19" Maxxis AT Tyres

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Originally Posted by DiscoJeffster

All of my sidewalk damages have been a rock squishing the tread between the rock and the rim. You can hear the clear thud of the rim in the vehicle. This results in a cut in the sidewall. Now I attribute a lot of that to shallow sidewalls and low pressure in most cases. Would higher pressure have helped? Unsure. Maybe the rock would have sliced it before it got to compress to the rim at higher pressure? Dunno.
As has been said, bad luck and poor line is a heavy contributor.

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Only side wall damage I’ve had is in Karajini NP in northern WA, (the gravel is very sharp and hard edged)running highway pressures (my own stupid fault) but on non LT rated tyres. IMHO running LT rated tyres at higher pressures makes sense, deflecting stones rather than allowing them to gouge the rubber. Driving to conditions makes even more sense...

Y

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Originally Posted by Grentarc

I run 265/65R18 on my D4, and as it has the 6 speed box, it is not detrimental having the taller gearing associated with the larger diameter.
This gives me a 172mm sidewall height over the 140mm sidewall of the 255/55R19

The max legal diameter increase is 50mm, which equates to a 25mm taller sidewall (max lift heights before engineering are 25mm tyre and 50mm suspension) which means a max diameter of 814mm, which is a 31.9" tyre.

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Ahhh yes, thank you. I was too tired last night to think it through - thought it was 50mm but couldn’t get my head clear enough.

So a 255/65x19 would be perfect. :thumbsup: Bring it on!

David

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Originally Posted by Odysseyman

Y

Ahhh yes, thank you. I was too tired last night to think it through - thought it was 50mm but couldn’t get my head clear enough.

So a 255/65x19 would be perfect. [emoji106] Bring it on!

David

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The problem then is that it takes a bit of work making a tyre that size actually fit in the wheel well, as when in cross axle situations, the compressed side will tuck higher into the arch than when it's just sitting on the bump stops (as they are springs it sits on as soft stops before it hits the hard stops) - this means arch liners need removing and chassis possibly gets in the way on full lock. Better idea is 31.5" tyres and 18" rims.

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Originally Posted by Grentarc

The problem then is that it takes a bit of work making a tyre that size actually fit in the wheel well, as when in cross axle situations, the compressed side will tuck higher into the arch than when it's just sitting on the bump stops (as they are springs it sits on as soft stops before it hits the hard stops) - this means arch liners need removing and chassis possibly gets in the way on full lock. Better idea is 31.5" tyres and 18" rims.

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By my calculation the 31.5”x18 having a rolling diameter of 800mm and the 265/65x19 a rolling diameter of almost 815mm.

I get it, thanks Justin.

David

I have been reading this thread with great interest. There seems to be a great disparity with peoples thoughts on lowering pressures or not. Sidewall damage in rocky areas is a real issue, one that i encountered last year and as such am now part of the crew that wont lower pressures in rocky areas.
Have a look at an old timers view on the issue, Jack Absalom, travelling the Birdsville track in his Sigma Wagon!!! The Tyres are disucssed in the first few minutes,
YouTube

I look forward to hearing peoples thoughts???

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Originally Posted by DunnToImpress;2860890. Have a look at an old timers view on the issue, Jack Absalom, travelling the Birdsville track in his Sigma Wagon!!! The Tyres are disucssed in the first few minutes,
[URL="https://www.youtube.com/watch?v=YovHsehhiME"

YouTube[/URL]

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I reckon Mr. Absalom knows what he was talking about. Gotta keep that sidewall off the stones and provide enough pressure to carry the load (car+occupants+equipment+...) AND deflect rocks etc.

The Maxxis AT890s are rated for 1215kg at 80psi cold in single configuration, I reckon running at 50psi (hot)is not unreasonable, perhaps even higher depending on load, would not be a bad idea on roads such as the Birdsville track.

just my 2c worth...

Been looking and can not find where you got the 80PSI??? Sounds high.

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Originally Posted by DunnToImpress

Been looking and can not find where you got the 80PSI??? Sounds high.

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It will be on the sidewall of the tyre. 80Psi is normal for the maximum pressure on LT rated tyres, although some are 65Psi.

An issue is most service station air compressors are limited to 60-65 psi, but I guess most of us are carrying our own air anyways. Not sure if I'd ever run at higher than 65 psi though. Assuming fully loaded I'm at 50psi cold and from Mr.Absaloms video, would need to be at around 53-54, then allowing for the 3psi rule, I'd be at 56-57 psi.

I recently drove around NZ south island on LTs (motorhome), they needed to be at 70psi, could not get them there, best was 65psi, at least the pressure was the same on all tyres.

I am afraid that the 4WD cannot go through some difficult level tracks with such high pressure. It should work on rocky and easy tracks.