its well known that a dencent number of 38.5x14inx15in Swamper SXs come out of round and are basically very hard to tolerate on road.

now, ive posted a bunch of times asking about makign SXs streetable, and from alot of the repsonses, it seems that the 38.5 size is the main culprit with out of roundness. ppl with 36in sxs that ive spoken with report relative smoothness onroad.
my question is to those with experience with the 38x12.5inx15in SXs.
do they have the same problems with so many of the m coming out of round?
i am willing to do just about anything to make sxs tolerable, but its no good to me if i cant go over 50mph.
thanks
~John

my 38.5 sx's were fine. my new 42" tsl's on the other hand bounce pretty good. neiter were/are balanced so take it for what it is worth.

My 36" SXs sucked donkey balls. I ran them at 8 lbs on the street so the bounce would be less noticable, and that was with balancing.

My 38x12.5 TSLs have less bounce and they're at 17psi, on beadlocks, and unbalanced.:D

good lord...any rhyme or reason i was developing with this just went straight out the window.
haha, thanks anyways guys. id still like to hear from anyone runnin the 38x12.5in SX though.
:smokin: :trooper: :flipoff2:

ditto on the 38.5's, they suck on the road. I was thinking about trading them for some brand new 39.5's but I don't want to lose the sidewalls. They are the shit on the trails!!!

I run my 38.50x14.50 SX's on the road all the time.
I drove the Jeep up to Tahoe a few weeks ago, and was averaging 70 -80 mph on the highway. The round trip is about 225 miles.
I run 25psi for street pressure.

I am deffinitely seeing a pattern here though.
You guys who are running low pressures on the road to help smooth the ride are doing excactly the opposite. When your rig sits on those tires all night long at 15 psi, they create a bulding flat spot on one side, which is textbook typical for a bias tire. then you park it and let another flat spot form before the memory from the earlier one has even had a chance to go back to round again. then you try to drive it down the highway, on semi square bias ply tires without enough pressure for them to maintain there profile at speed,....duh I wonder why the tires dont perform well
Geeze you cant run trail pressures on the highway, and expect it to perform well. :rasta:

You're right about the flat spots. I run 13 on the road to keep the contact patch right. 15x9 wheels make the tread baloon out. My biggest problem isn't round it's linearity ??? one of them wobbles (not the rim)

Originally posted by H8monday
I run my 38.50x14.50 SX's on the road all the time.
I drove the Jeep up to Tahoe a few weeks ago, and was averaging 70 -80 mph on the highway. The round trip is about 225 miles.
I run 25psi for street pressure.

I am deffinitely seeing a pattern here though.
You guys who are running low pressures on the road to help smooth the ride are doing excactly the opposite. When your rig sits on those tires all night long at 15 psi, they create a bulding flat spot on one side, which is textbook typical for a bias tire. then you park it and let another flat spot form before the memory from the earlier one has even had a chance to go back to round again. then you try to drive it down the highway, on semi square bias ply tires without enough pressure for them to maintain there profile at speed,....duh I wonder why the tires dont perform well
Geeze you cant run trail pressures on the highway, and expect it to perform well. :rasta:
good points....nice rig dude.

I know you were looking for people with experience with the 12.5" version......but...........my experience with my 14.5's.

Out of 5, one is out of round enough that I don't run it in the front for fear of steering coming apart. It's ok in the rear and smooths out at freeway speeds. With the 4 good ones on and a lot of time and effort getting them balanced as good as possible, I can run 75 mph with no issues.

So it appears that the 38.5's are ok, if you could selectively choose what you get!!! Interco does not warranty for out of round on that tire (unfortunately).

Just my .02cents.

Geeze you cant run trail pressures on the highway, and expect it to perform well.

I know that. Believe me I tried every pressure imaginable from 30 to 6 in 2 lb increments, with balancing, without, all kinds of shit. I finally gave up, left them at 6, and dealt with it. Don't know if it was the tires or not, don't really care. but I was not just dumb enough to say "oh well run 'em at 6 lbs and they better ride perfect, if not they suck:rasta: "

:D

Couple of minor points:

1) having researched the Sxs, the only one that seems to have a worse reputation for being hard to balance and out of round are the ones I have: 35 X 15.5 15 SX. Be hard pressed to find many people who have 4 that are OK. I have at least 2 that are drastically out of round.

2) Due to my death wobble problem, I've tried every combination of air pressure, swapping tires, balancing, blah blah blah. The air pressure for street driving thing is exactly what H8 says: running higher pressures reduces flat spotting, and reducing flat spotting drastically reduces the problems with running these tires.

On the face of it you would think you need less pressure, because at 25 psi only about 1/3 of the tire (in the center) is actually making contact with the road. However, it does reduce flat spotting, and for me, anyway, that goes a LONG way to reducing my death wobbles.

In fact, because I got a set of street tires that I swap on when I have to DD it, I've gone the full route - I try to NEVER leave it parked on the swampers. I mount up my mounted, BB balanced, beadlocked SXs the morning before I go on a run. Because they have not been sitting on the damn things all night long, there is no flat spotting, and they ride as smooth as can be. Makes all the difference in the world.

So the real point is that SXs flat spot terribly.

Also, another thing I found with air pressure: Although running higher temperatures will reduce flat spotting to begin with, I've found that running lower pressures will reduce the amount of time it takes for the carcass to heat up and therefore work the flat spot out of the tire. So for a while I would air UP when I parked it to reduce the flat spotting, then air DOWN when I was about to drive the next morning to get the carcass to flex for that first few miles and try and get it to run smooth. Now you can see why I just take 'em off, eh?

This is why after bouncing and wobbling my way all the way to a trail, they would run smooth as silk on the way home - because you air down at the trail, then flex the hell out of the carcass on the trail, and the flat spots are gone.