If you're asking the OP, I don't think his air pressure is causing the wear, since he'd have to run it very high which I already do.

My Hankook V12's are squirmy like people say so I worked up to 46 hot front, 43 hot rear on the track.

When I rotated the wear arrows on the front were in better shape, and I found about 44 hot front and rear worked the best.

The Hankooks ride so much smoother than the kuhmo SPT's that I leave the pressure there until next track day, which is about 40 cold.

AND I even went down to 225/40r18 instead of the stock 225/45r18.

 

So what do you think I should tell them? Less negative in the rear chamber?

 

Yeah, I wasn't running high PSI. I was running 33 PSI on all four tires, so like Red said it can't be my PSI. I Think it has to do with the Alignment. At least I hope...

 

I'm with notapreppie. Looks like over inflation based on the center of the tire being gone. but not the edges. If it were camber or toe, it would be way more worn on the inside edge.

redrx3rx8: The v12's are a much stickier and different tire than what he's running. You're also talking track temps and pressures. Most tires don't like 40+ psi, but there are some that do like your v12's (from what i've heard). 35 psi cold is usually pretty good for a street tire, especially an all-season.

OP, check your tire pressures, get an alignment to stock specs, and rotate your tires front to back every other oil change (normal schedule, i rotate mine every oil change due to them being only 140 tread wear).


edit: posted while i typing.

 

Yeah I will plan on rotate my tires every other time I change my oil.

Also, I got my Continental DWS on my car! love them. Now time to get an alignment hopefully that will fix it. What is the stock specs for the alignment anyway?

 

They should be able to look them up at the shop. I don't remember them off hand, but they're posted in this thread https://www.rx8club.com/rx-8-racing-25/alignment-settings-street-track-use-43308/ there's also some good talk about settings and effects in it.

 

I'm one of the few guys that aligned my car for the track without changing any of the suspension.

My goal was to tweak what Mazda designed, and the alignment is so good that I don't have to keep chasing the suspension adjustment.

I was running the recommended 32 psi cold on My Kumho SPT's to try to get all the tires to wear evenly.

The rear tires still wore twice as fast, and that was before I discovered HPDE.

So, after 1.5 years, 8k miles, and 4 track days, I have even wear on all tires except the front might be wearing slightly more than the back.

I'm running way more inflation now with psi set for feel instead of how I think the tire might wear, and I have no wear problem.

IMO I'm the only guy here that has the info the OP needs to fix his problem; he said himself that he's not over inflated.

 

Yeah! No more than -1.7 neg in the rear will stop your excess wear there. More neg camber up front also will give you a more neutral handling car.

I can see that rear neg camber on lots of modern cars, and some people like the look, but it is designed in to make sure a bad driver doesn't oversteer in the wet, etc.

My 8 had a big thump, and jump on speed bumps, but now I barely watch for them.

 

I completely agree with running between 1.5-2.0 rear negative camber, but I don't think it was too much negative camber that caused the OP's tire wear. If you have zero toe, and -3.0 camber, you will not have that kind of wear. His problem was too much toe. Get an alignment with zero rear toe, or maybe 0.1 degrees toe in for stability.

 

Yeah, don't listen to me!

What would I know anyway?

Never mind that I checked the alignment I had before I changed it to see what might be off, and the alignment was close to spec, except for -2.1 camber on one side and -1.9 on the other rear side.

Have you had a 8 do what the OP described, aligned how I said, and with the rears not wearing anymore?

If not, then, you have no relevant input!

 

Congrats on having some track time. It doesn't make you an expert. You're reading too far into what i said, and obviously missed my edit that i had posted mine before seeing his tire pressure answer. I said what i said because you were comparing sticky tires in track conditions to eco/all seasons in street conditions so what you run your tire pressures at doesn't automatically translate over to his condition. You must have also missed where i told him to get a stock spec alignment and start there. All cars wear different front to rear. FWD cars wear the fronts faster, RWD cars wear the rear faster. Why do you think tire rotation is recommended? Yes you can adjust you alignment to correct for that, but you'll lose performance somewhere. The factory alignment is a compromise between performance and tire wear. I agree that if he's worried about tire wear he shouldn't be any more than -1.7 or so in the rear. He needs to look at his toe as well. It's most likely more of the problem than camber. As I stated before if he has too much toe and too much camber the inside of the tire would be gone first. Since it's not over inflation, and it's worn pretty evenly, it suggests too much toe, and probably too heavy of a right foot. JCrane is right. His input is valid. Toe kills tires faster than camber.

