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Have to replace all 4 tires?
Posted by: pdq
Date: September 26, 2022 05:35PM
A friend of ours got a nail in her tire, and long story short, she ended up with four new tires, even though they were only 8 months old.

It's an all-wheel-drive car. I told my wife it might be possible they could just patch the one tire, but apparently not.

I kinda understand they like to replace modern radial tires in pairs, but throwing three otherwise perfect 8 month old tires away seems kinda extreme.

How much of this is well-grounded, and how much is nonsense? What say you?
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Re: Have to replace all 4 tires?
Posted by: hal
Date: September 26, 2022 05:38PM
speaking with no expertise at all, that's insane.
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Re: Have to replace all 4 tires?
Posted by: gadje
Date: September 26, 2022 05:38PM
was this at Costco?

Costco is well known for their very strict policy of not even touching a tire with any potential side wall damage.

I think she could have gotten by with 1 or maybe 2 new tires, not all 4. But it's too late now.



Edited 1 time(s). Last edit at 09/26/2022 05:38PM by gadje.
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Re: Have to replace all 4 tires?
Posted by: mrbigstuff
Date: September 26, 2022 05:39PM
Unless she put something like 20k miles on those tires, nope. But really, it's all about the tread depth. A few 32nds difference is fine, more than that you can probably replace the two front or rear, and more than a certain amount, all four.
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Re: Have to replace all 4 tires?
Posted by: Gareth
Date: September 26, 2022 05:41PM
Some of it is going to depend on where the puncture is, and some of it is going to depend on what AWD system it is, and some of it will depend on the tread depth of the tires vs a new tire.

So, it's all just speculation unless you can provide the above details.
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Re: Have to replace all 4 tires?
Posted by: C(-)ris
Date: September 26, 2022 06:04PM
It depends. Age has nothing to do with it. I had 18k miles on the factory tires on my Forster in 8 months and they were hitting the wear bars and definitely would not be patchable or be able to get away with replacing just one. Would have to know how much tread depth they started with new and what was left to make that call.



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Re: Have to replace all 4 tires?
Posted by: DinerDave
Date: September 26, 2022 06:20PM
I overheard warnings said to an AWD vehicle owner to replace all 4 at the same time.
Sequential AWD like Subaru's have all 4 connected.
I kind of understand the explanation I heard, but 8 month old tires seem extreme to me.
Thinking the tread wear would bo so minimal that it wouldn't matter.
Disclaimer...
I'm not an expert, nor did I stay at a Holiday Inn Express last night.

Dave



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Re: Have to replace all 4 tires?
Posted by: davester
Date: September 26, 2022 06:30PM
Replacing all four 8-month old tires?...that's ridiculous and she was cheated. If there was excessive wear it might make sense to have the new tire shaved to match, but that would be vastly cheaper than buying a new set of tires.



"In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion." (1987) -- Carl Sagan
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Re: Have to replace all 4 tires?
Posted by: Gareth
Date: September 26, 2022 06:40PM
Quote
DinerDave
Sequential AWD like Subaru's have all 4 connected.

Yup, the idea is that since power is sent to all 4 wheels all the time, and often there are various devices which will limit the difference in how quickly one tire can spin compared to the other.

Thus, if the tires are mis-matched in size, one is going to want to spin faster than the other when you're driving in a straight line, which is going to put strain on the AWD components.

A "simpler" AWD system that has open differentials and might use braking to control the wheel spin might be ok with mis-matched tire systems.

And this is why your standard run of the mill FWD or RWD drive vehicle is "ok" with different tire sizes, because they are going to have open differentials (and obviously nothing connecting the wheels on the non-driving axle), so the wheels can spin at wildly different speeds (i.e. one can get all the power and be spinning, and the other not spinning at all), and that's how you can get stuck in such a system.

Apparently, from a little browsing, Subaru recommends no more than a 1/4" difference in the CIRCUMFERENCE of the tires. So, you'd have to do the math on what that translates to in terms of tread depth for the tire size being used, but apparently, for the common sizes, it might mean that only 1/32" to 3/64" in tread depth difference is ok.
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Re: Have to replace all 4 tires?
Posted by: wurm
Date: September 26, 2022 07:07PM
Yeah, it stinks. We've had Subarus in the past and we know going in that's a strong possibility. The hope is that there are enough miles on them that one can justify getting four new ones when trouble happens.

More often than not, these are time-is-of-the-essence decisions, but you may get lucky and find a single tire of the exact same make and model and similar mileage and age on Craigslist, eBay, etc.

