Tire Question

[Doc1647545523]

A friend has a 2006 Audi A6 (AWD) and had a blowout on one tire. He went to a discount tire store, and they told him that he needed to replace the full set. His remaining 3 tires are Continentals (I don't know the specs) and they measured 6/32" tread depth all around. The tire salesman said that the new tire would have 10/32" tread depth, and that it would be unsafe to have one tire (regardless if mounted to front or back) with that much difference in tread depth. The tires have no cupping or uneven wear and are 18 months old with about 22k miles.

 

Unsafe if he installs just one new tire? Poor handling? If he adds just one new tire, should it be to the front or rear?

 

Your opinions will be helpful.

[Mr. Jones]

IIRC Audi says that the tires must be within 4/32nd of each other.

I'd have him read his manual, if it's the same brand/size of tire, i'd say it would probably be just fine.

[BoostedAce]

Its not good on the cars drivetrain.

[Mr. Jones]

Its not good on the cars drivetrain.

 

It isn't if kept within specs.

[Evolved8]

A friend has a 2006 Audi A6 (AWD) and had a blowout on one tire. He went to a discount tire store, and they told him that he needed to replace the full set. His remaining 3 tires are Continentals (I don't know the specs) and they measured 6/32" tread depth all around. The tire salesman said that the new tire would have 10/32" tread depth, and that it would be unsafe to have one tire (regardless if mounted to front or back) with that much difference in tread depth. The tires have no cupping or uneven wear and are 18 months old with about 22k miles.

 

Unsafe if he installs just one new tire? Poor handling? If he adds just one new tire, should it be to the front or rear?

 

Your opinions will be helpful.

 

Doc,

 

It's sounding like b.s. The main thing you dont want to do on AWD systems is mismatch tires meaning brand front to rear or the other way around. But the most inportant thing is tire size. You do not want to mix tire sizes as it will screw up the AWD system. If his tires are at 6/32'nds a new matching tire would be the proper thing to do. If they were at 3/32nds or worse I would say do the set. Its not going to hurt a thing and he will notice NO changes in traction. He will just have 3 tires measuring at 3/32nds when he goes to replace and one at probabally 5/32nds. No worries there sounds like they are trying to get some GROSS. Hope this helps

[Evolved8]

Its not good on the cars drivetrain.

 

How so...... What data do you have to back this up?

[TurboRust]

they preach2/32nds indifference at ntb also, Doc i'm pretty sure he can buy one on tire rack and have it shaved for this reason.

 

per tire rack

This necessitates that four-wheel drive and all-wheel drive vehicles use tires that are very closely matched. This is because different diameter tires roll a different number of times each mile as a result of the variations in their circumferences. Tire diameter variations can be caused by accidentally using different sized tires, tires with different tread designs, tires made by different manufacturers, different inflation pressures or even tires worn to different tread depths.

As an example of different tire diameters resulting from tires worn to different tread depths, we'll compare two 225/45R17-sized tires, a new tire with its original tread depth of 10/32-inch and a second tire worn to 8/32-inch of remaining tread depth. The new 225/45R17-sized tire has a calculated diameter of 24.97", a circumference of 78.44" and will roll 835 times each mile. The same tire worn to 8/32-inch of remaining tread depth is calculated to be 1/8" shorter with a diameter of 24.84", have a circumference of 78.04" and will roll 839 times per mile. While the difference of 1/8" in overall diameter doesn't seem excessive, the resulting 4 revolutions per mile difference can place a continuous strain on the tires and vehicle's driveline. Obviously, the greater the difference in the tires' circumferences, the greater the resulting strain.

 

 

 

While the cost of our street tire shaving service will range from $25 to $35 for each tire, it is significantly less than the cost of unnecessarily replacing the remaining two or three good tires with lots of mileage still available from them.

Here are recommendations from some of the manufactures that the Tire Rack currently serves for matching the tires used on their four-wheel drive and all-wheel drive vehicles. Additional recommendations from other Original Equipment Vehicle Manufacturers is pending.

AudiAs published in their vehicle owner's manual, "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth.PorscheCayenne within 30% of the other tire on the same axle's remaining treadwear.SubaruWithin 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth.

[Not Brian]

Brand new tire = larger circumference, which means it spins slower than the other three. The AWD system will see those other three wheels moving faster and assume they're always slipping. Fractions of an inch, but over tens of thousands of miles it will exhaust the differentials and other shit.

 

I could be wrong but that's info I recall hearing back when I had a Subaru.

 

edit: yeah, what Derek said.

[AJ]

How so...... What data do you have to back this up?

 

different size tire all the way around on AWD can burn up the transfer case and/or the front or rear diff. front wheel drive with a mini spare can burn up a transmission which is why you are supposed to mount the spare on a non drive wheel. rear wheel drive with two different sizes side to side can burn up a limited slip, or a transfer case if the front tires are smaller/bigger and you put it 4WD. it has to do with the RPM of the tires (revolutions per mile) and some cars are very sensitive to mismatched tire sizes.

