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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Wheels and Tires Forum Sponsored by The Tire Rack > Help with tire sizes for 2007 bmw 328i Sport



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      04-25-2012, 08:57 PM   #1
Kngli
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Help with tire sizes for 2007 bmw 328i Sport

Hey guys,

I have a 2007 BMW 328 w/sport package and came with stock tires of these sizes
front: 225/45R17 on 17x8 RIM
back: 255/40R17 on 17x8.5 RIM

i was looking to get a new set of Michelin Super Sport (keeping the stock RIMs) but Michelin SS doesn't come in those sizes. The closest is

front: 225/45R17
back: 245/45R17

the back wheels thus will be slightly lower (approx 4mm in radius) than the stock ones.

Can anyone tell me if this is exceptable configuration and what/if there's any negative performance imapct.

Thanks appreciate your help!!!
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      04-25-2012, 09:26 PM   #2
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If you had the sport package you'd have 18s, not 17s.
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      04-25-2012, 09:41 PM   #3
Kngli
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Its a sedan it has 17s.
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      04-25-2012, 11:03 PM   #4
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I would just buy the Michelin Pilot Sport 2 tires in the correct size.
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      04-26-2012, 05:38 AM   #5
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Many functions of your car, such as the DSC, rely on accurate speed data going to the computer. The tire's overall diameter affects the speed information that goes to the computer.

The speedometer on your E90 shows the speed based on the rear wheels. The diameter of the new rear tires would be 0.66 inches more than the current rear tires, or a 2.53% difference. For a passenger car a 3% or under difference is generally considered acceptable.

The speed difference with the larger diameter tires at 60mph would be +2mph. BMW feels that a speedometer error of up to 10% + 2.4 mph is acceptable. So at 60mph the speedometer could show up to 68.4mph (60+6+2.4). Add to this factory built in calibration error the 2mph increase attributed to your new tire size and the speedo could show 70.4mph when you are actually going 60mph. Other than that, you should be ok.
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      04-26-2012, 07:01 AM   #6
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I have a similar question.

The diameter of the stock 225/45/17 front tires is 25" (833 revs/mile)
The diameter of the stock 255/40/17 rear tires is 25".

Since Michelin doesn't make the 255/40/17 for the PSS, there are 2 options:

The diameter of the 245/40/17 rear tires is 24.7". (841 revs/mile)
The diameter of the 245/45/17 rear tires is 25.7". (810 revs/mile)

What difference would the 10mm narrower and 4mm shorter (98 mm vs 102 mm) than stock 245/40/17's make in handling? It seems like narrower would reduce understeer and shorter would increase understeer. Would there be any noticeable difference in handling?

How about the 245/45/17's? They are 10 mm narrower but 8 mm taller (110 mm vs 102 mm) than stock. Once again, 10 mm narrower would reduce understeer but 8 mm taller would also reduce understeer. Would the net effect be oversteer?

The 245/40/17 seems like the better choice. That's what the e46 sedan with sports package had in back with 225/45/17's in front.

Regarding speedometer error....

I think our speedometers normally read at least 5% too high. If we went with 245/40/17's in the rear, the circumference would be about 1% smaller, which would help reduce the discrepancy.

Last edited by driverman; 04-26-2012 at 09:09 AM.
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      04-26-2012, 01:26 PM   #7
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Thanks for your response. I'm just being little too hard headed on the Michelin SS, the PS2 would do but its an older model, not as good, and suprisingly more expensive than the SS....it doesn't make sense to go wth PS2.

I'm going to check with the dealer but they would likely say stick with recommended sizes even if nothing wrong, i mean why would they recommend anything different unless they are your friends .
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      04-26-2012, 03:07 PM   #8
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This is the best information i've found so far

http://www.automobile-catalog.com/ti.../bmw_330i.html

The site doesn't list the specific model (2007 328i w/sp) i'm looking for but the 2006 330i is pretty close.

The spec for the tire diameter difference is pretty consistent for all bmw which is
+3%/-2% in diameter.

And these BMW model uses the configuration i'm looking for....

2002 BMW Z3 3.0i Front Tires 225/45ZR17
2002 BMW Z3 3.0i Rear Tires 245/40ZR17
2000 BMW 328Ci ZR Wheel Package Front Tires 225/45ZR17
2000 BMW 328Ci ZR Wheel Package Rear Tires 245/40ZR17
2006 BMW 330Ci Sport Package Front Tires 225/45ZR17
2006 BMW 330Ci Sport Package Rear Tires 245/40ZR17
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      04-26-2012, 06:19 PM   #9
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2008 BMW 335i  [5.00]
You can put 225s all around. The difference is 0.2% - last I checked.
That's like nothing! At the top of the tire section of this forum is a tire calculator.

Having 225s all around will help make the car feel more neutral in corners. I don't think the 328i would have a hard time putting down its power on 225s.
I would recommend spacers for the rear if your go that route to make sure the car looks extra spiffy!
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      05-17-2012, 09:36 AM   #10
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Can an expert (like Gary) chime in on this?

Many of us with 328 E90 sedans with ZSP would like to get a set PSS's but we don't know what the effects would be of installing 245/40/17's in the rear instead of 255/40/17's.

- 245/40/17 are .4" narrower than 255/40/17 (wheels are 8.5" wide)
- 245/40/17 go 841 revs/mile; the 255/40/17 go 833 (1% difference)

Would we notice a difference in normal driving? Spirited driving?
If so, could we increase tire pressure in back to compensate?

Thanks.
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      05-17-2012, 10:49 AM   #11
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245/40R17 is such a small difference in size compared to 255/40R17 that you would not see or feel any real world differences in normal or spirited driving. You could add a psi or two in the rear but that is also not something you would notice.
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      05-18-2012, 07:49 AM   #12
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Thanks Gary.
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      05-18-2012, 08:18 AM   #13
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My 328i sport came with style 160s, a square 17x8J setup calling for 225/45/17 on all four corners. The PO has some all seasons on there. No trouble with rear grip and it's nice to have a square setup.
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