Run flats, M998, sand & low tire pressure, help needed

[RichDane]

I have search but have not found any threads which address this specific issue:

I have basically rebuilt this M998 I have owned over the last two and a half years (My True Love, Don't Tell My Wife). New A2 motor, 4 speed 4l80, and too many other additions to mention.
I have plans on moving to Hatteras Island next October and I can't seem to find any threads that address this issue: I have run flat in my 37's, to drive on the beach, the lower the pressure the better....how low of air pressure can I run with the run flats ????? Will the footprint of the tire enlarge with the run flats installed?? and lastly, how low can one go without have the fear of popping a bead

Thanks for your input
Richdane

 

[Bulldogger]

If I recall correctly, the operators manual says 15psi minimum for bad off road conditions. I've run 10psi for short duration on scraggly mountain hills covered in broken branches, rocks and leaves without incident. If you're placing lots of stress on the tires over rough ground (not sand) you run the risk of the run flat attacking the inside of the tire with very low PSI.

If you're going to be in sand, you can probably run 10psi, or rather "I would" for what it's worth.

You should bring the pressure back up to 15psi when done, or you can run 15psi, which is OK in the manual, and see how it goes.

BDGR

 

[RichDane]

Perfect, Thank you Sir....bought a new air gauge, will see how it goes, as soon as I figure out whether to tow it or drive it 403 miles to my southern front door in Hatteras NC..seems like a long way in a HUMVEE

 

[riderdan]

Perfect, Thank you Sir....bought a new air gauge, will see how it goes, as soon as I figure out whether to tow it or drive it 403 miles to my southern front door in Hatteras NC..seems like a long way in a HUMVEE

It's doable. I drove mine from Tennessee to Kansas (920 miles) when I bought it.

 

[Katavic918]

You won't pop a bead. The runflats have built in bead locks.

 

[DatGuyC]

Some company makes PVC beadlocks you can run instead of the factory runflats so you can air down as much as you want and not worry about popping the bead.

 

[RichDane]

It's doable. I drove mine from Tennessee to Kansas (920 miles) when I bought it.

I am just now completing the install on a new motor and I already have the 4L80 pluged in...I will probably give the 400 mile trip a try.....once I know everything is running well....motors in at the moment but I have a unidentified battery drain which is driving me crazy.......

 

[RichDane]

That does make sense Katavic.....thanks

 

[Raklatif]

20 PSI is good for regular driving in moderately packed sand, and 12-15 PSI on soft sand works absolutely fine.

 

[RichDane]

Raklatif,,,,,,, I would have to say that being from Dubai, would more than likely make you an expert on sand driving..........Unless my sand is radically different, I will use your advice//....Thank you !!!

 

[Raklatif]

To avoid any un-needed stress on your drivetrain, i would start off in HIGH range on the TC, and try and keep momentum, as the main problem with a humvee is when you stop and it bogs down. If at any point you feel like your tires are spinning underneath you (you should be able to tell by feel alone) i would completely take my foot off the accelerator, put it into neutral until you come to a stop, then go into HIGH LOCK range and continue driving. only EVER use LOW range if you get stuck somewhere.

If the sand isn't that soft, you should be able to enjoy a whole day without having to use HIGH LOCK at 15 PSI.

Again, all this pressure info is assuming you are running the stock humvee 16.5 wheels and are on the BF goodrich Chevron/SS/Kevlar tires.

Also, you can run down to 0 psi and the bead will not separate., i dont recommend running lower than 2-5 psi though because you might start to wear out the inside of the tire with the runflat

 

[cwajciec]

Hey let me know how it goes; I’m thinking of taking mine to Oregon Inlet next month. The sand can be very fine and soft so airing down is recommended. I’ve been to Hatteras in various trucks and there are always people stuck there.