P38A 19" L322 tyre pressure?

TallPaulB · Mar 8, 2019

I recently put 19" wheels from an L322 on my P38 (yes, I used spigot rings!).

I think @wammers has the same setup. Since there's enough debate about tyre pressures on the standard tyre sizes, what's best as a starting point for these?

wammers · Mar 8, 2019

TallPaulB said:
I recently put 19" wheels from an L322 on my P38 (yes, I used spigot rings!).

I think @wammers has the same setup. Since there's enough debate about tyre pressures on the standard tyre sizes, what's best as a starting point for these?

I use 30 front 40 rear. If you use 2 psi more for each inch increase in wheel size over standard maintaining rolling radius you won't go far wrong.

TallPaulB · Mar 8, 2019

Thanks @wammers I'll give those a go.

By the way, is there any way to tell if spigot rings are the correct size? they fit into the wheels fine, but they didn't seem particularly tight on the hubs. I'm 99% sure they're fine, just that niggling concern in the back of my mind that my wheels are going to come flying off on the motorway.

tarphenry · Mar 8, 2019

I have the 19" Snowflake wheels and the spigots are a good fit ,with a coat of "Copperslip" they just push on.They are also a good fit in the wheel

ukadamwest · Mar 8, 2019

I have the 19's on my p38 and run 28psi all round. have done for 4+ years and get dead even wear across the tread face.

Usual load is 2 adults in the front empty boot and use the same pro for towing tilt trailer with a RR on it.

Its good economy to ensure your tracking is on the money

TallPaulB · Mar 8, 2019

tarphenry said:
I have the 19" Snowflake wheels and the spigots are a good fit ,with a coat of "Copperslip" they just push on.They are also a good fit in the wheel

Hmm, I (stupidly) didn't check the rings on the hubs, I put the rings into the wheels, then put the wheels on. The wheels didn't feel particularly loose or anything, but they weren't at all difficult to push onto the hubs.

wammers · Mar 8, 2019

ukadamwest said:
I have the 19's on my p38 and run 28psi all round. have done for 4+ years and get dead even wear across the tread face.

Usual load is 2 adults in the front empty boot and use the same pro for towing tilt trailer with a RR on it.

Its good economy to ensure your tracking is on the money

The rears have a different pressure than the fronts for a reason. But if you are happy with that so be it.

ukadamwest · Mar 8, 2019

wammers said:
The rears have a different pressure than the fronts for a reason. But if you are happy with that so be it.

Indeed. I ran a higher pressure at first and got wearing across the centre band. at 28 all round it gives even wear. I monitor it with an electronic gauge and that gives the even wear. go figure!

myfirstl322 · Mar 8, 2019

...and what's the reason wammers?

wammers · Mar 9, 2019

myfirstl322 said:
...and what's the reason wammers?

Viscous coupling.

Datatek · Mar 9, 2019

wammers said:
Viscous coupling.

The rear is slightly lighter than the front unloaded and could be considerably heavier when fully loaded, so why would the tyre pressure difference be for the viscous coupling? As far as I can ascertain, it's to accommodate the potential load.

wammers · Mar 9, 2019

Datatek said:
The rear is slightly lighter than the front unloaded and could be considerably heavier when fully loaded, so why would the tyre pressure difference be for the viscous coupling? As far as I can ascertain, it's to accommodate the potential load.

To keep the coupling primed.

Datatek · Mar 9, 2019

wammers said:
To keep the coupling primed.

With 2 sets of vanes in a bath of silicon fluid, how does it get "Primed"

wammers · Mar 9, 2019

Datatek said:
With 2 sets of vanes in a bath of silicon fluid, how does it get "Primed"

Now come on Keith have a think about it.

kermit_rr · Mar 9, 2019

Oh dear, I have 19s on my p38. What's a spigot?
Want to go back to something a bit more of an original size when these wear out, 19 inch tyres seem more expensive and the only real reason for bigger wheels is aesthetic

wammers · Mar 9, 2019

kermit_rr said:
Oh dear, I have 19s on my p38. What's a spigot?
Want to go back to something a bit more of an original size when these wear out, 19 inch tyres seem more expensive and the only real reason for bigger wheels is aesthetic

The wheels are centralised by their fit on the hub centre. The hub centres on L322 are slightly larger than the hub centres on the P38. So a spigots are needed to centralise L322 wheels on a P38 hub.

kermit_rr · Mar 9, 2019

Thanks! Just checked and yes there is a metal band round the hub to make it bigger. Presume that's a spigot! Never noticed before!!

Grrrrrr · Mar 10, 2019

If you want comfort and you don't go on motorways much I'd look out for 16" rims on the bay. If most driving is A roads / motorway then 18".

wammers · Mar 10, 2019

Grrrrrr said:
If you want comfort and you don't go on motorways much I'd look out for 16" rims on the bay. If most driving is A roads / motorway then 18".

19" look so much better and compliment the car. Make it more balanced looking. On normal roads the ride is no different.

Datatek · Mar 10, 2019

Grrrrrr said:
If you want comfort and you don't go on motorways much I'd look out for 16" rims on the bay. If most driving is A roads / motorway then 18".

I have one on 16" rims and one on 18", the ride on the 16's is noticeably more supple on our country lanes.

P38A 19" L322 tyre pressure?

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