How low can I go

[Austin]

So I'm wondering what a safe psi is to drop 35x12. 50x15 super swampers too

[Jim]

I have BFG KM's (35 / 12.5 / 15) and typically run 10 to 12 PSIg but have gone down to 8. Never popped a bead. I haven't tried 6 and don't often use 8 - though 10 - almost every trip.

EDIT: Moderate trails have been the experience. Twists / turns on boulders haven't been much if at all encountered.

[The StRanger]

I run 33X10.50R16 And iv run them at 12. Ir ran them down to 10, But that feels a little soft for my likin..

[BLOODBANE]

Ive been down to 8 with my BOGGERs once. 35x14.5x15's I run a 15x10 rim though, and they are on a SWB FORD Ranger.

[Jim]

This does not directly apply, but they are fun numbers...

http://www.mickeythompsontires.com/tech.php?bulletin=s3

[The StRanger]

It seems the bigger the tire, the lower you can go.
I know a guy that runs his 40s at 5 psi.

[Robert B]

it also depends greatly on on the rim to tire width and what load rating the tire is (the letter rating) on a 12.50 tire with a 8 inch rim yes 10 works and maybe lower depending on the tire but i ran a 12.50 tire with a 10 inch rim and never went below about 18 at most because of the way it bulged out differently and i am also running load range C tires so they are very soft......

[Austin]

Well that helps me out I'm thinking ill run about 15 in them and see how that goes thanks for all the info

[The StRanger]

Yup. Basic rule is " without beadlocks, Under 10 is risky."
Other than that its all personal preference !!

[xaza]

Starting at 15 sounds like a good start, that is lower than I ran my 31" km2s. They were a very a soft tire and wrapped around rocks nicely at that pressure. My BFG AT 35s don't seem to be as soft and I am still tinkering with where I want them. The key is to make the tire soft enough to wrap around the rocks without being at risk of bottoming out rim if you happen to hit a rock hard, which should keep you high enough to maintain a bead. You also want to take into account the sidewall of the tire, lower tire pressure puts the sidewall onto rocks and can lead to a rip if it is not thick enough.

[ColoJeeper]

I've run the 35's on my CJ down as low as 6 lbs. without beadlocks, but also carry air so I can reseat the bead when I knock one off, and have done that a couple of times. Usually I run it about 12 lbs.

[Mr6dwg]

I have gotten a little braver with my tire pressure. I thought I was brave. I see others running at 10 and 12 pounds, I guess I am not that brave. I run mine at 15 pounds. I have run them at 12, but I did not push my limits.

[Jim]

I've run the 35's on my CJ down as low as 6 lbs. without beadlocks, but also carry air so I can reseat the bead when I knock one off

I carry a can of starting fluid (the explosive type with Ether - not the dumbed down, "safe" type) and jumper cables for a spark...

[Cr33p3r]

On my 35/12.50×15s I've run them down to 12-15 with no problems.

[Myrtle Turtle]

I think that knowing what you're doing on a specific day is important too, not just one number you use every time. I run that same tire size on an 8" wheel and usually run 10-12 psi on harder trails, the low end if it's raining, but I ran 20 psi yesterday and was just fine on the easier trail riding kind of stuff. It was just enough to knock the edge off the bumps and I don't think lower would have given me anything.

[Haku]

haha....I ran mine with 0 pressure for a snow run once, but I have HMMWV double beadlocks. Without beadlocks, I'd agree with most here and say don't do below 10psi but I wouldn't be afraid to go that low personally. I know it makes a huge difference with ride quality on even washboard roads, not to mention that slightly chunky but still low clearance rocky trails.

[gm4x4lover]

Belive it or not the wheels make a huge difference. Not only in width but also how tall the safety bead is. It's not standard so they do very from manufacturer to manufacturer. 2 wheels that come to mind with larger safety beads: H2 wheels and Rubicon wheels. FYI 16.5's have no safety beads. That's why when a 16.5 goes flat the tire debeads. I ran my 40" pit bull at 4 psi on the trail and 10 on the street, my 37" mtrs at 6 psi on the trail and 12 on the street. Both of those were on a 6500lb K5 with 17" H2 wheels. 35x12.50x15 bfg km's at 10 psi on the trail and 25 on the street. That was on a suburban with factory rally wheels. 35x12.50x15 big o xt's 8 psi on the trail and 15 psi on the street. I have never debeaded a tire. There is a lot of Science behind proper air pressure. I would be willing to bet that most of you run too much psi on the street.

