Tyre pressures

Submitted: Friday, May 02, 2003 at 16:39
ThreadID: 4695 Views:1756 Replies:11 FollowUps:3
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Age old discussion, what's the concencus out there about the tyre pressures, I have a 92 GQ with the little wheels 31.5 X 10R X 15 BFG All -Terrains, I normally run around the 38 psi mark, my mate has a 96 GQ and has the 265 X 75R X 16's BFG All-Terrains and he runs around the 50 psi mark. He seems to have a lot more punctures when out in the bush, I think he's running the pressures a tad to high, because of that we've decided to go out to the audience, my phone a friend option didn't cut the mustard, I've had I realise different pressure for different applications what's the feeling? Keep the shiny side up
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Reply By: Member - Bob - Friday, May 02, 2003 at 17:06

Friday, May 02, 2003 at 17:06
I reckon you vary the pressure depending on the load. Unladen, the rears on a big truck might run at 30 psi. With a load and trailer you might increase to 45 or 50 psi to preserve tyre profile (and reduce heat build up due to flexing) and protect the sidewall from road contact, but you will have an increased risk of puncture/ stone damage through tread. That's the cost of carrying the greater load.
AnswerID: 18989

Reply By: Andi - Friday, May 02, 2003 at 17:46

Friday, May 02, 2003 at 17:46
I have exactly the same tyre and wheel combo on my 60 series cruiser & I run them at 32psi on front and 35 on the back, running for 3 years and no damage yet, must admit though 80% of driving is on bituman with tradesman trailer on back.
I think your friend may be sacrificing side wall wear for a frustrating time in the bush if you have to keep stopping to fix punctures.
AnswerID: 18991

Reply By: bruce.h - Friday, May 02, 2003 at 18:16

Friday, May 02, 2003 at 18:16
Gday Martyn
its a bit like sticking a pin into a balloon the more air in it the less flexabilty & more resistance thus making it easer for the pin to enter the balloon the less air the more give in the wall the harder it is for the pin to penitrate as to best preasure as others have siad it is horses for courses but i aways run mine on 35 -38 psi & can count the number of puctures ih ave had on one hand
Regards bruce
AnswerID: 18994

Reply By: GPA - Friday, May 02, 2003 at 18:41

Friday, May 02, 2003 at 18:41
91 GQ SWB 31x10.5x15 Yokohama Geolandar's

Normally I run 32psi front, 34psi back - up to 36/38 loaded for hols. Tracks at 24/26psi and beach at 18psi (all round) and occassionally down to 12psi. So far no punctures and no tyre damage (touching wood).

The previous owner towed a 17ft boat, and had them at 40/42 - however there are clear signs that they were over inflated as the centre of the tread is noticeably worn.
AnswerID: 18997

Reply By: Member - Martyn- Friday, May 02, 2003 at 20:43

Friday, May 02, 2003 at 20:43
Sorry about the spelling "CONSENSUS",
dear Explor Oz.com, spell checker please................Keep the shiny side up
AnswerID: 19009

Reply By: diamond - Friday, May 02, 2003 at 21:11

Friday, May 02, 2003 at 21:11
a general rule we use at work(iim in tyre buisness)a big fat tyre 31x10.5x15 265x75x15 ect being big and wide is whats known as a baloon type tyre so there lots of air in there so it heats up a fair bit so we run then at about 32psi to start and then consider in what the customer uses there vehicle for.as in a builder who has lots of loads on roof rack or tow a trailer with big loads on it then we adjust to suit so if they carry heaps we set at about 40psi in rear and 34-36 in front and go from there.where as if you have a 205x16 750x16 being a little taller but skinny we run then at about 40 to start with and adjust the same as the bigger tyres more weight more pressure.if people come in and say does it look like my tyre presures are right i look at the tyres and if there running flat i leave them.if there a little high in the middle add a few more pounds or if middle is wearing more let them down a few pounds.from what ive seen in 15 years of tyres theres no such thing as the right tyre presure to suit every one.as for your friend running 50psi no wonder hes getting punctures.the tyre has no give in it to conform around things.its a little like when you drive on sand let your tyres down low.reason being they give you more area on sand and become a little more floatier.and when on rocks or rocky tracks you also let them down to allow tyre to drive over rocks and being soft allow tyre to absorb(only word i could think of)rocks and not go straight through tyre because of no where to go
AnswerID: 19011

Follow Up By: Member - Willem- Friday, May 02, 2003 at 21:23

Friday, May 02, 2003 at 21:23
Thanks for your insight Diamond. It makes a lot of sense. I found that running 7.50x16's at 50psi gave me lots of punctures mainly due to tube failure. These days I run pressures around 35psi and, touch wood, have had no punctures in the last two years.

