fitting larger tyres on rear

Si-M240i · 05-20-2009, 01:50 AM

I am thinking of replacing my 245/35/18 runflats with 255/30/18 runflats which are used on the 335. I thouight this may help to get more traction down in 1st and 2nd gear and limit wheel spin, which in turn will help the tyres last a little longer. On a tyre conversion chart it equates to a 3% error in speedo reading, which is only and over reading of 1.5MPH at 50MPH.

Has anyone else done this ?
Do you think the lower profile will make the ride too hard ? I actually like the firm feel with runflats, but didn;t know if this would overdo it.

emm3tt · 05-20-2009, 02:02 AM

the 335i uses 255/35-18 and 255/30-19. 255/30-18 is an oddball size, Tirerack only lists 1 tire in that size.

Endre · 05-20-2009, 02:02 AM

Works great.

Had 225.40/255.35 setup last year, and it worked great! But bught stock size again this year to keep it as stock as possible...

Eyeman · 05-21-2009, 09:11 PM

I'd for sure just go with 255/35's unless I had some big reason like a huge cost savings to go with the 30 profile. I don't even want to go with 30 profiles on my 19" wheels, those things have awfully thin sidewalls.

05-20-2009, 01:50 AM	#1
Si-M240i Major 137 Rep 1,450 Posts Drives: M240i LCI Join Date: Aug 2008 Location: England iTrader: (0)	fitting larger tyres on rear I am thinking of replacing my 245/35/18 runflats with 255/30/18 runflats which are used on the 335. I thouight this may help to get more traction down in 1st and 2nd gear and limit wheel spin, which in turn will help the tyres last a little longer. On a tyre conversion chart it equates to a 3% error in speedo reading, which is only and over reading of 1.5MPH at 50MPH. Has anyone else done this ? Do you think the lower profile will make the ride too hard ? I actually like the firm feel with runflats, but didn;t know if this would overdo it. __________________ M240i LCI (Mineral Grey):- M2 Door Mirrors, M2 Black Kidney Grills, Lower grille inserts, MP Exhaust, Dinan Carbon Fibre CAI, hot climate intake elbow
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05-20-2009, 02:02 AM	#2
emm3tt Out Driving 29 Rep 685 Posts Drives: Join Date: Jun 2007 iTrader: (1)	the 335i uses 255/35-18 and 255/30-19. 255/30-18 is an oddball size, Tirerack only lists 1 tire in that size. __________________ Emmett 01 E46 M3
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05-20-2009, 02:02 AM	#3
Endre Lieutenant 17 Rep 420 Posts Drives: E36 M3 3.2 (321hp) Join Date: Mar 2008 Location: Molde iTrader: (0) Garage List 2008 E82 120d [10.00]	Works great. Had 225.40/255.35 setup last year, and it worked great! But bught stock size again this year to keep it as stock as possible... __________________ 120d, M-sport, H&R springs,Remus Exhaust, 135I kidneys, 18"BMW performance with Toyo T1R.(summer) 17" style 207 with Michelin Xice(winter), 17" M3 replica with Toyo R888 (Track), Hardwired H/K GPS 810. SOLD! Now driving E36 M3 3.2 (321Hp) Track and Autox
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05-21-2009, 09:11 PM	#4
Eyeman Colonel 121 Rep 2,037 Posts Drives: 2008 135 blk, blk, step Join Date: Jan 2009 Location: Atlanta, GA iTrader: (0) Garage List 1994 Porsche 968 Cab [0.00] 2017 AMG GTS [0.00] 1994 Porsche 968 Coupe [0.00] 1977 Mercedes 450SE ... [0.00] 2008 135 [8.00]	I'd for sure just go with 255/35's unless I had some big reason like a huge cost savings to go with the 30 profile. I don't even want to go with 30 profiles on my 19" wheels, those things have awfully thin sidewalls.
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