Tyre pressure advice needed....

[TRBN8R]

HI guys.....

Got out with guys from work to Lake Lyle, Mount walker etc this friday. I was running my new MTZs for the second time in the bush on 18psi. Some spinning happened on Mt Walker and on a small climb after the river crossing, But nothing I would call extreme spinning. Today I was looking at the tyres and discovered severe chipping and cutting on the tread blocks on the outer tread blocks of the rear tyres.

I had STTs before and ran them on 18psi but never had such extreme chipping. My JK has only mild mods with 2.5 inch lift, Mopar front bar and AEV rear bar. I was carrying 1 passenger and about 70 Kilos in tools, food supply etc. I do not have any racks, drawers etc to add weight. Tyres are 285/70/17 MTZ with only 5000 Ks on them. Cant understand what I am doing wrong. Can I have some advice from the brain bank whether to increase the tyre pressure or take it further down for terrain like Lake Lyle.....

Cheers

Mani

[jeep_jk112]

You would be in shock if you had seen the sate of my atz's after only a year....
Even noticed one of the outer blocks are completly missing ???
Thinking of hassling tyrepower and mickey thompson about it, seeing as my tyres are now worthless after only (1yr)10,000 k's......
On the other hand a mate had the same issue with slicing on his new mtz's and mickey thompson replaced 2 tyres without dramas.
Can't comment on pressures as im no expert, but i run 20psi everywhere off ashphalt.
Go and have a chat to the place where you bought them from and voice your concerns about the state of your tyres, can't hurt??
It payed off for my mate.

Cheers,
Matt

[ick72]

As far as I know a lot of mud tyres have a hard compound base . This causes problems when running on hard surfaces I once ran simax diggers on a hilux and only two months in use (traveling to qld and nt ) they were shot . I was missing complete lugs and others had large gauges out of them . I would speek to Mickey t about the concerns as I would not be happy with that for the price . This is just my finding and point of view

[Paul-JK]

Matt, I had the same thing with my ATZ's. First trip out (just got them fitted for the trip) they chipped up a lot more than I was expecting, and a lot more than the OE Wranglers ever did regardless of what pressures I ran or how much shit I gave them. I had 1 replaced as it tore under one of the side biters and that was on a relatively easy trip. The guy I was with was running near bald HT's and got through OK so it wasn't that hard! All in all they'd done about 3000km at that point, at least 2500km of which was on tarmac.

Mani, I'm surprised you had so much chipping at 18psi. Like Matt I now run mine (285/70/17 MT ATZ's) at 20psi as soon as I get off road and have found they don't seem to chip too badly at that pressure. The trip I mentioned above I had them at between 22psi and 25psi depending on the terrain, which was a bit lower than I would have run the OE Wranglers at on similar terrain but in truth that just wasn't low enough for these tyres. For more difficult stuff I'd expect to drop them bit further but to be honest I'd probably have tried something like 18psi as well. I had a run around that area a few months back (though didn't try Mt Walker itself) and didn't notice any significant chipping, and that was probably at 20psi.

I'd have a go at speaking with MT. I found them very accommodating when I spoke to them. Can't hurt anyway. Probably wouldn't bother speaking to the tyre shop as unless it's an obvious manufacturing error they're unlikely to push too hard to get you new tyres but if you go direct you can push as hard you want. I found I got a better response from them telling them about everything you did to avoid tyre damage (ie low pressures) and then comparing them to other guys on the same trip running different tyres (who presumably didn't have any damage) and then asking them is that what they expect of their tyres, rather than having a go at them and demanding they do something.

Paul

[Bear]

I run my MT MTZ at 40psi on the black stuff and 20psi off road with no noticable chipping. The tyres are fitted to standard JK 17inch rims, and have done approx 25000k.
I have noticed that if I drop the pressure below 20psi in an off road situation they have a tendancy to roll a bead and lose pressure.

Bear.

[Miraz]

The MTZ's have a bit of a bad reputation for chipping and breaking up - it's worth having a word to the tyre shop, as the distributor has been replacing them in response to complaints. I ran a set of 33" MTZ's for a while and they damn near fell apart - whole lugs ripped off them....35psi on the road, 15-25psi off the road.

