Calgary Jeep Association
4x4 Related Groups => Tech Talk => Topic started by: jenny on April 20, 2008, 11:57:00 AM
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Can the folks who do serious offroading suggest from their experience what is the best tire pressure to run at? I have 35 MTR's..not sure if this makes a difference or not?
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I run my 31's @ 15psi with out bead locks, but with bead locks you can run as low as 6-3psi.
gotta make sure you have a reliable way to refill before you hit the pavement again.
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Can the folks who do serious offroading suggest from their experience what is the best tire pressure to run at? I have 35 MTR's..not sure if this makes a difference or not?
I generaly run my tires at 8-12 PSI off road.
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i ran my rubicons with 33" at 10lbs. nathan did the same, same rims with 31" mtr's when were out together.
they are 8" aluminum rims. tires do matter. sidewall strength matters the most. blowing a bead is not a huge deal, puncturing a sidewall is the suck.
i'd start at 15 and see how they are.
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i have 33" mtr's on 8" wide rims. ive had them down to 8psi without blowing a bead. but ive never had them that low and driving fast into a hard turn. they have excellent traction at the 10psi mark. and yes, a good air pump is mandatory.
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I run 33" TSL's at 12 psi on 8" rims with no problems.
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A good way to determine the safe amount of deflation for your setup, if you have tubeless tires, is to measure the sidewall height versus pressure. Park on a flat and level surface and inflate to the maximum shown on the tire sidewall. This will be the 100% height. Now deflate and keep track of the sidewall height. Make sure the amount of load within the vehicle is typical of what you would normally carry.
85% is usually a safe all around height. A rule of thumb that I’ve heard before for sand driving is 75% and is a reasonable minimum choice for off road winter driving in our area. For general off roading, 85% makes a safe point and very rarely have I found a bead popping at this level. You can run lower, but more care should be exercised when turning and when using power as you go lower and lower.
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It has a lot to do with the tire and rim you rare using. I used to run my 31" MTRs at about 14 with a 8" rim, but now with my 33" SSRs I have had them down to about 8 psi but typically run about 11-12 psi. The SSRs have a much thicker sidewall. If you are running a wide or very narrow rim you chance of popping a bead get bigger.
The biggest difference you will notice is going from like 30 psi down to about 15 psi and after 15 you don't gain that much more footprint.
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It really depends on the tires.
Our toyo's dont really work until they are under 6lbs, but they are a stiff tire.
Soft tires like boggers, bfg's, and 15" mtrs will flex at higher pressures.
I wouldnt go below 12psi without beadlocks as a general rule. Although I've popped them at higher pressure, 12 is fairly consistent.
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I've run the following:
33x12.5x15 Yokohama Mud Diggers @ 6Lbs (Toyota)
33x12.5x15 Big O XT @10Lbs (Toyota)
33x12.5x15 Swampers @ 8Lbs (Toyota)
33x12.5x15 TRXUS MT @11Lbs (TJ)
31x10.5x15 MT/R @11Lbs (TJ)
30x9.5x15 BFG AT KO @15Lbs (XJ)
All of the 33's were on 8 wide...the 30 and 31 were on 7 wide.
I agree with Bnine, depends on the tires construction and compound, vehicle, terrain and driving style. ;)
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Hi,
I'm running BFG Mud-Terrain T/A KM2 on a stock '06 Rubicon. Tire size is 245/75R16 and I believe the rims are 8 inches wide. The tires have 3-ply sidewalls and BFG brags about the sidewalls being one of the toughest and puncture/tear resistant out there.
From what I read earlier in this thread, it looks like I'd be OK to run them at 15 psi. At the last Open Run (my first), folks suggested 20 psi, and hinted that going lower is risky. From what I read here, it looks like the risk isn't much higher at 15 psi than at 20.
Does 15 psi sound reasonable for my current setup?
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You'll be okay going down to 15 psi. I ran that with the same size Goodyears with no problems.
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Typically I run 12psi in my 36" and 37" IROKs, radial and bias ply. The radials definitely bulge more than bias ply did. I live in Cochrane so I don't worry too much about running that short distance on the highway from Waiporous to here.
In Moab I was running the bias ply IROKs at 8psi and they were conforming quite nicely to the rocks. However the trials down there start on the edge of town so not much highway driving to speak of.
I'm running an 8" wide rim with either a 12.5" wide tire(radial) or 13.5(bias ply). The recommended rim width for those tires is 10" but I prefer the 8" as I think the narrower rim is less likely to pop a bead. Has worked good so far.
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I ran my 35" MTR's on 8" rims (non beadlock) at 8 psi when wheeling, never once had a bead pop. Once you start running single digit air pressure you'll discover 2 things, first is how much difference in traction a 1 psi drop makes when you're running single digits and second, why did I ever wheel with double digit tire pressure? ???
I once "rolled" a 35" BFG AT off the rim enough to lose all the air but not un-seat it. When I checked the rest of the tires one was at 4 psi and still on the rim. At that time all the tires leaked when aired down due to the bead mounted balancing weights.
Bottom line, keep airing down a little at a time until you start having problems and then add a couple of psi.
Of course, like others said, an air supply is a must before hitting the highway.
Vince
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seeing as how its a 245/75r16, stock size, i think going to single digit pressures could cause a tire to come off the bead much easier then a wider/taller aftermarket tire. 245's are pretty skinny so i think sticking with double digits until you upsize tires will be your best bet. 15psi would probably be a good place to start.
i wheeled with 33/1250r15's on 8.5" wide rims. had them down to 8psi and they were great. usually id just have abotu 12 up front and 8 in the rear. that set up worked well.
adjust as you go. buy a good air compressor.