A couple of examples of places I've had success:

ntireshop
Champtires
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Re: Have to replace all 4 tires?
Posted by: Michael
Date: September 26, 2022 07:50PM
We were driving to Birmingham to drop off the cat before we flew to the Baltic a month ago. Twenty miles outside of Birmingham a tire just failed on our 2020 AWD CRV with 24,000 miles. We couldn't find the same brand of tire on that Sunday afternoon so we went to Costco. The tire manager was the one who told me the tire just failed--there was no puncture or tear. He said something about a belt delaminating. He would replace a pair of them but not just the failed one. He didn't require that we replace all 4, however. He was willing for us to have whatever the original brand was and a new pair of Michelin's on the front and the back. I went ahead and had him replace them all because they were about 2/3 worn to the bars and I just didn't want to have different tires on front and back. It was rather expensive because the ones that had a nice discount weren't in stock. But, we got to the ATL airport the next day.
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Re: Have to replace all 4 tires?
Posted by: Cary
Date: September 26, 2022 08:40PM
It has nothing to do with tread depth.

AWD systems need to have (at a minimum) each axle (both tires) with equal outside diameter, and no more than 1/2 inch difference between front and rear, and best case, all 4 tires with equal outside diameter.

Greater variation can cause significant damage to the transfer case.

This situation is exacerbated by the fact that tires sizes, while nominally identical (i.e. 235/75R17), can have significant actual differences in overall diameter.

Costco (and other tire retailers) does not want potential responsiblity for claims due to tire mismatch.



Edited 1 time(s). Last edit at 09/26/2022 08:43PM by Cary.
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Re: Have to replace all 4 tires?
Posted by: davester
Date: September 26, 2022 09:21PM
Quote
Cary
This situation is exacerbated by the fact that tires sizes, while nominally identical (i.e. 235/75R17), can have significant actual differences in overall diameter.

Costco (and other tire retailers) does not want potential responsiblity for claims due to tire mismatch.

Which is why many of them default to replacing all four rather than doing the actual work of assessing the situation, measuring the tires, offering tire shaving, etc. This is a (widespread) scam.



"In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion." (1987) -- Carl Sagan
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Re: Have to replace all 4 tires?
Posted by: MikeF
Date: September 26, 2022 09:36PM
They should have gone after the spare as well...
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Re: Have to replace all 4 tires?
Posted by: Markintosh
Date: September 26, 2022 09:48PM
This used to be a big thing until places like Les Schwab figured out that offering tire shaving to make a new tire match older tires made happy customers.



“Live your life, love your life, don’t regret…live, learn and move forward positively.” – CR Johnson
Loving life in Lake Tahoe, CA
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Re: Have to replace all 4 tires?
Posted by: cbelt3
Date: September 26, 2022 10:03PM
Quote
MikeF
They should have gone after the spare as well...
What is this spare you speak of ?
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Re: Have to replace all 4 tires?
Posted by: davester
Date: September 27, 2022 09:27AM
More information on this issue: [www.tirerack.com]



"In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion." (1987) -- Carl Sagan
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Re: Have to replace all 4 tires?
Posted by: Acer
Date: September 27, 2022 09:48AM
So, who does tire shaving? Just certain shops?

"Discount Tire does not offer tire shaving. We do not endorse it as it may void the warranty and coverage of your Certificates purchased with your tires." (This in regard to performance tires, but they don't appear to offer it at all.)



Edited 2 time(s). Last edit at 09/27/2022 09:52AM by Acer.
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Re: Have to replace all 4 tires?
Posted by: NewtonMP2100
Date: September 27, 2022 10:33AM
….that’s….tiring….



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I reject your reality and substitute my own!
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Re: Have to replace all 4 tires?
Posted by: davester
Date: September 27, 2022 10:55AM
Quote
Acer
So, who does tire shaving? Just certain shops?

Yep. Look around for shops that cater to racers as well as regular folks. Shaving is a common practice for race cars because it increases traction by eliminating tread squirm.

BTW, here's another tire shaving advice article: [www.consumerreports.org]



"In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion." (1987) -- Carl Sagan



Edited 2 time(s). Last edit at 09/27/2022 10:57AM by davester.
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Re: Have to replace all 4 tires?
Posted by: pdq
Date: September 27, 2022 02:06PM
Quote
davester
Quote
Acer
So, who does tire shaving? Just certain shops?

Yep. Look around for shops that cater to racers as well as regular folks. Shaving is a common practice for race cars because it increases traction by eliminating tread squirm.

BTW, here's another tire shaving advice article: [www.consumerreports.org]

That's a great article- directly addressing the topic, and from a respectable organization with no particular dog in this fight. Thanks!
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