Tyre Pressures - Guidance Please ...

[JimmyRichE85]

I've recently acquired a 2005 E85 which came with a lovely set of Alpina alloys, which were fitted by the dealer when new. I think they are called Dynamic (?) and were the original wheel fitted to the Alpina Roadster S - see picture - they are 235/35 ZR19 on the front and 265/30 ZR19 on the back - Michelin Pilot Sports are fitted on each corner.

I found a scribbled note in the handbook that read 30 psi on Front and 32 psi on Rear - I've checked them today and all are reading 39 psi...

Any guidance on what the optimal psi would be is highly appreciated - thank you

 

[Rsipad]

Depends on what you want. Lower psi = more grip for the tire but more rolling resistance. I run 30F 35R on my 225/40/R18 x 255/35/R18 street set. Helps reduce understeer caused by the stagger in the front and makes the rear grip, but you can break traction on demand

I experimented with 35F 40R and the car felt unstable with that. Going 5 psi lower than 30F 35R also didn't seem to help grip levels much, but decreased mpg significantly. I'd say stay in the 28-38psi range.

 

[enuff_zed]

[ref]Number5[/ref] and [ref]True-Blue[/ref] both have Alpinas.
I'm sure they can advise?

 

[Number5]

I set my Alpina at 32 back and front and that feels right and handles as I’d want it to.

39 seems high, so maybe they’ve been over pumped for storage periods to avoid flat spotting

 

[JimmyRichE85]

I set my Alpina at 32 back and front and that feels right and handles as I’d want it to.

39 seems high, so maybe they’ve been over pumped for storage periods to avoid flat spotting

Many Thanks Number 5 - I think I will put them down to 32 and see if that helps eliminate the tram lining I was experiencing today

 

[Rockhopper]

Another consideration - if run them too high then you’ll wear out the centre of the tyre first, if you run them too low then you’ll wear out the edges first. If you run them very low then you risk overheating the tyre which might make it fail.
Most tyre places seem to inflate them to the pressure in the book which is for run flat tyres, non run flats need a rather lower pressure.
What the exact pressure needs to be for your tyre/wheel combination to maximise tyre life is very difficult to determine!

 

[JimmyRichE85]

Another consideration - if run them too high then you’ll wear out the centre of the tyre first, if you run them too low then you’ll wear out the edges first. If you run them very low then you risk overheating the tyre which might make it fail.
Most tyre places seem to inflate them to the pressure in the book which is for run flat tyres, non run flats need a rather lower pressure.
What the exact pressure needs to be for your tyre/wheel combination to maximise tyre life is very difficult to determine!

Thank you - good advice I’m thinking the over inflation might be contributing to the tram lining too…?

 

[Rsipad]

Another consideration - if run them too high then you’ll wear out the centre of the tyre first, if you run them too low then you’ll wear out the edges first. If you run them very low then you risk overheating the tyre which might make it fail.
Most tyre places seem to inflate them to the pressure in the book which is for run flat tyres, non run flats need a rather lower pressure.
What the exact pressure needs to be for your tyre/wheel combination to maximise tyre life is very difficult to determine!

Thank you - good advice I’m thinking the over inflation might be contributing to the tram lining too…?

That's definitely possible but I'd say alignment and tire model play a bigger factor.

 

[brillomaster]

Standard pressures on 18s are 30f 33r, I'd add 2psi by going up to 19s, so I'd start with 32f 35r.

 

[JimmyRichE85]

Standard pressures on 18s are 30f 33r, I'd add 2psi by going up to 19s, so I'd start with 32f 35r.

 

[Number5]

Standard pressures on 18s are 30f 33r, I'd add 2psi by going up to 19s, so I'd start with 32f 35r.

The OP has 19 inch rims

 

[JimmyRichE85]

Standard pressures on 18s are 30f 33r, I'd add 2psi by going up to 19s, so I'd start with 32f 35r.

The OP has 19 inch rims

Many thanks again Number 5 - I reduced psi down to 32 on each corner and it has transformed the car! The twitchy front end has gone and the ride is radically more forgiving! Roll on the next drive