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seeing as how its a 245/75r16, stock size,
Quoted from the OP: I have 35 MTR's
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i meant to quote the guy that resurected this post.
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seeing as how its a 245/75r16, stock size, i think going to single digit pressures could cause a tire to come off the bead much easier then a wider/taller aftermarket tire. 245's are pretty skinny..........
I recall reading on the goodyear page that the stock rubicon rubber was good up to a 7.5" wheel? I see the new MT/R's are good to 8". For what it's worth.
I've been running 12ish psi in my 33's on a 8" wide wheel. Seems to work well for me.
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i meant to quote the guy that resurected this post.
LOL, I didn't even notice how old the original post was.
Vince
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LOL, I didn't even notice how old the original post was.
Vince
lol - what can I say...search works ;D
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Well my '04 Rubi has 8" rims from the factory... so I'd hope that the factory tires were good to 8". Perhaps they spec'd narrower for the newer ones?
The new MTR's are recommended for 6.5-8" wheels. I' read on the goodyear page a while back the old MT-R's were only recommended up to 7.5". I can't see the extra half inch wider than recommended wheel being a bad thing if they are fully inflated??
http://www.4x4review.com/Reviews/ProductReviews/TiresandWheels/GoodyearWranglerMTR/tabid/441/Default.aspx
LT245/75R16 116P OWL 6.5- 7.5 30.7 9.7 "3,042"
I'd use it as an excuse to go bigger though :)
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I ran my 35" MTR's on 8" rims (non beadlock) at 8 psi when wheeling, never once had a bead pop.
It's because you drove your Jeep like an old French lady Vince ;D
My Pitbull Rocker starts working well at 4psi... but I poped a few beads at 8psi without bead locks. I guess my old French lady driving is not as good as Vince. :P
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It's because you drove your Jeep like an old French lady Vince ;D
My Pitbull Rocker starts working well at 4psi... but I poped a few beads at 8psi without bead locks. I guess my old French lady driving is not as good as Vince. :P
I backed my Jeep further through trails than you'll ever drag that little station wagon :o
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at 65 year old, you have a few years on me ... I understand
Hows your Jeepathfinder Vince? ;D
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at 65 year old, you have a few years on me ... I understand
Hows your Jeepathfinder Vince? ;D
the last time I saw 65 was 1865...
It was a Jeepxterra and was replaced with a JeepTundra.
I do have a 7 slot, open top 4x4 in the garage, I'll have to hook up on a run if you ever get the grocerygetter runnin' again
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I have not unloaded the last load of grocery since the Jeep has been in the shop for the last 6years... Thanks God it's canned goods and diapers. Don't mind the best before date when you get your stuff Vince.
PS: sorry about the confusion on the Jeepoyota/ Jeepissan
Milan might come over to my newly built garage for a cold one....I do have a few at room temperature for you. I know it's hard on your stomach ;).
Cheers Bud
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Thanks God it's canned goods and diapers.
diapers??? Dom must have a leaky valve... are they pull-ups or depends?
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First...35" MTRs start working at 8psi as Vince said. 5-6 is better for more traction. 4 even works well in snow. Anything lower and they get too mushy but hey some of us like that. Below 8 you do have to watch the beads a bit. Of course new tires act differently than broken-in ones, I like to run low pressures first to break them in and after while you can use a bit more psi with enough sidewall flex.
Second, I did see Vinny go backwards quite well few times. The Jeep would always take Vince "where he wanted to go". Some say he's a damn good driver. I say the Jeep was way more capable than the monkey behind the steering wheel. ;) :P ;D Isn't the 7 slot machine just a go-cart Vince? I'm sure it is. But I bet it's faster and more economical than my Jeep :'(
Third, typical Czech Lager like the Original Budweiser (now called Czechvar), not the crap sold here, or any decent beer should usually be served at 7 deg C. Anything cooler than that kills the taste. The only time I'll drink an ice cold beer is if its 30+ and I'm on a beach by the ocean somewhere or in the desert. I may even put a slice of lemon in the one called Corona as it's more like a lemonade anyway. Lemon or anything else in any other beer ruins both the lemon or whatever and the beer. Only people that don't understand beer put anything in it. Proper Lager or Pilsner style beer is a meal on it's own, no fruits or veggies necessary. ;) And you're on for a cold one in your garage. Maybe this week?? I'll give you a call.
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Hi,
I'm running BFG Mud-Terrain T/A KM2 on a stock '06 Rubicon. Tire size is 245/75R16 and I believe the rims are 8 inches wide. The tires have 3-ply sidewalls and BFG brags about the sidewalls being one of the toughest and puncture/tear resistant out there.
From what I read earlier in this thread, it looks like I'd be OK to run them at 15 psi. At the last Open Run (my first), folks suggested 20 psi, and hinted that going lower is risky. From what I read here, it looks like the risk isn't much higher at 15 psi than at 20.
Does 15 psi sound reasonable for my current setup?
The answer: No - not for this tire/rim combination.
I was running 15 psi this weekend. On the driver's side, both tires got roots or twigs driven/stuck between the rim and tire (and couldn't be removed), and the front tire ALMOST broke the bead (I could put my finger between the rim and tire bead...then I realized putting my finger there was a bad idea so I used a small stick to scoop the mud out instead). 32 PSI put the bead back in place.
I don't recall any driver side impacts or slides so I'm not sure where the beads slipped/opened up.
I think the tires are just a tad too narrow for the rim width (or rim too wide for tires) for 15psi. I think I'll try 17 next outing and see how that goes. I really liked the traction at 15 psi though...I don't recall slipping even once on the rocks.