BFG A/T's - tyre pressures and fracturing

Submitted: Wednesday, Sep 04, 2002 at 00:00
ThreadID: 1908 Views:1869 Replies:10 FollowUps:4
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Hi all .... I was having a chat with the guys at a local tyre place yesterday and he recommended that I never let the air pressure in my BFG A/T's go below 38psi. The reason for this being that fractures occur at the joint between the sidewall plies and the belting across the tread area. For the last three years I've been running them usually at 35psi all round on a Jackaroo and the only problem I have experienced is a nail through the tread of one tyre (when it was only 2 weeks old). Has anyone else heard about the 38psi recommendation and fracturing?
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Reply By: pathfinder - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
my understanding is that sidewall fractures on rough roads are more likely to occur at high tyre pressures rather than low pressures, with some recommending pressures as low as 25psi for rough dirt roads. On bitumen 36psi plus should be fine depending on load.
AnswerID: 6340

Reply By: ExplorOz Team - David - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
Savas,We love this question (and in fact we are going to release a hot topic feature on tyres). We run our tyres on our heavy 80 series at 34PSI tar, 28PSI for every type of dirt/off road location. Touch wood we have not had any tyre failures for over 18months (since we reduced our driving presures). Yes as soon as we hit a bit or serious dirt the tyres come down. Previously we ran the tyres on the 38+ PSI ranges and we used to blow them (destroy/fracture) all the time.Our current recommendations come from the manufactures and not the retailers. Unfortunately however, every manufacture/tyre and vechicle seems to be different in it's requirements but rest assured reducing your preasure will reduce your stone fracture failures. Also if you have had no problems at 35 or so then do not change. With tyres and presures, the one solution fits all approach does not work.Good luck David
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Follow Up By: Member - Trevor - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
Hello david - What pressures were you using when you did the sidewall in on the Coopers you were using at the start of your trip? Trev
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Follow Up By: Exploroz Team - David - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
Trevor,If you are refering to our trip last year we killed the tyre when it had 35 PSI off road. Since lowering I have not had a flat. The tyre you mentioned happend 18 months ago and was the last one we did before lowering our presures. As it is now we will always always recommend lower presures.David
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Reply By: paul - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
David

What sort of rubber then do you run on you 80 Series - BFG A/T's ?
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Follow Up By: Exploroz Team - David - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
Paul,Currently Coopers S/T and soon to be Coopers STT but even with the BFG we believe less is best. We used to run BFG A/T on our last vehicle and now I will not even look at them. I killed two full sets in less than two years with each lasting about 15-20K kms. I admit we are hard on our vehicle but at this stage we have had much better wear with the Coopers and in fact the best tyres I think we had were Toyo. Anyway, horses for courses there are many choices and as we now fully understand it does not matter what tyres you choose because in no time flat you will wear them out and have to put the hand in the pocket again - Don't like what you get this time try soemthing else next time. For my money I will give the Coopers STT's a go when we next change - about 6 months away I think.Regards David
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Follow Up By: Johnsy - Monday, Sep 16, 2002 at 00:00

Monday, Sep 16, 2002 at 00:00
david interesting subject tyres !i run the bfg 265/75 r16 on my 4.2 td nissan rotate every 5000 ks and will replace 1st set from new at 60000 swhich i feel is a good run ,no blowouts punctures and my standard op pressure on the black top is 50 psi and 35on the dirt sand .the thing that gets me is the the wear pattern is showing as under inflated .by way of usage its about 15000 dirt 20000 high speed 110+ and 20000 rounabouts and stop lights .location the largest beach front real estate in oz (alice spings)just waiting for the tide so there is another piont of view cya johnsy
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Reply By: andy - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
Every time I have bought tyres from retail outlets I have been given quite different advice on tyre pressures from their staff. I called 3 tyre stores for the correct running pressures for my latest set of all terrains and they all gave me different figures. I am on my 3rd set of All Terrains and from my experience on correct tyre info take the advice of people that actually do trips in 4WD vehicles and have "real" experience such as the ones who use this forum. Andy.

