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Omni Extaris
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Discussion Starter · #1 · (Edited)
Just bought a 330i with sports pkg. One of the rears was fixed with a nasty plug which caused a bulge in the sidewall.

I quickly removed the wheel and put the spare on which is a '45 profile (meant for the front).

I need to replace the tire and move the spare back where it belongs...

The car has 23k miles. Came from MASS.

I am in SF, CA.

The tires are stock Continental Conti Sports. They look like they have some decent tread left.

1. Do I JUST replace the one bad tire?

2. Do I replace BOTH rear tires, reasoning that I will always have a mismatched pair of rears?

3. Is it unsafe or bad from a peformance issue to have a new rear mixed with a 23K miles old tire on the other side?

4. Are Continental Conti Sports crummy OEM tires and I should run for the hills and get a different brand.

I am a newb with this stuff. :(

Impart wisdom.
 

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lurking
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18,069 Posts
23K miles on summers... almost time for new ones anyways. i would replace both if it was for me. i think some manufacterurs use different compound near the end treadwear mark.
 

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Omni Extaris
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Discussion Starter · #3 · (Edited)
HW said:
23K miles on summers... almost time for new ones anyways. i would replace both if it was for me. i think some manufacterurs use different compound near the end treadwear mark.
I was thinking the same.

What's the life expectancy (mileage) on them. They look clean. Since the car is an east coast vehicle - I wonder if the original owner swapped to winter tires for part of the year.

So.. go for the OEM stuff or swap to something else for the rear...and then I have to ask - would I then have to go new all around (fronts too)?
 

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TMS
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9,288 Posts
paulg said:
What's the life expectancy (mileage) on them.
I have to replace my rears once a year. I can recommend Roger Kraus Racing in Castro Valley as an installer, and they're on Tirerack's list of recommended installers.
 

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Omni Extaris
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6,228 Posts
Discussion Starter · #5 ·
Cliff3 said:
I have to replace my rears once a year. I can recommend Roger Kraus Racing in Castro Valley as an installer, and they're on Tirerack's list of recommended installers.
I have one '45 and one '40 profile on the other side - I want to get those suckers matched up but quick.

Am I damaging anything waiting for tire rack to send me a pair or can I afford the wait?

Their prices are very competitive and don't mind waiting for shipment BUT I am more concerned with damaging the car or unsafe conditions arising from a mismatched pair of rears.

Does DOOM follow if I drive with this mismatched set?
 

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lurking
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paulg said:
I was thinking the same.

What's the life expectancy (mileage) on them. They look clean. Since the car is an east coast vehicle - I wonder if the original owner swapped to winter tires for part of the year.

So.. go for the OEM stuff or swap to something else for the rear...and then I have to ask - would I then have to go new all around (fronts too)?
depends on driving habits but you can measure using a US dime i think. 2/32" remaining tread is time for new tires. most tires start at 10/32" tread.
 

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lurking
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paulg said:
I have one '45 and one '40 profile on the other side - I want to get those suckers matched up but quick.

Am I damaging anything waiting for tire rack to send me a pair or can I afford the wait?

Their prices are very competitive and don't mind waiting for shipment BUT I am more concerned with damaging the car or unsafe conditions arising from a mismatched pair of rears.

Does DOOM follow if I drive with this mismatched set?
probably no damage. i don't see why there would be but safety will depend on how aggressive you drive and weather conditions. running on those donuts are OK upto 80klics so i guess real tires means you still can go faster than that. :dunno:
 

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TMS
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Unless you're planning on running in an autocross soon, you can drive on the spare for a few days. After all, what's the point of having a full size spare? After one of my original tires failed, I replaced my rears with Bridgestone S03's and kept the original B-stone RE040's on the front until they wore out. I ran in a few autoxes that way too - for fun only - it was probably not an ideal thing to do but it allowed me to hold off on replacing the fronts until they wore out.
 

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If you dig deep in car manuals and/or tire brands web sites or other literature you will find that it is not good to run different sized tires on the rear for very long. Why?

Because it makes the spool gears in your diff work all the time. Those gears are not meant to be runnning continuosly, only when the car turns. Running them all the time wears them out prematurely and the metal shavings will ruin the main bearings in the carrier. (In the diff unit)

I've read that a worn out tire on one side and a new tire of the same make model and size on the opposite side is too much variance. Also that new tires of the same size and type but different mfgrs is also excessive and recommended against.

This same reasoning would apply to the front pair of a front wheel drive vehicle.
 

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Omni Extaris
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Discussion Starter · #10 ·
franka said:
If you dig deep in car manuals and/or tire brands web sites or other literature you will find that it is not good to run different sized tires on the rear for very long. Why?

Because it makes the spool gears in your diff work all the time. Those gears are not meant to be runnning continuosly, only when the car turns. Running them all the time wears them out prematurely and the metal shavings will ruin the main bearings in the carrier. (In the diff unit)

I've read that a worn out tire on one side and a new tire of the same make model and size on the opposite side is too much variance. Also that new tires of the same size and type but different mfgrs is also excessive and recommended against.

This same reasoning would apply to the front pair of a front wheel drive vehicle.
Thanks. The good rear was practically brand new so I didn't have to replace both at the same time.
 
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