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      08-26-2013, 02:00 PM   #1
DINAN_GT
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20" vs. 21": Does it really affect performance?

On my next F07 (similar to F01/F02), I was thinking of going from 20"s to 21"s. Now I've seen many guys on here go as far as 22's on their 7ers, but my question was, do 21" rims really affect performance that much compared to 20"s?

I was talking my my SA, who told me that I should stick with 21"s, but I've seen F10s (not F01s) with 21"s with no complaints about poor performance, and our tires have a higher profile as well...

Thanks guys.
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      08-26-2013, 03:28 PM   #2
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Was running 22" on my F01 and it was running great with the aggressive drop also. The car rode better on the 22" than the stock 19" w/run flats
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      08-26-2013, 04:13 PM   #3
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Originally Posted by PlatinumEdition View Post
Was running 22" on my F01 and it was running great with the aggressive drop also. The car rode better on the 22" than the stock 19" w/run flats
What about Performance wise? Did you feel the car was slower with 22"s? And what tires were you on?
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      08-26-2013, 04:30 PM   #4
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Quote:
Originally Posted by PlatinumEdition
Was running 22" on my F01 and it was running great with the aggressive drop also. The car rode better on the 22" than the stock 19" w/run flats
+1
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      08-26-2013, 04:32 PM   #5
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Originally Posted by 1_BAD_F01 View Post
+1
Did the performance change at all? Did the car feel slower or was running slower than before?
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      08-26-2013, 05:48 PM   #6
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If I replace my stock 19" cast wheels with 22" forged wheels, I don't think I would be able to tell difference in unsprung weight. The OEM 19" would weigh more than forged 22". As for 21s, those tire size are not common so it will be very expensive compared to 20s. Consider the cost of ownership of 21s vs 20s.
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      08-26-2013, 05:55 PM   #7
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Originally Posted by JNoSol View Post
If I replace my stock 19" cast wheels with 22" forged wheels, I don't think I would be able to tell difference in unsprung weight. The OEM 19" would weigh more than forged 22". As for 21s, those tire size are not common so it will be very expensive compared to 20s. Consider the cost of ownership of 21s vs 20s.
Thanks JNoSol, but ownership costs are not a problem. I've done research and 21" tires are not that scarce, both Hankook and Michelin make tires (non-Rft) for those sizes. My main concern is, what about performance? Are the numbers worse on 21"s? compared to 20s
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      08-26-2013, 09:06 PM   #8
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If you're comparing two identical wheels, then yes. 21s will perform worst than 20s, as 21s will weigh more (more unsprung weight). The 2 main reasons why wheels are getting bigger are: (1) to accommodate larger brakes (2) stiffer side walls for better handling.

I don't think you have brakes that need 21s over 20s. With 21s, you'll have less rubber protecting your wheels and your behind. If the cost of tires is not an issue and you just want 21s for the better look, go for it.
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      08-26-2013, 10:14 PM   #9
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Originally Posted by JNoSol View Post
If you're comparing two identical wheels, then yes. 21s will perform worst than 20s, as 21s will weigh more (more unsprung weight). The 2 main reasons why wheels are getting bigger are: (1) to accommodate larger brakes (2) stiffer side walls for better handling.

I don't think you have brakes that need 21s over 20s. With 21s, you'll have less rubber protecting your wheels and your behind. If the cost of tires is not an issue and you just want 21s for the better look, go for it.
Well 21" forged wheels are lighter than 20" cast wheels, so 20" forged don't weigh much less than 21"s. And I may get BBK for my next F07.

My main concern is, how badly does it affect performance. For example, is it like 0-60 with 20"s: 4.30s, 0-60 with 21"s 4.34s, or something huge like 0-60 w/ 20"s, 4.3s, 0-60 w/ 21"s: 4.8s?
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      08-26-2013, 10:51 PM   #10
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Most 20s will fit the largest BBK for your F10 (I suggest doing an M5 brake conversion, it's much cheaper than buying after markets). Car and driver did a test below, as you can see the 0-60 (assume braking as well) time will suffer but handling got better as the wheel size goes up. Up to a certain size (18" for this test vehicle), you'll reach diminishing returns for both 0-60 time and handling. IMO, the peak for an F10 is 20" before reaching diminishing returns on overall performance and ride quality. Still, 21s look amazing. Just expect to pay more for tires, get more bent wheels, harsher ride, and more rubbin.

The difference in weight on the same forged wheels may 2-3lbs as you go up in size, but when it's spinning at 100mph those 2-3lbs add up (imagine hanging onto a Mary-Go-Round). It's rotational unsprung weight.

http://www.caranddriver.com/features...d-tires-tested
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      08-26-2013, 11:08 PM   #11
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Originally Posted by JNoSol View Post
Most 20s will fit the largest BBK for your F10 (I suggest doing an M5 brake conversion, it's much cheaper than buying after markets). Car and driver did a test below, as you can see the 0-60 (assume braking as well) time will suffer but handling got better as the wheel size goes up. Up to a certain size (18" for this test vehicle), you'll reach diminishing returns for both 0-60 time and handling. IMO, the peak for an F10 is 20" before reaching diminishing returns on overall performance and ride quality. Still, 21s look amazing. Just expect to pay more for tires, get more bent wheels, harsher ride, and more rubbin.

The difference in weight on the same forged wheels may 2-3lbs as you go up in size, but when it's spinning at 100mph those 2-3lbs add up (imagine hanging onto a Mary-Go-Round). It's rotational unsprung weight.

http://www.caranddriver.com/features...d-tires-tested
Really, how much is an M5 Brake conversion? I like them better than BBK anyways.

Also, the F01 and F07 have thicker profile than the F10, so going 21" is the same as going 20" on a F10... what do you think?

And btw, forged wheels are less like to bend, and I've heard the ride isn't affected that badly...
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      08-27-2013, 08:08 AM   #12
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21s do fill the wheel wells better. Go for it. Which brand wheels.

F10 - M5 brake parts below. You'll have to contact LTBMW on the custom caliper brackets. Also, some realized that it requires front fender flares (front M5 conversion) so the wheels don't stick out. I don't know if your F07 requires fender flares or not.

Left Caliper 34117845747 $767.66
Right Caliper 34117845748 $767.66
Left Rotor 34112284101 $394.57
Right Rotor 34112284102 $394.57
Pads 34112284369 $346.10

http://f10.5post.com/forums/showthread.php?t=702414

Those are M5 calipers, painted classic Brembo color. Technically, M5 calipers are made by Brembo.
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