Alloy wheel tyre pressures

[giraffeinbath]

I'm sure this has been asked a thousand times but a search hasn't brought any definitive results and I'm sure it's an easy answer for those running a similar setup...

Do the standard pressures as per the original steels on the front/rear tyres still apply, or is there a deveation from this relative to the change of size?

Front 175/55 R15
Rear 195/65 R15

 

[sparkywig]

I've got 175/55/15s and 195/70/15 and running 36psi front and 48 rear. Even tread wear and rides OK.

 

[giraffeinbath]

Cool, thanks

 

[fallingoffalot]

I think it depends on your tyres. I've got C16 van tyres on rear with about 50 psi. And smaller extra load 4x4 tyres on front with 42, rides really well, look to be wearing evenly and, most importantly, is stable in cross-wind.

 

[milfredo]

Do you just look on the tire for the psi? How would one determine what pressure to inflate them to?

 

[fallingoffalot]

Pretty much, yeah, on the rears I think it says max 65psi, and the load rating is 106 or something like that. On the fronts the LR is 94 and max is 55 I think. So I just put a little less in as I'm not a fully laden van and it's not as heavy as a 4x4. But the load rating is correct when the tyre is at its max pressure.
Just for comparison, when I got the van it had 16" alloys on, with normal car tyres inflated to about 35 psi. Thought nothing of it until I drove down a dual-carriageway with a gusty cross-wind, I was all over the place, it was quite scary.

 

[naskeet]

If

Pretty much, yeah, on the rears I think it says max 65psi, and the load rating is 106 or something like that. On the fronts the LR is 94 and max is 55 I think. So I just put a little less in as I'm not a fully laden van and it's not as heavy as a 4x4. But the load rating is correct when the tyre is at its max pressure.
Just for comparison, when I got the van it had 16" alloys on, with normal car tyres inflated to about 35 psi. Thought nothing of it until I drove down a dual-carriageway with a gusty cross-wind, I was all over the place, it was quite scary.

If one researches tyres in more detail, one finds that the maximum permissible inflation pressure, is not generally the inflation pressure at which the maximum load rating is defined.

WHAT IS MAXIMUM LOAD FOR A TIRE?​

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=195

WHAT IS MAXIMUM LOAD INFLATION PRESSURE FOR A TIRE?​

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=196

There is a lot of discussion about 1968~79 VW Type 2 tyre pressures on The Samba "bay-window bus" forum. The factory-standard tyre pressures for my 1973 VW "1600" Kombi based Westfalia Continental, with 185 SR14 Reinforced radial-ply tyres are 30 psi at the front & 37 psi at the rear with up to 3/4 of maximum load and 40 psi with 3/4 to full load.

For 6 x 16 inch, 6.5 x 16 inch & 7 x 16 inch alloy wheels, one can obtain a wide variety of Reinforced / Extra-Load or Commercial-Van tyres, in 60-Series & 65-Series.