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I have a newish set of Potenza RE-71s on my car. They have 3 track days on them at this point. All tracks have been run CCW, which means most turns are to the left. The right side tires are wearing in a pattern I have not seen before.
The outsides are wearing much more than the insides (need more -camber?), but look at the profile of the center rib.
These tires are directional, so they are rotated front to back after each track day, but not to the other side of the car.
The tires are 245/40/18s mounted on 18x8 aftermarket rims. The car is aligned properly and has about 1.8 degrees of negative camber up front and 1.5 degrees in the rear. Pressures are always carefully monitored and have been 36 front and 34 rear when cold. There are no signs of excessive roll on the sidewall (arrows are intact). What is happening here?
Looks tread squirm / street tire related to me - I've seen similar out of the stock Bridgestones and Conti DWs. I bet it maybe could be improved with a tenth or three more negative camber but I don't know that you can fully eliminate the graining & chunking.
May want to get the tires "flipped" on the wheels a bit more often if you seem to be repeating a bunch of CCW directions / layouts for the events you're running also.
I'm afraid if I go any lower than the pressures I have been running, I will roll these tires. The left side of the car is 34 front and 32 rear. These tires have somewhat of a unique construction and seem to have less stiff shoulders than some other designs.
BTW, I know I can technically rotate them to the other side, but 2 of my 3 track days have been in the rain.
all else being equal generally as you increase camber you will drop pressure due to it not rolling over onto the outside corner as much. Per the pictures it's just at the tip of the sidewall rollover indicator triangles.
I can't recall anyone ever running anything near -4 deg static camber on an RX8 (except for the low-offset wheel street poseurs). That's generally where strut suspensions run, not camber-building dual A-arm suspensions. Rotating tire positions and flipping tires on wheels is another strategy to get the most from them as you can. Stiffer swaybars or springs will help minimize camber-defeatng body roll too.
all else being equal generally as you increase camber you will drop pressure due to it not rolling over onto the outside corner as much. Per the pictures it's just at the tip of the sidewall rollover indicator triangles.
I can't recall anyone ever running anything near -4 deg static camber on an RX8 (except for the low-offset wheel street poseurs). That's generally where strut suspensions run, not camber-building dual A-arm suspensions. Rotating tire positions and flipping tires on wheels is another strategy to get the most from them as you can. Stiffer swaybars or springs will help minimize camber-defeatng body roll too.
I was going to mention sway bars, remember reading in one off his other posts that his front bar is Progress Miata bar..maybe he needs bigger bar or at least set it to firmest setting?
Did do some digging around. Will likely need -2.5 to -3.0 camber front, figure within 1/2 degree less or so in the rear. 28 - 34 psig seems to be the range, but obviously camber dependent. Essentially you have no inboard tire wear/grip. Too much body roll and/or too little camber. When you only use the outer part of the tire like that you are concentrating all the load/heat there. Once you get the load evened out the wear will improve, but generally these tires are wearing faster due to the high grip. 1.4 and 1.5 G loads being reported. On the track times are not that far off of Hoosier, well at least closer than past street tires. Pretty awesome for a 200TW street tire.
Also, looking closer you definitely don't have enough pressure for the current camber setting (which is too low). You have darker scrub marks well past the triangle indicators. While higher pressure will help some ultimately you'll need more camber if you want to optimize the wear and performance.
I don't actually know my hot tire pressures with these tires. The reason for that is, I jump off the track and onto the highway for ~5 miles of additional [brake] cool-down before parking in the paddock. The pressures after that are low 40s.
I have the rear Progress Miata bar sitting in my garage. I can put it on and adjust the front to a stiffer setting and see if that helps. I can also move the tires to the left side on dry days. It looks like the monsoon season is mostly behind us, so that really becomes an option.
The car's ride height is ~13.75" all the way around, and it is corner balanced. The coilovers are Bilstein PSS9s, and I run the rebound between 4 and 2 depending on the track and the day (medium-fast to fast). I think I have already outgrown these and am looking at FCM or KW for next season.
The car is at Cobb Tuning in Plano for adjustments to the alignment today. They are supposed to call me when they find out how much they can get out of it.
Those springs are fairly soft and it's probably too high to get much more camber out of the front. Can swing by there after lunch if it will help. Need to go by there any way.
