Changes to overall diameter/fitment advice

user01011 · 06-19-2014, 07:15 PM

Hi guys.

I have a 2010 E90 335i M-Sport.

I've bought a set of HRE FF01 and expect them to arrive in the next few weeks or so.

The sizes that are HRE verified to fit will be:

Front: 20x8.5 +30
Rear: 20x10 +40

Apparently the fitment advice for tyres from HRE themselves are:

Front: 245/30/20
Rear: 285/30/20

However according to the tyre size calculator this nets an overall change of +6.81% diameter in the rear.

I was wondering it it might be wiser to stick with a 285/25/20 tyre which ends up being an increase of only +2.33%.

Considering the front in the 245/30/20 size will be an increase of +2.79% diameter I suspect the car will be happier in terms of traction/stability control when the diameters match what they did from the factor more closely?

What's your opinion on this? Is HRE's advice of a +6.81% increase in diameter sound?

Thanks heaps in advance.

wdeerfield · 06-20-2014, 07:55 AM

They may be giving you sizes for the f-code cars. 20s on an e90 are huge to begin with though. 245/285r25 might work out better.

06-19-2014, 07:15 PM	#1
user01011 New Member 0 Rep 8 Posts Drives: '10 E90 335i Join Date: Feb 2014 Location: New Zealand iTrader: (0)	Changes to overall diameter/fitment advice Hi guys. I have a 2010 E90 335i M-Sport. I've bought a set of HRE FF01 and expect them to arrive in the next few weeks or so. The sizes that are HRE verified to fit will be: Front: 20x8.5 +30 Rear: 20x10 +40 Apparently the fitment advice for tyres from HRE themselves are: Front: 245/30/20 Rear: 285/30/20 However according to the tyre size calculator this nets an overall change of +6.81% diameter in the rear. I was wondering it it might be wiser to stick with a 285/25/20 tyre which ends up being an increase of only +2.33%. Considering the front in the 245/30/20 size will be an increase of +2.79% diameter I suspect the car will be happier in terms of traction/stability control when the diameters match what they did from the factor more closely? What's your opinion on this? Is HRE's advice of a +6.81% increase in diameter sound? Thanks heaps in advance.
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06-20-2014, 07:55 AM	#2
wdeerfield A family of bimmers 2831 Rep 7,763 Posts Drives: '18 G01 X3M40i Join Date: Jan 2012 Location: Clifton Park, NY iTrader: (0)	They may be giving you sizes for the f-code cars. 20s on an e90 are huge to begin with though. 245/285r25 might work out better. __________________ 2018 PB/Black G01 X3M40i \| 699M \| ZDA \| ZPP \| ZPX \| Maxton front lip \| X3M vents \| 15mm Spacers \| Diamond G20 style grills
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