[Java]

According to the internet this works, but I've never tried it.

make one of these hoses http://www.frontrange4x4.com/forums/showthread.php?14188-Perfect-Tire-Pressure-Tip and you can use it with any compressor and your spare tire to reset a bead. Take off the flat and strap it tight. Fill your spare to 80 psi, hook up the hose. It can flow out of the spare as fast as it can flow into the flat.

[gm4x4lover]

You could fill a low of flat tire with that but you probably wouldn't be able to reset a bead with that. The hose diameter is to small, there isn't enough volume of air, and most likely the spare will be flattened in the process. I also wouldn't recommend filling a tire that is rated at 35 psi to 60 or 80 psi that is very dangerous.

[Java]

IDK, I just have it in my brain as an emergency thing to try. Hopefully it never comes up... :)

[gm4x4lover]

The power tanks are a great way to go. Also for emergency times the cheap little 12 volt compressors are hard to beat. They can be had new for $25. You will never get 60 psi out of one bet 35-40 isn't an issue.

[Austin]

Ok well I went out Saturday and I ran 15 in them and they worked out all rightoso I'm thinking ill most likely stick with that

[gm4x4lover]

Don't be afraid to go lower. The will burp before they debead.

[Myrtle Turtle]

I would be willing to bet that most of you run too much psi on the street.

^^^ even after I told them what I wanted, I came home from the tire store the other day and let 10 lbs out....I will chalk this week and get it just right, I think I'm still a little high

[gm4x4lover]

What do you think u should be at?

[Jim]

I know that if I over inflate for the street, my highway speeds show a marked increase (prolly better MPG too).

For now, I've not chalked, but am watching center to edge wear and to see that my center wear is less than my edge, so I'm happy with being too high for street (mine's no DD).

[Robert B]

I know that if I over inflate for the street, my highway speeds show a marked increase (prolly better MPG too).

For now, I've not chalked, but am watching center to edge wear and to see that my center wear is less than my edge, so I'm happy with being too high for street (mine's no DD).

that does not make sense to me lol since too high causes high center wear

[Jim]

Yes, I should elaborate...

1) It's not a DD so no extensive street riding - just to/from trails
2) I typically go 10 to 12psi on the trails (and get edge wear).
3) I used to go to 24 for street - for no specific reason
4) I wasn't getting much center wear and was getting more edge wear...

Thus I started to inflate more for street use (30/35PSI which I think is crazy high for that size tire), and noticed easier running at highway speeds, and I anticipate more center wear while on the street to even out the edge wear I get on the trails. The goal is an even wear rate, over the life of the tire, across the thread.

So, chalking, would tell me what I should do for even street use but not for the mix of street-trail use that my tires see. A side note on chalking: One would bias towards center wear on the chalk test, even for street only use, as cornering introduces edge wear that straight line chalk tests don't show.

In a similar vein, I've had two near identical Honda Accord station wagons. Between the two I have about 700,000 miles. I've gone through SETS of tires. I know that if I run at factory PSI, I'll toast the edges decently before the centers (perhaps I like faster cornering that biases edge wear). So, I know that to get even wear in the life of a set, I have to inflate 3-5 PSI over recommended.

In summary, trail riding will give me more edge wear. That's just the way it will be as I want a smoother trail ride. So, when on the street I want to inflate to give the centers more wear than the edges. In the end, I hope to achieve even wear across the tread. A bonus is better MPG on the street (assuming I'm not crazy / dangerously overinflated while on the street).

[Robert B]

okie the more context makes it make perfect sense lol i run 32 psi on the street on my 35 12.5 15s ....to get pretty even wear on them .. i think last time i ran 30 and the edges went little faster than center but hey then i will go to about 15 or fuzz less on some trails that require it