[BoostedAce]

Thank god derek typed it.

[6 Speed S4]

Funny thing is Doc, the guy you posted about is my dad! Its a small world! I shared the info with him. He is going to leave his full sized spare which is at 4/32 and all the others are at 6/32. Wait until they wear out then get a full set.

[Cordell]

Have to agree with AJ and Derek, with it being AWD there is some risk of damage even though 4/32nds isn't much.

 

Of course if the tire is 8/32nds taller, it adds about 25/32nds or .79inch to the cicumfrence (8/32nds*pi). Kind of a toss up in my opinion, if it was a GM car I'd say do it.

[IVRINGS]

Funny thing is Doc, the guy you posted about is my dad! Its a small world! I shared the info with him. He is going to leave his full sized spare which is at 4/32 and all the others are at 6/32. Wait until they wear out then get a full set.

This sounds like the best idea if he wants to get the most out of the others, but is the full sized spare same tread and size? If I was selling your dad tires I would of told him to buy a new set of tires myself. I myself don't take my tires down to 4/32 even in the summer, but I'm a wheel whore and have extra sets.

[BoostedAce]

Have to agree with AJ and Derek, with it being AWD there is some risk of damage even though 4/32nds isn't much.

 

Of course if the tire is 8/32nds taller, it adds about 25/32nds or .79inch to the cicumfrence (8/32nds*pi). Kind of a toss up in my opinion, if it was a GM car I'd say do it.

 

No credit for the "emo" kid you make me cry.

[6 Speed S4]

This sounds like the best idea if he wants to get the most out of the others, but is the full sized spare same tread and size? If I was selling your dad tires I would of told him to buy a new set of tires myself. I myself don't take my tires down to 4/32 even in the summer, but I'm a wheel whore and have extra sets.

 

The full size spare has the exact same tire and size as all the other wheels. He is one of those people who likes to get his money worth on anything haha

[Cordell]

No credit for the "emo" kid you make me cry.

 

You need some love do you?

 

Get a dog

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fag

[BoostedAce]

I need a million dollars not another dog. Thanks

 

[EDIT] I need more days off. I take that back.

[IVRINGS]

The full size spare has the exact same tire and size as all the other wheels. He is one of those people who likes to get his money worth on anything haha

It's no problem. I can see replacing tires that have 60% tread to be hard, but to me I only see another 1/4 left I would still use since I replace more then others.

[AJ]

Have to agree with AJ and Derek, with it being AWD there is some risk of damage even though 4/32nds isn't much.

 

Of course if the tire is 8/32nds taller, it adds about 25/32nds or .79inch to the cicumfrence (8/32nds*pi). Kind of a toss up in my opinion, if it was a GM car I'd say do it.

 

can maybe, makes funny noise in an AWD equinox lol.

[Cordell]

I need a million dollars not another dog. Thanks

 

[EDIT] I need more days off. I take that back.

 

Eh you didn't even make a point just a basic statement, and I got no love for you?

 

You shouldn't take CR so seriously, then maybe when you see me out this summer you won't be afraid to come say hi.

[BoostedAce]

Really don't take it seriously anymore, I did when I first joined. Don't really know people and there faces on here besides a handful.

[Doc1647545523]

Thanks to everyone who posted. I learned a lot. I had always thought about the problems being traction mis-matches and had never considered the drivetrain wear because of the slight differences in diameter. I guess I was thinking that the slight differences in tire pressures (in the real world) and differences of tire deformities due to load (front tires often being pushed down more than the rear) would have accounted for more diameter differences than tread height would have.

 

I guess my thinking is stuck in the 1960's.

 

Special thanks to Derek for taking the time to explain it correctly and post all that text. I'd actually recommended you to Joe's pop when he first asked me about it.

 

Joe, what can I say ....... I won't tell your Dad about your late-night, ricer-taunting exploits if you don't tell him about mine. (I don't think he'd believe you anyway.)

[6 Speed S4]

Thanks to everyone who posted. I learned a lot. I had always thought about the problems being traction mis-matches and had never considered the drivetrain wear because of the slight differences in diameter. I guess I was thinking that the slight differences in tire pressures (in the real world) and differences of tire deformities due to load (front tires often being pushed down more than the rear) would have accounted for more diameter differences than tread height would have.

 

I guess my thinking is stuck in the 1960's.

 

Special thanks to Derek for taking the time to explain it correctly and post all that text. I'd actually recommended you to Joe's pop when he first asked me about it.

 

Joe, what can I say ....... I won't tell your Dad about your late-night, ricer-taunting exploits if you don't tell him about mine. (I don't think he'd believe you anyway.)

 

 

 

haha, I just think its funny your working with my dad. Maybe you can teach him cool stuff about cars and convince him to buy a project car, or do some bolt-ons to the Audi