Camber settings weren't causing your clunk. Both the front and rear suspension on our car are designed in a way that camber, toe, and caster will not effect the path of the shock travel. If you've ever replaced the struts/springs you would see this right away. Even lowering the car does nothing to effect shock movement, as the pivot point still stays on the original path of movement. You likely had something loose that was tightened properly when the next alignment was done.

I'm on my 3rd set of tires in the 3yrs and ~ 40k miles I've had my 8. I got ~10k out of a set of 140 tread wear tires, and almost ~30k out of a 400 tread wear all-season. No track days, but quite a bit of autox and a lot of it on windy backroads, including a trip to the Dragon. This doesn't make me any more or less qualified to answer his question though, even though i have 5 times more street miles which is the issue here.

You are obviously not the only person who can help the op. You have pretty much shown that you don't know what toe is and you don't understand how camber works. It's not a crutch to save people from having the back end step out in the wet. When used properly it gives the outside tires more contact patch when cornering. Not to mention that our suspension is design to go further negative as the suspension compresses.

You seem to be well respected around here man. but you're missing a lot of the handling vs. tire wear equation in your posts, and nothing you've posted qualifies you to give the only answer.


Back on topic. OP, hopefully you found the factory settings in that thread i linked. If not the shop should be able to look them up. Tell them you want to be on the lower side of the recommended toe, and you want your alignment done with you in the car. This will most likely fix the excessive wear. Make sure you're rotating your tires like you currently are. Check them ever so often for wear and rotate them more often if necessary.

 

Ok, I'll try again!

The crummy first alignment ended up with slight toe out on the rear and -1.9 deg camber. I'm very well aware that the rear suspension toes inward, and cambers more negative as it squats during cornering and acceleration.

That's why you get the static ( standing still) alignment around -1.6 or so because it does change during bump motion.

I wouldn't call the V12's sticky: they still lost traction on the rear WITH MY 6SP AUTO, so I knew I had to realign from -1.9 to -1.65.

Since I'm not an expert on the 8, I changed one thing at a time to pinpoint the issue.

As soon as I drove off from the garage, I could turn right, jump the gas, and go without any drama which the "factory alignment" must have missed. In fact the car drove like it had never been aligned until I aligned.

Without the tire slipping, there's no wear, and no dcs drama.

This was about the easiest thing I fixed on the 8 without being an expert, but maybe all those tires I used to sell and adjust helped me think a little better on how to solve this issue with only logic.

 

The toe out on the first alignment is what was likely killing tires. Did you set your static toe to 0? If so that's what's saving your tires, not the static camber. Toe cause tire scrubbing, which causes wear. 0 toe however makes cars seem less stable at speed in a straight line. Constant scrubbing is way worse than sometimes slipping. I don't necessarily consider V12 sticky either, but in this context and compared to the OP's tires the are

Sorry if I seem as if I was attacking you, but I'm just tryin to show that camber isn't everything in tire wear, and that toe makes a bigger difference.

My soon to be alignment will have 0 toe in the rear to help with tire wear on the inside edge.

 

Yeah, I will tell them to set my toe a little bit lower then the recommended for the 8. Also just set the recommend camber for my 8 too. I honestly think whoever had my car tracked my car, but that's only what I think. My first engine went out at 35k :/ and my catalytic converter went out at 32k! and changed all the wires, plugs and wires as well. Runs good except for the tires :/

 

For a daily driver I would watch setting the rear toe to zero....you would be better off with 1/16 or so TOE IN...it will make the rear a lot more stable and will not impact on the tire wear.

Not sure where some of the crazy theories come from....for a stock suspension stick with stock specs...just make sure that they make sense....I have seen some crazy stuff fit into "stock" specs. I doubt that your alignment is/was the issue with these tires.

Those tires are totally worn out....get an alignment and rotate the new ones, drive like it's your car....and see what happens

 

I ran the first set of Kumho SPT's without doing anything to the stock GT sport suspension until about 15k miles, when I rotated tires front to rear.

