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E46 Xi Forum
The E46 XI was produced from 01-05 in sedan and touring body styles. Powered by either a 2.5L inline 6 in the 325xi or a 3.0L inline 6 330xi. Discuss all thing about BMW AWD E46 'Xi' here.

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Old 03-18-2014, 03:14 PM   #1
MiniXP
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Front/Rear Tire Diameter Difference

So I know this topic has been gone over before and I've always bought tires for my XI in a set of 4, but I am having an issue with that.

I have started to do Auto-X which has been causing some uneven wear between the front and rear tires.

My fronts got pretty worn, so I swapped them to the back, but for now that leaves me driving around with rear tires that have a decent amount more wear than fronts. Has BMW published a specific size difference that is too much?
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Old 03-18-2014, 07:15 PM   #2
tomoyer
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As long as the tires (given that they are the same size when new, i.e. 205/55/16), as long as the tires have 2/32 inch of tread on them (the amount of tread that is remaining when the Wear Bars show) there dis nothing to worry about. Now if you are talking about different sizes front to rear (a staggered tire set which is usually on staggered size wheels as well, i.e. an M3) then we are talking about no more than 2% overall diameter difference. Of course, one would ask why you are Auto-Xing on your normal street tires and don't have a set of wheels with tires on them to race with?! A lot of guys I know that Auto-X will have another set of wheels with half worn out tires on them to race with.
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Old 03-18-2014, 07:19 PM   #3
MiniXP
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As long as the tires (given that they are the same size when new, i.e. 205/55/16), as long as the tires have 2/32 inch of tread on them (the amount of tread that is remaining when the Wear Bars show) there dis nothing to worry about. Now if you are talking about different sizes front to rear (a staggered tire set which is usually on staggered size wheels as well, i.e. an M3) then we are talking about no more than 2% overall diameter difference. Of course, one would ask why you are Auto-Xing on your normal street tires and don't have a set of wheels with tires on them to race with?! A lot of guys I know that Auto-X will have another set of wheels with half worn out tires on them to race with.
In the process of buying Auto-X tires and wheels, I'm going to go with 18x8" style 67s all around for that. Just wondering if it's bad if the same thing happens to those.
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Old 03-18-2014, 07:45 PM   #4
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Next question, why would you go to a Plus 2 sized tire and wheel set to Auto-X? That wheel and tire set will weigh more than your stock 16 inch tire and wheel set and will actually slow you down (added rotational weight). Use the stock 16 inch wheels for Auto-X and if you need the "cool big wheel factor, use them for your everyday street tires (but you should really only go Plus 0 or Plus 1). No matter what size tires and wheels you put on to Auto-X with, you are going to get uneven tire wear! Thats part of that type of racing and why lots of auto-crossers look for their favorite brand of tire in the size they need as used tires with a cheap price and 4 to 6 32nds of tread on them.
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Old 03-18-2014, 08:42 PM   #5
Kubica
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In the process of buying Auto-X tires and wheels, I'm going to go with 18x8" style 67s all around for that. Just wondering if it's bad if the same thing happens to those.
Where are you racing? You need Direzzas or Rivals for autox. I just ordered 245/40/17 Direzzas for this season. There is no good 18" direzza. The 235/40/18 is taller than stock. They don't make 245/35/18. They may make that size in the Rival. 225 is too narrow.

I have a set of 18s and 17s that weigh less than 18 lbs each- I prefer the feel of 18s for autox, but again there's not a good tire size for the 18s.
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Old 03-19-2014, 07:32 AM   #6
MiniXP
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Where are you racing? You need Direzzas or Rivals for autox. I just ordered 245/40/17 Direzzas for this season. There is no good 18" direzza. The 235/40/18 is taller than stock. They don't make 245/35/18. They may make that size in the Rival. 225 is too narrow.

I have a set of 18s and 17s that weigh less than 18 lbs each- I prefer the feel of 18s for autox, but again there's not a good tire size for the 18s.
I'm just doing them with a local club in NC. 17" is what I actually want, but I was looking at some 18" M3 fronts for a square setup since 8" is the widest I can go for a wheel (STX class w/ awd) and they were a good deal.

Yea I know the Direzzas are better, they're pretty pricing though. This will be my first season doing Auto-X, so I don't want to drop too much money right away. The hankooks are supposed to be just below the direzzas performance wise from what I have read. Right now I'm just trying to get off autocrossing my all seasons.

I want to buy a ZHP or 335 within the next year, which I would probably run in a stock/street class so that's another reason I don't want to drop too much money on a whee and tire setup for this car.
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