i went to rotate my tires today and i noticed an odd thing on my passenger side rear tire.

this is what most of the tire looked like:


but then there is one small patch of increased wear:



it seems to me that is quite the difference in wear on just that one spot on the tire. what could cause this? the tires, BFG Gforce Sports, have about 20k km on them, and a bunch of autocross events. the only thing i can think of is that is caused by locking up the brakes at autocross, but i have only ever locked up the brakes for a second or two at most, and it strange that it would only be on that one tire.

any opinions appreciated...i am going for a longer drive tonight and i will see if i notice anything weird driving.

 

Definitely a flat spot.

If the tire was like that all the way around I would have suggested over inflation.

When you lock up the tires braking all four don't lock at the same time, unless you've really dialed in the brake bias, but even then the most stressed tires will lock up first.

 

it's interesting that just that one rear tire had a flat spot, i would have expected a front tire to have the flat spot when i locked up the brakes. i guess these things are not so certain when you are throwing a car around an autocross course.

i went for a drive, up to speed on the highway, and everything seems fine.
anything i should watch out for with a flat spotted tire?

 

yeah, vibrations

 

Production cars are setup to lock the fronts first so the rear end doesn't lock and go out of control. But end-user changes like aggressive rear brake pads or simply using the hand brake can result in rear lock-up. A stuck rear brake caliper could contribute as well.

However, if a wheel is out of balance, or the tire goes out of round, that can also cause the tire to wear in one spot faster that the rest of the tire as well. When was the last time you had the tires balanced?

-Max

 

tires were balanced when they were first put on, so not since then.

i am running EBC Green pads front and rear, stainless steel lines, Turbo model calipers (new rebuilt units about 2 years ago) with a non-turbo master cylinder and proportioning valve, which i believe has moved the bias towards the rear a little bit. however i am quite happy with the brake balance.

these tires don't have too much life left to them anyways, i just wanted to make sure it's not an issue with the car itself...

 

Right on.
I over inflated tire will create and wear pattern more centered the more over inflated the tire is.

And yes autocross and locking the E-Brake will cause flat spots lol.

If its in the middle i doubt its an alignment issue.

 

how frequently do you rotate tires?? seems like thats just caused by locking... because if it was a suspension issue or unbalanced tire it would cause cupping all over the tire... it looks like you due for a new set anyways... just play close attention to that side and rotate your tires sooner

 

i usually rotate once a year, which usually works out to about 5000km-7000km on each rotation.
and yeah, this set needs to be changed in the near future...