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      01-08-2015, 11:30 AM   #1
Jamescc75
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Recommended tires for 640i XD GC?

I am just replacing my 373M 20" wheels with runflats for the 343M M5 20" wheels and need recommendations on tires. My goal is to make my Alpine white GC look aggressive, sporty, the tires be not too expensive and they be all-weather tires as I live in Seattle. I also don't want to mess the rotation of the tire too much so that it affects the speedometer/drivetrain more than needed. Some of the searches I have done on here have revealed:

Hankook R-S3 rears: 285/35/20, fronts: 245/40/20
(Can't remember the brand) Rears: 285/30/20, Fronts: 255/35/20

Any ideas based on the above info is greatly appreciated!
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      01-08-2015, 01:34 PM   #2
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You have to make sure the total size of wheels be the same or very close...
The size of wheel is calculated this way:
Rim diameter + 2 side walls where the side walls are related to the size of tire.
The first number shows how wide your tire is in mm.
The second number is aspect ratio which is the ratio of side walls.
For example: 285/35/20.... the width is 285 mm or 11.22"
The side wall is 11.22 x 35/100 = 3.92"
The total wheel size = 20 + 3.92 + 3.92 = 27.84"
if the new wheel (rear rim+tire) is larger than this size your actual speed is more than what you see on speedo. If the new wheel is smaller than this size, your actual speed is less than what you see on speedo.
BTW, your speedo normally shows a bit more than actual speed
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      01-08-2015, 02:49 PM   #3
Jamescc75
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Quote:
Originally Posted by M6-Coupe View Post
You have to make sure the total size of wheels be the same or very close...
The size of wheel is calculated this way:
Rim diameter + 2 side walls where the side walls are related to the size of tire.
The first number shows how wide your tire is in mm.
The second number is aspect ratio which is the ratio of side walls.
For example: 285/35/20.... the width is 285 mm or 11.22"
The side wall is 11.22 x 35/100 = 3.92"
The total wheel size = 20 + 3.92 + 3.92 = 27.84"
if the new wheel (rear rim+tire) is larger than this size your actual speed is more than what you see on speedo. If the new wheel is smaller than this size, your actual speed is less than what you see on speedo.
BTW, your speedo normally shows a bit more than actual speed
Very useful info, thank you. Now I need to calculate
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      01-09-2015, 05:01 AM   #4
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Use this http://www.rimsntires.com/specspro.jsp and it will do all of the calculations for you
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      01-09-2015, 05:54 AM   #5
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The Continental Extreme Contact DWS is a highly rated all season performance tire that comes in the sizes you need.
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      01-10-2015, 02:45 PM   #6
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Quote:
Originally Posted by Bönz View Post
The Continental Extreme Contact DWS is a highly rated all season performance tire that comes in the sizes you need.
I agree 100%. They don't handle as well as the OEM run-flats in the dry (warm), but they are doing just fine here in Chicago this winter and the ride is much nicer. Still think I'm going to put the RFTs back on this spring/summer.
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      01-16-2015, 05:44 PM   #7
Jamescc75
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Thanks for the advice. I think I am going to go with the Bridgestone Potenza 255/35 and 285/30.

There shouldn't be any issues with switching the TPMS from my 373M to 343M wheels, should there?
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      01-16-2015, 05:51 PM   #8
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Nope.
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      01-16-2015, 06:25 PM   #9
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Quote:
Originally Posted by Jamescc75 View Post
Thanks for the advice. I think I am going to go with the Bridgestone Potenza 255/35 and 285/30.
Just making sure you are aware those are summer tires. It shows you are in Seattle - not sure where in Seattle, but I thought you guys occasionally got bad stuff there?
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      01-16-2015, 09:24 PM   #10
Jamescc75
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Quote:
Originally Posted by doug_999 View Post
Just making sure you are aware those are summer tires. It shows you are in Seattle - not sure where in Seattle, but I thought you guys occasionally got bad stuff there?
Tirerack says the Potenza RE970 are all-season
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      01-17-2015, 09:05 AM   #11
doug_999
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Quote:
Originally Posted by Jamescc75 View Post
Tirerack says the Potenza RE970 are all-season
Ahhh, you had neglected to mention which Potenza you were getting

I only saw the RE050, S001, and RE760.

Two things
1. BMW has changed the recommended tire size for that wheel I believe. I don't know if they changed the wheel itself or what -but I noticed that the width went up 10mm at somepoint.
2. Can I ask what is making you go with the Bridgestones? I was not aware of them (they don't show in the 373 size), but when I click on the survey results at tirerack, they are ranked 10th whereas the Conti DWS are ranked 1st.
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      01-17-2015, 09:36 PM   #12
Jamescc75
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Quote:
Originally Posted by doug_999 View Post
Ahhh, you had neglected to mention which Potenza you were getting

I only saw the RE050, S001, and RE760.

Two things
1. BMW has changed the recommended tire size for that wheel I believe. I don't know if they changed the wheel itself or what -but I noticed that the width went up 10mm at somepoint.
2. Can I ask what is making you go with the Bridgestones? I was not aware of them (they don't show in the 373 size), but when I click on the survey results at tirerack, they are ranked 10th whereas the Conti DWS are ranked 1st.
Good point. After more research, I decided to go with the Continental Extreme Contact DWS 255/35, 285/30
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      01-18-2015, 06:37 AM   #13
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Right choice. That's what Doug and I suggested at the beginning
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      07-06-2015, 01:03 AM   #14
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Quote:
Originally Posted by Jamescc75 View Post
I am just replacing my 373M 20" wheels with runflats for the 343M M5 20" wheels and need recommendations on tires. My goal is to make my Alpine white GC look aggressive, sporty, the tires be not too expensive and they be all-weather tires as I live in Seattle. I also don't want to mess the rotation of the tire too much so that it affects the speedometer/drivetrain more than needed. Some of the searches I have done on here have revealed:

Hankook R-S3 rears: 285/35/20, fronts: 245/40/20
(Can't remember the brand) Rears: 285/30/20, Fronts: 255/35/20

Any ideas based on the above info is greatly appreciated!
Hi James,

What made you go 285 over 295 on the rear? Some of the guys here did it but in the UK, we have a legal limit with wider tyres where it should not stick out beyond the wheel arch.

Thanks,
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