tyre pressure verses ride comfort

Submitted: Wednesday, Apr 07, 2004 at 19:03
ThreadID: 11911 Views:1650 Replies:9 FollowUps:0
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Tyre pressures!!! Yes I've read the archives. My question is about comfort. Didn't find any threads on that topic. I fitted Geolanders on a 1990 Jackaroo and have kept the pressure high (36+lbs) as recommended by the supplier. I'm noticing the tyres wearing in the middle, due to the extra pressure. At the same time as purchasing the tyres I fitted Cofap shockies from Fulcrum Suspensions (Brisbane). The stiff shockies took out most the body roll. The tyres gave me grip and the high pressure gave better handling, but the comfort level is... "compromised" is a polite word. I feel every bump on bitumen and hitting a pot hole is quite an experience. My 82 year old mum nearly had a heart attack.

I recently lowered the pressure to 34lbs, as recommended by Yokahama. A much better ride but this effects the other aspects of handling as well as slightly worse fuel consumption. My question is, those who recommend 38+ lbs in their tyres what is the ride like in your 4bys?
Paul
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Reply By: GO_OFFROAD - Wednesday, Apr 07, 2004 at 19:23

Wednesday, Apr 07, 2004 at 19:23
Tyre wear is your best indicator of correct pressures, wearing centre, to hard, wearing outsides, to soft.

I run 34-36 psi on road, up to 40 psi loaded, 25 psi for gravel work, 28 for high speed gravel, and my vehilce would be about the same weight as your jacker.
AnswerID: 53589

Reply By: crowie - Wednesday, Apr 07, 2004 at 19:37

Wednesday, Apr 07, 2004 at 19:37
Paul1

Tyre pressures, compfort, handling is a compromise. It all depends on your springs, shockers and type of tyre. I agree that 38+lbs is too much for normal motoring, even with a full load. Unladen you are likely to get wear in the centre treads. I had Koni adjustables on a 92 GQ Patrol an on the softest settings and running 36/38 it was uncomfortaable until the vehicle was fully loaded.

Personally I don't mind around 38lbs rear and 34lb front for day to day town running in my GU Patrol. It certainly is firmer but I don't mind that. I'm quite prepared to run them at 29/34 outback, particularly on dirt and gibber, sometimes lower.

If you want comfort run whatever you like, in cooleor slower conditions let them down a bit, in heat or faster running on sealed roads put them up.
AnswerID: 53593

Reply By: Savvas - Wednesday, Apr 07, 2004 at 19:58

Wednesday, Apr 07, 2004 at 19:58
Paul,

I have BFG A/T KO's on my Jack ... I run them at 38psi and the ride is hard, but they are wearing somewhat evenly.

I occasionally drop them to 35psi all round without too much loss in handling, but consumption does rise as a result.

If I do the Holden recommended 31 psi front / 35 psi back, with the BFG's I get noticeable understeer.
AnswerID: 53596

Reply By: Paul1 - Wednesday, Apr 07, 2004 at 20:40

Wednesday, Apr 07, 2004 at 20:40
Thanks guys, this is really useful. What I am learning is that people give advice, but the advice is meant for a specific situation and not meant to be a rule for most situations. I think I'll go with the idea of carrying/installing a compressor at all times so I can adjust the tyre pressures for each situation. My last trip away was fully laden but on bitumen, except for one stretch of dirt and the high pressures over the corrigations nearly shook the Jack apart. I couldn't let the pressure down as I wasn't carrying the compressor to inflate them again.

Thanks again
Paul
AnswerID: 53605

Reply By: The Banjo - Wednesday, Apr 07, 2004 at 21:02

Wednesday, Apr 07, 2004 at 21:02
Indeed re the compressor....they say that most people know that they should vary pressures but don't because they have no compressor.....mine is underbonnet, with tank and a presure cut out. With a 6m hose (runs to the trailer as well) you can do what you like, when you like.
AnswerID: 53612

Reply By: Bob Y. - Qld - Thursday, Apr 08, 2004 at 05:53

Thursday, Apr 08, 2004 at 05:53
Paul,

Run BFG A/T KO's, 265/75x16, on an 80 series, and have run them at 32 psi all the time. Occasionally, will increase to 34 if weather is hot. Never had a blow-out or destroyed a tyre.

We are almost 200 clicks from nearest bitumen, but don't change pressures, though no doubt ride would improve on dirt if we did.

BFG's don't like stone, and wear a bit severely if subjected to too much.

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AnswerID: 53647

Reply By: Glenn D - Thursday, Apr 08, 2004 at 09:13

Thursday, Apr 08, 2004 at 09:13
Hello all- I might be a bit slow but I dont get the bit about changing pessures due to outside temp ?? and if you did wouldnt you have to let them down when it got hotter ??.
AnswerID: 53659

Reply By: Member - Jeff M (WA) - Thursday, Apr 08, 2004 at 11:10

Thursday, Apr 08, 2004 at 11:10
I run my surf at 38 front 42 rear with 10r Bridgstone Desert Dullers and find the ride "acceptable" I used to run my rocky at 42 f 42 r but it had a much heavier motor and gearbox than the surf. Lot's of gravel work, sht yeah I let them down, sand I run 12psi most of the time. I'm lucky in that I still have my factory shocks with a soft/hard setting which actually works very well and get's a lot of use. My "day to day" trips are 45 mins of 80/90km/h cruising each way to and from work on bitumen. No noticable wear on insides of tryes. In fact on my rocky even at 42psi f and r I still was chopping the sides out of my tryes, however I think that knackered suspension and exccesive body roll that was the main cause for that.
AnswerID: 53669

Reply By: Moose - Thursday, Apr 08, 2004 at 13:31

Thursday, Apr 08, 2004 at 13:31
If they're wearing in the middle the pressure is too high. Try the 4PSI trick to determine correct pressure.
AnswerID: 53683

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