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2008 mazda3 hatch.

So I had thought I bent a rim, but sure enough when I rubbed my hand over the rear drivers side tire its cupped? really bad on the inside ti middle of the tire, feels like its wavy up and down across the length of the tire.  The tires were new 8k miles ago (bought the car with brand new mastercraft avenger touring lsr tires on them, treadwear 420 I believe).  All 4 Wheels were aligned after I got the car in June.  I did autocross it 3 times but the surfaces were completely flat.  There's got to be a root cause, bearing\damper\shock?  Its only happening on one side.  4 wheel alignment done in June (8k miles ago) by mazda dealer.

Heres a pic where you can see the dark spots on the inside
Debating on whether I need 2 new tires or just one, mind you the other side is perfectly fine.
click the thumbnail for a bigger pic (its on the right side of the tire)



Thanks so much.  

auto crossing exerts additional forces that can shift wheel alignment settings... bend and tweak things...

just because the wheels were aligned... does not mean it was properly done..   i have had a huge problem with the current crop of wheel alignment machines...  hook them up...  every thing is in the green...  but the car still pulls...

the specs say.. within  + or - 3/4 of a degree...  if one side is on the plus side..  and the other is on the - side...  it can still be in the green on the machine.. and no alignment changes are done.. but the alignment is off...


find a specialist wheel alignment shop... depending upon where you live... they can be easy to find..  or hard to find..   you might want to look for a frame repair specialist....  they usually are really good at getting all the wheels pointed in the right direction..


most shops have a computerized wheel alignment machine.. be sure to ask for a print out of your before and after measurements...  so you know what the settings are actually at...

since you autocross the car.. you might make friends with them... as you are probably going to need their services again...

there are several interesting articles spread out through the many magazines on this site..
Honda Civic Si - Poor Man's Alignment
It might be because you're cheap. Or maybe it's because you don't trust your Honda Civic Si in the hands of the gas station ...

http://www.hondatuningmagazine.com/tech/htup_1006_honda_civic_si/index.html


2. Camber, Caster, and Toe Wheel Alignment - Get It Straight (Or Not)
Here are some of the basics you should know before you ruin your cars alignment. Find out how proper camber, caster, and toe wheel ...

http://www.superstreetonline.com/techarticles/sstp_1004_camber_caster_toe_wheel_alignment/index.html

3. AWD Alignment Tips What To Do, Why To Do It - Garage
Check out this comprehensive guide for alignments for your all wheel drive vehicle.

http://www.turbomagazine.com/tech/0711_turp_awd_alignment_tips/index.html

4. Alignment - Getting It Straight
Sometimes, When You Want Something Done Right, You've Got To Do It Yourself.

http://www.importtuner.com/features/0608_impp_alignment/index.html  

The long and short of it is this tire is not rolling "flat", as a tire that rolls flat tends to wear flat. An alignment to "spec" is only as good as the end result which may take weeks, months or longer to present any inherent problems, then, if there has developed a wear issue it is too late as the damage is done (as evidenced by your photo). If I were a betting man this appears to be a camber/strut issue. On some vehicles correcting rear alignment problems can be shockingly expensive and is quite often overlooked for this reason. In most cases that $79.00 four wheel alignment wont get it done (correctly)!  If this were my car and the "rumbling" was great enough as to be a nuciance I would reverse the rotation of the tire by installing it on the right side of the car and move it to the drive axle (front). Standard rotation protocal calls for the non drive tires to be crossed when performing a four tire rotation....time to rotate your tires.  

First, I am not fond of the term "cupping", because it is commonly mis-used. In the days of bias ply tires, tires could develop a "cup" due to a bad shock or an out of balance condition.  But today's modern radial tires don't behave like the old bias ply tires and a bad shock /out of balance produces a wear pattern that is fairly hard to distinguish from irregular wear.

Irregular wear is caused by mis-alignment and aggravated by insufficient iflation pressure and insufficient rotation practices.  By "mis-alignment" I mean alignment not conducive to even wear.  It does not mean "Within Spec"!

I've heard lots of reports of irregular wear from Mazda3's.  While I haven't seen the alignment specs, I suspect the 3 has a lot of built-in camber.  My experience says that anything over 1° may produce irregular.  But toe is a HUGE contibutor as well.

My experience also says that the tolerances published by the vehicle manufacturers are too wide - by half.  So while an alignment tech will see everything within the "Green", that doesn't mean the tires will wear evenly.  Plus many alignment techs think that if the vehicle doesn't have built-in adjustments, it can't or shouldn't be adjusted.  That is just plain wrong.  EVERY alignment setting can be adjusted, but it may take an eccentric bolt or a adjustable plate to be able to get the proper setting.

But you have an additional problem - autocrossing.  Street cars are not designed specifically for high tire slip angles.  Autocrossing causes the suspensions and steering gepmetry to operate outside the normal range of values - and that can result in unusual wear patterns.  

But if you set up your car to do well in autocrossing, those alignment settings are going to cause unusual wear patterns when the car is driven on the street.  In other words, no matter what you do, an autocrosser is going to have bad tire wear.