[SteveC]

Mani
While I have not run mtz I do have a set of KM2 and never had reason to let them below 22. They work well with only very minor cuts so far, but you'd have to look hard. I had them on the WJ a much heavier Jeep and now on the JK. I would not expect the MT's to be that different IMO . I run them at 35 on road, as stated in the placard.

[Miraz]

The KM2's are much better in this respect...very different construction

[redrubi]

Mani,

I run my MTZs at about 18 psi depending on terrain sometimes 14 - 15 psi (Mt Walker etc)

Some minor chipping but nothing noteable.

Cheers

Andy

[Steve F]

The KM2's are much better in this respect...very different construction

Yep, I found the KM2's dont seem to chip at all (my Maxxis Bighorns did), I run them pretty low (15psi) off road though as the XJ is quite light and the 35's pretty stiff. When we were doing reccies for Jambo there were a couple of times where I didn't air down on impromptu trips through the tracks back to the main road and even at 30psi no chipping or traction issues.

Cheers
Steve

[TRBN8R]

Thanks guys.....

Will try talking to Mickey T and say what they say. Will run at lower pressures probably 15 from next time..... Just another question... My old STTs were Load rated D.... These MTZs are Load rated E... Will this require lower pressures to acieve same amount of bagging out....... Washed the car and re checked the tyres. the chipping is moderate and not as extreme as it first apeared....

Cheers
Mani

[Paul-JK]

E load rated tyres will have stiffer side walls and so require lower pressures than D load rated. I thought the 285/70/17's we generally D rated though (the 265/70/17's are usually E rated for some reason).

Just checked on the MT website and the 285's are 8 ply (which I thought was equivalent to D rating) where as the 265's are 10 ply.

[SKIZZI]

Mine are in pretty bad shape but I'm not kind to them at all any more. Don't even bother airing up until I get to a servo. I run them at 12psi off road and until i air up (sometimes 40km after i get on the asphault) and even though they are missing half the lugs they give good grip and have not had problems yet :P
Ill be kinder to the 40s when i get them :P

[Wooders]

Yep, I found the KM2's dont seem to chip at all (my Maxxis Bighorns did), I run them pretty low (15psi) off road though as the XJ is quite light and the 35's pretty stiff. When we were doing reccies for Jambo there were a couple of times where I didn't air down on impromptu trips through the tracks back to the main road and even at 30psi no chipping or traction issues.

Cheers
Steve
On my XJ I'd generally drop to 12PSI and on a few occassions went to 8-10PSI.
I've always thought a most of people run too much pressure in their tyres which means they are generally more suseptable to tyre damage (& miss out from more traction).
IMHO if you aren't accasionally poping a bead chances are you are running too much pressure.

[D.K.]

The only down side to running low pressures, say 12 psi and less, is that i have found it more likely to get muck or grit trapped in bead. Usually have a deflated tyre after sitting in garage for a few days.

[reyzor]

Beadlocks!!!!!!!!!!!!!!!!!!!!

:p

[Steve F]

The only down side to running low pressures, say 12 psi and less, is that i have found it more likely to get muck or grit trapped in bead. Usually have a deflated tyre after sitting in garage for a few days.

Yep, even at 15 I had to occasionally pop the bead off at home and clean the crap out to stop a slow leak.

Cheers
Steve

Sent from my GT-I9300 using Tapatalk 2

[Wooders]

Yep, even at 15 I had to occasionally pop the bead off at home and clean the crap out to stop a slow leak.

Cheers
Steve

Sent from my GT-I9300 using Tapatalk 2

That's just par for the course when playing in the goop.
But how many times did you lose a bead on the trail? ;)

[rupicon]

mani i recommend you experiment with lower pressures while leaking beads are a pain the gains are worthwhile.
i run my 35baja claws well below 10 psi i am addicted to how this improves grip and makes life easy on the drive train.
i do have beadlocks which have their pros and cons too.
in my experience on a dry run not much chance of developing a leaky bead but when its wet or your hitting every bog hole thats another story.

[Wolfe]

I used to run as low as 5psi with the maxxis creepy crawlers now I run good years down about 10 psi