20” Tyre Pressure

[Trevor S]

Hello all

On 275/35 and 265/40 applications we’ve always gone with and recommended 40psi all round. Recently we’ve been experimenting with different pressures.

We’ve had two t32 Kombi s running Bilsteins and 265/40, one on 36psi and the other on 40psi. Both have covered 12000 in a year.

The rear tyres are worn out on the 40psi van, evenly, but illegal. The other van still has 3mm + left.

Bilstein B14s does increase tyre wear, as more is demanded of them, but running slightly pressures, not only increases ride comfort, but also tyre life.

We are playing around with the pressures on our demo van, running the 275/35 tyre and will report back.

What pressures are you all running, on 20’s and anything to add?

 

[Trevor S]

Running 275/40 on 20'' calibre alloys, checked the pressures, and was horrified to discover 50psi all round. Thought that must have been OK until I looked on here.
I'll try 40psi I think, at least the ride should be a bit softer!

 

[BognorMotors]

My GY F1 tyres are nearly 13,000 miles on a REVO'd 4Motion 204PS and still 4mm+left on them front and rear at 36psi all round

 

[fezza68]

The sticker inside my door says 52psi front and 46psi rear for a 17" tyre. Im running 18" bandeds with 255/55/18 tyres. The advice given to me is to run them to what the sticker says. Mines a t32 lwb shuttle. Anyones thoughts on this please?.

 

[Skyliner33]

The sticker inside my door says 52psi front and 46psi rear for a 17" tyre. Im running 18" bandeds with 255/55/18 tyres. The advice given to me is to run them to what the sticker says. Mines a t32 lwb shuttle. Anyones thoughts on this please?.

This is similar to me. Im not convinced the OEM sticker can be right. Too many variables. ie the OEM wheels will not be as wide (and you have less sidewall than a 17' wheel), does it matter the size of the tyres, Im running 235s

 

[fezza68]

Oli from bognor suggested i refer to the sticker,it doesnt make sense to me though?.

 

[CarpyT6]

I run 36 psi all round, nice ride. Previously had at 40 and was harsh, rough and worse on mpg.

 

[Shredder]

Surely it can't be just a 'one pressure fits all' for everyone on 20's ? ..... don't other parameters matter, like weight of your particular van LWB ? DSG ? 4 Motion ?etc. Weight carried, Camper conversion, work loads etc ?

Leighton Vans also told me 40psi when I collected but over time experimenting I've creeped up to 42psi all round. I run LWB, DSG, 4Motion on 20 x 9 275/40 so it's on the heavier end of the spectrum (bar campers)

 

[CarpyT6]

Surely it can't be just a 'one pressure fits all' for everyone on 20's ? ..... don't other parameters matter, like weight of your particular van LWB ? DSG ? 4 Motion ?etc. Weight carried, Camper conversion, work loads etc ?

Leighton Vans also told me 40psi when I collected but over time experimenting I've creeped up to 42psi all round. I run LWB, DSG, 4Motion on 20 x 9 275/40 so it's on the heavier end of the spectrum (bar campers)

I'm on t28 swb 2wd with only 4 passengers and a couple of mountain bikes, 36 all round

 

[fezza68]

See 36psi seems low to me use on my t32 lwb dsg shuttle se.

 

[Pauly]

Oli from bognor suggested i refer to the sticker,it doesnt make sense to me though?.

Some stickers cover 18 inch wheels also, think thats what he may be referring too ?

 

[Robert]

This is my SWB T30.

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[fezza68]

I think you might be right but mines got info for 16"&17" tyres only.

 

[CALLAKN]

36666666

 

[DaveD]

I run 36 psi all round, nice ride. Previously had at 40 and was harsh, rough and worse on mpg.

That's a surprise to me, how can lowering tyre pressure ever result in better fuel economy, surely rolling resistance is inherently lower at higher inflation pressure?

 

[Dieseldonkey]

That's a surprise to me, how can lowering tyre pressure ever result in better fuel economy, surely rolling resistance is inherently lower at higher inflation pressure?

Don't think 4 psi would make much difference at all, but in theory the higher tyre pressure should fractionally reduce your recorded mileage over over a set distance. In effect, your increasing the radius from the centre of the wheel to the contact patch. So may give the impression of lower mpg if you don't compensate in calculation.

In the same way I run slightly oversized tyres, so have to multiply my mileage by 1.0362 (3.6%) before I do an mpg calculation, when comparing to factory standard size tyres.

 

[DaveD]

So may give the impression of lower mpg if you don't compensate in calculation.

Yes, the pressure does have a slight effect on the rolling radius of the tyre, I believe that is how my tyre pressure monitoring system works, it flags up one or more tyres rotating faster than the others because its rolling radius is reduced by its reduced pressure.
But in relation to real fuel economy, it's simple physics, deflating tyres, even by only 4 psi, cannot improve fuel consumption when driving on tarmac, it can only worsen it.

 

[Dieseldonkey]

Yes, the pressure does have a slight effect on the rolling radius of the tyre, I believe that is how my tyre pressure monitoring system works, it flags up one or more tyres rotating faster than the others because its rolling radius is reduced by its reduced pressure.
But in relation to real fuel economy, it's simple physics, deflating tyres, even by only 4 psi, cannot improve fuel consumption when driving on tarmac, it can only worsen it.

Agreed. Hence the use of the word 'Impression'.

 

[OllieGBR]

I'm running 40psi on 275/40/20 and it feels a little harsh.
I'll try 36psi - is this both front and rear?

 

[BognorMotors]

Yes give it a try and see how you get on.