Influence of camber angle on directional ability
05-07-2009, 04:23 AM
#1
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Influence of camber angle on directional ability
This should read: Influence of camber angle on directional stability
Hi, my C5 is a daily driver, but it is modified to allow for occasional track usage as well. I have the Z51-option, and the engine is tuned to 430 hp. I used C5-Z06 sized rims and non-runflat (Michelin Pilot Sport PS 2) tires. The wheel alignment is essentially the one of the C5-Z06 (FE4) with -1 degree camber on both front and rear.
I noticed that after the last engine tuning stage, I often have problems “to get the power on the road.” That is, when accelerating in a straight line or in a smooth curve, the rear wheels tend to break loose to an extend that is much larger than I would expect from additional 80 hp (+20 %). With the stock engine I had 275/40-R18 in the rear, but the additional 7 % increase in tire width (when going to dimension 295/35-R18) does not seem to compensate for the power increase.
I drive my car at all kinds of conditions and, if conditions permit, on the German autobahn at some 150 mph, even in (light) rain. At such speeds on wet roads, the last thing one wants is a rear end that tends to break loose, especially when there are puddles leading to occasional aquaplaning. Recently, I went to a 1/4 mile event and, somewhat to my disappointment, I was barely able to achieve times in the high 13s when I expected to reach 12s. I attributed these results mainly to my inexperience in this sport, and to my (after 125,000 miles) somewhat worn out gearbox (MN6) that is reluctant to allow for quick gear changes. I am aware that a zero degree camber would be best here, but does a little camber (of say – 1 degree) substantially deteriorate quarter mile results?
To tell the whole story, I recently noticed a little play on the left rear wheel and I plan to exchange the corresponding tie rod joint soon. Indeed, my car becomes a little unstable when passing the expansion joints on curved bridges at 120+ mph. Perhaps this minor play influences directional stability (even at lower speed) more than I expect.
Anyway, my question is: What is the influence of the camber angle on directional ability? Let’s say I reduce the camber angles to say -0.7 degree (which is spot on FE4 spec of -0.7 +/- 0.5 degree). Would I be able to accelerate and break significantly better or do values in the 0 to 1 degree range primarily only influence cornering ability and tire wear and not directional stability to a significant extend?
Thanks, Robert
Hi, my C5 is a daily driver, but it is modified to allow for occasional track usage as well. I have the Z51-option, and the engine is tuned to 430 hp. I used C5-Z06 sized rims and non-runflat (Michelin Pilot Sport PS 2) tires. The wheel alignment is essentially the one of the C5-Z06 (FE4) with -1 degree camber on both front and rear.
I noticed that after the last engine tuning stage, I often have problems “to get the power on the road.” That is, when accelerating in a straight line or in a smooth curve, the rear wheels tend to break loose to an extend that is much larger than I would expect from additional 80 hp (+20 %). With the stock engine I had 275/40-R18 in the rear, but the additional 7 % increase in tire width (when going to dimension 295/35-R18) does not seem to compensate for the power increase.
I drive my car at all kinds of conditions and, if conditions permit, on the German autobahn at some 150 mph, even in (light) rain. At such speeds on wet roads, the last thing one wants is a rear end that tends to break loose, especially when there are puddles leading to occasional aquaplaning. Recently, I went to a 1/4 mile event and, somewhat to my disappointment, I was barely able to achieve times in the high 13s when I expected to reach 12s. I attributed these results mainly to my inexperience in this sport, and to my (after 125,000 miles) somewhat worn out gearbox (MN6) that is reluctant to allow for quick gear changes. I am aware that a zero degree camber would be best here, but does a little camber (of say – 1 degree) substantially deteriorate quarter mile results?
To tell the whole story, I recently noticed a little play on the left rear wheel and I plan to exchange the corresponding tie rod joint soon. Indeed, my car becomes a little unstable when passing the expansion joints on curved bridges at 120+ mph. Perhaps this minor play influences directional stability (even at lower speed) more than I expect.
Anyway, my question is: What is the influence of the camber angle on directional ability? Let’s say I reduce the camber angles to say -0.7 degree (which is spot on FE4 spec of -0.7 +/- 0.5 degree). Would I be able to accelerate and break significantly better or do values in the 0 to 1 degree range primarily only influence cornering ability and tire wear and not directional stability to a significant extend?
Thanks, Robert
Last edited by UncleRobb; 05-07-2009 at 05:28 AM. Reason: Typo in subject line. Mod plz correct.
05-07-2009, 08:06 AM
#2
Race Director
First things first, I would get the tie rod replaced, and double check your Toe to make sure it is withing OEM range.
If you still have problems, you could experiment with camber. It sounds like you are having stability concerns while mostly driving Straight, NOT in high speed corners, so you don't need a lot of camber. However, -1.0 isn't a lot of camber, so I would think your current setup would work well.
There are very few people on this forum with access to roads where 120-150 CRUISING speeds can be achieved, so we may not be very helpful. However, having a bad tie rod end will certainly cause major instability problems, and is likely most of your problem. You should check all of them, as well as your wheel bearings, lower concentrics etc for any other issues.
If you still have problems, you could experiment with camber. It sounds like you are having stability concerns while mostly driving Straight, NOT in high speed corners, so you don't need a lot of camber. However, -1.0 isn't a lot of camber, so I would think your current setup would work well.
There are very few people on this forum with access to roads where 120-150 CRUISING speeds can be achieved, so we may not be very helpful. However, having a bad tie rod end will certainly cause major instability problems, and is likely most of your problem. You should check all of them, as well as your wheel bearings, lower concentrics etc for any other issues.