I was watching all the tires wear like a bad religion, since I still had some of those tread depth gauge thingies that I used to measure leftover tread when adjusting tires.

I might have even had a little practice in getting accurate readings with all those tire measurements I used to do, and could see the rears wearing approx, about, etc. twice as fast as the fronts.

The slight toe out on the rears was only there a few thousand miles, but the wear already occurred with the factory alignment.

I was telling the guy what I wanted for alignment, and the second time he was setting the camber one side would only go down to -1.65 so I made them both that, and he dialed the toe to o, but tolerance to slightly in as I wanted, which was touchy to get right.

So without moving anything but alignment bolts, and settings, when I rotated the Hankooks after 7k miles the wear was so even I might have not needed to rotate.

Can I tell you all the physics of why? Probably not, but it's mostly the rears not getting the right bite on acceleration, thus, the slip, the DCS, and the wear.

Whatever it is, I spent serious alignment $'s to get those rears straightened up to help the handling and wear.

When I had the rears toed out, I couldn't tell much difference about stability over it slightly toed in now.

Let us know how the alignment turns out, and you can mail me a dead crow if I'm wrong.

 

A little touchy are we? This is a great forum, and plenty of people are knowledgable and helpful. Lets try to keep the postings helpful to those who need it.

As for your comment; no I have not had a RX8 do what the OP described, but I have had a previous car have an alignment issue (due to incorrect toe) that wore tires drastically. I do know what I am talking about, and I am not sure why you are arguing the main point I was trying to make. Just to be clear, my main point is:

Out of spec toe will cause much more tire wear than too much negative camber.


Are you arguing that you saw high rear tire wear with in spec toe but -1.9 and -2.1 rear camber?

 

Yes, when the rear slips and traction control hits there is already tire wear!

Yes, out of spec toe will cause more tire wear than camber, WHEN ITS ON A NON DRIVEN WHEEL.

What I'm pissed about is that a few people came out and **** on my idea I figured out without trying it out first, like you're more important or something.

Hey, I'm not the tear apart the 8 and put it back together expert, but I spent time and logic to tune my suspension and was trying to help others.

If someone has done something DON"T **** ON IT IF YOU HAVEN"T TESTED IT!

 

REDRX3RX8

We're not shitting on your idea. JCrane and I aren't making this up. It's a proven fact that toe causes tire wear. It has nothing to do with driving style, ability, or a lack thereof. Toe causes constant scrubbing of the contact patch while a wheel is in motion because the wheels aren't completely parallel to each other. Because of this, toe causes the tires to constantly wear out. It's not just when the tire spins or loses traction, the scrubbing is constant. It will do this on both drive and non drive wheels. Drive has nothing to do with it.

A lot of camber can give you a smaller contact patch in a straight line, therefore limiting grip off the line, but we're talking a lot of negative camber to do this, like -3.

If you look at the OPs tires, the inner edge isn't gone and the wear is pretty even across the center of the tire. I'd love to see the numbers when he gets his alignment. I'm willing to bet that hes close to -1 for camber and either has a ton of toe in or toe out, like .3 on each side or so.

We're not telling you that your wrong in what you think camber is doing for your car, we're telling you that there's more to it, and that toe is probably what is causing his wear.

You even said yourself that you had toe out before your alignment that started saving tires. I've had plenty alignments done on multiple cars. I've tried quite a few things. I'm taking mine in for it's 3rd alignment because I don't daily it as much anymore so i'm going to get all of the toe taken out of the rear so that it stops chewing up the inside edge of my tires where i have my camber set. No toe = less constant tire wear. End of story. I would say ask any alignment shop, but anymore, they're just kids that can follow directions and actually have no idea what they're really doing.

 

REDRX,

It is true that you could see the OP's tire wear with a heavy right foot. I think a few other's have commented on that. Since the OP stated that he doesn't even redline it daily, or track it at all, that I doubt he is spinning tires on every corner.