Yeah. The springs are midrange at best, and these coilovers are a compromise in every regard. I am still foolishly trying to cling to the idea of setting up the car to be good enough on the track while still compliant enough on the street--and do it all on a budget. It isn't working.
reach the tip of it, but you can see darker color rub marks well past them. Don't really want those past the tip IMO, but not easy to do without the proper camber setting. Will require jacking up the pressure a lot, but more of a band-aid approach.
I saw the car out front at Cobb today. It will need to be lowered and/or add camber bushings to get more.
They could go as far as 2.4 on the front with a lot of compromise to caster. They ended up at 2.2 in the front and 2.0 in the rear. One thing is for sure: it drives like crap on the street now. I must be making progress. I'll try it and see how it goes. I could lower the car more, but I have trouble with my steep driveway when lower than this. The car is lowered about 1.25" at its current ride height.
I'll go ahead and install the new rear bar on its softest setting, and adjust the front bar to the middle setting and see if that helps as well. I'll also jump out of the car and measure my hot pressures before hitting the highway for my extended cool-down laps. I can go to TNIA the evening of July 14 to test things out. These tires will be on the left side of the car then for sure.
Thanks again for all the help. Feel free to keep it coming.
Last edited by Steve Dallas; 06-24-2015 at 06:54 PM.
Very common in RE71r. Like said above, adjust the setup a little and it'll help...but it's just what they do to some extent.
After spending a few hours reading various forums, I am inclined to agree with you. People are loving the tire, but finding they need 4ish degrees of negative camber and higher than normal tire pressures to make them behave. With those adjustments, wear is still faster than normal for a supposed 200TW tire, but less weird at least. (Let's face it; everyone knows this is nowhere near being a 200TW tire.)
Further evidence that these tires are a strange animal is the fact that my NT01s exhibit normal wear patterns at lower pressures.
Originally Posted by TeamRX8
Did do some digging around. Will likely need -2.5 to -3.0 camber front, figure within 1/2 degree less or so in the rear. 28 - 34 psig seems to be the range, but obviously camber dependent. Essentially you have no inboard tire wear/grip. Too much body roll and/or too little camber. When you only use the outer part of the tire like that you are concentrating all the load/heat there. Once you get the load evened out the wear will improve, but generally these tires are wearing faster due to the high grip. 1.4 and 1.5 G loads being reported. On the track times are not that far off of Hoosier, well at least closer than past street tires. Pretty awesome for a 200TW street tire.
Also, looking closer you definitely don't have enough pressure for the current camber setting (which is too low). You have darker scrub marks well past the triangle indicators. While higher pressure will help some ultimately you'll need more camber if you want to optimize the wear and performance.
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I must have come across the same info you did when I finally had time to do some searching this evening. Everything you wrote here has been echoed by experienced time trialers and autoXers.
Cobb got me pretty much all the camber they could with my current setup. I'll reduce body roll through stiffer bars, watch the pressures, and see what happens.
What I can tell you about these tires is that, even though not properly tuned, I gained 2 full seconds over my old RE-11As, and both of my logging devices are showing 0.2G improvement--from 1.0 to 1.2. My NT01s are still slightly faster, but these tires inspire more confidence and actually warn me with a low groan that they are about to break loose. And, they oddly sound like duct tape being peeled off the road, which is unique and interesting. Who doesn't want that feature?
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Last edited by Steve Dallas; 06-24-2015 at 09:31 PM.
got it. looks like i am going over too far on my tires a lot of the time and will have to start with a little more air next time.
thanks!
Originally Posted by TeamRX8
reach the tip of it, but you can see darker color rub marks well past them. Don't really want those past the tip IMO, but not easy to do without the proper camber setting. Will require jacking up the pressure a lot, but more of a band-aid approach.
I saw the car out front at Cobb today. It will need to be lowered and/or add camber bushings to get more.
I would have minimized caster to get all the camber, pretty common on this car, caster isn't that beneficial on this suspension
your front camber was quite a bit lower than you thought which lends itself towards the end result, and quite a bit lower than the rear too.
betting you'll need more front bar than rear now ...
front camber bushings will get you about 1/2 degree more without lowering, about 1 deg if you do both upper & lower but the lower ones are spherical which will get noisy on the street
06-23-2015, 07:38 AM
