Shop Put Wrong Tire On - Subaru WRX Forum
 
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#1 Old 10-18-2011, 04:24 PM
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Shop Put Wrong Tire On

I went to go get some new 225/45/17 tires at my local Discount Tire store on Saturday. I then proceeded and got an alignment on my car which was right down the street from my house. On Sunday, I drove to work and realized that my car was pulling drastically to the right. I immediately think that they messed up on the alignment and had to have my wife take my car in to get the alignment redone. However, after numerous test drives and trying to figure out why the car was pulling to the right they realized that it was one tire that was causing the issue. Discount Tire put the a wrong size tire on my vehicle. They put 235/45/17 on my WRX. During the many test drives that the alignment place was taking my car started to smoke. Do you think this could have been my differential or drivetrain? Has anyone else had this happen to them and what did they do? I am obviously going to go complain to Discount Tires, and ask for an inspection on my vehicle to see if there was any damage since this is their fault. Any advice would be greatly appreciated.
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#2 Old 10-19-2011, 05:56 AM
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The tire is just a little wider, it shouldn't make a difference for that short of time. Now height is a different story. Was it the same brand and model tire as the others?

Where was it smoking from ?

Paul
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#3 Old 10-19-2011, 06:57 AM
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How far did you drive since installation?

Also you're gonna need a new alignment when they replace it.
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#4 Old 10-19-2011, 10:12 AM
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235 isn't just wider, it's taller. However, it's not THAT much taller. Your spare tire in the trunk would be far worse. How far did you drive total on the wrong size tire? If it's <50 miles, I wouldn't worry about your diff.

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#5 Old 10-19-2011, 11:45 AM
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^ Ok, explain how it's taller. I've heard of this, but no one really explained.

I remember looking for 235/45/18's and only a few brands actually made them (garbage brands for what I wanted) but 235/40/18's were all over the place.

Edit: found several threads on other forums. Didn't realize this. 2-3mm difference. Wonder if it's that way on all tires?

Paul
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#6 Old 10-19-2011, 03:34 PM
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I went around 150 miles on mountain roads. I was not there when the car was smoking as my wife had to take the car back to the shop where we got the alignment. After a few test drives the mechanics at that shop said it was smoking and smelt liked burnt oil. They tried to look at where it was smoking from but could not find it.
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#7 Old 10-19-2011, 04:53 PM
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Rear Diffs don't smoke like that. There's not much oil in them to burn. Neither do transmissions really. If that's the only symptom, I'd say it's unrelated. Maybe a shop guy had oil on his hands and bumped your exhaust while he was down there... 150 miles is a lot for an incorrect tire mismatch. Subaru only allows the spare to be used for a maximum of 50 miles (but again, the spare is a more extreme mismatch). It wasn't good for it, no.

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Originally Posted by pzr2874 View Post
^ Ok, explain how it's taller. I've heard of this, but no one really explained.

I remember looking for 235/45/18's and only a few brands actually made them (garbage brands for what I wanted) but 235/40/18's were all over the place.

Edit: found several threads on other forums. Didn't realize this. 2-3mm difference. Wonder if it's that way on all tires?
The first number is a width, in millimeters.
The last number is the wheel diameter, in inches.
Most people are OK understanding those parts. What they DON'T get is the middle number.

The middle number, say it's 45, is NOT IN ANY UNIT OF LENGTH AT ALL! It's actually a ratio, in percent. It's a ratio between the width of the tire and the sidewall of the tire. So, for any tire with a middle number of, say, 45, the sidewall is 45% of the width (and there's a sidewall on the top and on the bottom when it's mounted so it basically contributes twice to the total tire height/diameter).

So, our 225/45R17 tire is 225mm wide, and each sidewall is 45% * 225mm, or 101mm. That's about a 4 inch sidewall (divide by 25.4) and a 8.9 inch width. Add sidewall + wheel + sidewall to get the total tire diameter, 4 + 17 + 4 = 25.0 inches.

Repeating the same for 235/45R17, the tire is 235mm wide, and each sidewall is 45% * 235 = 106mm. That's about a 4.2 inch sidewall (divide by 25.4) and a 9.3 inch width. Add sidewall + wheel + sidewall to get total tire diamter, 4.2 + 17 + 4.2 = 25.3 inches (removed rounding)

If you do the math, the 235/45R17 tire is 0.36 inches taller than the 225/45R17 tire, or about 1.4% taller.

On a more extreme example, all '45' sidewall tires are not the same. A 155/45R17 tire is 22.5" tall while a 305/45R17 tire is 27.8" tall. One has a tiny tiny sidewall, the other has a fat sidewall. The only thing the ratio is useful for know independent of the width is for determining wheel size. both the rediculous hypothetical tires I just made up would require a wheel width that's within the same range as the tire width. The tire has a range of about 5-30% wider than the wheel width for almost all '45' sidewall tires.

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#8 Old 10-20-2011, 06:12 AM
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You rock Mosc... Thanks for the tutorial on the sidewall as well. My BFG's seem to be the same if not shorter than the 225's I had on it.

Paul
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