Puma failure in the Simpson

I have a Tyredog TPMS with internal sensors, they are pretty accurate on the pressure gauge, so I suspect they are not to bad on the temperature side. There is a definite temperature increase on the sunny side, as much as 5 degrees which leads to a corresponding increase in pressure by a psi or two.

Judging by hand, the hubs are cooler than the tyres. Damage may be concentrated in the centre, but the wear is constant - tread depth was almost exactly the same on the edges as the middle.

I'll drop the tyres down to 28 psi cold at the rear on the dirt, and see what happens with the Bighorns.

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Originally Posted by Iain_B

I'll drop the tyres down to 28 psi cold at the rear on the dirt, and see what happens with the Bighorns.

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You'll need more pressure with the Bighorns than what you ran with the BFG's.

Re-read my post above, I need roughly 5psi more for the same load compared to the old KM's, and I'm guessing the KM2's will be much the same.

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Originally Posted by Iain_B

I drove it over a weight bridge before I left.

I'll drop the pressures further over the next leg of the trip. Anyone know how hot tyres can safely run at?

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depends on the tyre build...

I dont like letting tyres get over about 50 deg c. on the tread face...

ball park you should be able to put your hand on the tread for about 5 seconds.

rubber isnt a bad insulator, and the real heat will be inside the carcas where the belts laminates and rubber are all squirming over each other.

if your tread damage is concentrating in the center your pressures are too high, generally, the same chart they use for highway wear patterns applies for off road (unless you're really ripping up the tread on heavy sharp stuff or side scuffing in ruts)

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Originally Posted by Blknight.aus

depends on the tyre build...

I dont like letting tyres get over about 50 deg c. on the tread face...

ball park you should be able to put your hand on the tread for about 5 seconds.

rubber isnt a bad insulator, and the real heat will be inside the carcas where the belts laminates and rubber are all squirming over each other.

if your tread damage is concentrating in the center your pressures are too high, generally, the same chart they use for highway wear patterns applies for off road (unless you're really ripping up the tread on heavy sharp stuff or side scuffing in ruts)

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Bridgestone says over 90c on the tread face is too high, 80c is fine. Other tyre manufacturers say keep it under 100c. The tar mine was parked on last week was 52c... 70c is around the limit for leaving your hand on something IIRC.

Strongly agree re tyre wear patterns. To the OP, I'd run 24 psi cold, keep an eye on your temps and drop from there.

On a solid beam vehicle most of your small bump compliance is in your tyres - they're probably over half of your suspension. However most seem concerned at running low pressures, not sure why - I run down to 8psi offroad and get very little tyre wear - last set of MTs still have an easy 20k left in them after having done 65k including plenty of high country work and offload towing.

50*C in a tyre is nothing.

If you've ever done any pyro readings on tyres, and i mean real pyro readings where we stick the probe into the rubber, degredation doesn't start to occur until you exceed around 90*.

IIRC we can only tolerate around the upper 40* range for skin touch.
I know I can't pick up spanners on 47* days, but maybe that's just not wanting to work in stupid heat either!

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Originally Posted by djam1

Really Pat its such a good sport so few words can get such a huge reaction.
A bit like PhillipA found the in the D4 thread.
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What do you mean? ...us Disco owners never get cranky at Fender owners telling us Disco's are rubbish. ...;)

Interesting to see Dave throwing Puma's under the bus at every opportunity. ...:angel:

Anyway this is a very interesting thread with lots of good reading, even if the old school feel the need to put down Puma's at every chance. ...:angel:

You people are givinmgme the irrits. The missus has given me a leave pass for another Defender BUT the $ would only extend to a Tdi or TD5 (and the latter scares me - a lot).

I just need one of you buggers to have a Puma coming off lease and sell it to me for residual value ! :D

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Originally Posted by VladTepes

You people are givinmgme the irrits. The missus has given me a leave pass for another Defender BUT the $ would only extend to a Tdi or TD5 (and the latter scares me - a lot).

I just need one of you buggers to have a Puma coming off lease and sell it to me for residual value ! :D

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If you want it as a daily driver I'd say stretch to a Puma, otherwise I'd be inclined to go a well maintained TD5 and spend any change on upgrades :D

Me, I'm saving my coin for a 3.2l conversion in a couple if years time :twisted:

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Originally Posted by rick130

50*C in a tyre is nothing.

If you've ever done any pyro readings on tyres, and i mean real pyro readings where we stick the probe into the rubber, degredation doesn't start to occur until you exceed around 90*.

IIRC we can only tolerate around the upper 40* range for skin touch.
I know I can't pick up spanners on 47* days, but maybe that's just not wanting to work in stupid heat either!

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My MTR's were too hot to touch when they fell to bits but the ambient temp was almost 60*C when it happened,I had them between 30 and 45psi but it those situations nothing but a stronger tyre would have helped. Pat

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Originally Posted by PAT303

My MTR's were too hot to touch when they fell to bits but the ambient temp was almost 60*C when it happened,I had them between 30 and 45psi but it those situations nothing but a stronger tyre would have helped. Pat

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The step fathers XZL's fell to bits in similar temps on his old 130 too, IIRC they just started to lose lugs.

The heavier duty a tyre is the more heat is retained as it just can't dissipate the heat fast enough.

IIRC we used to aim for around 85* in the race tyres, although we mostly just went off hot pressures, the pyro only came out during testing with the tyre companies.