Square setup=same tire psi all around too??

ziominix · 08-27-2012, 08:19 PM

Switched to 235-40-18 all around on new wheels obviously. Should I maintain the factory tire psi specs with higher pressure in the rear or run same psi all around now??

Thanks for any input.

ziominix · 08-28-2012, 12:58 AM

No ideas?

John_01 · 08-28-2012, 02:36 AM

I use a square setup with 235 all around. I suggest to front pressure should be lower than the rear. Too much pressure in the front makes the ride very poor. I recommend the fronts around 36-37 and the rears 38-39, but you may prefer lower pressure for softer ride quality.

cvc 22349a · 08-28-2012, 11:06 AM

Depends on if your tires are rft or not. If they are rft, go with BMW's recommendation; if non-rft, add 2-3 psi to the front tires from what BMW recommends.

Tom K. · 08-28-2012, 11:16 AM

Start with the OEM pressures and experiment from there. Decreasing the front/back differential will tend to reduce understeer but will make the car less stable at speed, especially in crosswinds.

The non-staggered 16" tires on my E91 call for 32/39 but I prefer 34/37 when the car is lightly loaded and 34/42 when carrying 1/2 ton of stuff.

Tom

Gary@TireRack · 08-28-2012, 04:37 PM

It would be no problem to stick with the factory psi recommendations, run flat or no. Some prefer slightly higher pressures for faster steering response when going to a non run flat, but it is not needed.

ziominix · 08-28-2012, 04:46 PM

Yeah not running run flats. Pole position 970AS. Would equal pressures for same size tires not lead to more even wear characteristics?

CJ421 · 08-28-2012, 06:58 PM

Quote:

Originally Posted by ziominix

Yeah not running run flats. Pole position 970AS. Would equal pressures for same size tires not lead to more even wear characteristics?

No. Only if the pressures are extremely off would there be wear problems ...and wear would be the least of your worries at that point.

Start from stock pressures listed on your driver side door and go from there as noted. I run 34 front, 38 back, almost stock with my non RFT. Perfectly fine.

flip4335 · 08-28-2012, 11:00 PM

On my door jamb, it reads for speeds up to and over 100 mph, recommended setup is 39psi front/45psi rear, a 6psi difference between front and rear.

I run a COBB tune, so the higher pressure in the back helps with grip, but I run 36psi front/42psi rear for a softer ride (hehehe) and in anticipation of temperatures increasing the inflation plus or minus 3psi front/rear.

I also have a Quaife diff, so I like to drift with the higher pressure.

08-27-2012, 08:19 PM	#1
ziominix Private First Class 3 Rep 168 Posts Drives: 2011 335i xDrive Coupe Join Date: Nov 2009 Location: WV iTrader: (2)	Square setup=same tire psi all around too?? Switched to 235-40-18 all around on new wheels obviously. Should I maintain the factory tire psi specs with higher pressure in the rear or run same psi all around now?? Thanks for any input. __________________ CURRENT--2014 2LT Z51 Corvette Coupe-7MT PAST--2011 335i xDrive coupe-6MT-
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08-28-2012, 12:58 AM	#2
ziominix Private First Class 3 Rep 168 Posts Drives: 2011 335i xDrive Coupe Join Date: Nov 2009 Location: WV iTrader: (2)	No ideas? __________________ CURRENT--2014 2LT Z51 Corvette Coupe-7MT PAST--2011 335i xDrive coupe-6MT-
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08-28-2012, 02:36 AM	#3
John_01 Colonel 232 Rep 2,643 Posts Drives: E90 325i, E82 135i Join Date: Mar 2009 Location: Sydney, Australia iTrader: (0)	I use a square setup with 235 all around. I suggest to front pressure should be lower than the rear. Too much pressure in the front makes the ride very poor. I recommend the fronts around 36-37 and the rears 38-39, but you may prefer lower pressure for softer ride quality.
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08-28-2012, 11:06 AM	#4
cvc 22349a Colonel 164 Rep 2,556 Posts Drives: 335i Join Date: Sep 2007 Location: SF Bay iTrader: (11)	Depends on if your tires are rft or not. If they are rft, go with BMW's recommendation; if non-rft, add 2-3 psi to the front tires from what BMW recommends. __________________ 2007 E90 335i, TiAg, 6AT, ZPP, ZSP, ZCW, 6FL, HD Quaife lsd, ETS fmic, GIAC s/w, Dinan intake/exhaust/oc, Koni/M3 susp, Apex Arc 8, Mich PSS
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08-28-2012, 11:16 AM	#5
Tom K. Major General 124 Rep 5,627 Posts Drives: '07 328iT, '13 Boxster Join Date: Mar 2008 Location: Maryland iTrader: (0)	Start with the OEM pressures and experiment from there. Decreasing the front/back differential will tend to reduce understeer but will make the car less stable at speed, especially in crosswinds. The non-staggered 16" tires on my E91 call for 32/39 but I prefer 34/37 when the car is lightly loaded and 34/42 when carrying 1/2 ton of stuff. Tom
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08-28-2012, 04:37 PM	#6
Gary@TireRack Moderator 369 Rep 4,745 Posts Drives: Formerly 1995 M3 Join Date: Oct 2006 Location: South Bend, IN, Tire Rack HQ iTrader: (2)	It would be no problem to stick with the factory psi recommendations, run flat or no. Some prefer slightly higher pressures for faster steering response when going to a non run flat, but it is not needed. __________________ Gary. Tire and Wheel Forum Moderator. Tire Rack Sales Rep Gary@Tirerack.com http://www.tirerack.com/a.jsp?a=AH8&url=index.jsp Please refer to 'Gary/E90 Post' as your previous contact when you order online to help support this forum.
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08-28-2012, 04:46 PM	#7
ziominix Private First Class 3 Rep 168 Posts Drives: 2011 335i xDrive Coupe Join Date: Nov 2009 Location: WV iTrader: (2)	Yeah not running run flats. Pole position 970AS. Would equal pressures for same size tires not lead to more even wear characteristics? __________________ CURRENT--2014 2LT Z51 Corvette Coupe-7MT PAST--2011 335i xDrive coupe-6MT-
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08-28-2012, 11:00 PM	#9
flip4335 General Nuisance in a Private Conveyance 77 Rep 1,907 Posts Drives: like it's rented Join Date: Nov 2008 Location: behind the wheel iTrader: (1) Garage List 2007 BMW e90 335i [7.30]	On my door jamb, it reads for speeds up to and over 100 mph, recommended setup is 39psi front/45psi rear, a 6psi difference between front and rear. I run a COBB tune, so the higher pressure in the back helps with grip, but I run 36psi front/42psi rear for a softer ride (hehehe) and in anticipation of temperatures increasing the inflation plus or minus 3psi front/rear. I also have a Quaife diff, so I like to drift with the higher pressure. __________________ BMWCCA Member # 414198 \|E90\|SGM\|6MT\|Premium\|Cold\|Sport\|Tint\|LCI MSport Conversion\|MTech\|Blacklines\|219M\|PSS\|Quaife\|Helix FMIC\|M3 Suspension\|Megan Racing\|GC Camber Plates/Coilovers\|Eibach 440/800#\|AR Catted DP\|Cobb AP\|StopTech Drilled/Slotted\|SS Brake Lines\|DWS Quaife Review: http://www.e90post.com/forums/showthread.php?t=311570
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