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2023 Sport 6 Speed Crystal White Pearl
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303 Posts
Discussion Starter · #1 ·
Howdy,

I keep reading about how important it is to replace ALL FOUR TIRES if only two need to be replaced. The reason being that even a slight difference in tread wear will cause you and your loved ones to fly off a mountain and straight into the fiery furnace of hell. [Or something. I might have read it wrong]

Have you ever heard of anyone having problems with their AWD because of tire wear? Have YOU?

Do I have to sweat over this? Or can I rotate them like I normally would with any other car? [I usually have the tires rotated every time I have the oil changed]

Thanks

:unsure:
 

· Super Moderator
2020 Crosstrek Premium
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1,877 Posts
You should still rotate your tires regularly. That's not what they're saying. Follow the instructions in your user manual.

You shouldn't mix and match different size tires, even to the extreme of not just replacing one or two when you get a blowout.

It would destroy your AWD system. You'd end up needing a new transmission. There are lots of good technical explanations about how and why on here and every other Subaru forum and also on YouTube if you're interested in the details.
 

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26 Posts
Howdy,

I keep reading about how important it is to replace ALL FOUR TIRES if only two need to be replaced. The reason being that even a slight difference in tread wear will cause you and your loved ones to fly off a mountain and straight into the fiery furnace of hell. [Or something. I might have read it wrong]

Have you ever heard of anyone having problems with their AWD because of tire wear? Have YOU?

Do I have to sweat over this? Or can I rotate them like I normally would with any other car? [I usually have the tires rotated every time I have the oil changed]

Thanks

:unsure:
You're not going to fly off the road but you might end up with an expensive repair bill. Nearly all Subaru's, and other full time all wheel drive vehicles from the last decade, read the wheel speed of each wheel and make many decisions behind the scenes based on those readings. If your tires are different diameters the vehicle can be mislead into making some poor choices that can stress the drive train. You can and should rotate your tires per Subaru's guidelines. But you should not replace just 2 tires when the other 2 are significantly worn from not rotating them correctly. Likewise if one tire is damaged you should have the replacement shaved down to match the other 3 tires.
 

· Registered
2021 Magnetite Grey Crosstrek Sport
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64 Posts
Hoping for some help here. Recently had a flat in El Paso, we live 3 hrs away, very remote. The sidewall was compromised so we had to buy a new tire. Bought a brand new, different brand, (not the Geolandars that came on our 2021 Sport), but the same size as the other three. Our Crosstrek has almost exactly 30K on the clock, 95% highway miles. My concern is tread depth. Though the new tire is the exact same size as the others, will tread depth difference have a similar effect on the transmission like a different sized tire/wheel would? Really hoping I don't have to buy a new set of tires, but will if this will potentially affect the car's health and my warranty. I'm working on getting an accurate measurement of the tires. Any advice there is also helpful. Thanks!
 

· Registered
21 Sport
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2,556 Posts
Hoping for some help here. Recently had a flat in El Paso, we live 3 hrs away, very remote. The sidewall was compromised so we had to buy a new tire. Bought a brand new, different brand, (not the Geolandars that came on our 2021 Sport), but the same size as the other three. Our Crosstrek has almost exactly 30K on the clock, 95% highway miles. My concern is tread depth. Though the new tire is the exact same size as the others, will tread depth difference have a similar effect on the transmission like a different sized tire/wheel would? Really hoping I don't have to buy a new set of tires, but will if this will potentially affect the car's health and my warranty. I'm working on getting an accurate measurement of the tires. Any advice there is also helpful. Thanks!
this comes up ALL THE TIME. the answer: it depends on who you choose to listen to. my tires have almost 29k miles on them. if i needed to replace a tire i would replace all four. if i had 20k miles on them i would also replace all four

it's not worth the risk to me to squeeze out a few extra bucks
 

· Resident Curmudgeon
2020 Crosstrek Limited
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1,569 Posts
Hoping for some help here. Recently had a flat in El Paso, we live 3 hrs away, very remote. The sidewall was compromised so we had to buy a new tire. Bought a brand new, different brand, (not the Geolandars that came on our 2021 Sport), but the same size as the other three. Our Crosstrek has almost exactly 30K on the clock, 95% highway miles. My concern is tread depth. Though the new tire is the exact same size as the others, will tread depth difference have a similar effect on the transmission like a different sized tire/wheel would? Really hoping I don't have to buy a new set of tires, but will if this will potentially affect the car's health and my warranty. I'm working on getting an accurate measurement of the tires. Any advice there is also helpful. Thanks!
My concern is that one of the four is not like the others. Construction, physical size, tread depth, traction and handling WILL be different with that odd tire. You can buy one of the exact same tire (as the other three), and have the tread shaved down and 'probably' be OK; certainly better-off than with the odd tire.
The other option is to put on four new matched tires.
 

