Tire Center Bar Wear Question
 

I was at Thunderhill last weekend, running the dunlop starpec 2s. I've been experimenting with tire pressures, starting at 35lbs and letting a little air out at a time. At 32lbs the tires feel most consistent to me. However, when I looked at the tires at the end of the day the center bar was worn in a slope towards the right side of the car. I suspect that this is normal, because the track is mostly left-hand corners, but I wanted to verify that this is normal, and not under-inflation.

If you've got some experience with tire wear at the track can you chime in?

Front Passenger
https://dl.dropboxusercontent.com/u/...2013.05.49.jpg

https://dl.dropboxusercontent.com/u/...2013.07.04.jpg

Rear Passenger
https://dl.dropboxusercontent.com/u/...2013.08.36.jpg

https://dl.dropboxusercontent.com/u/...2013.09.07.jpg

If you start to see wear like that you can have the tires flipped. These tires are directional so you don't have too many options with rotating. I also use around the same PSI for mine and they tend to wear a bit more on the outside edges.

More camber :)

How much camber are you running? Mine did the exact same as you describe when I went to laguna last winter, I was on -0.3 (I can't see your pics for whatever reason).

Even after 10k street miles, 7x AutoX's (~50 runs) and 2x track days (both Laguna 100 mins each) my ZII SS can still lay down a quick lap in the hands of a good driver.

My RE-71R looked similar, except one side of the center bar was almost down to nothing after two track days at Autobahn South. Stock suspension with -2.1* front camber, 0" toe, rear stock settings.

Same here with Nitto NT05. Stock suspension, -1.5 front camber, 0 toe.

Interesting, I'd always heard the chance of slippage was much higher with camber bolts in both holes. Anyway -1.5 was all I could get with a single set of whiteline lobed bolts on the top hole.

I'm also getting pretty close to the struts with 235/40/17 tires on +42 offset wheels, so that's a concern as well.

@CSG Mike - do you know anywhere that I can get a good suspension setup that would allow me to add more camber?? ;)
@strat61caster - I'm running 1.5 degrees of caster with the crash bolts and total toe is 0.7mm at the front. Rear camber is 1.8 degrees and total toe is 3.3mm.

It seems this will be normal until I can add more camber.

Yes. PM me with what exactly your goals are, and your budget, and we'll see if there's anything that matches your goals.

if it was worn out in the center I would suspect the tires were over inflated, when you say starting at 35 psi do you mean the target/hot pressures? otherwise it would be insane IMO :D, even for a lighter car like ours...

But in the picture where you're holding the level it looks like it wears from the outer/right side which may be normal with the lack of more negative camber (or vice versa if it's the inner side) + more left turns + over-inflated tires..

It may well be a combination of those factors but hard to say which contributes more

maybe @rice_classic can chime in and spot more lights on that since he changes his alignment between sessions during the race :)

Yes sir! Sometimes I change my alignment during the race! The last time that happened I had 45 degrees of positive camber!
To the OP: The tread pattern is directional, not the rubber nor the carcass (very few exceptions to this). So long as the track is dry (no standing water needs to be displaced) then you can run them in whatever direction you please and considering your wear, you should consider this. Just rotate them back on your drive home... in case it rains. :D

If, for some reason you're weird about tread direction, then you can rotate the tire on the wheel before rotating the wheels, but unless you own a tire machine, this gets pricey.
OP should do this.
I hope the level was just for purposes of illustration but yeah weird wear patterns can show up when a tire is under or over inflated. The Toyo R888 was famous for it's "groove of death" that looked similar to this albeit much more pronounced.

However, I don't think that's what's happening here. It looks like you just have accentuated wear on one side which is to be expected and the "groove" is more of a factor of the tread squirm under cornering loads.

32 hot is probably on the low side while 35 cold would put on the high side. Aim for 35-40 hot.

Another option: have a friend ready with one of these right as you come off track and check inside/middle/outside temps.
https://images.duckduckgo.com/iu/?u=...~60_35.JPG&f=1

Mike already has a deposit from me for the CSG Unicorn Suspension so I'm just yanking his chain.

I started out trying 35psi hot (measuring the tire pressure at the end of a session) and then lowered the hot pressure 1lb at a time each session until I got to 32lb hot. At 35lb hot the tires seemed to get "greasy" and I was sliding around after a few laps. Not so much with the lower hot pressure.

I have been switching the front and back tires on the same side after each track day. I'll move them to the opposite side of the car next time I'm at the track and see how that goes.

I trailer the car to and from the track - so no worries there :)

Oh, I did this a long time ago. Mike told me I drive like an old granny and I don't need suspension until I start breaking the 50mph barrier :)


I have one of those, but no friends. I've been trying to remember to use my one of these instead:
http://flir.com/flirone/asset/img/FLIR-ONE-buy.png

That fancy adapter for the iphone isn't the droid you're looking for (no phone pun intended). Just like an infrared gun, it's only going to show you surface temp but what you want is the temp about 1/8' or so inside to actually measure the temperature of the tread band. And worse, if you aren't getting a reading immediately coming off, you're not getting accurate data anyway.

Actually, the thermal imaging could be utilized usefully if it were being viewed in real time while the tire was going through the corner.

However, watch the video below, look how fast the surface temp rises and falls... Almost immediately after leaving the corner the tire goes back to purple, then black with the exception of the high cambered edge. So if you're trying get an accurate reading like the average joe, then you actually have to stick the needle in the tire.

[ame]http://www.youtube.com/watch?v=VNYUkRKslEw[/ame]


Now, with all that being said, there is more than one school of thought here. Some racers advocate dialing in your camber by using this method and measuring inside/middle/outside temps while others setup their camber by actually measuring how the tire is wearing and adjusting from there in small increments.

Anywho... none of this really matters, go back to the track it's more fun there anyway. :)

32psi hot is very low IMO... even low for R comp tires, I would start from 30-31 psi cold and shoot for 37-38 hot psi by checking the pressures between sessions ..

keep in mind when you lower your tire pressures they will also have tendency to overheat easier especially with the street-able aggressive tires like yours and if you start too high you reach the target PSIs more easily but not because you heat them up properly but because you start higher , in other words starting very low and very high have similar effects sometimes (e.g. 25 psi cold vs 35 psi cold) , one will overheat and become greasy and the other one won't heat up as much so it will also feel greasy.. because in reality they're still cold so you're not warming them up yet.. same symptoms from different causes.. so the ideal starting temp is essential....


you may also check with your tire manufacturer to make sure what's the ideal cold-hot PSI and cambers ...(I know it's between -2.5 and -5 for NT01 and similar with Hankook Z214s)

with that said starting low for R comps may become quite helpful sometimes,...since I sometimes have hard times heating up the tires (245/40/17 R comps) , I typically start with 27-28 cold psi and shoot for 35psi but, typically, by the time I heat up the tires well I also get closer to the limits of my cooling and oil temps' safety zone ..(thanks to the FI) so I have to act strategically and put down 3-4 hot laps and get in to a cool down lap :D