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Old 05-16-2013, 07:19 AM   #1 (permalink)
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Default All tires the same?

I borrowed the quote below from another thread.

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Originally Posted by 1 Lucky Texan View Post
make sure the tires are all the same brand and wear level. Do tight circles on dry pavement at idle to check for torque bind.
I bought a 2006 OB a few weeks ago with different brand tires. Mastercraft on the rear and Yokohama on the front. All are 225/55/17 and I measured around each tire to check that they are within 1/4" of each other and they are.

Do I have a problem?
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Old 05-16-2013, 08:15 AM   #2 (permalink)
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The biggest problem is the fact that different brands , or even different models within the same brand , will have different traction characteristics . This could definitely lead to AWD issues . Would tend to be more pronounced as you start to rotate the tires for even wear . If you do the rotation correctly , you will end up with different brands on the same axle . This is " not good ".
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Old 05-16-2013, 08:44 AM   #3 (permalink)
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Quote:
Originally Posted by 2BluSubaru View Post
I borrowed the quote below from another thread.



I bought a 2006 OB a few weeks ago with different brand tires. Mastercraft on the rear and Yokohama on the front. All are 225/55/17 and I measured around each tire to check that they are within 1/4" of each other and they are.

Do I have a problem?
I'd say you are 'less likely' to have a problem than most people with mixed tires. Good job measuring the circumference.

for a little more confidence, I guess you could find a long, straight shot in a big parking lot or little-used service road, mark the bottom of each tire, then drive straight forward as far as possible. Stop and see if the marks are all 'clocked' at the same position. The AWD system is just happiest when the tires all roll the same distance. If there is a 'slight' difference, it's hard to predict if that takes off 500 miles or 50,000 miles of service life. You might be OK.
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Old 05-16-2013, 02:25 PM   #4 (permalink)
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Originally Posted by MrFixit1 View Post
The biggest problem is the fact that different brands , or even different models within the same brand , will have different traction characteristics . This could definitely lead to AWD issues . Would tend to be more pronounced as you start to rotate the tires for even wear . If you do the rotation correctly , you will end up with different brands on the same axle . This is " not good ".

IIRC, Subaru recommends straight F-R rotation. For non-directional tires you can do a diagonal swap as well, but both front axle tires should be moving rearward and both rear axle should be moving forward. You should not be mixing front and back tires.

The only time this would happen is if you do a "five-tire" rotation, where you rotate the spare into and out of the mix. This is only done on vehicles with a full-size spare. This is NOT factory recommended on Subarus.

For reference, there are some handy-dandy diagrams here:
Tire Tech Information - Tire Rotation Instructions

The only time you *might* do a 5-tire rotation on a Subaru, is if you have a special setup and carry a full-size spare around on your roof rack. In that case, you would buy 5 of the exact same tire, and rotate VERY frequently in order to keep all the tire circumferences within limits of each other. Again, this is NOT the factory recommended way to do things, it is only a possibility if you have a special setup (for offroading or adventuring, for example). Also, you MUST use the same brand and model of tire, and start with them all brand-new in order to ensure even wear characteristics.
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Old 05-16-2013, 04:23 PM   #5 (permalink)
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Thanks for the replies.

I understand they would have different traction but they are half worn out and will be replaced before winter. I doubt I will even need to rotate them since I don't drive that much these days. If we go anywhere far we take the wife's Legacy.
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Old 05-16-2013, 05:45 PM   #6 (permalink)
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Quote:
Originally Posted by 2BluSubaru View Post
. . . .
I bought a 2006 OB a few weeks ago with different brand tires. Mastercraft on the rear and Yokohama on the front. All are 225/55/17 and I measured around each tire to check that they are within 1/4" of each other and they are. . Do I have a problem?
The idea of measuring the circumference applies to tires that are the same make/model/size. It's less applicable to different models, and certainly different makes. This is due to different ways the tire will react in actual use, e.g. because of different sidewall or tread stiffness based on how the tires are made.

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Originally Posted by 1 Lucky Texan View Post
. . . . for a little more confidence, I guess you could find a long, straight shot in a big parking lot or little-used service road, mark the bottom of each tire, then drive straight forward as far as possible. Stop and see if the marks are all 'clocked' at the same position. The AWD system is just happiest when the tires all roll the same distance. If there is a 'slight' difference, it's hard to predict if that takes off 500 miles or 50,000 miles of service life. You might be OK.
Very good advice. This will help provide additional confidence by establishing if the slow speed rolling circumference of the four tires might be significantly different.

I'd suggest rolling the car so that one marked wheel makes exactly ten revolutions. This way, if the marks on the other tires are not at the bottom again, the distance of the mark from the bottom (in inches), divided by 10, indicates the difference in apparent rolling circumference. (A 2.5 inch difference = 1/4 inch difference in circumference.)

The rolling circumference will be different at different pressure, load (weight) and speed. But by measuring the circumference, and doing the rolling test, will provide a first approximation.

Last edited by plain OM; 05-17-2013 at 06:34 AM. Reason: clarification
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Old 05-16-2013, 07:42 PM   #7 (permalink)
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Another thought is that different tire models will wear at different rates. You don't want to mix a 30,000 miles tire with an 80,000 miles tire.
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Old 05-16-2013, 09:16 PM   #8 (permalink)
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The dealer gave me a 3 month power train warranty.

I wonder if they would rather give me tires or fix the AWD.

Just for kicks I'll ask them about the tires.

Either way I think I should get new tires, was hoping to make it until winter.
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Old 05-17-2013, 09:30 AM   #9 (permalink)
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if you can get the dealer to replace the tires do that.
all 4 the same, brand new would be best.

short of that i would have one of each brand on the front, and one of each on the rear.
this will guarantee that the average speed of the rear axles is the same as the average speed of the front axles. even if the tires wear differently this will work. when you rotate make sure to keep matching tires on diagonal corners.

but this will not work very well if you have a limited slip rear diff. i assume the 06 OB does but i do not know.

keep track of the tread wear. if they start to get out of spec, change how you rotate them. if two are wearing faster, put them on the rear and leave them there , as long as they are with in 1/4 inch.

i would get the dealer to replace the tires. two new to match (same brand, tread, size, pressure) the best ones on the car may work out if they are not too worn. most tire shops use 2/32 as the max tread wear difference.

you will not know how the tires will wear for a while. and by then the dealer probably will not want to help you out.
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Old 05-17-2013, 10:46 AM   #10 (permalink)
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Quote:
Originally Posted by 2BluSubaru View Post
The dealer gave me a 3 month power train warranty.

I wonder if they would rather give me tires or fix the AWD.

Just for kicks I'll ask them about the tires.

Either way I think I should get new tires, was hoping to make it until winter.
How much do you drive? Are you expecting to put less than 5,000 miles on before winter (when you plan to replace them anyways) since you indicated you probably wouldn't even need to rotate them before winter?

If so, I'll third what lucky texan and plain OM have suggested to just do the rolling test to make sure the tires rolling circumferences aren't significantly different (basically to measure how much the different makes of tires deflect when under load--thus potentially impacting the rolling circumference). If it passes this test and you'll be driving less than 5,000 miles, then I doubt you'd have enough tire wear to impact the circumferences before winter (of course, this is assuming that they are not soft compound winter tires--in which case you'd like the way your car handles in the summer better with some new all-seasons anyways).
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