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Tyre pressures
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old iron



Joined: 22 Mar 2016
Posts: 185

PostPosted: Sun Oct 17, 2021 4:26 pm    Post subject: Tyre pressures Reply with quote

Hope somebody can help me out on this, I have been searching around trying to find the correct or as near correct tyre pressures for my Austin J4 cotswold
camper van. Cant find any info’ at all and I have no idea even as a guess.
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lowdrag



Joined: 10 Apr 2009
Posts: 1585
Location: Le Mans

PostPosted: Mon Oct 18, 2021 6:28 am    Post subject: Reply with quote

Firstly it would depend on usage and weight carried, just like all cars show two pressures inside the filler cap depending on two or four people. I have always found that there are no really correct pressures because different makes drive differently. I needed higher pressures in my Michelin XWX compared to my Blockleys on the E-type for example. I guess it is a "suck it and see" approach. If they look too flat, add a bit, and vice versa. For the front, is the steering light or heavy. And you'll arrive at your own happy compromise.
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alastairq



Joined: 14 Oct 2016
Posts: 1950
Location: East Yorkshire

PostPosted: Mon Oct 18, 2021 9:08 am    Post subject: Reply with quote

When investigating tyre pressures, I learnt [from chassis design gurus] that the pressure differentials between front & rear were the important tbit, as they dictated how the vehicle 'handled.'

I would try 30 psi fronts, and 34 psi rear to start with.

[Are the tyres cross ply or radial? Cross ply tyres may well have lower pressures than radials]

Are the tyres 'van' tyres , or 'car' tyres?
[VAn tyres have more plies in them than car tyres, so requiring less in the way of support from air pressure.]

In the past, when investigating ranges of optimal tyre pressures for trialling, it was useful to have a patch of sand handy on the ground. Then, after selecting one's tyre pressure, drive slowly over the sand with the appropriate wheel, and examine the tyre impression.

This can show whether the centre of the tread is pressing down [too much pressure] or whether the tread centre is lifting up [too little pressure].
It will also show how much the edges of the tyre were digging in[what I was really looking for]...
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
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Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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old iron



Joined: 22 Mar 2016
Posts: 185

PostPosted: Mon Oct 18, 2021 10:40 am    Post subject: Reply with quote

Thanks guys, some great advise as always.
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lowdrag



Joined: 10 Apr 2009
Posts: 1585
Location: Le Mans

PostPosted: Mon Oct 18, 2021 6:25 pm    Post subject: Reply with quote

My crossplies run at 26 psi (with tubes inside) and my radials at 30 psi to give you an idea
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Rick
Site Admin


Joined: 27 Apr 2005
Posts: 22429
Location: UK

PostPosted: Tue Oct 19, 2021 9:01 am    Post subject: Reply with quote

As a starting point I'd get hold of a J4 handbook, it may not cover campers but even van tyre pressures would be a starting point. Ebay has loads for just a few £

https://www.ebay.co.uk/sch/i.html?_from=R40&_nkw=%28austin%2Cmorris%29+j4+handbook&_sacat=0&LH_TitleDesc=0&_sop=15

RJ
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old iron



Joined: 22 Mar 2016
Posts: 185

PostPosted: Tue Oct 19, 2021 12:16 pm    Post subject: Reply with quote

Thanks Rick, I have ordered one of the books.
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