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Old 07-15-2009, 12:12 AM   #1
pwnx0rz
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Default Is running two different treads ok?

Is it okay to run stock STI tires up front, and Fuzion HRi tires in the rear? My impression is that this is NOT okay, right?
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Old 07-15-2009, 12:48 AM   #2
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Same wheel diameter is all that matters. Tire tread & width doesnt.
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Old 07-15-2009, 08:47 AM   #3
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NOOO! It will mess with your diffs, not a good idea.

Your tires should all match so that traction on all 4 corners is the same.
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Old 07-15-2009, 10:14 AM   #4
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Originally Posted by BeatLA View Post
NOOO! It will mess with your diffs, not a good idea.

Your tires should all match so that traction on all 4 corners is the same.
AGREE!!!! this is what we tell people at my job
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Old 07-15-2009, 11:46 AM   #5
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All the Diffs care about is wheel diameter/revs per mile. (Going off of REAL measurements, not the size printed on the sidewall)

A matched set of tires is preferable, as they will wear in a consistent fashion...but Diffs can't read, so they don't care what brand the tires are.

Running tires that have the same dimensions, but different tread will not 'mess up your diffs'...the difference would be insignificant.
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Old 07-15-2009, 12:11 PM   #6
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Quote:
Originally Posted by Crawdads View Post
All the Diffs care about is wheel diameter/revs per mile. (Going off of REAL measurements, not the size printed on the sidewall)

A matched set of tires is preferable, as they will wear in a consistent fashion...but Diffs can't read, so they don't care what brand the tires are.

Running tires that have the same dimensions, but different tread will not 'mess up your diffs'...the difference would be insignificant.
Still not buying it. I know diffs can't read, but if you have 2 different sets of treads running, it's going to be working to figure out why there's better traction in the front or back 100% of the time. I think it's just not good business to run different tires on any AWD car.
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Old 07-15-2009, 12:41 PM   #7
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Still not buying it. I know diffs can't read, but if you have 2 different sets of treads running, it's going to be working to figure out why there's better traction in the front or back 100% of the time. I think it's just not good business to run different tires on any AWD car.
I don't know about your commute, but during mine, I am not constantly breaking traction.

If you are that concerned about diff wear, you should probably avoid driving your car any direction except for straight. The wheels turning different speeds while turning might cause damage.

Running mismatched compound tires might not be a good idea for a few reasons, but angering the diffs probably isn't one of them.
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Old 08-30-2009, 05:54 PM   #8
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Still not buying it. I know diffs can't read, but if you have 2 different sets of treads running, it's going to be working to figure out why there's better traction in the front or back 100% of the time. I think it's just not good business to run different tires on any AWD car.
he has a WRX not an STI, so he's only running a direct drive system... it's not like he's got the automatic that puts varying amounts of force to the different wheels

at least that's my impression...

If he had an STI with that option then it could pose a problem.
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Old 08-30-2009, 09:08 PM   #9
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he has a WRX not an STI, so he's only running a direct drive system... it's not like he's got the automatic that puts varying amounts of force to the different wheels

at least that's my impression...

If he had an STI with that option then it could pose a problem.
Old thread buddy...it just got dragged up with a new question.
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Old 08-30-2009, 11:16 PM   #10
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Old thread buddy...it just got dragged up with a new question.
oh my bad....

but yeah... this is where tire rotation comes into play... every 3-6k depending on your driving habits. I personally just do it with each oil change... That and it helps out with prolonging time between tires and such.

This is one thing I didn't really consider though when I bought my car. I did some digging shortly after I put my down payment on the car and figured out it's not all that big of a deal.
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Old 07-15-2009, 12:35 PM   #11
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Doubt that it will make any difference with the diffs, but I'll bet the front tires end up with twice the grip of the rears. Your car could really get squirelly, 'specially in wet weather! RP
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Old 07-15-2009, 12:55 PM   #12
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Originally Posted by Crawdads View Post
All the Diffs care about is wheel diameter/revs per mile. (Going off of REAL measurements, not the size printed on the sidewall)

A matched set of tires is preferable, as they will wear in a consistent fashion...but Diffs can't read, so they don't care what brand the tires are.

Running tires that have the same dimensions, but different tread will not 'mess up your diffs'...the difference would be insignificant.
Agreed; the small insignificant difference in treadwear characteristics from other manufacturers or different tread patterns will NOT cause any damage. The circumference HAS to be the same.
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Old 07-15-2009, 01:12 PM   #13
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From the TireRack website:

Four-wheel drive and all-wheel drive vehicles are equipped with additional differentials and/or viscous couplings that are designed to allow momentary differences in wheel speeds when the vehicle turns a corner or temporarily spins a tire. However, if the differentials or viscous couplings are forced to operate 100% of the time because of mismatched tires, they will experience excessive heat and unwarranted wear until they fail.

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.

