39.5x13.50-15LT Irok

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May 26, 2004
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Atlanta, GA
To Big?

I have a 71 40 w/ longs and chromo inners. The rear axles are stock as well as the corse spline pinions. Am I just asking for trouble or is this a reasonable setup?

SOA shackle reversal, and cut fenders so clearance shouldnt be an issue.
DSC0047.JPG
 

John Smith

In the garage
 
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I just went through this decision process and opted for the 36x13.5x15 flavor instead. I know a few guys running the 39s on toyota minitruck based truggys and buggys and even with those light rigs they are having axle failures more often than when they were running 36s and 37s.

If you have a light right foot you may be ok. I want to see pictures if you do get them.
 

woody

unhelpful spotter
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I've got a set of 39.5 x 13.5 - 17 IROK's for mine....great tire. Your coarse spline rear pinion will be a major weak point, but it is regardless. Longs/chromos will hold in front, but your knuckles will be the next to go.

I ran a set of 37 x 13.5 - 17 Pitbull Rockers this past weekend....IMO, they performed as well or better than the IROK's on everything, and were amazing on hardpack steep climbs...I've never had a tire with that kind of traction on launches. Tried a climb in 1st with zero approach, and they tossed major ground as they bit in...tried the same climb with a 2nd gear launch, and it zipped me to the top so fast I wasn't sure I could stop...two of the guys with me are truck pullers and they claimed to be ordering a set immediately just on the tire's performance on that one climb.

The clearance advantage of the 39.5's was the only issue, but the truck still made quite a few lines that it has failed at in the past.

I'm VERY torn now between keeping the 37's as my only tire, or keeping both sets....I was positive I'd like the IROK's better, but am not so sure anymore.... (see the Attica pics in TrailRides)
 

Rascal

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71-CRUISER said:
To Big?

I have a 71 40 w/ longs and chromo inners. The rear axles are stock as well as the corse spline pinions. Am I just asking for trouble or is this a reasonable setup?

SOA shackle reversal, and cut fenders so clearance shouldnt be an issue.
Micheal,

A lot depends on how you drive and what trails you take. The rear pinion is currently your weakest point. After that it is probably a rear axle. No guarantees - just my experience. I was running 38.5 TSL-SX's with Longs and 4340 inners... and with the trails I was running (ie trying to keep up w/ Woody, Nolen, RockTaxi...) I was breaking somethin major every trip. See https://forum.ih8mud.com/showthread.php?t=51130. I'd say if you are not trying to tackle 5 & 6+ rated trails and you are light on the skinny petal then you'll survive for a while. But if not - carry a lot of spares ;)
 
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