kanji1jz

This is a tire that is worn from a toe angle that is out of adjustment. Many times people assume that only the front end of a car is necessary to align, but the rear end is just as essential. As in this case, the right rear toe angle was out by about a tenth of a degree. For how long? I don't know, but what I do know is that the end result is really worn out tires, as well as lost fuel economy. Now some other factors could be involved here, such as worn bushings or struts, to cause a similar problem, but if you look at the way the wear pattern is diagonal gives away the toe angle issue immediately. The other thing to check for when you see this is worn bushings. Worn bushings can change the angles of your tires as you drive down the road so make sure that when you take your car to get an alignment you have them check you suspension and steering components as well.

Loren

Hate to be contrary (no, really, I do!), but that's not how I'm reading that tire at all.

I see a tire with overall fairly even wear, no feathering... with flat spots. Flat spots are caused by braking. The banded triple flat-spot makes me wonder if maybe the car has ABS.

Once a flat spot is started, the tire tends to want to lock up in the same spot easier under hard braking, so the flat spot will get worse rather than better.

So, if my ABS guess is correct, these are obviously not high-performance tires and they're probably old and hard... so some aggressive-braking driver liked to late brake and eventually got a flat-spot started on the right rear tire (the one with the least weight on it under braking). Now, the way ABS works, as soon as it senses the lockup, it releases and reapplies the brakes... that's why there are three flat spots. "Chirp, chirp, chirp" until the car is slowed enough to no longer lock up that tire.

That's what I see. I'd be curious to know if my ABS guess is correct.

.1 degrees of toe out won't cause flat spots. If it caused wear, it would be simply excessive wear all around the tire. .1 degrees probably isn't enough to cause feathering... more like .2 degrees might. But, in any case... flat spots are not an alignment issue.

kanji1jz

But wouldn't a flat spot due to braking be straight across and not in a diagonal pattern? Now granted, I'm not disagreeing with you as it was a female college student in a ford focus with multiple other problems, but I can't recall if this was a ABS car or not. And a toe out condition where the tires are never rotated can cause a diagonal swipe across the tires. This is due to extreme neglect of rotation as well as an out of aligned vehicle. And this tire was on the left rear. I will take a picture of the other tire (the right rear) and you can see that it is not worn like the left rear. I included the tire size straight off the sidewall so you don't think that I just took a picture of another worn out tire. I know they are two different tread patterns and brands but these are the exact tires that were on the car. Now are there other issues that could have helped this??? yes, I'm not saying there aren't. Oh and thanks for the reply I like to discuss these things so that other people are aware of what's going on with their car and don't get screwed over by dishonest shops.

kanji1jz

and that swipe goes all the way around the tire. I guess I forgot to mention that as well. That particular section was the least extreme of it all, yet the best pictures I had of it.

Loren

I have to admit that diagonal wear like that is new to me, I haven't seen that one. But, I wonder, too, if maybe it's an indication of a worn shock? Sort of like how old tires used to "cup" around the edges with blown shocks. Maybe it's something to do with that?

Or could be a combination of things.

My experience comes mostly from performance tires in a performance environment. Things happen a little differently on an aggressively driven car that's wearing through a set of tires every 10-15k miles than they do on a "normally" driven car with 40k mile tires.

That RR tire looks okay to me. Maybe slightly under-inflated to cause the edges to wear more than the middle, but pretty evenly worn. I'm gonna bet they got their money's worth out of that tire.

kanji1jz

correct on the under inflation. From what I can remember on the alignment it was just the left side that was out. Yeah wear on performance vehicles/ tires are alot different than just regular old p-metric "R" series tires. worn shocks/ struts do play a part as well as bushings ( as stated in the initial post), but many times (just as you said) tires tend to cup instead of wear with a diagonal swipe.

Loren

Could also be dealing with a manufacturing defect or just an engineering quirk of this particular tire model.

Toe settings are a funny thing, though. Toe being out by .1 degree on one side would probably have the effect of making the whole back end of the car "dog track" just a little bit so that the net effect was "equal toe" on both rear tires in their direction of travel. (just like what happens in the front of the car when toe is off on one side, except that the steering wheel angle compensates in the front) So, I could be wrong, but I don't think that toe being out A LITTLE (.1 is a little... not like half a degree or something) would cause wear on one side, but quite possibly on BOTH rear tires. Where things would get weird there is in cornering, the car would handle completely differently when turning in one direction vs the other.

I'm going with weak shock... and still a little curious about the ABS idea. Regardless of how those "flat-spots" started their life, they would behave as flat-spots under braking and want to lock up.

kanji1jz

Well toe might have been a little worse than .1 but I can't remember exacts at this point. A tire defect is possible, as is worn bushings and struts and possibly ABS. Again not alot of people are going from 120 to 30 in 20 feet like they do on the race track so the likelyhood of this being a ABS issue on a non-riced out focus driven by a female foreign college student is highly unlikely. Again not trying to rule anything out but the fact still remains I've seen this alot and 8 times out of 10 it's a toe issue. Dog tracking still doesn't equal out rear toe. The reason it equals out in the front is due to the fact that the steering gear/ rack equals itself out due to it having that capability with moving parts. The rear is set and tightened (unless obstructed by way of bent parts, collision, etc.) without anyway for it to completely equalize like the front ( unless you want to get wayyyyyyy technical about this and start in on the aws vehicles). Does dog tracking come into play here? A little. but dog tracking is mainly when you have a solid rear axle or there is very extreme deviation in toe from one side to the next. In this case I really believe that it has everything to do with neglect to rotate tires and a toe specification issue on just that left rear.

I agree that a weak shock can help accelerate this flat spot, and I did not drive the car before aside from pulling it in and replacing both rear tires and doing the alignment.

senor honda

That's the most unusual wear pattern I ever saw.
............but we don't know the history of how/why/etc. that it went through during it's lifetime....we only know about it's last owner.

If I had to create that wear pattern for a stunt car/movie, or to prove a point....(if the bet was high enough) I could do it with some used tires, but not solely by driving it. -Bob

SleepingB18

Fairfield Tire Center Inc. | Tires... dont mean to pull up an old post, just saw this site..