Air down tires for high speed off-roading?

[privateer35]

I stumbled upon this this video recently (linked below) showing a Bronco Raptor going down a dirt utilities trail at a very fast speed.

For running something like this, should you air down at all? Or are you running highway PSI because of the high speed?

Now, I’ve always been taught a good rule of thumb is to never exceed speed higher than your PSI when you air down. Doing so can avoid popping a bead and for general safety when you need to turn, stop, etc. E.g. If you air down to 25psi, try to not exceed 25mph.

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[Tbrownski]

I’ve ran plenty of trails at speed like that at 25 psi. I usually go to 25 if I plan on getting up to speed for sustained distance. If we’re planning on most of the day getting through rocks or super rough stuff I’ll go 18-20.

That’s with method bead grip wheels. I’ve been told they’ll run single digit psi without issues

 

[Trees]

I’ve ran plenty of trails at speed like that at 25 psi. I usually go to 25 if I plan on getting up to speed for sustained distance. If we’re planning on most of the day getting through rocks or super rough stuff I’ll go 18-20.

That’s with method bead grip wheels. I’ve been told they’ll run single digit psi without issues

I had my 703s in the sand dunes at silver lake Michigan down to about 8psi.

Don't tell the better half... but... I did a bunch of donuts in an attempt to get them to debead and they didn't care one bit.

I think next time (when the better half isn't with me) I'd like to see how low I can go before I blow a bead

 

[swamp2]

It depends on the surface, both composition and hardness. It will also depend on tempratures since that can be a killer for underinflated tires at high speeds when both friction and a hot surface are heating the tires.

Speed equal to or lower than psi is way too conservative though. For example, 60 mph at 15 psi in the sand is fine. Would I run 15 psi at 60 on the asphalt, no. That said it also would not be immediately catastrophic. I would run 25 psi on many off road surfaces at high speed, loosely 60-80 and the pressure would be more for comfort than traction.

In snow or sand, even without bead grips or bead locks, you can push well below 10 psi. Its the tough rock crawling that increases debeading risk as snow and sand just don't load the sidewalls too much laterally.

I doubt there are any published rules on this...

 

[LightningLou]

I've run 80+ with only 22psi on some wide open trails with long straights and no issues here in the Sonoran Desert. Felt completely safe and in control.

 

[Dirtyjed]

I ran up to 103 across Black Rock Playa with 18 psi on stock Samsquatch rims with Ford Performance beadlocks. That was flat and straight though.
We were getting up to low 90's on the dirt roads and felt comfortable the whole time.

 

[Qarlos]

I drive on sand and hard pack - no rock crawling here, although the occasional gravel hill climb. No higher than 15 psi if I’m hitting sand and often lower depending on the conditions. In between dunes I’ll cruise at 80kph (50mph) on 15 psi, no problem. If it’s just hard pack I’ll run at 25 psi for comfort and grip and go a lot faster.

 

[murphtron]

I ran up to 103 across Black Rock Playa with 18 psi on stock Samsquatch rims with Ford Performance beadlocks. That was flat and straight though.
We were getting up to low 90's on the dirt roads and felt comfortable the whole time.

103? Dang. I could only get to 101 last week on my non-sas 2.7 Badlands. Was fun though! I was at road pressure. Aired down to 18 once I got to the bumpy stuff.

 

[vrtical]

I ran 25psi for dirt the last time I did it.

 

[Lxatoledo]

Full pressure, 37's 70-80MPH. No issues WT 2.7

 

[Snacktime]

15-18psi in the dirt fast or slow.

 

[Bronco1971]

I run 15psi on deep sand washes. I found that the increase in traction throttle on made it more stable.

 

[duel007]

Yes absolutely - mostly for comforts sake. I'm mostly a newbie and my first two trails I did at highway PSI and about rattled my teeth out from how rough it was. I was also wondering why everyone seemed to be flying past me.

Next few trails I did I aired down to 18-20PSI and it was a world of difference in the ride. I was able to do 70-80 on some of the sandy roads in Moab no problem.

 

[Canyon Coolers]

I was running high speeds in Baja for a week with 19 other Bronco's. Most of us were at 20psi if not lower and we hit high two digit speeds, if not three digit. I did utterly destroy one OEM tire, and saw two others get taken out of service, but I would credit a sharp rock and an overly light weight tire. Nothing aftermarket was any lighter and none of them had any issues.

You can always feel the side of the tire for heat, but I routinely go well over the PSI to Speed limit rule. You might be overly conservative there.

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