Desser has a new 31" tire out that I was thinking about buying. Kicking around the idea of mounting them on my Gar-Aeros. Upside is the price, fairly light, Downside possible durability, and valve stem shearing.

http://www.desser.com/aircraft-tires-an ... -4-PLY.asp

I understand the advantage of Bushwheels in that one can't shear off the valve stem. I also know it only takes one such incident to make for a really bad day. I have Bushwheels on one of my planes.

But I wonder, how many people have ever had a valve stem shear off?

I've been thinking about these tires for a couple weeks. They seem like a reasonable alternative to Bushwheels because they are less expensive but can you imagine the result if you do shear a valve stem? That's a lot of rubber going flat; ~10" vs maybe 5" on a 850x6. I don't know if it would really be any different than a smaller tire shearing a valve stem but it sure seems like it would. What somebody needs to do is make a 10" wheel that has a bead locker like the off-road guys use.

Im curious to know how "tubeless" with a split wheel works. I have heard of kits to seal the wheels but never seen how it works.

This would eliminate the fear of valve stem shearing. No?

Even if you can't run them as low as AK bushwheels, the larger diameter would certainly help on rough surfaces. Assuming you're landing on dirt at both ends I think you could run them pretty low. I run my Goodyears as low as 11psi without a hint of slippage.

I guess the thing to do would be to get a set and see how low you can run the pressure in a skid without them moving on the wheel.

I glue my Goodyear Blimps onto the rim with Barge Cement to prevent slipping. I don't really know how much it helps, but intuitively it seems like it would dramatically increase the shear strength in the tire/rim interface. Removing the tires later on is no big deal, and the rims clean up fine with a little avegas.

I've heard of people putting sheet metal screws through the rims, but drilling holes in the weakest part of the rim doesn't excite me.

Most bicycle rims can be converted to tubeless by wrapping the inside of the rim with tape to keep air from escaping out the spoke holes, and for the life of me I can't think why that wouldn't work with airplane rims assuming you can put the tire on the rim once its assembled. It seems like going tubeless would be pretty simple, though I don't know what would happen when a tubeless tire spun on the rim. Nothing? Something?

Crzyivan13 wrote:Im curious to know how "tubeless" with a split wheel works. I have heard of kits to seal the wheels but never seen how it works.

This would eliminate the fear of valve stem shearing. No?

They have an o-ring seal at the mating surface.


Tubeless does eliminate the stem shearing issue but it presents a new one. Instead of shearing the stem when the bead slips the air just blows out because the bead is no longer sealing. It is one of the reasons off road guys use bead lockers.

Something sorta kinda like this is what could see happening when running tubeless at low pressure.

So if you have bead lockers is there any reason to run tubeless? I mean, if you can slip the tire on the rim regardless then you might as well keep the tube.

tedwaltman wrote:I understand the advantage of Bushwheels in that one can't shear off the valve stem. I also know it only takes one such incident to make for a really bad day. I have Bushwheels on one of my planes.

But I wonder, how many people have ever had a valve stem shear off?

I had a valve stem tear due to tire slippage once. Fortunately it didn't blow out on landing, rather it was flat when I returned to the plane after a long hike. It was a real pain in the arse, dealing with fixing it in the field. The taller the tire, the more likely it is to slip.

Perhaps the presence of these new tires in the market will encourage Airframes AK to lower the cost of Bushwheels, though they do seem to sell plenty of them at the current prices.

These tires are tubeless but they do have a tube for it. I haven't heard of anybody having 29" Airhawks slipping.

What's the approval basis for putting these 31's on a 185? Does desser have an STC?

soyAnarchisto wrote:What's the approval basis for putting these 31's on a 185? Does desser have an STC?

I'm putting them on a experimental Cub, but they are TSO'd so it shouldn't be a problem to get them field approved for a 185.

tedwaltman wrote:I understand the advantage of Bushwheels in that one can't shear off the valve stem. I also know it only takes one such incident to make for a really bad day. I have Bushwheels on one of my planes.

But I wonder, how many people have ever had a valve stem shear off?

We had one at the year one of the Maule Roundup. I had one two weeks ago and am thus getting an education into getting parts in Mexico. So I think it's a fairly common occurrence when one tries to land short.

Crzyivan13 wrote:Im curious to know how "tubeless" with a split wheel works. I have heard of kits to seal the wheels but never seen how it works.

This would eliminate the fear of valve stem shearing. No?

I have Grove tubeless wheels on my my Kitfox. I'm running Desser 21x800-6 tires on them without tubes at 10#. So far, no problems.

Time and operational experience will tell the tale on these tires.

That said, unless Desser acquires STCs for these tires they won't sell as many as they might. Good luck getting field approvals.

