Tire dilemma - buy 1 or 4?

[StHalcyon]

A few weeks ago I hit one of them famous Chicago craters and cracked the sidewall of one of my tires in 3 different spots. =( I was wearing the Pirelli PZero Nero M+S.

 

Anyway, Subaru recommends that:

A) treads be the same on all 4 corners, and

B) the difference in tread depth between all 4 tires be no greater than 2/32 inch.

 

All 4 of my tires get rotated every 6 months along with alignment service, and had 5/32 left. Since I plan on having the city pay for the tire replacement, I thought I could just get a new replacement PZero Nero and have Tire Rack shave it down to 5/32.

 

But I now realized that the Spec.B's factory alignment spec for camber is -0.5 degree, which means that of the 4 grooves across my tires, the outside and middle two grooves measure 5/32 tread depth, and the inside groove at 2/32!

 

I am thinking that even if I shave the new tire down to 5/32 (Tire Rack can only perform even shave across), realistically speaking that new tire will be different from the other 3 by 3/32 of an inch, because of that camber, right?

 

If you are in my shoes, what would you do? Replace the 1 tire and shave it down to 5/32 even, or chuck the rest and buy a whole new set of tires?

[BAC5.2]

Get 4.

 

Camber doesn't wear tires like that. You need an alignment too. It was off before you hit the pothole. I've been running -2 degrees of camber in the rear for the past 8k miles, and all four tires are evenly worn.

[StHalcyon]

I wasn't suggesting that the pothole caused all 4 tires to wear off the inside faster. I suspect that the alignment specs may have caused that.

 

Every 6 months, I always have my wheels rotated and aligned only because of the horrendous amount of potholes here in Chicago. Perhaps I left that part out.

 

But regardless, given that 3 of my tires have worn off 3/32 of an inch faster than the middle and outside of my tires, should I:

1) go ahead and replace 1 tire with shaving down to 5/32 evenly, or

2) replace all 4 tires?

[BAC5.2]

Then the shop is doing a bad job. 3/32" across a tire is FAR too much wear. Half a degree of negative camber won't cause that.

[GTTuner]

Buy four and get your car aligned, do it right and forget about it.

[turbodog]

You have too much toe out in the front or rear or both. That is what is prematurely wearing the insides of the tires.

 

Static camber has to get into the 3+ degree range before it would cause that kind of wear.

[StHalcyon]

Well, I've been getting them aligned every 6 months, and forgetting about it. It's only because of the sheer chance of having a pothole incident that I was forced to measure the tread depths of all 3 tires that I discovered this. What's to say that my next alignment won't cause the same thing 10K miles later?

 

BAC5.2 is causing me to suspect the quality of work at my Subaru shop, supposedly ranked best in the state of IL by Subaru America. Or it could be that I have overinflated them? But I usually go 1 or 2 PSI over the recommendation front and back, unless my tire pressure gauge is really screwed up.

 

I guess I'm going to buy a whole new set of tires, since even if the inside of the tire is at 2/32 and the mid and out are at 5/32, technically my tire is considered worn.

 

At this point, I just need to ensure the same problem won't happen to my new set of tires. Do you suppose low profile tires may be a factor (which I seriously doubt)? Or the fact that the Spec.B's alignment spec is just drastically different, like perhaps in the toe-in spec? I suspect that because the WRX STi's toe-in is drastically different from even the regular WRX, according to a Subaru technician.

[BAC5.2]

I have a hand print on my headliner from the "SOA best dealer in MD". Don't put any stock in what they say.

 

Your bad wear is from a bad alignment. Find out where the local racers get alignments and go there.

[StHalcyon]

So I just looked up the electronic version of my owner's manual, and I was surprised to see that the wheel alignment specs didn't differentiate between the regular Legacy Sedan from the Spec B. Does that sound right?!?

 

Toe

Front: 0 in (0 mm)

Rear: 0 in (0 mm)

 

Camber

Front: -0deg 15'

Rear: -0deg 40'

 

I thought for sure the Spec B would have a different wheel alignment spec. Waiting to go home and look at the printed manual instead.

[PhilT]

The alignment that the car comes with for the factory is fine for everyday driving. That goes for all cars, not just the mighty spec b

[StHalcyon]

LOL Well, if that's the case, then with the specs above, there is no way in hell a proper alignment could've caused the kind of wear that I experienced...

[BAC5.2]

LOL Well, if that's the case, then with the specs above, there is no way in hell a proper alignment could've caused the kind of wear that I experienced...

 

Which is what was said in post #2.

 

It's so easy to fool an alignment machine, it's ridiculous. Just a lean will get you in the green, push print and your done. The technician gets paid an hour of labor for 5 minutes of work, the customer with unfailing faith in the dealership is none the wiser and is left thinking the poor wear is the fault of the tire or "par for course" for the car. It happens all of the time, because 9/10 times the customer isn't going to know better.

