42" Bias Ply Irok's


Here's another tire write-up, this time on the 42" Irok's I have been running for the last year and a half. this isn't meant to be a tire review, rather a write-up with my thoughts on the tires performance based on what I have seen and used on the trails here in Arizona.  The pictures used are in chronological order from oldest to newest and reflect the tires condition as time progressed.

First, a little back story. Project BMP was designed with 39" tires in mind, specifically some 39" Pitbull Rocker's.   I was impressed with the grip of the sample tires we ran down here yet a little concerned with the sidewall strength after seeing some of the 35's slit pretty easily.  After months of waiting the 39" tire Pitbull released ended up being too wide for my chassis/axles (measuring 16.50 wide at full pressure). I ended up limping along on my old 37" Baja Claws for a few months as I evaluated my options.

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The front runner was the 39" bias ply Irok that had been recently released.  After doing some research I discovered their tread depth was a little on the light side (.65) and the tire itself had a balloon shape (I was after a taller more squared off tire). 40" MTR's were out due to their weak sidewalls and tame tread.  About this time Scott got rid of his 37" Krawlers and mounted a set of 42" Irok's on his buggy.  I was impressed with the 42" tire's shape, it was tall and square looking with deep lugs (.75").  

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Here are the 14/42-17 Irok's mounted on a set of two piece Trailready beadlocks. This tire/rim combo weighed in at  129lbs, 31lbs for the beadlock and 98lbs for the tire (which is very light for a tire this size).  The rubber itself seemed much softer than my 37" Baja Claws (when new), I found I could push a screwdriver into a lug and the impression would slowly go away.

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Out on the trails the tires conformed very well to the terrain.  Optimum air pressure for my rig was 5psi.  Anything more than that and the tires had difficulty hooking up on some surfaces. I really liked the sidewall height with the 17 inch rims, there was enough sidewall to let the tire flex yet not so much that the tire would roll over it's own sidewall while turning.  After a few runs I measured the height of the tire at trail pressure (5psi) and came up with 40". 

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Steep stuff still required some momentum although I am finding a lot of that was due to the lack of horsepower. Doing the same obstacles now with the bigger motor has proven easier than with the old 4 banger.

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Tire condition at the beginning of 2006.

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After about 7 months of use the tires were still looking very good despite my 4 cylinder motor being shot.  The edges were rounded and the tires didn't sit quite as tall when new due to the sidewalls being broken in.  As you can see by the shape of the beadlock ring in the second picture, these tires weren't babied. During this time I suffered one puncture on Collateral Damage.  I ran with some plugs in the cut for a few weeks before taking the tire and getting a patch vulcanized over the puncture. 

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Pictures of the tires 1.5 years from when they were first mounted up.  They are ready for a sidewall flip since the outer sidewalls are rubbed smooth. The tires have never come off the inner bead in all the time I have used them. As far as tire wear, I still have .50" of treat left on the tires of the original .75". 

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If it weren't for the special competition compound tires I would place these tires on the top of my tire list. I like the weight, tread depth, tire height at trail pressure and the grip.  I really could not find any downsides for an all around rockcrawling tire. Out on the trail you'd be hard pressed to find a tire that has all these qualities,  Interco's own 39.5" x 17 TSL would come close if it weren't for it's meager 37.5" measured height. 

My next tires will be a set of red label 39" BFG Krawler's.  I realize I am giving up tire durability and longevity in exchange for unmatched grip but as always I try and let the trails determine where my rig needs improvement and right now this looks like a spot for improvement.