By the way I run my 31x10.5x15 A/T's on my Hilux duel cab at 36 on road and reduce it to 18 on sand. 25 when in mud or dirt when loaded. I have never recieved a puncture to date off the bitumen with these pressures.
AnswerID: 6354

Reply By: paul - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
I have BFG's on my 90 Series. Tyre people put them on and said have between 38 and 42 depending on load or you will wear the outside edges down first thus reducing offroad grip of the tyres. After my next service at Toyota the techies let them down to 34. have posted this issue on the Overlander site and never really got a satisfying reply - ....
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Reply By: Will - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
Savvas,

I have been running my 265/75 16 on my GU Patrol for 85000kms, 35psi on bitumen and 25 on dirt, not even a puncture yet.
Did W28631, Vic High Country several times and the Simpson and they are still OK.

Proves the point that the retailer is wrong...!!

Will
AnswerID: 6362

Reply By: Cairns Offroad Training & Tours - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
Most ppl run too much pressure in thier tyres in the mistaken belief they will have fewer punctures. In fact the opposite is true. If a tyre has too much pressure it is unable to conform to rough ground allowing a sharp rock or similar to punch into it, braking and grip also suffer markedly. If your tyre is run at the correct pressure it will conform to the road surface better, grip better and run at its correct temp thus increasing its life, your ride and comfort level also improve dramatically at the coreect pressure and your suspension has a much easier job. Tyre sidewall flex is designed in to become an active part of a vehicles suspension. I usually run my 31\10.5\15 tyres on my cruiser at 34lb cold I have just tried some new 32\11.50\15 tyres and due to thier heavy construction I am down to 30lb all round after dropping in 2 lb increments from 40lb. Tomorrow I will go back to 32 in the front and 30 rear as at 30 I lost a touch of steering precision. Generally I go as low as I can go without effecting my steering control, then I check my pressure after an hours quick run to make sure it has risen by no more than 4lb when hot or it would have been too low to start with. Offroad around 25 sand no lower than 15 or you run a real risk of rolling tyres off your rim. Hope this helps. Cheers Rob
AnswerID: 6368

Reply By: kezza - Thursday, Sep 05, 2002 at 00:00

Thursday, Sep 05, 2002 at 00:00
On road - check appropriate pressures for wide O/R tyres by smearing some silicon in a band across the tyre let it cure then drive 10ks or so see how the silicon wears off the tread do it twice 1/vehicle empty and 2/ vehicle full for long distances (obviously if the middle is disappearing 1st then tyre is overinflated for that weight - edges disappearing then underinflated.) Take notes, use common sense and adjust as necessary.
This method removes the debate on recommended pressures as tyre width, vehicle weight etc etc all vary so 30 psi in a light zook may be overinflated and 34 in a laiden patrol may be way under depending on the tyres.

Offroad you now have a baseline to work with eg 10 psi in a cruiser or patrol plain silly on a zook probably great.
happy bouncin,
kezza
AnswerID: 6379

Reply By: gary - Thursday, Sep 05, 2002 at 00:00

Thursday, Sep 05, 2002 at 00:00
If you think of your tyre as a balloon, and when it's blown up tight and you poke it with something sharp compared to when it is half blown up, you will notice that it takes a lot more effort to puncture it when it is half full.
AnswerID: 6404

Reply By: mike - Wednesday, Sep 11, 2002 at 00:00

Wednesday, Sep 11, 2002 at 00:00
I've used BFG A/T's - LT 235/85/R16's - run them highway 48-50 psi , work great with the 4psi test after about 30 mins driving . I'm now on second set on 92 MAV diesel no probs.-- 60,000 kms. out of first set. Let them down to 38 psi on dirt and - SLOW DOWN - to suit conditions. I have experimented with lower pressures on bitumen --highway and around town , but any less than 48psi feels like you're driving on marshmellows ! Hope this helps all you experts out there.
AnswerID: 6542

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