Suspensions are complex systems, and tire wear like the OP's can be due to a couple options.....but high negative camber would not seem likely. I only say this based on the information given by the OP. Also the high negative rear camber will provide better rear traction during cornering, limiting the rear tire slip (again only during cornering). So unless the OP is lying and is doing burnouts regularly, it appears he has too much rear toe. I am very interested in his current alignment numbers, and am willing to suggest some starting alignment numbers for the OP if he is interested.

I am also one of those "tear apart the 8 and put it back together" individuals, and perform my own alignments on all of my cars. I also have a very good understanding of suspension systems,as my last job assignment with my current company was suspension system owner.

I am sorry that you think I am trying to "crap" on your ideas, I just know what is typical. I understand that you saw rapid rear tire wear with "in toe spec" and -1.9 to -2.1 rear camber, but that doesn't prove that your wear was caused by the camber. As said earlier, a heavy right foot and frequent hard cornering under throttle can also cause this kind of wear.

One thing to remember about suspension/alignment settings is that there is no magic right answer for perfect setup. Each car has slightly different stock adjustment settings due to tolerance stackups, and each driver wants a different feeling car. The key is to find out what you want, set alignment accordingly, and test/tweek alignment to better perfect it. I have a decent idea what works for my driving style, but I am still learning/tweeking every year.

 

I have a 6 spd auto with 28k miles most of which is highway at 75 mph on the way to track day four times a year.

In other words, I'm not doing burnouts, but I had double the wear in the rear, and I only caught it a few times while accelerating on a right turn.

I was about to get my friend 9krpmrx8 to put in my s techs, but traded them to him to put in my BHR stuff ( He's a super nice guy, and one of those "tear apart the 8 and put it back together guys" that I value since I'm too weak to try anymore).

This forum has been unbelievable to find nuances on the 8 that I have tweaked, and I decided against changing any suspension parts because I could see people changing the springs and bars, then, not being able to find the handling balance they wanted or sagging springs.

I'm pretty sure I could have taken my new 8 to the dealer with the "why does my car lose traction when full throttle turning", and it'd not be figured out, but I knew it wasn't balanced even though it still cornered better than anything I've ever driven.

I've won TTOD with a 73 RX3 that I balanced myself ( front toe was all I could tweak); I did it with sway bars. I've also won my class with a 80 Scirocco that lifts it's rear inside wheel since it's front wheel drive, so this ain't my first Rodeo.

Anyway you're welcome in advance, but I see ideas only work to the OP asking what to do, and in the future I'll use the PM feature to give up my ideas. I've hired enough people that I've been amazed at how many people are mechanics, but still don't have spatial concepts or scientific method ( not saying I'm good at it, just better than most). I can read what people do to their car where they do several things " while I'm there", and can't tell which one fixed the problem.

 

I wish I could do burnouts, but I'm a poor college student so I can't go wasting my tires ha. Like I said before I only redline like twice a month, I don't speed up so fast to get to that speed limit, My PSI is always at 35. Hm not sure what else :/

Also I set up my appointment with Mazda on Wednesday at 1:30pm! So when the alignment is done, do they give me the numbers of my camber and toe? or do I have to ask them for it? I just wanna know what the numbers are now and what they are after the alignment.

 

The tech will provide you with before and after measurements for caster, camber and toe. Since you are taking it to a Mazda dealer, they will align according to the service manual for either the standard or sport suspension (depending on what you have). The factory specification allows cross caster and cross camber to be off up to one degree. If you sweet talk the tech he may be able to take the time and do better than this. Factory toe specification also has a wide tolerance range.

Be sure to get a print out of the before and after numbers. The before numbers will be a clue to use to determine the rear tire wear. If the specs are within tolerance, then you can't blame the alignment (within reason).

I have posted the Sport Suspension factory alignment specs for Series I.

 

Okay, so I just came back from Mazda and this is what they said.

Both Front and Rear Toe was out of Spec.
Adjusted Front and Rear Toe
Caster and Camber in Spec.

Unfortunately the tech guy didn't give me the numbers like I asked...
Owell least we know now it was the toe!!

:]

Hopefully...

 

Well most of use knew it was toe before you realigned.

Keep an eye on your wear and tire pressures to make sure the problem was indeed your out of spec toe.

Hopefully next time you will specify to the tech that you want before and after numbers. I can't emphasize enough how important it is to understand/know where you alignment is.