All tires within 1/4" of each other???
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All tires within 1/4" of each other???
Hi all,
2002 Imprenza, 29.9k miles original Bridgestone Potenza RE92 tires, P195/60R15/87H
I just shredded my left rear tire on the freeway, and the tire guy says I have to replace all 4 or it voids the warranty. The local Subaru dealer said they all should be within 1/4" circumference but did not say anything about the warranty being voided. At the tire dealer we pulled out the owner's manual and there's nothing in there except generic warnings.
I first went to Costco and the guy measured only 20% wear on all 4 tires, so you can understand why I'm reluctant to replace all 4. I just measured the new one vs the old one on the same side and there's a 3/4" difference. Anyone ever heard of this??
Thanks,
Steve
2002 Imprenza, 29.9k miles original Bridgestone Potenza RE92 tires, P195/60R15/87H
I just shredded my left rear tire on the freeway, and the tire guy says I have to replace all 4 or it voids the warranty. The local Subaru dealer said they all should be within 1/4" circumference but did not say anything about the warranty being voided. At the tire dealer we pulled out the owner's manual and there's nothing in there except generic warnings.
I first went to Costco and the guy measured only 20% wear on all 4 tires, so you can understand why I'm reluctant to replace all 4. I just measured the new one vs the old one on the same side and there's a 3/4" difference. Anyone ever heard of this??
Thanks,
Steve
Last edited by greenscooby; Jun 15, 2004 at 01:34 PM.
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Car Info: 2005 CGM WRX Wagon
When I bought mine I specifically remember the dealer telling me that all four tires had to be close to the same circumference or it would mess up the differentials. I don't remember any exact measurements, but I know I heard it.
I would err on the safe side (you're almost out of the warranty, and it would take a bit of driving for the problem to present itself in the diffs.). Besides, don't you want to get rid of the crappy RE92's?
I would err on the safe side (you're almost out of the warranty, and it would take a bit of driving for the problem to present itself in the diffs.). Besides, don't you want to get rid of the crappy RE92's?
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I recall about a year ago, an Audi owner writing to Road & Track (tech talk) about a similar situation. he was really upset because his tires were very expensive. Unfortunately, R&T's answer was what you heard already. The awd system differentials aren't tolerant of variation of tire diameters.
20% wear after almost 30,000 miles? Those tires have to be rock hard!
20% wear after almost 30,000 miles? Those tires have to be rock hard!
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Unfortunately, the tires do have to be very close in size. Otherwise, the tire that rotates the least each mile will have to continually "catch up" with the tire rotating the most. It plays "catch-up" through the drivetrain leading to stress leading to breakage. However, you can have a new tire shaved to match the diameter of the other tires.
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tire answer
Sorry, was gone for a week for work. Thanks for the replies.
We checked the owners manual and there’s nothing in there about the tires having to match. I just went out and measured all the tires. The 3 old ones are within 3/8”, the new one is smaller than the others and is within ¾” of the biggest (the right front). So if I wanted to go the shaving route I’d have to shave the other 3 to match the smaller new one. (I checked the inflation pressures and they match the door sticker, the car has sat overnight and the tires are stone cold.)
The tire dealer only had 1 of the replacement tires in stock at the time so even if I had wanted to get all 4 new I could not have. Of course now I’ve put 200 miles on the new tire so I can’t exactly take it back. Shoot….
Oh well, I have to get my 30k workup done anyway, I’ll ask the mechanic for more advice. Will pass on what else I hear. thanks for the advice gang.
-fwiw, I bought the extended warranty for the car, and what tires would you recommend replacing them with? I drive to/from the airport to work about 1/week (it's ~100 miles) in addition to general driving around.
We checked the owners manual and there’s nothing in there about the tires having to match. I just went out and measured all the tires. The 3 old ones are within 3/8”, the new one is smaller than the others and is within ¾” of the biggest (the right front). So if I wanted to go the shaving route I’d have to shave the other 3 to match the smaller new one. (I checked the inflation pressures and they match the door sticker, the car has sat overnight and the tires are stone cold.)
The tire dealer only had 1 of the replacement tires in stock at the time so even if I had wanted to get all 4 new I could not have. Of course now I’ve put 200 miles on the new tire so I can’t exactly take it back. Shoot….
