Tyre Pressures - The Unofficial BMW M5 Messageboard (m5board.com)

Bader · 8th July 2004, 17:25

Hi guys...

I have the 3.8 alloys on my car so I have the wider 9j x17 alloys on the rear.

so thats 235/45/zr17 on the front
255/40/zr17 on the rear

does anybody know what my tyre pressures should be in PSI

i looked at the chart and it lists them in BAR but this has my rear tyres at 44psi

someone please help!!

Mmm-Five · 8th July 2004, 17:29

39-40psi front and 42-44psi rear!

Bader · 8th July 2004, 17:34

Quote:

Originally Posted by Mmm-Five

39-40psi front and 42-44psi rear!

Cheers m8y.

Just out of curiosity...on the tyre wall (and personally speaking I dont think they are marvelous tyres on my car) on the rears it says max psi 44....should i be remotely worried about this ..

its wierd cos the fronts say max psi 50

Mmm-Five · 8th July 2004, 17:36

Are they the same tyre make/model on each end? Have you checked the load rating of the tyre (something most people don't do when they buy a tyre)?

Bader · 8th July 2004, 17:37

Quote:

Originally Posted by Mmm-Five

Are they the same tyre make/model on each end? Have you checked the load rating of the tyre (something most people don't do when they buy a tyre)?

mmmm...

you know what I have no idea!!!

I think its the same make of tyre all round but I havent checked the load rating...in fact...i havent put these tyres on..they came with the car.

what should the load rating be for the m5?

Mmm-Five · 8th July 2004, 17:42

Probably looking for something with a load rating above 93

Bader · 8th July 2004, 17:45

Quote:

Originally Posted by Mmm-Five

Probably looking for something with a load rating above 93

I can answer that.

It said 94w after zr17

i just dont know whether to be worried about such high psi in them?

i will have a proper look when i get home later (shes sleeping under the car port away from the nasty weather

)

Thanks for your help anyways

Mmm-Five · 8th July 2004, 17:47

You've got me thinking now as well, as if I have 42psi in the tyre and then do a good motorway blast, I could feasibly have more than 44psi in the tyre!

Pepsmeister · 8th July 2004, 21:44

Tires can be inflated to a little over twice the Max PSI pressure written on the sidewalls. The reason why the manufacturers put a Max PSI rating is just to be on the extremely safe side.

In the e34 parallel wheels (18s) the pressure can be anything from 43 to 50psi. This depends on the amount of weight on the car and the speed that will be traveled. Keep in mind that for every 20km/h above 200km/h (120mph), it is recommended to boost the pressure by one PSI.

All tires should be inflated when cold, keeping in mind that pressure will build up even more as the tire temperature increases.

If your tires are under inflated, you will wear the outer tread of the tire a lot more than the center of the tread. Also, when hitting a pothole with an underinflated tire, a bubble may appear on the sidewall, which means that the sidewall structure has been damaged.

Overinflated tires will cause greater wear on the center of the tread.

All this was taught to me at the Advanced BMW Driver Training Course.

cheers

Brian M5 · 9th July 2004, 00:34

I agree with the above post.

However in all the time I've been running an M5 (and keeping the tyre pressures at recommended levels) I've always ripped the centres out of the rear tyres rather than getting even wear across the tread. On the fronts It is the opposite.

I've always attributed this to the dynamics of the beast. Loads of wear during acceleration dealing with the rear centres and steering load causing more outer tread wear at the front.

Also with the width of the tyre is it normal to achieve even tyre wear.

Or maybe I need to go back to skool.

BTW There are great deals on Dunlop SP 9000 on UK ebay just now £120 approx.