Tyre pressure confusion

MarkB1983 · Post by **MarkB1983** » Thu Jul 14, 2016 6:13 pm

I've had my Z4 20i M Sport (auto) for a few weeks. I wanted to check the tyre pressures to make sure everything is in order, but first need to determine what the correct tyre pressures should be. I took readings from the tyres as they are now and get 40 psi on the front and around 43 psi on the back (according to my foot pump). This seems higher than the sticker inside the door indicates. I interpret that diagram as 33 psi on the front and 41 psi on the rear.

The code on the front tyres is "225/35R19 88Y" and on the rear tyres it is "255/30R19 91Y".

Does anyone know what the pressures should actually be (for normal driving, conditions, etc)?

mr wilks · Post by **mr wilks** » Thu Jul 14, 2016 7:09 pm

Sounds high

i'm on 235 40 19 front / 255 35 19 rear running 34 & 36 but you can play around with the numbers until you find what suits

David-H · Post by **David-H** » Thu Jul 14, 2016 7:15 pm

Are the tyres runflats or non-runflats?

MarkB1983 · Post by **MarkB1983** » Thu Jul 14, 2016 7:17 pm

DLH wrote:Are the tyres runflats or non-runflats?

They are run flat.

David-H · Post by **David-H** » Thu Jul 14, 2016 7:25 pm

MarkB1983 wrote:
DLH wrote:Are the tyres runflats or non-runflats?
They are run flat.

The recommended pressures for my 19" runflats are 36psi (F) and 42psi (R).

The_Dude · Post by **The_Dude** » Thu Jul 14, 2016 7:33 pm

Was wondering what mine should be on my non runflats?

Any suggestions; they're the 18" size as indicated in the attachment above.

Pastry · Post by **Pastry** » Thu Jul 14, 2016 7:33 pm

I ran mine as per DLH's post above. Ive had non run flats delivered today and I'll be running those a few PSI less as per Mr Wilks post

David-H · Post by **David-H** » Thu Jul 14, 2016 7:35 pm

I run my non-runflats at 33F and 36R.

mr wilks · Post by **mr wilks** » Thu Jul 14, 2016 7:39 pm

42Psi on a 255 30 19 runflat

then folks wonder why the ride is crashy & the alloys split so easy

on Msport susp that must be unpleasant to say the least

Pastry · Post by **Pastry** » Thu Jul 14, 2016 7:48 pm

mr wilks wrote:42Psi on a 255 30 19 runflat then folks wonder why the ride is crashy & the alloys split so easy on Msport susp that must be unpleasant to say the least

And now you know exactly why I've just spent £400 on uniroyals I didn't need! That is much cheaper than new wheels and a weekly visit to my osteopath

Geezah · Post by **Geezah** » Sat Jul 16, 2016 12:21 pm

You really need to take a closer look at your door pillar. I don't understand why the confusion, though it doesnt help when people are giving you pressures for anything other than your 2.0i.

Here is some real world advice. I run non run flats at the recommended 2.0 and 2.2 bar on the door sticker and the car handles great, wear rate is excellent too. Sorted.

Maniac · Post by **Maniac** » Sat Jul 16, 2016 12:47 pm

I confess I run my non run flats a few psi under the door sticker and wear is even. Running at door values is notably harder on the ride. It's important with run flats to run them at or just over the door values otherwise you'll get rapid shoulder wear.

Ultimately only wear patterns will tell you if you're right or wrong so take regular readings while you get the best value for you.

David-H · Post by **David-H** » Sat Jul 16, 2016 1:31 pm

Geezah wrote:You really need to take a closer look at your door pillar. I don't understand why the confusion, though it doesnt help when people are giving you pressures for anything other than your 2.0i.

Here is some real world advice. I run non run flats at the recommended 2.0 and 2.2 bar on the door sticker and the car handles great, wear rate is excellent too. Sorted.

Good advice, noting that the pressures for an 2.0 E85 are different to those for a 2.0i E89 on runflats of course!

Angie4m · Post by **Angie4m** » Sat Jul 16, 2016 1:52 pm

DLH wrote:
Geezah wrote:You really need to take a closer look at your door pillar. I don't understand why the confusion, though it doesnt help when people are giving you pressures for anything other than your 2.0i.

Here is some real world advice. I run non run flats at the recommended 2.0 and 2.2 bar on the door sticker and the car handles great, wear rate is excellent too. Sorted.
Good advice, noting that the pressures for an 2.0 E85 are different to those for a 2.0i E89 on runflats of course!

And on 18inch rims too. However it is a point that there is a sticker in the door.

What I want to know is are the pressure readings from cold/not moved as they should be checked or after a run out and then a check?

techathy · Post by **techathy** » Sat Jul 16, 2016 2:13 pm

Tyre pressures should be checked pre-drive when cold.

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