Tire Pressure

[stan001]

Dear all,I recently purchased a E46 325i Japan spec and was a little confused on the tire inflation pressure.The stickers at the door stated like 20 bar front and 25 bar for rear tire but the manual stated like 30 bar (210) for front and 35 bar (240) for rear. I felt whatever stated in the stickers are a bit low.What should be the correct inflated pressure ?I bought a tire pressure gauge to measure the tire pressure so that I get accurate readings when the tires are cold.Currently inflated all the tires to 210 kilopascal.The car comes with 16" tires.Thanks

 

[Mouse]

i think following the manual is the best, if i am not mistaken, they have summer and winter pressure for your tyre. yours is japan spec, hence, i assume the sticker is meant for cold country like japan. so follow the summer pressure in your manual

 

[alxy]

Have same E46 325. I'm using 210 (F) and 240 (R) as per the manual. So far seems OK, though it feels light when going above 180km/h. But then, that's probably the suspension more than anything else.

 

[stan001]

Thanks, I think I should stick to 210(F) and 240(R) as stated in the manual..

Any idea why the rear pressure is higher ? Is it b'cos the engine is heavier at the front ?


Stan

 

[jasonnn]

Could it be becoz its a rear wheel drive car?? Hence higher pressure for the rear..?

 

[Mouse]

Thanks, I think I should stick to 210(F) and 240(R) as stated in the manual..

Any idea why the rear pressure is higher ? Is it b'cos the engine is heavier at the front ?


Stan

not very sure, but did u guys notice all the recommended tyre pressure is with full passanger + luguage. hence, i will assume the rear pressure is higher because of 3 adult passanger + luguage in the boot that will add up to more than 200+kg. my rear tyre pressure recommended is 270kpa (sticker on pilar B), however, i only pump 240kpa because i always drive alone. during hot weather or long journey drive, your tyre will definately expand to additional 20-30 kpa making my tyre pressure at 260-270kpa. however, we dun borther about tyre pressure expansion while running, most important is the currect pressure during cold (eg. measure the pressure early morning before driving your car). any tyre expert can confirm & agree with me?

 

[alxy]

Thanks, I think I should stick to 210(F) and 240(R) as stated in the manual..

Any idea why the rear pressure is higher ? Is it b'cos the engine is heavier at the front ?


Stan

It's RWD. My Accord pressure is higher in the front as it's FWD. Though that is also not a hard and fast rule. Basically it also depends on how the R&D guys design the car.

 

[Mouse]

It's RWD. My Accord pressure is higher in the front as it's FWD. Though that is also not a hard and fast rule. Basically it also depends on how the R&D guys design the car.

meaning FWD must have higher pressure on front than rear and RWD must have higher pressure on rear than front? can anyone confirm this? i am learning something new here........

 

[acidburn]

Hey Guys,

I did ask AB specialist and he also recommended as what the manual says 30 bar (210) for front and 35 bar (240) for rear provided all 4 tyres are the same spec, size and thickness.

Always aware on the recond car because some already done offset.
( Example : F- 235/40/18 and R-255/35/18 )
This offset is not advisable to follow the above tyre pressure

 

[alxy]

meaning FWD must have higher pressure on front than rear and RWD must have higher pressure on rear than front? can anyone confirm this? i am learning something new here........

Err...no scientific explanation (you can check www.tirerack.com if you want to know more about the science behind it), but more based on observation on all the cars I have owned and some of my pal's as well.

 

[taggnas]

My tyre pressures are

Front: 28 PSI
Rear: 30 PSI

Was advised by my tyre shop people. By the way am using 18/40/235 for both front and rear tyres.

 

[LCP]

Err guys, 20, 25, 28, 30, 35 are not in bars, that's psi... If bars that's plenty of exploded tyres as 1 bar is around 14 psi...

BMW recommends higher rear pressure than front, presumably to induce a bit more understeer, which is a safer compromise... To reduce understeer you can make the front pressure same as rear... I run 260kPa all round... 225/45/17 all round on my E36.

As for FWD cars, there's already default understeer to begin with, so, the front pressure is higher to neutralise the handling a bit... of course this assumes stock standard suspension.

 

[LCP]

And Mouse, yes, tyre pressure must always be checked when cold... or if too poor to have own tyre pressure gauge (because BMW banyak makan wang), drive slowly (no hard braking, acceleration, cornering) to nearest neighbourhood petrol station... mine's 1km away (actually there's another one just 400m away, but I don't patronise them)...

 

[taggnas]

Sorry for the mix up between Bar and PSI! Made the necessary changes to my previous post!