Discussion
I raced my 2000 Ultima GTR in the 2005 One Lap of America, and after 17 track events and 3500 street miles over 6 days, the front tires (Pirelli P0 235/35 ZR18) were down to cord on the inside edges. The toe, camber, and tire pressure were set to the factory specs. The bushings are somewhat worn, but my mechanic doesn't think they're bad enough to explain the tire wear.
Any help is greatly appreciated. The 2006 event starts in two weeks, and although I'm not driving myself, my Ultima is entered.
Any help is greatly appreciated. The 2006 event starts in two weeks, and although I'm not driving myself, my Ultima is entered.
Sounds like a tad bit too much camber in the front. There's a trade-off with what's best for the street and what's best for the track. Also, 17 events and 3500 miles is a lot of wear on tires. How much camber are you running up front? 1-1.5 degrees at static ride height? Try backing out the top ball joint one turn. You'll have a little less grip in the corners though.
Also, check with pirelli on how much camber to run with their tires.
Good luck with the events!
Cheers!
-Mack
Also, check with pirelli on how much camber to run with their tires.
Good luck with the events!
Cheers!
-Mack
Thanks, yes, I would like that article on adjusting out bumpsteer.
The track events are only 3 hot laps each, so we think its the street miles causing the wear.
The camber was set to -.4. The tire pressure was 18 psi. The ride height was in the middle. We will decrease the camber (towards 0). Should we adjust the ride height and/or tire pressure?
The track events are only 3 hot laps each, so we think its the street miles causing the wear.
The camber was set to -.4. The tire pressure was 18 psi. The ride height was in the middle. We will decrease the camber (towards 0). Should we adjust the ride height and/or tire pressure?
That just doesn't sound right. Something else is going on here b/c that's just not a whole lot of camber. Did you measure the camber with the car on the ground at the specified ride height? Is it both tires or just one?
I went to your website and looked at the GTR that you have and it looked like there was more than .5 a degree of camber in the tire. I may be wrong though.
Keep me posted.
Cheers!
-Mack
I went to your website and looked at the GTR that you have and it looked like there was more than .5 a degree of camber in the tire. I may be wrong though.
Keep me posted.
Cheers!
-Mack
The wear was on both tires. The camber was set just before last year's race, which is after that picture on the website was taken.
What about increasing the tire pressure? My mechanic thought 18 psi might be too low.
The tires the (used) car came with were not similarly afflicted (I still have them). Also, the 3500 street miles were mostly highway, at speeds of 80-100 mph.
Thanks
don
What about increasing the tire pressure? My mechanic thought 18 psi might be too low.
The tires the (used) car came with were not similarly afflicted (I still have them). Also, the 3500 street miles were mostly highway, at speeds of 80-100 mph.
Thanks
don
I'm running 18psi front and 22psi rear on the goodyear's. I don't think this is a tire pressure issue. The risk of running too low a pressure is that it can cause the tire to rotate on the rim and its a good idea to mark the tire and rim with paint in a discrete area. Too high a pressure and it causes excessive wear in the center of the tire and too low will cause excessive wear on both of the outer edges. How heavy are the driver and passenger? Sorry to have to ask, but I have seen cases where a really heavy passenger or driver 250 lbs+ will lower that side of the car or both sides and cause excessive camber and tire wear that you describe. Or it could be that you've lowered the ride height so much that you have even more camber at static ride height. I also had very heavy tire wear on the inside of the tire when I first built my car and it was due to bad camber measurement to start with. You could be seeing some bump steer though. I still contend that you need to find a flat area and remeasure the camber with the car on the ground, maybe put the passenger(s) in it, and use a camber gauge or digital angle finder. Those spring perches can back off by the way and is another area to check.
Cheers!
-Mack
Cheers!
-Mack
This is all IMHO, I've been tracking my car for the last four years and the best set-up to date is as follows, front camber 1.5 - 2.0 degrees (track dependant), rear camber 1.5 degrees, tyre pressures are more heat dependant that static, "ergo" aim to get your hot pressures around the mid thirty's mark, i.e. 12C ambient would have a start prtessure of 26-27 psi. If your doing three hot laps ( dependant on ambient) go slightly lower psi. Hope this helps!
The factory pressures work in a comfort/performance compromise but the more flexible sidewall of the lower pressures dials out the camber benefits
The factory pressures work in a comfort/performance compromise but the more flexible sidewall of the lower pressures dials out the camber benefits
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