Now I'll probably get a flat tomorrow:-)))Cheers, Willem
Never a dull moment
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FollowupID: 11934

Follow Up By: Member - Martyn- Friday, May 02, 2003 at 21:58

Friday, May 02, 2003 at 21:58
Diamond,
Seeing you are a bit of a tyre guru I'm just about to re shoe my "bush hack" my trusty Rangie, I'm really struggling as to which way to go with brands, I've always been a BFG person but I hear more and more about Coopers, I also hear some bad things about BFG's now they are coming out of Tiawan, is any of this truth in any of this? personally I've never had any bad experiences with BFG All - TerrainsKeep the shiny side up
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FollowupID: 11936

Follow Up By: diamond - Friday, May 02, 2003 at 22:19

Friday, May 02, 2003 at 22:19
nothing wosre than trying to tell people what tyres are the best someone will always disagree.i use cooper s/t on my gq.we dont sell cooper as bendigo already has a distributer.cooper tyres from what i see are doing the ks less punctures coming in from cooper compared to bfg.now they say(bfg)have improved the new tyres.all they did was run the tread down the side wall(ko) they tell you to give you more grip but its been done to improve the strength of the side wall.rather than actually strenghthen it.some sales people will go on about bfg having tri guard side walls(3ply)cooper have 2ply side walls.difference being bfg 3ply size of your pinky compared to coopers 2 ply size of your thumb.there for cooper actually stronger.i see people day after day telling me they got 100000ks from there last bfg and will be lucky to get 50000ks from my new ones.true.we are a bridgestone dealer but dont even ask about duellers(lol).new sales man at work was good year dealer(beaurepair) and claims department and tells me of lots of claims.(dont hasstle me lol there his words)so basically if it was bfg or cooper i would go the cooper everytime.im actually waiting for the new st to come out.sell my tyres and update to new ones.
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FollowupID: 11939

Reply By: zigglemeister - Friday, May 02, 2003 at 23:11

Friday, May 02, 2003 at 23:11
Something people don't always consider is that the more pressure you have in your tyres, the more vibration you are transferring to your car on uneven surfaces. If you're running on bitumen, not a problem, but if you're doing a heap of k's on corrugations, it is worth thinking about. Even if choosing lower pressures means you do get a few less k's on your tyres, you're potentially saving wear on steering components, shockies, etc, etc, and reducing the chance of stress cracking in the chassis and body. Personally I'd never go near 50 psi - your 38 is about as high as I've ever run. In the bush I'd run lower - on the 60 series I used to have, I would run low 20's, and I never had a flat.
AnswerID: 19019

Reply By: Truckster (Vic) - Friday, May 02, 2003 at 23:37

Friday, May 02, 2003 at 23:37
Another thing to consider, is how much crap does each car carry..

One has winch, wich bar, rear storage, fridge, recovery gear etc,is going to warrant higher pressures.

Your magte can sort this out real easy ... try lower pressures a few weeks in a row around same terrain he gets flats on now regularly, and there you go...



YMMV
AnswerID: 19021

Reply By: Slammin - Saturday, May 03, 2003 at 00:06

Saturday, May 03, 2003 at 00:06
This threads getting long but I'll throw my 2c in. I drive 75% dirt and the thing I look at is the profile, you need a bit of a bulge but not so much that the sidewall is in easy contact with protrusions, keep that in mind and the load doesn't matter.
As above remember the tyres are the 1st part of the suspension. I can judge by eye and find I'm right on the recco press. Tubes are important because they help prevent star punctures.
The motor sport where you need most grip, dirt biking I run 15psi in the front and 12 in the back!

AnswerID: 19022

Reply By: Member - Martyn- Sunday, May 04, 2003 at 20:00

Sunday, May 04, 2003 at 20:00
Thanks to all out there for the info. Great stuff. I'm new to this web site and it's worth every cent.Keep the shiny side up
AnswerID: 19106

Reply By: Chris from North West Camper Trailers Hire & Sales - Wednesday, May 21, 2003 at 23:45

Wednesday, May 21, 2003 at 23:45
Sorry about adding to a long thread but I remember reading a couple of years ago in a 4X4 magazine about this subject and their way of working it out no matter what surface or size tyre was to measure the pressure cold and then drive for 1/2 hour or so that the tyre is warmed up and then remeasure, the aim was for approximately 4 psi rise in pressure, if there was a higher rise then you needed more air due to the tyre being down too much and heating up, and if less than 4psi let some air out.
Seemed to make sense at the time but I havn't tried it.

Chris
AnswerID: 20726

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