Oh well, I have to get my 30k workup done anyway, I’ll ask the mechanic for more advice. Will pass on what else I hear. thanks for the advice gang.
-fwiw, I bought the extended warranty for the car, and what tires would you recommend replacing them with? I drive to/from the airport to work about 1/week (it's ~100 miles) in addition to general driving around.
Last edited by greenscooby; Jun 24, 2004 at 09:27 AM.
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Car Info: 2005 WRX Wagon
There's an explanation about the 1/4" rule on the Subaru web site. Look on my.subaru.com and follow the links to "Car Care Tips" and then "Tire Wear, Rotation, Replacement, Temporary Spare Tire Operation." There it states the rule about 1/4" circumference. However, it doesn't mention anything about voiding the warranty (not to say it wouldn't).
It seems like an awfully strict rule for the tire sizes. A .25" difference in circumference equates to a .04" difference in radius, i.e. if (2)(pi)(r)=.25 then r=.04... I would think a minor difference in inflation pressure alone could result in .04" difference in the radius. It's only 1/25th of an inch.
It seems like an awfully strict rule for the tire sizes. A .25" difference in circumference equates to a .04" difference in radius, i.e. if (2)(pi)(r)=.25 then r=.04... I would think a minor difference in inflation pressure alone could result in .04" difference in the radius. It's only 1/25th of an inch.
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After all was said and done yesterday, I decided to go ahead and bite the bullet and am getting all 4 replaced today. I talked to several mechanics at dealers and indy shops and a great majority said Yes, if the tires are more than 1/4" different the diff's will be messed up. And since I tend to buy cars for the long term (My last one was a Mazda GLC that got 250k before I bought the Scooby.) it is a cheap investment long-term.
Another bone to throw out there: Anyone ever heard of "Siping the tires"? They do it as routine and I had never heard of it, but it looks like a good idea. http://search.yahoo.com/search?p=sip...t&cop=mss&tab=
take care
On All-Wheel Drive (AWD) vehicles, it is extremely important that the rolling or outer circumferences of the tires be within 1/4 inch of each other. This means that you must physically measure the size of the tire. This is best done with the weight of the vehicle off the tire and at the tread centerline. Also be certain that the tires are properly inflated since this can affect your readings.
If you need to replace just one tire, the same holds true. The measured difference in circumference between the replacement tire and the other tires on the vehicle cannot exceed 1/4 inch.
Depending on the vehicle mileage, it might be better to replace all four tires.
If the vehicle mileage is low and the tires have been rotated and driven at the proper inflation pressures, then you may be within the allowable 1/4-inch difference in circumference.
If the difference between the new/replacement tire and the current tires is within this 1/4-nch maximum, then the tire should be compatible. If it is not, then other tires will need to be replaced to conform to the 1/4-inch rule.
Exceeding this 1/4-inch difference in tire circumference can place unnecessary wear on drivetrain components, possibly causing them to wear out prematurely.
If you need to replace just one tire, the same holds true. The measured difference in circumference between the replacement tire and the other tires on the vehicle cannot exceed 1/4 inch.
Depending on the vehicle mileage, it might be better to replace all four tires.
If the vehicle mileage is low and the tires have been rotated and driven at the proper inflation pressures, then you may be within the allowable 1/4-inch difference in circumference.
If the difference between the new/replacement tire and the current tires is within this 1/4-nch maximum, then the tire should be compatible. If it is not, then other tires will need to be replaced to conform to the 1/4-inch rule.
Exceeding this 1/4-inch difference in tire circumference can place unnecessary wear on drivetrain components, possibly causing them to wear out prematurely.
take care
Last edited by greenscooby; Jun 25, 2004 at 07:51 AM.
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The 1/4 in thing doesn't really have to do with voiding the warranty. It has to do with the awd transmissions. If the tires (any of the four) are more than 1/4 in, it is best to replace the ones that would bring the tires within 1/4 in of all of the others to best reduce the amount of miss alignment within the tranny.
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1/4 inch rule is true
I went through the same experience last year.
If you go through the Subaru website or your manual they talk about the ¼ inch rule. I bought a used Legacy a year ago with 20k miles. The dealer noticed a nail in a tire and did me a favor by replacing one rear tire.
