20” Tyre Pressure

Good morning,

Just thought I’d pose the question, I took my van in to have the 4 wheel alignment done yesterday, all done but informed that my tyres are well under inflated.

I’ve never really looked into it much, as when I purchased the van the guy stated he runs them at 44psi all round and that’s what I’ve stuck too.

Now I’ve been informed that they should be at 52psi which is a considerable jump up. My tyres are 255/35/20 102xyl.

what do others with 20’s run at please.
 
I run 275/40ZR 20 106 W XL and at 22k miles I’m about to put a new set on.
The fronts have worn at the edges on both sides of each tyre. I have my wheel alignment checked every six months and they have been spot on - so no tracking issues.

There are two times this pattern of wear occurs
1) either the tyres are running overloaded, carrying too much weight- which is not the case
2) the pressures are not high enough

either way both scenarios cause the vehicle weight to be carried on the tyre shoulders and tending to make the central tread face lift up - hence the wear pattern.

The rears are evenly worn across the tread face


So the point of this-
I’ve been running with 40 PSI front and rears.

Now, with the new set, I’m going to up the front pressures to 46-48 PSI to offset the shoulder wear.

So 40 rear and 46 fronts

HTHs
 
I run 41psi front and rear. I've done about 15k so far and I've plenty of life left.

I don't carry much load ever, but I do tow a trailer.
 
Great answer Oldrat.
I also run 275/40ZR20 106w xl on a T28. Haven’t had the van long only 2k in miles from new.

I’m playing with pressures at the moment and have 43 in both front and back. I’m thinking like you that the rears should be less than the fronts but was waiting
to cover a few more miles before measuring the tread depth across all tyres to see how they are wearing.

I bet having your front tyres at 46-48 you notice a lot harsher ride?

Carl1974 - Measure the tread depth of all your tyres at three points, middle and both edges. (Slightly inboard from the edge) If both edges are wear faster and evenly than the centre then as Oldrat says it’s too low a pressure or overloaded. If either inner or outer edge is wearing differently then it’s alignment or you are driving your van too hard around corners. If middle of tread is wearing faster then pressure is too high. The trouble is that you have to wear through your first set of tyres to find what the ideal pressures should be.
 
Thanks Oldrat, slap ed for your in-depth guide.

I’ve only ever ran with them at 44psi, don’t get me wrong sometimes it has felt spongy but not thought any more about it.
The van is used to and from work and a kombi, so no driving hard and cornering. I will try and get a pic and upload if the inside edge of the tyre. Below is what I got from the alignment.

7BFC5FC6-8DA0-4088-8B54-80F6C812F8D8.jpeg

FA950C2D-6040-45BF-93D2-81023A17E654.jpeg
 
Here are 2 pics of my tyres,

1st pic you can see what appears to be a line which like a ridge.

2nd pic you can see that it’s not a slight wear it’s like a step down.

185A07F9-6220-4D51-980B-F136FDAAE63D.jpeg

9395845D-816C-42E6-84D4-04745FE98B5C.jpeg
 
On a 265/40 or 275/35 we recommend and have used extensively 36-40 psi all round. We now recommend all customers to run them at 36 psi, they seem to last longer and run perfectly. Tyre wears evenly across the width.

We ran two identically set up vans last year (both 20’s and Bilsteins), one at 36 all round an done at 40 all round. The 40 wore out completely a lot sooner than the 36. By 12k the 40 PSI van needed rear tyres where as the 36 was only just over half worn.

These vehicles are kombis, carrying passengers.

It all depends what you are carrying too.

My fronts wear on the outer edges, but i chuck my round everywhere, and especially hard around roundabouts!
 
If wheels are set up correctly they should wear evenly across the tread widths regardless of being chucked around.

Wear at the edges is a sign that something isn’t right, if it’s Wearing on both sides then it’s as I described previously above, otherwise look to alignment issues.
 
Sorry that’s not quite right. Most if not all cars/van have more wear on the outer edge of the nsf tyre. This is due to roundabouts and turning right more in their life. Have a look at most big 4wds. All the front nsf outer edges will be worn.

Mine isn’t both edges, just the outers. I’m running GY F1’s with B14’s and arbs. And I really do push it hard when driving. The front tyres take a beating with the weight and the extra work they have to do due to the suspension. The rest of the tyres are wearing perfectly and alignment is bang on.
Come and have a go and you’ll see how much fun it is to drive fast :)
 
Last edited:
Carl1974 - The second picture, assuming that the other 3/4 of the tread is wearing evenly and the other tyre on that axle is wearing in the same manner suggests excessive toeing out. This has the effect of scrubbing the inside tread of the tyres.
How much of the tyre was worn unevenly before you had it tracked?
 
I’m not sure SL,

both front tyres are identical in wear on the inner but just the f/n/s with outer edge wear. It was mot’d in July and it was very minor, so I gather since the 50mm lowering springs I guess.

Not that this helps.
 
BognorMotors said:
We are running 20” tyres in either 275/35 or 265/40 at anywhere between 36-40psi. The 275/40 is an oversize tyre. 46psi seems far too high. On our present 4-motion demo we are running 36 and this is what we recommending at present.

B14’s/arbs ask more of the tyres than the standard suspension. They tyres are working a lot harder, to keep the van stable and level, and provide a better ride. The rears seem to wear out quicker, even on the back of our old 2wd 300PS TSI, they lasted 7-8000 miles, this was at 40psi.

Remember as well, we are using softer SUV tyres on commercial vehicles which doesn’t help the life of them.
Click to expand...

Hi BognorMotor

Just to help with tyre pressure experiment are you using cold or warm to set at 36psi on 275/35/20 ?
Not much but noticed 2.5psi gain from cold to hot.
Also what tyres you running on test 36psi 275/35/20 ?
Thanks
 
Adebus said:
Hi BognorMotor

Just to help with tyre pressure experiment are you using cold or warm to set at 36psi on 275/35/20 ?
Not much but noticed 2.5psi gain from cold to hot.
Also what tyres you running on test 36psi 275/35/20 ?
Thanks
Click to expand...

Always cold, and Goodyear F1 and budgets
 
Interesting thread as earlier this year I bought a T28 campervan that running with 275/40/20. The guy I bought it from told me he ran them at 45psi all round. It seems to be a comfortable ride, but my question is: Does anyone know what the optimum psi should be?
 
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