Sand down tires??

[MarcusMaximus]

My friend has a AWD vehicle (Subaru Ascent). She is telling me that since she is replacing one tire, that Subari told her they have to sand down the new tire so that they match all the other tires. They say it's a 4WD thing. Is this true and is this something we would need to do on our Broncos?

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[peta8368]

It is true to some extend. I have seen that in the Audi manual before. The awd system typically have tolerance in rolling diameter (some only across the same axle, some even between axles, the manual should have more info). I would say replace 2 tires if the vehicle only requires matching on the same axle, and then start rotating the 3 once the 2 new ones are worn down to about the same level.

Peter

 

[Rednek]

Thus why putting the spare in rotation will benefit as it will be worn same as others.

 

[Brongo]

Thus why putting the spare in rotation will benefit as it will be worn same as others.

I’m guessing the spare on a Subaru is a temp donut spare.

 

[Werkedperformance]

It's called tire shaving, and it's real and it's the right way. The differential is designed to apply power evenly between wheels. It also allows the difference in speeds between wheels when turning. If your tires are different sizes the differential is always doing work... Like you are in a constant turn. If the difference size is great enough the center differential will also be under load. This why we want 4 equal sized tires on 4 or all wheel drive cars or trucks

 

[jjack50]

My friend has a 4WD vehicle (Subari Ascent). She is telling me that since she is replacing one tire, that Subari told her they have to sand down the new tire so that they match all the other tires. They say it's a 4WD thing. Is this true and is this something we would need to do on our Broncos?

Its an issue related to the AWD system Subaru uses. Sanding one down is better than having to replace all 4 tires due to needing 1 new tire. Manually controlled 4WD has greater tolerance in tire diameter variance. But generally, driven tires should all be approximately the same diameter if you want a vehicle’s dynamics to work right.

 

[MarcusMaximus]

Thanks everyone. Appreciate the answers. Honestly didn't know it was a thing. At first, sounded like total BS to me from the service center at some Subaru...

 

[rtaylor]

My friend has a 4WD vehicle (Subari Ascent). She is telling me that since she is replacing one tire, that Subari told her they have to sand down the new tire so that they match all the other tires. They say it's a 4WD thing. Is this true and is this something we would need to do on our Broncos?

single used tires with wear measurement available on ebay and elsewhere for this purpose...

 

[BroncoKong Jr.]

Captain Pedant here, at your service. No Subarus have 4WD; they have AWD.

 

[MaverickMan]

Yep underbuilt Japanese vehicles work great and reliable. But dont overload em, fiddle with, abuse them in any way. Sorry Im currently dealing with the dumb unobtainium toyota 4 speed in my comanche slipping.

This tire shaving stuff I would imagine would be more important in a high speed vehicle. But the amount of turns we go through and the fact that straight roads arent really straight they just look like it. Should make this not much of an issue especially if you adjust tire pressure a couple pounds. Not 10 but 4 or 5 psi. One could get out a tape and check circumference and adjust accordingly.

I would think any company with any sense would build stuff robust enough to hand a little extra spinning of the side gears in the diff.

 

[jsharpe]

My friend has a 4WD vehicle (Subaru Ascent). She is telling me that since she is replacing one tire, that Subari told her they have to sand down the new tire so that they match all the other tires. They say it's a 4WD thing. Is this true and is this something we would need to do on our Broncos?

Before I paid full price and then shaved a new tire I personally would look around to see if I cold find the same model used with the matching amount of tread. When my daughter's Volvo had tire damaged I was amazed at how easy it was to find a perfect match and how stupid cheap it was, even including shipping.. There are a bunch of reputable online companies that deal in used tires.

 

[Dillhole]

Thus why putting the spare in rotation will benefit as it will be worn same as others.

Say it louder for the naysayers in the back!

 

[North7]

The dealer had to do it to my wife's Subaru Forester replacement tire when the original had sidewall damage.

 

[jjack50]

Yep underbuilt Japanese vehicles work great and reliable. But dont overload em, fiddle with, abuse them in any way. Sorry Im currently dealing with the dumb unobtainium toyota 4 speed in my comanche slipping.

This tire shaving stuff I would imagine would be more important in a high speed vehicle. But the amount of turns we go through and the fact that straight roads arent really straight they just look like it. Should make this not much of an issue especially if you adjust tire pressure a couple pounds. Not 10 but 4 or 5 psi. One could get out a tape and check circumference and adjust accordingly.

I would think any company with any sense would build stuff robust enough to hand a little extra spinning of the side gears in the diff.

With different diameter driving tires the drive system is loaded as if it were in a steady state turn when going straight ahead. This will cause premature tire wear and messes with other parts of the drivetrain and any computers that may be involved.

 

[DeltaBravo]

strange coming to a bronco forum asking about subaru advice...

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