mixed Tire Question

ok... i've been blowing tires left & right the last 6 mnths. NY potholes are killers..

i just bought a set of rims with Bridgestone RE92s... i have fairly new BF Goodrich Sport A/S on the car...

how bad would it be to run the RE92s on the front for a few months, and the A/S on the back?

or should I sell off the 2 good RE92s and just buy another matching A/S?

i already know the answer.. just figured i'd throw this out for opinion...

As long as the front two match and the rear two match, you're fine.

Definitely not true.

In an AWD vehicle there are specs within which the tires MUST be to keep from damaging the center differential.

In Suby's that spec is 5/32 of an inch in diameter.

They don't have to be the same type, but they should be.

O.

definitely not true.

In an awd vehicle there are specs within which the tires must be to keep from damaging the center differential.

In suby's that spec is 5/32 of an inch in diameter.

They don't have to be the same type, but they should be.

 

O.

qft

Subaru states rolling circumference (part touch road) should be within 1/4" of each other. My mechanic(20yr+ Master Subaru tech) states 1/2" okay. Above 1/2" is broken transmission or drivetrain compenents.

So basically measure the distance around the tire down the center line, and make sure it meets that criteria.

The tread depth is meaningless unless its the same make/model of tire. 215/45/17 does not mean the same unless make/model is the same.

Subaru states rolling circumference (part touch road) should be within 1/4" of each other. My mechanic(20yr+ Master Subaru tech) states 1/2" okay. Above 1/2" is broken transmission or drivetrain compenents.

 

So basically measure the distance around the tire down the center line, and make sure it meets that criteria.

 

The tread depth is meaningless unless its the same make/model of tire. 215/45/17 does not mean the same unless make/model is the same.

On one hand, yes, rolling circumference is what matters. You are also correct that different brands and models of tires tend to be slightly different even when they are labelled as the same size.

You are wrong, however, that measuring across the center line gives you a proper reference for this measurement. You need to find the circumference (distance around), not the diameter (distance across).

The simple calculation is that Circumference = pi * Diameter

Rolling circumference is actually different from the standard circumference because it can be altered by certain variables that change the way the tire distorts when it is actually rolling. For the range of variation you are talking about with respect to the tires here it probably isn't critical, but you should be aware that even if you do a simple circumference calculation and things look OK, you could conceivably be outside the acceptable variance for the drivetrain.

Oops. Meant to say circumference.

O.

I had this very problem a few years ago when I ruined a Pirelli P Zero Nero A/S...I got a new one and check the circumference to compare it to my other 3 that had about 10,000 Km on them...Shocking!! The new one was actually smaller circumference that the used ones ...BE CAREFUL!!

I have found that the best way to accurately measure the "Rolling circumference" is make sure the pressures are the same them find a nice clean smooth concrete floor...Like my garage;) ....Get a friend with a nice fine tip Sharpie marker to draw a line across the tread (Use a ruler or straight edge) then drive the car forward...the Sharpie line transfers to the cement and "Presto"...you have the true "Rolling circumference" right there on the ground to measure....That would be the distance between the 2 Sharpie lines on the floor.....Repeat for each tire.....Hell of a lot easier than trying to stretch a tape around a mounted tire/rim.

I had this very problem a few years ago when I ruined a Pirelli P Zero Nero A/S...I got a new one and check the circumference to compare it to my other 3 that had about 10,000 Km on them...Shocking!! The new one was actually smaller circumference that the used ones ...BE CAREFUL!!

I have found that the best way to accurately measure the "Rolling circumference" is make sure the pressures are the same them find a nice clean smooth concrete floor...Like my garage;) ....Get a friend with a nice fine tip Sharpie marker to draw a line across the tread (Use a ruler or straight edge) then drive the car forward...the Sharpie line transfers to the cement and "Presto"...you have the true "Rolling circumference" right there on the ground to measure....That would be the distance between the 2 Sharpie lines on the floor.....Repeat for each tire.....Hell of a lot easier than trying to stretch a tape around a mounted tire/rim.

I thought I was the only one to ever get a new tire that ended up being smaller than the rest of my used tires....

My new micheline pilot sport a/s tire with 10/32 of tread was 1/8" smaller circumference than my tires with 9/32 of tread on them. Made no sense to me.

I personally think it's alot easier to measure the diamater and use simple geometry to find the circumference....

To the OP. Check out you NY state DOT website. You might be able to get reimbursed for the damages caused if you have proof (pictures).

I dented a rim and blew a 2 month old tire a couple years back (2/09) total cost was approx $480 for a new rim and tire. There were two HUGE potholes that were unavoidable. I took pics and found the procedure for WV and filed a claim. I had to go to a hearing because I didn't file an insurance claim, but once I showed proof I was insured and the damages didnt' exceed my deductible they agreed to pay.... I just got the liability waiver last week so I should get my check in the next couple of months.... 2.5 years after the incident, gotta love speedy gov't

I thought I was the only one to ever get a new tire that ended up being smaller than the rest of my used tires....

 

My new micheline pilot sport a/s tire with 10/32 of tread was 1/8" smaller circumference than my tires with 9/32 of tread on them. Made no sense to me.

I have a friend in the tire business......been a tire tech for approx 40 years now.......He says the chance of getting 2 tires of the same brand and model/size that are "Exactly the same dimensions are about the same as the odds of winning the lottery..everything in the world that is mass manufactured has a "+ or -" allowance built in........No way Michelin or any other tire manufacturer has only one mold for each model........so you get little variances:spin:

I just had to replace a tranny in a car that was driven with unmatched tires. I'm tempted to leave the rear drive shaft section out until I can verify I have a matched set of rolling circumference.

Seems like I should be OK if I do that.