Tyre pressure

[Newbmw]

Hi all I just checked my RFT on my E89 all round are 36psi is this right tyres size below
Rear 255/35/18
Front 225/40/18
Bridgstone poz fitted run flats

 

[Smartbear]

Hi, you should have a sticker inside the drivers door jam that gives you tyre pressures? See if it's there
Rob

 

[Busterboo]

Hi all I just checked my RFT on my E89 all round are 36psi is this right tyres size below
Rear 255/35/18
Front 225/40/18
Bridgstone poz fitted run flats

As Rob says, just look at the label on the sill.

Run-flats or non-run-flats, the figures are the same.

 

[ShaunKC]

I've always wondered about this, are the tyre pressures the same regardless of wheel / tyre size?

 

[Newbmw]

Thanks rob I'll take a look in morning

 

[Busterboo]

I've always wondered about this, are the tyre pressures the same regardless of wheel / tyre size?

Again, the answer's on the label on your sill.

 

[mr wilks]

I've always wondered about this, are the tyre pressures the same regardless of wheel / tyre size?

Again, the answer's on the label on your sill.

Here's one for you Buster , if you believe all you read from BMW do you keep to their service schedule RE oil changes every 15k :? :wink:

 

[Busterboo]

Yep.

Modern synthetics are wonderful.

 

[ShaunKC]

I've always wondered about this, are the tyre pressures the same regardless of wheel / tyre size?

Again, the answer's on the label on your sill.

Mmmm, I don't think you understood what I was asking. My car came with 18'' wheels, now it's running (non-stock) 19'' wheels with totally different tyre sizes. So what I'm questioning is, do the existing tyre pressures for 18'' wheels still stand? The stickers inside the door, obviously refer to stock wheels/tyres.

I suppose another question is, If the existing pressures that a car came out of the factory with stand, regardless of tyre specification, wheel size or even suspension, then is the pressure recommended for a tyre purely a reflection on the weight of the car?

I haven't got an issue with my tyres or car, just interested.

 

[Smartbear]

I think the tyre pressure sticker on my car displayed a range of sizes, not just the standard ones?
Rob

 

[ShaunKC]

I think the tyre pressure sticker on my car displayed a range of sizes, not just the standard ones?
Rob

I've had to double check my sticker, and on my car at least, it just shows pressures for the standard 18'' wheels.

Searching through the net, there seems to be no definitive answer, some say more pressure is needed for deeper tyre walls, so less for low profile, others say stick to the standard, others say put chalk on your tyre and see how/where they wear.

I think I'll just leave mine as they are and stop thinking about it!! 8)

 

[Busterboo]

I think the tyre pressure sticker on my car displayed a range of sizes, not just the standard ones?
Rob

I've had to double check my sticker, and on my car at least, it just shows pressures for the standard 18'' wheels.

Searching through the net, there seems to be no definitive answer, some say more pressure is needed for deeper tyre walls, so less for low profile, others say stick to the standard, others say put chalk on your tyre and see how/where they wear.

I think I'll just leave mine as they are and stop thinking about it!! 8)

My answers ...

#1 I don't know the ratio
#2 I asked the same question a while back and nobody answered
#3 Like Rob, I thought your label would give you the information for your car
#4 The label on my 35iS says 'For 17" wheels 2.4 & 2.9 bar' - 'For 18" wheels 2.6 & 3.1 bar'
(That's 34.8 & 42 psi and 37.7 & 44.9 psi)
#5 I don't know if the 17" to 18" ratio can be extrapolated
#6 My label's figures are for 2 passengers & luggage, so, for normal use, I run the tyres lower: 36 & 44 psi
#7 I'm used to similar high pressures on my 911
#8 Previous threads indicate that many members run their Z4 tyres lower than BMW's recommendations.

 

[alex]

I think the tyre pressure sticker on my car displayed a range of sizes, not just the standard ones?
Rob

I've had to double check my sticker, and on my car at least, it just shows pressures for the standard 18'' wheels.

Searching through the net, there seems to be no definitive answer, some say more pressure is needed for deeper tyre walls, so less for low profile, others say stick to the standard, others say put chalk on your tyre and see how/where they wear.

I think I'll just leave mine as they are and stop thinking about it!! 8)

My answers ...

#1 I don't know the ratio
#2 I asked the same question a while back and nobody answered
#3 Like Rob, I thought your label would give you the information for your car
#4 The label on my 35iS says 'For 17" wheels 2.4 & 2.9 bar' - 'For 18" wheels 2.6 & 3.1 bar'
(That's 34.8 & 42 psi and 37.7 & 44.9 psi)
#5 I don't know if the 17" to 18" ratio can be extrapolated
#6 My label's figures are for 2 passengers & luggage, so, for normal use, I run the tyres lower: 36 & 44 psi
#7 I'm used to similar high pressures on my 911
#8 Previous threads indicate that many members run their Z4 tyres lower than BMW's recommendations.

I checked the pressures on my 35iS on Sunday - pretty sure the sticker on the inside of my door said 2.4 & 2.9 bar for 19" wheels (which I have). Maybe I should double check!

 

[David-H]

Hi all I just checked my RFT on my E89 all round are 36psi is this right tyres size below
Rear 255/35/18
Front 225/40/18
Bridgstone poz fitted run flats

From my handbook:

 

[Newbmw]

Thanks

 

[Busterboo]

This is really helpful, DLH. Not least because my 35iS handbook doesn't have this data.

I'll bet the missing/over-the-page figures for "With Sport Package ... 18 ... Rear" are 44 and 46.