 

A VW dealer tried to pull this one over on me, SEARS tried to do it too.

 

Replace all 4 tires, find out where all of the local Subaru Auto-cross and track guys go to for work, and start taking your car there. You'll save money, and actually get what you pay for.

[dwolson2]

Which is what was said in post #2.

 

It's so easy to fool an alignment machine, it's ridiculous. Just a lean will get you in the green, push print and your done. The technician gets paid an hour of labor for 5 minutes of work, the customer with unfailing faith in the dealership is none the wiser and is left thinking the poor wear is the fault of the tire or "par for course" for the car. It happens all of the time, because 9/10 times the customer isn't going to know better.

 

A VW dealer tried to pull this one over on me, SEARS tried to do it too.

 

Replace all 4 tires, find out where all of the local Subaru Auto-cross and track guys go to for work, and start taking your car there. You'll save money, and actually get what you pay for.

+1 on the push/lean, I used to teach how to do alignments...lol

It sounds like your toe out is the culprit. Also, 2/32 on any part of your tire tread is cause to replace it (if your going by the book)

 

I would def go to another place and get an alignment, also, watch the guy and make sure he isn't doing "the lean" on it...

[seabass07]

The specs you referred are the ideal specs. Keep in mind that there is a range for an alignment. If you have 3mm of toe out on either side, you are at the edge, but within specs. That means the machine says it's green and your done. If they are not giving you a printout, then who knows what the hell they are doing. Find a shop that will not mind if you watch them work. Just say you are a DIY repair type and are curious about the process. Mechanics are extremely thorough when you are watching them work.

[StHalcyon]

They do provide printouts. I'm at work, but can't wait to go home to review them!

 

I may have to ask if I can watch them do the alignment. But at this point, since I'm replacing all 4 tires, I might even take this opportunity to get the alignment somewhere else.

[StHalcyon]

The last time I performed an alignment was June of last year. All values after adjustment, anything in parentheses mean tolerable ranges. (This should help those who in other threads have been asking for the Spec.B alignment values. According to the Subaru shop, the values used are for 07-09 2.5 Spec.B and 3.0R models.)

 

Front Left

Camber: -0.3° (-0.8 to 0.3)

Caster: 6.0° (5.2 to 6.7)

Toe: 0.02° (-0.08 to 0.08)

SAI: 14.3° (none provided)

Included Angle: 14.0° (none provided)

 

Front Right

Camber: -0.4° (-0.8 to 0.3)

Caster: 5.9° (5.2 to 6.7)

Toe: 0.02° (-0.08 to 0.08)

SAI: 14.0° (none provided)

Included Angle: 13.6 (none provided)

 

Cross Front

Cross Camber: 0.1° (-0.8 to 0.8)

Cross Caster: 0.1° (none specified)

Cross SAI: 0.3° (none specified)

Total Toe: 0.03° (-0.17 to 0.17)

 

Rear Left

Camber: -0.8° (-1.4 to 0.1)

Toe: 0.01° (-0.08 to 0.08)

 

Rear Right

Camber: -1.2° (-1.4 to 0.1)

Toe: 0.01° (-0.08 to 0.08)

 

Cross Rear

Cross Camber: 0.4° (-0.8 to 0.8)

Total Toe: 0.00° (-0.17 to 0.17)

Thrust Angle: 0.01° (-0.33 to 0.33)

 

Judging by the ranges, it seems like the camber is biased in the negative, more so in the rear. Perhaps this explains why the inside of the tire wears out faster.

 

And I just went to my storage to look at the OEM Bridgestone 050A tires that only saw 7k miles. I took a measurement, and the outsidess and middle of the tires are at 9/32, and the insides are at 7/32. No alignment was performed during the first 7k miles my Spec.B was driven. So, that leads me to believe this uneven wear is normal?

[seabass07]

This means that you need to drive faster around corners.

[BAC5.2]

Believe whatever you want. If you want to believe it's normal go ahead. I'm not sure how many other ways it can be said that it isn't normal.

 

I had 30k on my stock RE92's with zero toe all around. No uneven wear.

 

My Pilot Sports have been at -2˚ in the rear for about 8k miles. The wear across the surface is dead even, to the 64th of an inch.

 

On my old car, I ran -2.5˚ front and -2.2˚ rear camber and zero toe. I never had uneven wear problems.

 

Camber doesn't wear tires like that. Camber doesn't actually wear tires at all really. Toe does.

 

I'd find a better alignment shop, one that local performance enthusiasts use.

 

And FWIW, my Outback was WAY out of alignment spec when it came off the truck. I did an alignment at my first oil change at 1000 miles.