This makes maintaining the vehicle manufacturer's recommended tire inflation pressures and using "matched" tires on all wheel positions necessary procedures to reduce strain on the vehicle's driveline. Using "matched" tires means all four tires are the same brand, design and tread depth. Mixing tire brands, tread designs and tread depths may cause components in the vehicle's driveline to fail.


If it were up to me, I'd not risk the expensive repair later to save money now.
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Old 07-15-2009, 01:35 PM   #14
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Quote:
Originally Posted by BeatLA View Post
From the TireRack website:

Four-wheel drive and all-wheel drive vehicles are equipped with additional differentials and/or viscous couplings that are designed to allow momentary differences in wheel speeds when the vehicle turns a corner or temporarily spins a tire. However, if the differentials or viscous couplings are forced to operate 100% of the time because of mismatched tires, they will experience excessive heat and unwarranted wear until they fail.

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.

This makes maintaining the vehicle manufacturer's recommended tire inflation pressures and using "matched" tires on all wheel positions necessary procedures to reduce strain on the vehicle's driveline. Using "matched" tires means all four tires are the same brand, design and tread depth. Mixing tire brands, tread designs and tread depths may cause components in the vehicle's driveline to fail.


If it were up to me, I'd not risk the expensive repair later to save money now.
That is called 'Covering Your Ass' which is the unofficial motto of The Tire Rack...This is the same website that will not let you shop for wheels unless you tell them the make model and year of your car.

Subaru will also tell you that you should replace tires with ones identical to the factory equipment, and that it is not recommended to replace the wheels with those of a different size.

These are statements written by lawyers, not engineers.

I'm not saying that its a good idea in this case, I certainly wouldn't run these particular tires in such a way...but not for the reason that it might cause differential damage.
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Old 07-15-2009, 01:45 PM   #15
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That is called 'Covering Your Ass'
Right! And what are they covering their 'ass' from? People mixing tire brands or sizes, having their diff fail, and causing bad publicity since the tire rack never told them what was right.
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Old 07-15-2009, 01:59 PM   #16
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Right! And what are they covering their 'ass' from? People mixing tire brands or sizes, having their diff fail, and causing bad publicity since the tire rack never told them what was right.
I have come to the conclusion that you lack the basic understanding needed to carry on a conversation on this subject. Many of the points are going straight over your head.

I hope the OP can determine the answer to his question based on what has been posted. We really don't have enough information on his situation to give him a judgment one way or another. (For all we know, the tires might be completely different sizes, etc.)

Basically, if he is planning on running this combination for any extended amount of time, I would have to say that its a bad idea, based mostly on the extreme differences in the tire compounds. I think it *may* lead to some quirky handling...depending on his driving habits and usage. Plus, the RE070s will wear much faster than the HRi all seasons...especially with the Bridgestones on the front....(This could lead to a significant enough mismatch in circumference to warrant concern for the driveline)
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Old 07-15-2009, 05:59 PM   #17
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I have come to the conclusion that you lack the basic understanding needed to carry on a conversation on this subject. Many of the points are going straight over your head.
+1 I can't believe he argued the validity of a legal disclaimer regarding this subject following... good grief.
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Old 07-15-2009, 02:37 PM   #18
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That is called 'Covering Your Ass' which is the unofficial motto of The Tire Rack...This is the same website that will not let you shop for wheels unless you tell them the make model and year of your car.
SHENANIGANS!! i've ordered from tire rack before without telling them make/model
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Old 07-15-2009, 04:55 PM   #19
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SHENANIGANS!! i've ordered from tire rack before without telling them make/model
Tires can be searched by size, but wheels must be searched by make/model.
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Old 04-20-2011, 06:14 PM   #20
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Tires can be searched by size, but wheels must be searched by make/model.
I think this is probably because they're concerned with offset more than anything.
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Old 07-15-2009, 04:39 PM   #21
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agree
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Old 07-15-2009, 05:03 PM   #22
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it says they need the same size, width, tread pattern, wear ratio and ect...

read the manual for the car.

it says it there.

for me that's written in stone.
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Old 07-15-2009, 05:21 PM   #23
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it says they need the same size, width, tread pattern, wear ratio and ect...

read the manual for the car.

it says it there.

for me that's written in stone.

The same manual also states that the brake pads and linings should be replaced with only Genuine Subaru parts.

Following directions and recommendations while allowing for common sense is the best approach.
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Old 08-22-2009, 02:28 AM   #24
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The same manual also states that the brake pads and linings should be replaced with only Genuine Subaru parts.

Following directions and recommendations while allowing for common sense is the best approach.
strong point right there..
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Old 07-16-2009, 02:07 PM   #25
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I think some of you don't understand the meaning of "differential"

Even if you have the exact same tires all around they will not wear at the same rate. More often than not the left front tire will be the most worn followed by the right front tire and then the rears. You would have to get non directional tires and rotate them every 2k miles to make it stay within spec.
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