What tire pressure??

wichitagreg · 03-25-2019, 09:09 AM

My owner's manual recommends 33 psi front, and 41 psi rear for the tire pressure. It sure seems odd. Anyone care to try to explain their reasoning for this??

I normally run all my tires about 5 lbs above the recommended, on my F150 and my Harley. I get very good feel, braking, and tread life. I have not noticed a stiffer ride, except the Harley is a little worse than the recommended pressure.

Starting at 40psi cold all around, yesterday we had about 80 degrees outside, and I ran out on the interstate for a little bit, staying around 85-90 mph for about 20 min (I live in TX). Pressure increased to about 44psi, tire temp was about 102. Back in my two wheel racing days we would set cold tire pressure to get a certain predictable increase in tire pressure when at full operating temp.

2016 M235i
225/40 18 DWS 06 tires

Maynard · 03-26-2019, 12:24 PM

I believe that these specifics and the front-rear difference are an attempt to try to balance out handling. All street tires are designed for wider range of pressures in order to cover the heat-gain, so go by cold pressure unless on track (but OK to choose different settings). Personally, I run mine much closer to balanced as I prefer the tauter handling that higher pressures in front give you - but I'm on staggered performance tires (usually about 37f/40r). BMW fits tires to smallish rims, probably to get more sidewall shock absorption (or b/c you can't fit that much rubber into the fenders), so that is likely to magnify this effect. As long as you stay w/i tire manufacturer's safe limits it is fair game to try to find the settings that give the best feel and performance.

And FWIW, the only settings I see in my copy of the manual for non-staggered 225-18's is 36f/41r. It doesn't list specifics by brand, and they used about a half dozen different tires so you may have recc's just for that brand. I run my winter 225's at about 33 all around.

PeterWT · 03-26-2019, 05:50 PM

I have AS3+ in 235/40/18 front and 255/35/18 rear and I like 38psi cold all around.

240Newbie · 03-28-2019, 08:27 AM

I have a 19' M240 M Performance and mine says 41 and 44!!!! I was shocked but then again the side walls are very thin on the 19" wheels.

Shayan55 · 04-19-2019, 04:35 PM

I run 33psi cold on my NT01's, 245/40/18

03-25-2019, 09:09 AM	#1
wichitagreg Private 35 Rep 67 Posts Drives: 2016 M235i Cabriolet Join Date: Nov 2018 Location: Kerrville, TX iTrader: (0)	What tire pressure?? My owner's manual recommends 33 psi front, and 41 psi rear for the tire pressure. It sure seems odd. Anyone care to try to explain their reasoning for this?? I normally run all my tires about 5 lbs above the recommended, on my F150 and my Harley. I get very good feel, braking, and tread life. I have not noticed a stiffer ride, except the Harley is a little worse than the recommended pressure. Starting at 40psi cold all around, yesterday we had about 80 degrees outside, and I ran out on the interstate for a little bit, staying around 85-90 mph for about 20 min (I live in TX). Pressure increased to about 44psi, tire temp was about 102. Back in my two wheel racing days we would set cold tire pressure to get a certain predictable increase in tire pressure when at full operating temp. 2016 M235i 225/40 18 DWS 06 tires
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03-26-2019, 12:24 PM	#2
Maynard Colonel 3848 Rep 2,873 Posts Drives: 228iX & M2C Join Date: Mar 2016 Location: Upstate NY iTrader: (1)	I believe that these specifics and the front-rear difference are an attempt to try to balance out handling. All street tires are designed for wider range of pressures in order to cover the heat-gain, so go by cold pressure unless on track (but OK to choose different settings). Personally, I run mine much closer to balanced as I prefer the tauter handling that higher pressures in front give you - but I'm on staggered performance tires (usually about 37f/40r). BMW fits tires to smallish rims, probably to get more sidewall shock absorption (or b/c you can't fit that much rubber into the fenders), so that is likely to magnify this effect. As long as you stay w/i tire manufacturer's safe limits it is fair game to try to find the settings that give the best feel and performance. And FWIW, the only settings I see in my copy of the manual for non-staggered 225-18's is 36f/41r. It doesn't list specifics by brand, and they used about a half dozen different tires so you may have recc's just for that brand. I run my winter 225's at about 33 all around.
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03-26-2019, 05:50 PM	#3
PeterWT Lieutenant 254 Rep 558 Posts Drives: '17 M240i, AT, BSM Join Date: Dec 2016 Location: Florida, USA iTrader: (0)	I have AS3+ in 235/40/18 front and 255/35/18 rear and I like 38psi cold all around. __________________ My 2017 M240i: MHD, xHP, Modded OE Intake, AA GESi 400 CPSI Cat DP, Dinan Mid-pipe, M Performance LSD & Rear Diffuser, BMS Exhaust Tips, Apex EC-7 Wheels, M-Tech Front Lip, iND Painted Mirror Caps, Smoked Reflectors
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03-28-2019, 08:27 AM	#4
240Newbie Learning 62 Rep 121 Posts Drives: 19' M240 M Performance Join Date: Mar 2019 Location: PA iTrader: (0)	I have a 19' M240 M Performance and mine says 41 and 44!!!! I was shocked but then again the side walls are very thin on the 19" wheels.
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04-19-2019, 04:35 PM	#5
Shayan55 Captain 339 Rep 716 Posts Drives: F90 M5 Join Date: Jun 2016 Location: woodland hills CA iTrader: (1) Garage List 2105 BMW M235I [0.00]	I run 33psi cold on my NT01's, 245/40/18 __________________ (Sold) M235I Dinan intake, Active Autowerke FMIC, meisterschaft, TCKline coilovers, NT01's, BMS Oil cooler valve, VRSF DP&CP, BM3,StopTech Trophy BBK, Corbeau FX1 Pro seats, AP bar, Bimmerworld V3 Wing, APR Front splitter, Seibon Vented CF Hood 399.8whp on 91oct Hmu on Ig: @n55_shayan
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