Square setup=same tire psi all around too?? - BMW 3-Series (E90 E92) Forum

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 Drives: 2011 335i xDrive Coupe Join Date: Nov 2009 Location: WV Posts: 157 iTrader: (0)	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. __________________ --2011 335i xDrive coupe-6MT --Premium/Sport/Cold Weather/Nav/Comfort Access/Harmon Kardon --JB4 Stage 2 : BMS intake : Active Autowerke exhaust : ER charge pipe : cdv delete : M Sport shift knob : 12% tint : clear bra
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08-28-2012, 12:58 AM	#2
ziominix Private First Class Drives: 2011 335i xDrive Coupe Join Date: Nov 2009 Location: WV Posts: 157 iTrader: (0)	No ideas? __________________ --2011 335i xDrive coupe-6MT --Premium/Sport/Cold Weather/Nav/Comfort Access/Harmon Kardon --JB4 Stage 2 : BMS intake : Active Autowerke exhaust : ER charge pipe : cdv delete : M Sport shift knob : 12% tint : clear bra

08-28-2012, 11:06 AM	#4
cvc 22349a Lieutenant Colonel Drives: 335i Join Date: Sep 2007 Location: SF Bay Posts: 1,760 iTrader: (8)	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 tune, Dinan intake/exhaust, KW/M3/Meyle susp, Apex Arc 8, Mich PSS

08-28-2012, 04:37 PM	#6
Gary@TireRack Moderator Drives: Formerly 1995 M3 Join Date: Oct 2006 Location: South Bend, IN, Tire Rack HQ Posts: 2,879 iTrader: (1)	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 The Tire Rack, Sales Rep Gary@Tirerack.com http://www.tirerack.com/a.jsp?a=AH8&url=index.jsp 1-877-522-8473 ext 386 Refer to 'Gary/E90Post' as your previous contact when you order online. Credit E90post.com by ordering through the sig link.

08-28-2012, 04:46 PM	#7
ziominix Private First Class Drives: 2011 335i xDrive Coupe Join Date: Nov 2009 Location: WV Posts: 157 iTrader: (0)	Yeah not running run flats. Pole position 970AS. Would equal pressures for same size tires not lead to more even wear characteristics? __________________ --2011 335i xDrive coupe-6MT --Premium/Sport/Cold Weather/Nav/Comfort Access/Harmon Kardon --JB4 Stage 2 : BMS intake : Active Autowerke exhaust : ER charge pipe : cdv delete : M Sport shift knob : 12% tint : clear bra

08-28-2012, 02:36 AM	#3
John_01 Lieutenant Colonel Drives: E90 325i, E82 135i Join Date: Mar 2009 Location: Sydney, Australia Posts: 1,710 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.

08-28-2012, 11:16 AM	#5
Tom K. Major General Drives: '07 328iT, '13 Boxster Join Date: Mar 2008 Location: Maryland Posts: 5,220 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

08-28-2012, 11:00 PM	#9
flip4335 General Nuisance in a Private Conveyance Drives: like it's rented Join Date: Nov 2008 Location: behind the wheel Posts: 1,490 iTrader: (1) Garage List 2007 BMW e90 335i [3.20]	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 Slightly Modded\|e90\|SGM\|6MT\|LCI MSport\|Premium\|Cold\|Sport\|Tint\|Shadowline\|Blacklin es\|219M\|PSS\|Quaife\|Helix\|Cobb Quaife Review: http://www.e90post.com/forums/showthread.php?t=311570

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