A few months later I rotated the tires. Now the new tire was in the front. Since we broke the ¼ inch rule, I had a nasty vibration in the front end. The car pulled heavily to one side. I did everything to correct it (balancing, checked the wheel alignment, front-end, etc.) The different size tire will wreak havoc on your AWD. Then I read about the ¼ rule. I un-rotated the tires and decided to run the tires into the ground. The RE92 is a terrible tire anyway. All my problems went away with the new tire in the rear. After I ran them into the ground, I replace them with four Falken Ziex tires. Best decision I ever made.
Some people say if you have to replace a tire and don’t want to replace all four, at least replace two of them.
If you go through the Subaru website or your manual they talk about the ¼ inch rule. I bought a used Legacy a year ago with 20k miles. The dealer noticed a nail in a tire and did me a favor by replacing one rear tire.
A few months later I rotated the tires. Now the new tire was in the front. Since we broke the ¼ inch rule, I had a nasty vibration in the front end. The car pulled heavily to one side. I did everything to correct it (balancing, checked the wheel alignment, front-end, etc.) The different size tire will wreak havoc on your AWD. Then I read about the ¼ rule. I un-rotated the tires and decided to run the tires into the ground. The RE92 is a terrible tire anyway. All my problems went away with the new tire in the rear. After I ran them into the ground, I replace them with four Falken Ziex tires. Best decision I ever made.
Some people say if you have to replace a tire and don’t want to replace all four, at least replace two of them.
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spare tire ok for short distances?
My 2004 STi is my first AWD vehicle & after reading the owner's manual - & these posts - I'm a little concerned about the size of the spare tire. I haven't measured it but just by looking at it you can tell it is clearly significantly smaller than the stock tires. Since the manufacturer supplied the spare, I would think that it must be OK to use, at least for short distances, but of course you never can tell what the manufacturer is thinking.
We're planning to take the STi on a 2-week road trip, so obviously this is a big concern for us right now. Of course we don't want to damage the differential but we also don't want to get a flat on the interstate & be stuck in the middle of nowhere b/c we couldn't use the spare. Does anyone have any additional comments concerning this topic specifically related to the manufacturer's spare? Would it be safe to use for, say, 10 miles?
Also, our STi is only about 4 months old, & so far it has been terrific. But if anyone has any comments or precautions about taking it on a 2-week road trip, they would be much appreciated too.
We're planning to take the STi on a 2-week road trip, so obviously this is a big concern for us right now. Of course we don't want to damage the differential but we also don't want to get a flat on the interstate & be stuck in the middle of nowhere b/c we couldn't use the spare. Does anyone have any additional comments concerning this topic specifically related to the manufacturer's spare? Would it be safe to use for, say, 10 miles?
Also, our STi is only about 4 months old, & so far it has been terrific. But if anyone has any comments or precautions about taking it on a 2-week road trip, they would be much appreciated too.
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Originally Posted by LuvmySTi & GTS
My 2004 STi is my first AWD vehicle & after reading the owner's manual - & these posts - I'm a little concerned about the size of the spare tire. I haven't measured it but just by looking at it you can tell it is clearly significantly smaller than the stock tires. Since the manufacturer supplied the spare, I would think that it must be OK to use, at least for short distances, but of course you never can tell what the manufacturer is thinking.
We're planning to take the STi on a 2-week road trip, so obviously this is a big concern for us right now. Of course we don't want to damage the differential but we also don't want to get a flat on the interstate & be stuck in the middle of nowhere b/c we couldn't use the spare. Does anyone have any additional comments concerning this topic specifically related to the manufacturer's spare? Would it be safe to use for, say, 10 miles?
Also, our STi is only about 4 months old, & so far it has been terrific. But if anyone has any comments or precautions about taking it on a 2-week road trip, they would be much appreciated too.
We're planning to take the STi on a 2-week road trip, so obviously this is a big concern for us right now. Of course we don't want to damage the differential but we also don't want to get a flat on the interstate & be stuck in the middle of nowhere b/c we couldn't use the spare. Does anyone have any additional comments concerning this topic specifically related to the manufacturer's spare? Would it be safe to use for, say, 10 miles?
Also, our STi is only about 4 months old, & so far it has been terrific. But if anyone has any comments or precautions about taking it on a 2-week road trip, they would be much appreciated too.