· Super Moderator
2020 Crosstrek Premium
Joined
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1,877 Posts
Hoping for some help here. Recently had a flat in El Paso, we live 3 hrs away, very remote. The sidewall was compromised so we had to buy a new tire. Bought a brand new, different brand, (not the Geolandars that came on our 2021 Sport), but the same size as the other three. Our Crosstrek has almost exactly 30K on the clock, 95% highway miles. My concern is tread depth. Though the new tire is the exact same size as the others, will tread depth difference have a similar effect on the transmission like a different sized tire/wheel would? Really hoping I don't have to buy a new set of tires, but will if this will potentially affect the car's health and my warranty. I'm working on getting an accurate measurement of the tires. Any advice there is also helpful. Thanks!
According to your user manual you need a new set of tires or you risk catastrophic damage to your drive train that would presumably not be covered by your warranty. I just replaced a set of tires with ~25k miles because one was not repairable. I think of it as one of the costs of driving a subaru.

I wouldn't risk it.
 

· Registered
2023 Sport 6 Speed Crystal White Pearl
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303 Posts
Discussion Starter · #9 ·
THEN AGAIN...

This is a head scratcher for me. I can't find even ONE story online of a Subaru AWD being destroyed let alone destroyed because of the tires. And I find it hard to believe that most Subaru owners are making sure that all four tires on their car have the same circumference. So I have to conclude that there is more wiggle room when it comes to this than the owner's manual would have us believe.

Are YOU aware of anyone's AWD being destroyed on a Subaru because of tire circumference?

[I wrote this in reply to another topic thread]
 

· Resident topic drifter
'18 and '19 Crosstrek Limiteds
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17,795 Posts
I've been on walkabout and it's good to see we're still arguing about this, LOL. All four tyres/tires should be the exact same brand and type and very close in wear (why most professional tyre shops recommend shaving a new tyre to match what's on the car). Would you rather save $100 and have to replace the CVT?
 

· Registered
2023 Sport 6 Speed Crystal White Pearl
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303 Posts
Discussion Starter · #11 ·
I've been on walkabout and it's good to see we're still arguing about this, LOL. All four tyres/tires should be the exact same brand and type and very close in wear (why most professional tyre shops recommend shaving a new tyre to match what's on the car). Would you rather save $100 and have to replace the CVT?
I will ask you directly...

Are YOU aware of anyone's AWD [or CVT for that matter] being destroyed on a Subaru because of tire circumference?
 

· Registered
2023 Sport 6 Speed Crystal White Pearl
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303 Posts
Discussion Starter · #13 ·
No, just don't want to risk that for a nominal fee. Do YOU?
I don't.
But I also don't want to feel as though I have to measure the circumference of my tires once a week!
That said...
It it strange - it is not - that neither one of us are aware of any problems resulting from tires.
And neither is anyone. Apparently. Not on this forum at least. Or elsewhere for that matter.
 

· Administrator
2021 Crosstrek Limited, Pure Red
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5,845 Posts
It’s too bad this thread got pushed into the gutter yesterday, because it poses a valid question. I think we’d all agree that tires need to be matched for handling and safety reasons, and that there’s a tipping point where a level of tire mismatch has the potential to cause damage to an AWD vehicle, but in real world terms, I haven’t seen an analysis of exactly where that tipping point is.

I think it’s reasonable to assume that Subaru’s recommendations on this are pretty conservative, but it’s also reasonable to treat this as a situation where it’s better to be safe than sorry.
 

· Resident topic drifter
'18 and '19 Crosstrek Limiteds
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17,795 Posts
This isn't only a Subaru issue, it applies to all AWD vehicles. This article explains why and indicates that besides having the exact same tires all around that they should be within 2/32" of each other, hence shaving down a replacement tire to match.

 

· Three-pedal evangelist
2020 Premium 6MT
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1,853 Posts
This isn't only a Subaru issue, it applies to all AWD vehicles. This article explains why and indicates that besides having the exact same tires all around that they should be within 2/32" of each other, hence shaving down a replacement tire to match.

This is what my local indy mechanic says as well. When I buy new tires, I buy a set of 5 and use the spare in the rotation. That way, if a tire becomes unrepairable, I still have 4 equally worn tires.

@CanadaCraig does bring up a valid point and I have yet to hear of a viscous coupler failure as a result of unmatched tires. However, as others have said, I'd rather be safe than sorry.

This does bring up another issue. The compact spare is WAAAAAY different in diameter than the difference between the same size tires with different levels of wear. The question I have is how long can you drive on your compact spare before you trash your AWD system?
 

· Resident topic drifter
'18 and '19 Crosstrek Limiteds
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17,795 Posts
This is what my local indy mechanic says as well. When I buy new tires, I buy a set of 5 and use the spare in the rotation. That way, if a tire becomes unrepairable, I still have 4 equally worn tires.

@CanadaCraig does bring up a valid point and I have yet to hear of a viscous coupler failure as a result of unmatched tires. However, as others have said, I'd rather be safe than sorry.

This does bring up another issue. The compact spare is WAAAAAY different in diameter than the difference between the same size tires with different levels of wear. The question I have is how long can you drive on your compact spare before you trash your AWD system?
Also called a get-you home spare. I'd say 20 miles max.
 

· Three-pedal evangelist
2020 Premium 6MT
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1,853 Posts
Also called a get-you home spare. I'd say 20 miles max.
Yikes! What if I'm on a long trip and it's a Sunday? I was hoping the AWD system would tolerate it at least for the life of the compact spare which is about 300 miles.

I used to carry a full size spare in my old Outback, but there just isn't enough room in this car for that and all my other junk.
 
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