PSI for wheeling

[Heckraiser]

For you guys who regularly run at low psi’s:
How fast are you willing to go when the psi has been lowered?

How fast at 30psi?
How about 18psi?

I ask because I was recently on forest roads and discovered beauty of lowering the PSI. Not because I needed the traction but because the ride becomes so much better over the rough roads.
But then in smooth sections where I would normally go 45mph or so, I was hesitant to go that fast at my reduced air pressure.

"fast" is never really part of the equation for me when I'm aired down. But I guess sometimes I'll camp aired down (like at Sand Flats in Moab) and then run into town for a bag of ice or whatever and might hit 45mph on the dirt road. This is at 16ish PSI, but I'm not sustaining 45mph for more than a few minutes.

 

[coleAK]

The blowout effect at low psi is because the tire gets really hot and then de-vulcanizes. I don’t know the math but I presume tire temp increase more than linear with speed. Also bigger tires will have more contact area and generate more heat. That said I don’t actually know anyone who has had a tire come apart due to low pressure, though I did have a trailer tire blow out completely on me once, but that was due to edge wear (caused I think by a bad bearing or misaligned axle) combined with high ambient temps and me far exceeding the 62mph tire limit.

The ford explorer/firestone mess in the 90’s was due to too low a psi and many tires coming apart.

 

[linuxgod]

The ford explorer/firestone mess in the 90’s was due to too low a psi and many tires coming apart.

Yeah. Firestone said Ford has pressure set too low. Ford said the tires weren’t built to spec. I suspect Firestone was correct. Sorry when I said “I don’t know if anyone” I meant I don’t know of anyone that has happened to when running low pressure temporarily between trails or at moderate speeds on washboard type roads. (I also don’t personally know anyone who had a Firestone tire blow on them but I do realize that was a major problem).

I’m sure low PSI will eventually cause tires to fail, it’s just a question of how low and for how long. Half normal PSI is too low, but obviously a few feet doesn’t cause them to fail instantly. A few thousand miles almost surely does.

 

[coleAK]

Yeah. Firestone said Ford has pressure set too low. Ford said the tires weren’t built to spec. I suspect Firestone was correct. Sorry when I said “I don’t know if anyone” I meant I don’t know of anyone that has happened to when running low pressure temporarily between trails or at moderate speeds on washboard type roads. (I also don’t personally know anyone who had a Firestone tire blow on them but I do realize that was a major problem).

I’m sure low PSI will eventually cause tires to fail, it’s just a question of how low and for how long. Half normal PSI is too low, but obviously a few feet doesn’t cause them to fail instantly. A few thousand miles almost surely does.

I also don’t know anyone personally that has had a tire blow running a short distance on low PSI

I run 36 psi daily. Drop it to 28 when I run the Dalton, Steese, or TOW. Those places I run 35-50 mph for hundreds of miles of dirt/gravel/washboard, it is ~800 miles

Drop it to 18-20 psi for sand, mud and off road trails. I have run 15-20 miles on the pavement at <45 mph. When I’m running low pressure speed is what concerns me.

 

[Sinister]

I have my staun deflators set for 18 but I get impatient and stop them around 20, never had an issue on the soft beach sand.

 

[MCtree]

I guess Ronnie Dahl reads our formum!

He posted this video 6 days ago.



It addresses lots of the questions we discuss in this thread.

It’s interesting what he says about limiting one’s speed. And scary for me since I travelled faster than he suggests at low speeds.

 

[W4632018]

I always just use 20 PSI, never had any problems

 

[Adrenaline6]

I just ran my R/T Trails down a stretch of beach and the sand was pretty soft and deep in places. It has been hot in Florida and not much rain, so that is a recipe for cars getting stuck driving on the beach.

I didn't even air down. Ran 38psi and the LX could crawl at 5-10 mph with ease. I saw a new Tacoma stuck. Not sure if he had in 4wheel (probably not), but he was having a hard time.