18" Tyre Pressures

[Ian T]

Hi

I recently bought a set of very nice 18” alloys from SRGTD to replace my 17” Parkers. I must say he was an absolute pleasure to deal with.

Bearing in mind I’ve never really known how automotive engineers calculate the ideal pressure for a given car and wheels etc. Looking inside the door at tryre pressures for 18s I see 42 up front and 39 at the back, which seems excessively high to me. In my Golf R they were 36 all round and my S4 before that was 36 F and 33 R both on 19s

I’m just wondering has anyone experimented with alternative pressures to those stated on the plate?

Many thanks

Ian

[SRGTD]

Hi Ian.

I dare say a primary factor behind VW’s seemingly rather high recommended tyre pressures is mpg and emissions - the higher the tyre pressures, the lower the rolling resistance which will translate into better official mpg and emissions figures.

When I had my Polo GTI+, I used to set the tyre pressures at around 3 - 4 psi lower all round than VW’s recommended pressures. It might have been a placebo effect, but with my slightly lower tyre pressures, I felt the steering feel was better. As for mpg; my long term fuel consumption was around 44 mpg. I don’t know how that would compare to a real life long term mpg using VW’s recommended tyre pressures as I never ran my tyres at the recommended pressures over the long term.

[Ian T]

Hi Ian.

I dare say a primary factor behind VW’s seemingly rather high recommended tyre pressures is mpg and emissions - the higher the tyre pressures, the lower the rolling resistance which will translate into better official mpg and emissions figures.

When I had my Polo GTI+, I used to set the tyre pressures at around 3 - 4 psi lower all round than VW’s recommended pressures. It might have been a placebo effect, but with my slightly lower tyre pressures, I felt the steering feel was better. As for mpg; my long term fuel consumption was around 44 mpg. I don’t know how that would compare to a real life long term mpg using VW’s recommended tyre pressures as I never ran my tyres at the recommended pressures over the long term.

Thank you for being the 'Font' yet again mate .... On the existing tyres it looks like the wear is very even, I'll try doing that. Those recommended pressures seem a bit OTT to me

[TrebleTA]

The default seems best. From my experience. I set mine lower at front and would ware like they was under inflated.
Also note petrol garages and other air pumps can give incorrect preasures, as there not mantained.
I used a petrol garage set pressures drove 50miles got a warning on all 4 for low pressure.
Had to take to a tyre shop, too see my petrol garages machine was messing up, and was 10psi less in all tyres

P.s these are low profile tyres there always higher in preasure, also the polo gti now has a 2.0 l engine that is heavier compared to the 1.8

[Ian T]

The default seems best. From my experience. I set mine lower at front and would ware like they was under inflated.
Also note petrol garages and other air pumps can give incorrect preasures, as there not mantained.
I used a petrol garage set pressures drove 50miles got a warning on all 4 for low pressure.
Had to take to a tyre shop, too see my petrol garages machine was messing up, and was 10psi less in all tyres

P.s these are low profile tyres there always higher in preasure, also the polo gti now has a 2.0 l engine that is heavier compared to the 1.8

I agree I don't trust any forecourt air pumps because you never know when they were last calibrated, if at all.

Yes I'm aware of the low profile thing but I was still shocked by the recommended pressures compared to say my last two cars that had lower profile tyres and were heavier, especially the S4