As far as shearing a valve stem.....the difficulty totally depends on where the valve shear occurs. A maintenance facility right there on the field? Not TOO big a deal. Then again, it may be.......a story:

I was checking out in an amphibious Beaver, starting in Anchorage. After the second day of workout in the plane, we returned to ANC....that's Anchorage International Airport, and I was cleared to land on runway 32.....the long runway, generally used by the 747 freighters that are common there.

As I rolled out about halfway down the runway (near the taxiway to our aircraft division) and the airplane suddenly swerved and I braked to a halt. Shut down and we had a flat right main. I called tower and informed them that I now owned their main runway, and I couldn't move. It was a little after 5 PM.

Airport Security came up in his car and my check airman, Jack Corey, asked if he'd drive us to output car.....I asked if we shouldn't sort of, like....hang around or something till maintenance arrives?

Jack responded that unless I got an A & P certificate in my pocket, we're just a couple pilots, and we broke it, therefore our work is done for the day. Then he said "Oh yeah, you're buying the first round".

The next day, with four new tires on the plane, we taxied out for takeoff. When I switched to Tower and called for clearance, the controller asked if I was gonna take his runway away from him again? I responded that if he'd clear us, I promised not to come back at least for a few weeks. He responded: "deHavilland 765 is cleared for takeoff runway 32. And, thanks....I'm retiring next week."

MTV

mtv wrote:Time and operational experience will tell the tale on these tires.

That said, unless Desser acquires STCs for these tires they won't sell as many as they might. Good luck getting field approvals.

As far as shearing a valve stem.....the difficulty totally depends on where the valve shear occurs. A maintenance facility right there on the field? Not TOO big a deal. Then again, it may be.......a story:

MTV

As far as field approvals go its not that bad, I know 2 people who just got field approvals for 26" GoodYears which aren't approved for too many planes. The Feds aren't as gun shy about tires along as they are TSO'd and meet the load requirements, ICAs are fairly simple for a tire.

C185D wrote: As far as field approvals go its not that bad, I know 2 people who just got field approvals for 26" GoodYears which aren't approved for too many planes. The Feds aren't as gun shy about tires along as they are TSO'd and meet the load requirements, ICAs are fairly simple for a tire.

Was it a simple 337 field approval? Or was the whole "tundra tire worksheet" thing involved-- loading up and flying at max forward and max aft CG, etc? That really seems like reinventing the wheel-- putting a set of 26" GY's on a skywagon for example isn't really breaking any new ground. FWIW I'm really surprised that no one's ever gotten an STC for that since there's at least a couple of STC's for 850s on a 180. I've heard of STC's for 26's on other airplanes (Svenn's STC for Pacers, for example) but not for 180's.

hotrod180 wrote:

C185D wrote: As far as field approvals go its not that bad, I know 2 people who just got field approvals for 26" GoodYears which aren't approved for too many planes. The Feds aren't as gun shy about tires along as they are TSO'd and meet the load requirements, ICAs are fairly simple for a tire.

Was it a simple 337 field approval? Or was the whole "tundra tire worksheet" thing involved-- loading up and flying at max forward and max aft CG, etc? That really seems like reinventing the wheel-- putting a set of 26" GY's on a skywagon for example isn't really breaking any new ground. FWIW I'm really surprised that no one's ever gotten an STC for that since there's at least a couple of STC's for 850s on a 180. I've heard of STC's for 26's on other airplanes (Svenn's STC for Pacers, for example) but not for 180's.

Both Field Approvals were 337s only, one for a 180 and the other for a 182.

It would be awesome to see a picture of the 180 that had the 26" put on; a copy of the approval would be useful at the FSDO.

Is there a patent that protects the AK Bushwheels donut design?

That's the only reason I can think of for why Desser would ignore the convention for bushwheels. Using a 10" wheel means that most will have to find a new set of wheels to run these, and they have to be the O-ring type to run tubeless.

Mountain bikers have seen a lot of success with tubeless systems but the wheel-to-tire diameter ratio is pretty low, meaning there's a lot of area for the bead to grip vs the amount of leverage on it. With a tundra tire you get a a large tire with much less bead area from the smaller diameter wheel, so lots of leverage on that interface. Need a bead locking system like Whee said.

By the time you've bought 2 tires ($1500) and new 10" wheels ($500-1000) and then a bead locking system, you could have had proper bushwheels. Is that a crazy way of looking at it?

Zzz wrote:....
By the time you've bought 2 tires ($1500) and new 10" wheels ($500-1000) and then a bead locking system, you could have had proper bushwheels. Is that a crazy way of looking at it?

They don't last forever...the second set is going to be over a thousand dollars cheaper than Bushwheels. The Dessers MIGHT also last considerably longer, and be re-treadable. That could add up to serious savings.

Whether that savings is nullified by inferior performance is yet to be seen. I've wanted Bushwheels since I started flying, but the price-per-landing is just too dear. A more reasonably priced alternative is welcome.

FWIW, I saw the Bushwheel factory when they were in OR. Made by hand, one at a time. Lots and lots of work, so the price they charge is fair...just out of my budget.