Bead lockers for running low tire pressure with inner tubes

[Battson]

Hi everyone,

Following a question, I thought I would post a little "how-to" for running your Goodyear / Desser tundra tires at very low pressure, without risking the dreaded "rim creep" - a flat tire caused by the valve stem shearing off when the tire slips on the wheel.

The tire's bead is thick and strong, but relies on air pressure to hold it against the rim. When you run low pressure, say less than 20psi, very heavy braking torque can cause the tire to gradually slip on the rim, known as rim creep. Of course the inner tube follows the tire, but the valve stem is captive in the wheel. This causes the valve stem to fold over, and eventually shear off, leaving you with a very flat tire.

Basically, to stop this happening you want to lock the bead of the tire in place, so it can't creep on the rim. Some people recommend contact adhesive, but one way to do this mechanically is as follows. I know this works with Grove / Cleveland wheels, check your measurements if you try a different brand:

With disassembled wheels, drill to hubcap screw holes right through, without removing the thread. No need to add extra holes, three is plenty.

Tap the threads right through, 8/32 threads on the Grove wheels. Clean up any burrs or sprigs with your reamer.


Measure the depth of the holes carefully, mine were 7/16". Select screws long enough to protrude about 1/4" into the bead of the tire (for a 26" Goodyear). For other tire types - check your bead thickness first!! You want the screws to bed properly into the bead, but not so deep that they could poke right through and interfere with the inner tube!!

Reassemble your wheels with tires. Inflate.

Sharpen your measured screws to a point, and screw them into the tire. This shouldn't take a lot of force.


All finished (hubcap removed).
Notice the "slippage" mark painted opposite the valve on the wheel-tire interface. This allows me to check for rim creep with the hubcap installed, which I do every preflight as a matter of course. I highly recommend doing this regardless of whether you have bead locks, a flat tire is no fun.

[DRLPatrol]

Thanks, Great how-to write up. Do you do that on both wheel halves or just the outboard half. I'm hoping by the time I am ready Desser has come out with their bigger sizes and they put the stem in the sidewall. We can hope can't we.

Doug

[Battson]

I have only done one half, I think that should be enough. The forces during braking are huge, and the rim creep is so slow, so I expect it won't take much extra friction / resistance to stop that creep.

I think Desser have said in the Press Release that their tires will have inner-tubes?

Talking with Mr Grove Aircraft in the weekend, he said he prefers not to have tubeless wheels, because they aren't backwards compatible with tubes.

He did say they have a tubeless option in development (tooling up this week) which will be convertible between tube and tubeless. This will be achieved with a removable valve stem design, which sounds very clever as he explained it to me.

But until such time as that product is available, I am running tubes and bead lockers.



P.S. Also worth noting that the best thing about ABWs is not their size (but it helps), the super-soft compound they use in their rubber does most of the work, and you don't get that with Goodyear or Desser (yet). That softness is the same reason they wear out after just 100 landings on pavement. Desser won't be able to work miracles on that front. A hard-wearing tire has to sacrifice performance off airport.

[DRLPatrol]

I was on Dessers website and the press release that talked about the 8.50-6 smooth tundra, said upcoming was 27" and 31" that were going to be tubeless. We'll see.

Doug

[Battson]

Right - Desser said "Tubeless or Tube type application" - which probably doesn't mean sidewall valve stem and integral tube like a bushweel - it probably means the same thing as the 26" Goodyear are. Exactly the same design and same problems. You need to buy tubeless wheels to make the tires work tubeless-ly (inventing words here!)
But like you say, let's wait and see.

If you already have wheels, bead lockers are a cheap and easy fix. If not, waiting for the new wheel design from Grove could be a good move.

http://www.desser.com/pressrelease_tundratire.php

[X'N]

We use to do the same in drag racing.

[Russellmn]

Same here, but we called 'em "Rim screws". Beadlocks, to me, have always been clamping rings that physically clamp the bead to the outside of the wheel. Use them for rock crawlers/Jeeps/etc...

[RV9bushwheel]

Sorry to revive such an old thread, but I'd like to hear any further info you can provide after a few years of using these beadlocker screws. Did it work well? And how low of air pressure have you been able to safely run?
I have an RV9 (I know, I'm a square peg trying to fit in a round hole) with a set of 850-6 Aero Classic Tundra tires. The airplane used to be 9a (trike) that I converted to a tailwheel so that I could use these tires and now I'm learning to fly a tailwheel for the first time. At 15psi I get a pretty good bounce if I'm not perfect on my touchdown, but I have no rim creep. At 12psi it is significantly less bounce, but I begin to see a little rim creep. At 10 psi it really begins to dampen any bounce, but after a few circuits, I found the valve stems pulled hard over.
I would appreciate any further info you can provide

[Battson]

It works great. There were no issues at any stage. We ran pressure down as low as 10 psi, and I assume you could go lower. We never tried.

[RV9bushwheel]

Super, I'll get out and try to get that done this weekend so I can get that tire pressure down.
Thanks for indulging an RV guy....

[zkelley2]

I'm surprised matco or grove don't make something like a dirtbike rim lock. We'd run 2-3psi in soft stuff. No putting screws in your tires and at least on dirt bikes with stiff sidewall tires, you can run them completely flat at the risk of damaging your rim, but completely flat. In that arena where the tire and tube sees way more abuse, the only downside to a tube is the risk of puncture. We hardly have that.

https://www.youtube.com/watch?v=ABruQcmLBXE

[whee]

I local guy used some pvc pipe of appropriate diameter cut to appropriate length. As you tighten the wheel halfs together the tire bead gets squoze between the pvc and the wheel. Been working great for him.

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[mawilso8@gmail.com]

Do you have an update on how this beadlocker system has worked out for him over the years? What tire wheel combo was he running?

[Russellmn]

Whee, now THAT is a bead lock! I would imagine he got the idea from the off road guys that use PVC inside military HMMWV wheels. Double bead lock, run little to no air pressure and no problems.

edit: To get the appropriate size, you need to bolt your wheel together, measure from bead to bead. Then measure the thickness of the bead on your tires (both beads) add these together, subtract that from the total width, then add some back for clamping pressure. May take some experimentation to get the right amount of clamping force...

[whee]

He said the H1 hummer military wheels have either a steel or rubber "barrel" to beadlock the tires and provide some runflat ability. He figued if it is good enough for the Army on the H1 then its good enough for his little airplane.

[Russellmn]

Yeah, the "steel" insert is actually magnesium. Off road guys been using PVC or just cutting down the stock pieces so they won't pinch the tires.