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Discussion Starter #1
Hello all ,my first post as we`ve had our p38 4.6 hse on lpg about a month now and have just put 18" wheels on to replace the 16"s that were on I`d just like to ask your opinions on the 28 front and 38 rear pressures specified in the owners manual as the 16s looked fine but the 18s on the front look flat ,does anyone use different pressures? I`ve read the thread on the 255/55/18s but would just like to see if there is anyone with some new ideas. thanks Mick
 

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BBB.

With the 18 inch rims, I'd run 36psi all round on a P38 with a coil conversion and a pair of Poly air bags in the rear at 10psi ! !

Depending on the specification stamped on the sidewall of your rubber, check the tyre manufacturer recommended inflation ?

My weekend rocketship is fitted with 18" rims & I found 36psi the best balance between ride comfort and handling compromise.

Cheerio,


Vinniman
'88 Highline
Perth, W.A.
 

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2002-2005 Range Rover MkIII / L322
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Air pressures are more tire type dependant than size specific.

The best way to check is to do the chalk test.

Get some driveway chalk. Put a thick line of it across all four tires. Drive about 10 revolutions in a straight line. Look at the line on each tire. If it's lighter in the middle than on the edges, you have too much tire pressure. If it's lighter on the edges than the middle, there's too little pressure. If it's even across the whole line, you're good to go.

Post some pics of your rig. We like P38 porn here.

And welcome.
 

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Discussion Starter #4
I`ll try and get a few pics tomorrow as its just got dark here.The tyres are goodyear wranglers all 4 and I`ve only had a short 6 mile journey since fitting them and they feel good its just the look of them as though there flat maybe just need to get used to them
 

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Here's another method to get you in the ball park:

Find the max pressure rating on the side of the tire. Let's say it's 2500 lbs @ 55 psi for arguement's sake.
2500lbs x4 = 10,000 lbs. Let's say your rig weighs 5000 lbs with you in it. 5,000 lbs = 50% of 10,000 lbs.
So, using 50% of the max pressure should get you approximately where you need to be.
50% of 55 psi = 27.5 psi.

These are all just random numbers, and yours will definitely differ.
 

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I bought a set wheels w 255/55/18 from USA and all of them had 40PSI filled. B'cos of the road conditions here in LKA
I dropped it down to 34-36 PSI all round
 

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BBB.

The Goodyear's tend to have a more rounded sidewall and I noticed with the Lpg conversion there would be extra weight in the rear of your truck. Does your EAS equpped P38 Rangie level the height of your ride with the Lpg equipment in the back as well ?

Normally the difference with between cold inflation & hot inflation pressures should be no more than 4 Psi as a quick measure !

Just check with the Dealers to see what pressures values were recommended with the 18" fitment versus the 16" wheels too.

Cheerio,


Vinniman
'88 Highline
Perth, W.A.
 

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Discussion Starter #9
Hello vinniman thanks for the assistance , in answer to your question Yes the eas works great with the lpg system I dont carry a spare just one of those small cannisters for inflating the tyre after a puncture.
 

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Discussion Starter #10
hello kmagnuss I`m afraid I dont know how to post pics ,sorry I`m not very computer savvy
 

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Discussion Starter #12
Try this its the only pic I`ve got at the minute as the wife has pinched her this is bigbluebessie with her new wheels
 

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i run 40 front / 44 rear, the 28 psi for the front recomendation is far too low, i would say 36F/40 rear is best setup, maybe less if your roads are junk.
 

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Tire pressures are going to depend on the tire type used. It doesn't matter what Joe Bob, Bobby Dave, or Jesus himself used on his rig, it's all tire dependant.

I used 28/38 and had even tire wear. Doesn't mean squat if he's not using the same tires as me, in the same operating temps.
 

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Discussion Starter #15
Thanks for all the advice, I`m going to give it a run down the motorway and see what it feels like with 38rear 28 front and see how we go then maybe increase the fronts by maybe 2lb and experiment a little.
kmagnuss , I`ll try and get some decent pics as soon as the snow clears a bit.
 
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