troopy tyre pressure

Submitted: Monday, Apr 07, 2008 at 10:26
ThreadID: 56388 Views:5123 Replies:4 FollowUps:8
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Had nothing better to do while doing an oil change so I sat down with a cup of coffee and the owners manual for a 1995 75 series.

I was a little suprised at the tyre pressures. No mention of what pressure to use if you have a heavy load. Just high speed and normal driving pressures.

First question what is high speed and normal driving.

Second question is 35 in the front and 60 psi in the back for driving at 100km with a heavy load sound about right?

Regards Bob
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Reply By: Member -Signman - Monday, Apr 07, 2008 at 10:40

Monday, Apr 07, 2008 at 10:40
What wheel/tyre combination you running??

AnswerID: 297139

Follow Up By: Member - Boo Boo (NT) - Monday, Apr 07, 2008 at 10:43

Monday, Apr 07, 2008 at 10:43
Signman

I have 235/85R16 tyres and 6" sunraysia rims.
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Follow Up By: Member -Signman - Monday, Apr 07, 2008 at 10:49

Monday, Apr 07, 2008 at 10:49
Bob
I think the high(er) pressure for the rear is when fully loaded. I normally run 36psi front & rear (on the road) and might put a couple of extra in the rear when fully packed up.


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Follow Up By: Member - bushfix - Monday, Apr 07, 2008 at 10:54

Monday, Apr 07, 2008 at 10:54
maybe upgrade to 16" rims too eh?

just a suggestion....:)))
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Follow Up By: Member -Signman - Monday, Apr 07, 2008 at 10:56

Monday, Apr 07, 2008 at 10:56
235/85R16...
I think they are 16 ??

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Follow Up By: Member - Boo Boo (NT) - Monday, Apr 07, 2008 at 10:57

Monday, Apr 07, 2008 at 10:57
bushfix

For a monday morning you are very bloody funny, and sharp. How about 16" x 6".

My beloved gives me answers like that.LOL
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Follow Up By: Member - bushfix - Monday, Apr 07, 2008 at 11:09

Monday, Apr 07, 2008 at 11:09
yeah i can't work it out, it is monday morning indeed, must have been that bang on the head earlier.

high speed - open road highway/freeway

normal - built up/around city

re tyre pressures, signman should be on the money but depending on your load and the road/track type, I would check with the manufacturer/distributor if poss, for a guide, then experiment.

ha ha cheers.
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Follow Up By: splits - Monday, Apr 07, 2008 at 11:55

Monday, Apr 07, 2008 at 11:55
Boo Boo

I did check with the tyre manufacturer and was told to use factory pressures and a 1 psi increase all round would support an additional 70kg in vehicle weight.

I got a bit curious later on and decided to do a bit of calculating. I divided the maximum load one of them would support by the maximum permissable pressure and got the weight 1 psi would support. When I multiplied this figure by four, it came to 69 point something which ties in with a 1 psi increase supporting an additional 70 kg just like the manufacturer said.

When I worked out the weight on each wheel, ignoring the weight of the tyre at this stage, and divided it by the weight 1 psi would support, it came out less than 1 psi off the factory recommended pressures.

I have ordered a different type of tyre with a heavier load rating and have been told by the State distributor that they will need higher pressures. I tried the same calculations and the fully loaded pressures were about 6 psi above factory pressures for the lighter tyres which looked realistic and are about what I would have guessed.

When I get these tyres I will put each end of the car on a weighbridge and do the calculations again. That will give me a good starting point and I will see what happens from then on.

This may be the way pressures are calculated. As sure as can be the factory does not guess and they won't put something in the book that does not work.

Try the same calculations with your tyres and see what happens.

Your pressures do sound about right and from memory are what we used to put in troopies in a Government job I had a few years back. That was with 7.50 x 16 tyres though and yours may be slightly different. Try ringing the tyre manufacturer. It would be interesting to see if it can be worked out mathmatically.

Brian
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Reply By: Peter 2 - Monday, Apr 07, 2008 at 19:33

Monday, Apr 07, 2008 at 19:33
I owned four troopies from a 1981 45 series through to a mid 90's HZJ75.
Mostly ran 7.50 x 16 x 8 ply on splits and after the 100 series came out 235 x16's
With a load (family and camping gear) I always ran 40 psi front and 45 min to 55 max on the rear when loaded on the highway.
They were slightly lower especially off road and on the dirt but still in the 35 -45 range and speed kept below 80kph.
The 235's ran slightly lower pressures especially on the dirt and off road as they were not as stong a tyre.
The tyres always wore evenly and I never had any failures in over 25 years with usually 3 months of every year spent outback. The tyres were the standard Roadgrippers as supplied on new cruisers.
Peter
1996 Oka Motorhome

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AnswerID: 297248

Follow Up By: Topcat (WA) - Monday, Apr 07, 2008 at 20:49

Monday, Apr 07, 2008 at 20:49
I fully concur with Peter2. When my Troopy is fully loaded I run 40psi on the front-45psi on the rear(cold) & find the 4psi pressure difference from cold to hot running on the black stuff is pretty spot on running the same size rubber (235x16). Cheers.
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Reply By: Richard Kovac - Monday, Apr 07, 2008 at 21:42

Monday, Apr 07, 2008 at 21:42
Bob

we are the same as below

"7.50 x 16 x 8 ply on splits"

run 40 psi front and 55 psi rear fully loaded around 3.2 tonne, I will drop them by 10 psi all round from what ever they are reading at the time when on dirt full time,

when I check them in the morning they are pretty close to 30 front and 45 rear (maybe 40) this has worked now for around 4-5 years.

Cheers

Richard
AnswerID: 297288

Reply By: Member - Boo Boo (NT) - Tuesday, Apr 08, 2008 at 09:24

Tuesday, Apr 08, 2008 at 09:24
gentlemen

Thankyou for your advice, It is appreciated.

I'm due for a new set of tyres soon, but I will go to the archives for that one,LOL

Regards Bob
AnswerID: 297343

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