I don't understand my inside edge tire wear.

[Atroz]

Hello,

 

I have a 07 LGT wagon. In 07 I bought a set of wheels that are 18x7.5 with a 48mm offset running 225mm tires. My winters are the Subaru 17x7 55 mm offset rims with 215mm winter tires.

 

I've been having an ongoing problem with tire wear on the inside edge of all 4 summer tires. The wear is perfectly smooth, like somebody put them on a lathe. The first set of tires lasted 3 summers, but this most recent set has lasted only 2. That's averaging about 20,000 KM per tire. The winters have been wearing perfectly. I've had the wheel alignment done on the car a few times including immediately after putting the new rubber on 2 years ago. By the end of the summer the wear was already quite visible on all 4 tires.

 

By my calculations, with the 7mm difference in offset countered by the 12mm greater tire width, my inside edge of the tires are just 5mm (1/4") wider on the summer tires than the winter tires. I.e. The tire will be 5mm closer to the strut and 8mm wider to the outside. To me this seems about as good as I could go for a wider tire. My mechanic figures the wear is caused by the wider tires (and offset?) though.

 

I now need to buy new tires and I am seriously considering going back to factory sizes if it can get rid of this expensive problem. Also, my 18" rims are now bent from our rough Canadian roads and I'm getting tired of the harder ride so I'm considering a full wheel package but I keep finding 48mm offsets and I don't want to duplicate this problem as a 48mm offset with a 7" rim will just push the tires to the outside more and they will not line up with the factory setup. For the inside edge, instead of being 5mm inside, they will be 7mm outside.

 

What should I do to solve this? Do I buy the 48mm offset and get some spacers? Are the studs long enough? Is the problem even the offset? Is it the width? What is it??

 

Thanks for your help.

[BAC5.2]

Get an alignment.

 

Tire wear is not at all a function of wheel size, and is almost not at all related to width.

 

Toe wears tires.

[Atroz]

Get an alignment.

 

Tire wear is not at all a function of wheel size, and is almost not at all related to width.

 

Toe wears tires.

 

That's what I thought so I had an alignment done on the new tires and a five thousand KM later the tires were worn.

[BAC5.2]

Then your alignment was done incorrectly. Do you have the specs?

[Atroz]

Then your alignment was done incorrectly. Do you have the specs?

 

I'll have to go looking. I know I've had the specs from some, but I'll have to see if I can find this last one. I had a different shop do it, a good tire specialist shop.

 

Something else to add, My winter tires were driven on that same alignment and show no problem.

[Atroz]

Then your alignment was done incorrectly. Do you have the specs?

 

I don't have the specs but I found the receipt. Guess what it says? Tire Fitment data: 2007 Subaru IMPREZA WRX STI.

 

Now I don't know if this is what they used for the alignment though.

 

Anybody know if the alignment on a 2007 LGT should be the same as a 2007 WRX? Or did they totally screw up?

[BAC5.2]

It doesn't really matter what the alignment comparison was. It could have been for a Toyota Tercel. All that matters are the numbers.

 

Some tires wear differently than others, and you never mentioned what type of tire you are running on the 18's.

 

That said, there are a ton of people running that size and offset without issue. My bet is that it's either an alignment issue that the offset and size exacerbates, or it's a tire issue.

 

The impact of misadjusted toe gets worse as tires get wider and the scrub radius increases.

[Atroz]

It doesn't really matter what the alignment comparison was. It could have been for a Toyota Tercel. All that matters are the numbers.

 

Some tires wear differently than others, and you never mentioned what type of tire you are running on the 18's.

 

 

The tires are Goodyear Eagle GT. They are a 440-AA-A rating which should have meant a long life.

[BAC5.2]

Treadwear ratings are wholly arbitrary, but that's a tire that typically lasts a while.

 

I'd try to find the alignment record.

[Atroz]

Treadwear ratings are wholly arbitrary, but that's a tire that typically lasts a while.

 

I'd try to find the alignment record.

 

Unfortunately I don't have one. It would have been with the receipt in the file folder had I received one.

 

I can try calling up the shop and see what they can do but I don't know what leverage I have.

[BAC5.2]

You have no leverage. They might have kept a copy of the print out, but it's not entirely likely.

 

You just might have to pony up and pay for another alignment. But make sure you can go to a place that will allow you to specify exactly the alignment you want.

 

Zero toe, and -.5˚ of camber up front.

Zero toe, and as much camber as can be wiggled out of the rear (though the rear camber isn't adjustable without extra parts).

[Natas]

is the car on stock suspension bits. lowering a car you get inheret chamber which an alignment shop can't take of the rear... lowering springs give about -1˚ depending on the bit used.

[Atroz]

You have no leverage. They might have kept a copy of the print out, but it's not entirely likely.

 

You just might have to pony up and pay for another alignment. But make sure you can go to a place that will allow you to specify exactly the alignment you want.

 

Zero toe, and -.5˚ of camber up front.

Zero toe, and as much camber as can be wiggled out of the rear (though the rear camber isn't adjustable without extra parts).

 

Well, you called it right. I had another shop check the alignment and found all 4 wheels were off.

 

Front was -3/32 and -6/32

Rear was -9/32 and -9/32

[BAC5.2]

Figured as much.

 

You should be good to go now.

[Atroz]

Figured as much.

 

You should be good to go now.

 

Very good to go. I called the original tire shop and they agreed it was their fault and are replacing my tires tomorrow.

 

Thanks for your help.

[SBT]

Really glad this worked out well and the shop owned-up to it. That's a lot of toe. I'm surprised the tires didn't squall while you were driving. And I'm sure you'll like the way the car handles a ton better. Be sure to check the tire pressures too, as your LGT is meant for 2 PSI difference front-to-rear which does affect the handling. Stock setting is 35F/33R, I run at 36-38F/34-36R depending on the circumstances.