Plumb line goes from the outer edge of the top ruler down to somewhere near the outer edge of the bottom one, plumb weight has a point on the bottom which just rests against the top edge of the bottom ruler (if you see what I mean). The bottom ruler is marked in 0.5mm increments which gives me a resolution of 0.05 degrees. In practice I can move the car more than that just by pushing on it while I'm taking the measurement!
Or you can buy a Camber/Toe gauge from Demon Tweeks for about £100!
- As for me, I use my eyes! For normal road driving I have virtually 0 degrees camber on the front, (On my car, this promotes SAFE understeer on the road as opposed to oversteer and significantly reduces front tyre wear).
For track days however, I set the front camber to around -2.25 degrees which is the maximum adjustable, and only takes 10 minutes per side to do.
These settings are on my S2 and suit my suspension set up. The best thing for you to do, is experiment with it and find a setting which suits your driving style and balances with safety and tyre wear. Basically, more camber = more tyre wear.
One final point, is that if you run the standard TVR suspension, you will probably want around 1 degree of negative camber on the front and not much more, since when the car is under braking and the front of the car dives, the camber will go even more negative and you will have less tyre in contact with the road and braking distances will usually increase.
Jas.
- As for me, I use my eyes! For normal road driving I have virtually 0 degrees camber on the front, (On my car, this promotes SAFE understeer on the road as opposed to oversteer and significantly reduces front tyre wear).
For track days however, I set the front camber to around -2.25 degrees which is the maximum adjustable, and only takes 10 minutes per side to do.
These settings are on my S2 and suit my suspension set up. The best thing for you to do, is experiment with it and find a setting which suits your driving style and balances with safety and tyre wear. Basically, more camber = more tyre wear.
One final point, is that if you run the standard TVR suspension, you will probably want around 1 degree of negative camber on the front and not much more, since when the car is under braking and the front of the car dives, the camber will go even more negative and you will have less tyre in contact with the road and braking distances will usually increase.
Jas.
quote:
I set the front camber to around -2.25 degrees which is the maximum adjustable, and only takes 10 minutes per side to do.
Jas.
Jas,
could you please shortly explain the procedure to adjust camber? What screw(s) to loose, how to shift what, where?
Any clue about how to do this and toe to the rear trailing arms?
THX Patrick
quote:
quote:
I set the front camber to around -2.25 degrees which is the maximum adjustable, and only takes 10 minutes per side to do.
Jas.
Jas,
Q. could you please shortly explain the procedure to adjust camber? What screw(s) to loose, how to shift what, where?
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A. On the top ball joint there are two bolts which secure to the top wishbone. Slacken the bolts off and push or pull the ball joint in or out which changes the front camber. The holes in the wishbone are elongated so it's easy!
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Q. Any clue about how to do this and toe to the rear trailing arms?
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A. I've never done the rears since my car has been lowered significantly to give over 2 degrees of negative camber. As for Toe angles, the front is parallel, (adjusted via the steering rack rod ends). The rear has changed only in relation to the lowering of the car. If you want to change the rear toe or camber, you can use washers as spacers behind the driveshaft/hub securing flange bolts, (take off the rear drum and you should see the 4 bolts) I have not done this however.
Jas.
>> Edited by Paceracing on Monday 8th April 22:16
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