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      12-18-2012, 06:35 PM   #1
paul386
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Replace 275's in the back with 245's (like front)?

Its new tire time for me. I have a '11 X3 35i with 245-45x19 in the front and 275-40x19 rear. I was considering purchasing 2 new 8.5" wheels and going with 245-45x19 all the way around. Thoughts:

- 4x - 245's are about 10% cheaper than 2x - 245's and 2x - 275's
- There is something like a 50% larger selection of 245's than 275's.
- When driving in a spirited manner, I must be very aggressive on the throttle coming out of a turn for the car to be neutral. With smaller rear tires I should be able to achieve a more neutral feel with less aggressive throttle. This would allow me to push the stability control with aggressive throttle.
- Lower overall weight, lower rotating mass, and lower aero drag. Should increase acceleration and fuel economy. By how much, I am not sure.

The down side:

- Have to buy 2 - $500 wheels.
- Potentially the car feels a lot worse on 245's all around. I doubt this as BMW ships all X3's with 245's all around now.

Options:

- I could sell or trade the 275's to someone who is interested in the wider tire / more aggressiev look.

Thoughts?
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      12-18-2012, 06:42 PM   #2
Nahoa
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Quote:
Originally Posted by paul386 View Post

- When driving in a spirited manner, I must be very aggressive on the throttle coming out of a turn for the car to be neutral. With smaller rear tires I should be able to achieve a more neutral feel with less aggressive throttle. This would allow me to push the stability control with aggressive throttle.
- Lower overall weight, lower rotating mass, and lower aero drag. Should increase acceleration and fuel economy. By how much, I am not sure.
I don't buy these two points and don't think there's any real benefit to making the change. A 10% cost savings? If the price of tires makes or breaks it for you, you may have selected the wrong vehicle. You're in Florida (yes?), so you can run Summer performance tires all year. You're golden as is.
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      12-18-2012, 06:44 PM   #3
paul386
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Quote:
Originally Posted by Nahoa View Post
I don't buy these two points and don't think there's any real benefit to making the change. A 10% cost savings? If the price of tires makes or breaks it for you, you may have selected the wrong vehicle. You're in Florida (yes?), so you can run Summer performance tires all year. You're golden as is.
I guess I was pointing out that the cost of the tire is a wash... The cost of the new wheels is much more significant (like ~$1k). The performance / fuel economy is because I am a bit of a dork...

My biggest motivators are increasing tire choice and availability and driving feel (more neutral).

Last edited by paul386; 12-18-2012 at 07:25 PM..
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      12-18-2012, 09:43 PM   #4
Nahoa
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Ah, I'd misunderstood he 10% point. Sounds to me like you're considering changing for change sake. From my viewpoint your current setup will drive better and is more economical. Doesn't need fixing.
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      12-18-2012, 11:02 PM   #5
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I have to agree with Nahoa.

I have the 'square' setup from the factory and think either the staggered or square setup will work fine on the streets... with the nod going to the staggered setup for aggressive cornering.

Plus the staggered setup just looks cool.
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      12-19-2012, 07:40 AM   #6
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For winter driving with winter tires, yes. Otherwise, why???
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      12-19-2012, 02:26 PM   #7
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Keep the 275s. They look much better. Vanity.
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      12-20-2012, 06:21 AM   #8
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Quote:
Originally Posted by Chris55 View Post
For winter driving with winter tires, yes. Otherwise, why???
I sense the OP is after a slightly more neutral handling balance. Why the desire to "push the stability control" I don't follow. If that is the case, I'd say stick with wider rear wheels.

My last car, an E91 330d, I ran with 'staggered' summer wheels, and 'square' for winter use. The car was more nimble, with a neutral balance on the square set, not the slight understeer of the staggered wheels. All subtle stuff, but the better chassis on a square wheel set.

My present car, an F11 535i, I run 'square' summer and winter, for that same handling balance on both wheel sets.

My son's X3 is on 19" staggered wheels, I sense it suits the higher CG and gives a bit more stability/security to the top heavy chassis.

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