Front tyre size confusion

S

Sajk

Member
The tyre pressure sticker on my car shows two front tyre sizes. 225/45 and 225/40. The size fitted is 225/40. Does this mean that two sizes were offered from the factory or that the sticker is shared between M and non M vehicles.

I have read that the correct size is 225/45. This may explain the crashyness of the front over large bumps at low speed as the 225/40 fitted has less sidewall. At speed it's not an issue.
 
Afaik 225/40 was for winter tyres ..

Some ‘yoof’ element rendering another car uncomfortable…

What’s the rear tyre?

Same make n model?
 
According to the handbook 225/40 front tyres are recommended for winter tyres to allow clearance for snow chains.
 
The sticker usually covers multiple factory wheel options, not just one spec. Both sizes were likely offered depending on trim/wheel package.
 
Jimmy_Z4 said:
The sticker usually covers multiple factory wheel options, not just one spec. Both sizes were likely offered depending on trim/wheel package.
Click to expand...
The Z4M wasn't offered (as new) with any other wheel package.

You could of course buy the 7.5x18" 164M winter wheel set with 225/40r18 tyres as an additional set. The set had different ET for front and rear (et20 front, et41 rear) so not really swappable front to back...but I suppose you could use 4 fronts and have the rears stick out a bit, or 4 rears have them ticked in more?

Tyre Pressure Label.jpg

Z4M Tyre Pressures.png
 
Last edited:
Thanks i understand. The tyre place fitted the wrong size fronts. It will have to wait as they have only done about 10 kilos. Although I am not sure what the difference will be. Perhaps less crash over bumps at low speed. It feels like it hits the bump stops at times.
 
That little bit less sidewall shouldn't be causing the excessive harshness nor cause it to hit bump stops...sounds more like a spring/damper is knackered (and that's assuming that they haven't also fitted a run-flat in error as that's what was fitted at standard to non-M Z4s in that size).
 
Springs are good. Struts are new b6. At speed it's perfect but sharp changes in the road surface like when the tarmac for one part joins a new bit of road and the is an inch difference between road surfaces where they join need to be slowed down for at surbarban speeds. Or a pot hole badly repaired whic is a big hump. At 80km p hour it makes a big bang. I did wonder if the bump stops on the new b6 were set correctly when installed if that's even a thing.
 
You must log in or register to reply here.
Back
Top Bottom