[StHalcyon]

Not that I don't believe you, but humor me this. What's the full size specs of your tires? Maybe camber does affect uneven wear depending on the flexibility of the sidewall and the amount of sidewall? i.e. more of an effect on low profile tires? Couple that variable with how much air can truly be a problem? Here's my thought process. Low profile tires with shorter and less flexible sidewall + negative camber + overinflation = uneven tread wear on the inside. Granted, I keep my fronts at 34 (1 psi over recommendation) and my rears at 33 (1 over).

 

According to this support site, it appears that camber does affect the kind of tire wear that I am experiencing. With toe wear, the tread wear would be more gradual, like 9/32 on the outside, 8/32 in the middle and 7/32 in the inside. Not an even 9/32 out and middle, and a sudden 7/32 in the inside.

 

At this point, there is enough doubt that perhaps, just slightly so, that the Subaru shop I take my Spec.B to is doing a bad job, but given that they have had an alignment equipment upgrade during the time I've been going there plus the fact that they know I always demand the alignment before/after reports, it is kind of hard for me to outright claim that they don't do a good job. For the record, last night I took my car to another shop.

 

I simply need to be convinced that negative cambers of as much as -2.5˚ with zero toe definitively does not cause uneven wear, when all the information I've been gathering from sites and tire technicians indicate otherwise. Especially when the 4 original tires that only had 7K miles experienced the same problem in all 4 tires. Too much of a coincidence for it to be a bad shop/technician work.

[dwolson2]

Before I get in a pissing match, I would like to say I teach steering suspension and alignments and from our lecture, books, and other articles that I have read from reliable sources, camber will wear out the inside of your tires. CASTER has no effect on tire wear. Toe out will wear out the inside of a tire, just at a faster rate, as I can speak from personal experience. Also, your mechanic can easily fudge your numbers, so as a point to make sure its right, either look over his shoulder, or ask him ot leave it on when he is finished to verify his findings.

[BAC5.2]

225/55/17 is my tire size. I ran 225/45/17's on my first gen Legacy. I was running RE070's, and I got 60,000 miles out of them with 6-7k mile rotations.

 

I've never had tires wear because of camber, and I haven't seen problems like you are describing without seeing toe out of whack.

 

There are shops that use $100,000 laser Hunter racks, and still fudge the readings. Why? Because it's easy, and that big expensive machine makes people trust them. I'm not saying you got swindled by your dealer, but there is absolutely NO way you can wear 2/32's in 7,000 miles. That would mean that in less than 25,000 miles your tires would be COMPLETELY destroyed. RE92's have a tread wear warranty of 40,000 miles.

[GTTuner]

Technically there should be someone sitting in the car for the alignment, or put 175 pounds on the driver seat.

[turbodog]

I'm with BAC5.2 on this one. On previous cars, I've run highly modified suspensions with aggressive camber in the 2.5+ degree range, with zero toe, and had no abnormal tire wear. Granted, if you're running that kind of camber you're going to be doing a fair amount of hard cornering, so you do get increased, but even, wear. That said, I did plenty of highway driving with those setups.

 

Only time I shredded the inside of tires is with, you guessed it - too much TOE OUT.

 

It is very easy to check your toe at home for major errors. Park in a flat area and run a string around all four wheels at the axles. The front track width is nominally .4" wider, FYI. If you were to see an obvious (1/16"+) gap between the string and the rear edges of the front tires, or tightness of the string against the front edge of the rear tire, that would indicate a good bit of F or R toe out, respectively.

 

Or read this:

 

http://forums.nasioc.com/forums/showthread.php?t=1093484

[StHalcyon]

That article only covers adjustments for toes. The easiest thing to adjust, even with craptastic alignment equipment is the toes. I'm not disagreeing that toe ins will cause uneven wear. I am simply stating that from what I've read, camber can cause uneven wear as well. Just search for the term "camber wear" and you get an endless set of results. Plus, the fact that Monroe shocks has dedicated a section to tire wear with documentation of each type of wear with one being "camber wear" tells me that camber can in fact cause uneven wear.

 

Given how easy and prevalent toe adjustments are, I seriously doubt that the technicians at my Subaru shop would fudge the numbers or do some hanky panky. When I said that they had replaced their alignment equipment, it was done when they moved to a bigger facility. And the new facility has a window with a great view into the work area. But I'll be honest with you, the last time I got the alignment, I was working on my laptop and not really looking at the work done on my Subaru. But in any case, I have enough doubt that I'm hoping that this new shop will do a decent job. The fact that the technician I spoke to is a sports car enthusiast and claims to do some races for hobby gives me some level of confidence. But we'll see.

[seabass07]

Camber can cause uneven wear. But it takes way more than -1 deg of camber. 0 camber will give you worse tire wear than -1 because every time you turn, you will wear out the outside of the tire more. The point is not whether negative camber can result in inside tire wear. The point is that the little camber that you have should be giving you very even tire wear. That points to toe being fudged or the machine being off.