Tire pressure for 17 or 18 inch alloys please?

[chewbacca]

Hi guys.

I've used the search function, but struggling to find an answer.
Basically I've swapped my tires out for a different size and would like to get a sensible pressure to inflate to. I get its a bit of a guessing game, but can't decide where to start.
The bus is a tin top with a bit of a camper build inside. Not particularly heavy. (Except for when I'm in there! )
Tires are a 235 / 45 / 18 with a 98 load rating if that makes any difference.

Be nice to find out what works for the rest of you with big daft wheels.

Cheers.

[chewbacca]

So no-one then. I'm the only person on here with 18s.

[clift_d]

Maybe you could try and find some values for that size of tyre on a T4 or T5? I'm guessing the GVW of those vans is not dissimilar to a T25.

[chewbacca]

Thanks for the reply.

I did have a look but it seems to be all over the place. 1 guy is running at 60psi!

I guess I'll just have to keep watching the wear.

[kevtherev]

The van mass is the same, the number of road wheels is the same... so the pressures should be too
Use the VW pressures

[slowcoach]

Going from bicycle experience, it depends a lot on the volume of air/tyre volume. I weigh the same when I ride my mountain bike and road bike, yet one needs 40psi and the other 100psi. The only difference being tyre thickness and their volume.
I'm open to being shown wrong, but the difference there is huge (40psi on the thin road tyres is a flat tyre, 120psi on the mountain bike would blow the rims apart).
?

[chewbacca]

I sort of tend to agree with that. I've found pressures on lower profile tires are often completely different to stock. I'm certainly no expert though!

[chris7ian]

Although logic tells me to run stock pressures I run slightly lower than stock on my 17" (and 18s before them) summer wheels than I do my 14" winter wheels. Stock is stated at 53psi!!! on the rear of my Multivan but I've settled on 33/43 front/back.
On my bug with 17s however I run stock pressure

[RogerT]

Maybe this? It's an interesting question.


http://www.uklegacy.com/forums/index.ph ... pressures/" onclick="window.open(this.href);return false;

[kevtherev]

Boyles law is in operation here