Hello everyone

I’ve got a set of 31 ABW on my airplane, currently inflated at 10psi ! recommended range is 8-20
I find they seem to be very stiff I haven’t tried 8 psi yet as I’m just trying to get used to them.

I see many video’s on youtube which look like the some are way under inflated !! like maybe 4-5psi is my guess. I plan to operate on gravel bars, river beds, beaches ect... and would like some input from experienced folks with regards to the Pro’s Cons of various inflation.

Thanks,

V1VRV2

When I had them on my cub i usually deflated them until you start to see wrinkles on the lower part of the tire. I'm not sure how much PSI this was, maybe around 4 PSI. It seemed to be a happy medium between good rough field performance, and also being able to push the plane back into the hangar

On my Citabria I ran 6psi. Worked well.

10psi (or 8 psi) is fine if you are taking a trip and know you'll be landing on paved runways. I run 3.5 psi on the SQ2 with 35's for normal ops, 3 psi for STOL competitions where I'm dropping it in to landing and need the extra cush. They definitely should be "poochin" the sidewalls for off-airport stuff. If other pilots aren't commenting on how low your tires are you've got too much air in them.

Hi Everyone

Ok thanks for the help... I’ll drop them to 5-6 psi and see how they perform

Barnstormer wrote: If other pilots aren't commenting on how low your tires are you've got too much air in them.

Heh heh... this is the most reliable indicator.

I like 4 to 6 psi. One thing you'll notice at lower pressures, though, is that the airplane is going to be a lot harder to move around by hand, as into a hangar.

The price you have to pay....

MTV

Ok Guys
Great info but what does running at such low pressure vs the manufacturer set limit (8)psi do ? I don’t mean warranty or anything like that just operationally does the tire wear out more quickly, how about cuts, scrapes ect .. I guess it can handle it !!

Wear on Bush Wheels is all about how much you operate on pavement, vs gravel/grass, etc. If you operate on pavement a lot, a little higher pressure is probably a good idea.

Then again, if you operate on pavement a lot, you probably don't want to be using Bush Wheels.

MTV

Bob Breeden (may have been Jr. B) told me once that when operating on sharp rocks or shale, higher pressure is worse, lower pressure better, very low pressure even better. His simile was to think of a toy balloon inflated to near max pressure, and now slam it into sharp things...... take that same (or a new one probably) and blow it up just enough to be sorta round, and it will be much more resistant to damage. Makes sense to me. I run my 29 Airstreaks at 3.5 lbs, in spite of the min pressure stamped on the sidewall of (I think) 6 or 8 is it? About 1500 hrs now that way.

Another point Breeden made, if, as in my case, I am taking off at 5400 and climbing up to 8, 9, or sometimes (OK, once so far) over 10 K and then landing on embedded rocks and shale, go super low press. as they will expand a bit due to the lower atmospheric pressure up higher. The only disadvantage as many have noted, is harder to move around, it sure doesn't seem to hurt the tire.

I think you will be surprised by the change in sight picture and prop clearance between 5 psi and 10 psi.

No pavement only grass, sand, gravel I do taxi a bit on pavement when i have to go to the Int’l airport.
though.

4 psi seems to be about right for off airport. Usually it's right when you can hardly roll the airplane out of the hangar.

Ditto what most others have said. Almost all of my flying is back country and I usually inflate to 4 psi. If I know I'm going into town I'll inflate to 12 psi to reduce the wear on the tires. Higher pressure also makes it easier to move around but harder to see over the cowl on the ground.

Just a little devil's advocate here....

The lower pressure the tires are, the more work they have to do as they roll and change shape where they deform at the ground, especially on rough or abrasive surfaces.

Ever notice how aircraft with semi-flat tires are MUCH harder to push? All that extra pushing (work, or energy input over time) has to be absorbed by the tires. The energy doesn't disappear - it's causing the rubber to gradually damage itself at a microscopic level. This accelerates wear and vulcanisation (cracking), but of course it takes a long time to get to the point you notice it.

So flat tires chew their life up somewhat faster than correctly inflated tires do. Of course I have no empirical evidence of how much faster this happens in very soft tires like ABWs. It would not be hard to measure though, if anyone was that interested.

Just a trivial point to be aware of, given they are expensive you may or may not want to think about that!

29's in the Bearhawk, I run about 10 if I know I'll make some pavement landings. 35's 4 to 5 depending on what I'm landing on.

Tom wrote:4 psi seems to be about right for off airport. Usually it's right when you can hardly roll the airplane out of the hangar.

Has anyone measured takeoff disyance differences between soft and hard tires? If it's hard to roll into the hangar, it's also gotta be hard to roll or at least get rolling for takeoff.

Tire pressure will effect takeoff roll distance depending on the service hard or soft matters. On tar I can get off 25- 40 ft quicker going from 3 to 6 lbs. In real soft stuff (tundra) it will usually be better to stay soft and float over the ground. Landings at three lbs will really soak up a lot of poor piloting. You can always cary small 1 lb electric air pump with you if you need to air up after landing. For everyday play I usually run 6.5 lbs. If I think I am going to stuff it in hard or on real soft stuff I will drop to 3-4 lbs.
One thing to remember is less than 8 lbs of pressure is hard on the sidewalls when the plane is in storage. Don't leave the plane sit all winter at 3 lbs or you will have sidewall cracks show up. If they are on the plane in winter and you are not flying much pump them up and keep them away from UV light with wheel covers or in a hanger.
DENNY

mtv wrote:Wear on Bush Wheels is all about how much you operate on pavement, vs gravel/grass, etc. If you operate on pavement a lot, a little higher pressure is probably a good idea.

Then again, if you operate on pavement a lot, you probably don't want to be using Bush Wheels.

MTV

All the bushwheels I've seen actually wore out, as oposed to weather checked bear bit etc, were worn down to the belts in about a two inch wide strip right down the middle from landing pavement with them pumped up like rocks. All of these were on planes that never left the pavement and had bushwheels on them because that's the cool tires to have on your scout, husky,supercub etc.
I think airing them down somewhat spreads the wear over the surface of the tire and makes them last much longer even on pavement.

I have not seen that much center crown wear, but around here people tend to run them low. The cords start showing up near the outer edge of the contact patch. I think this is due to the wheel camber or people locking there break and spinning on the tire . It has been recommend that you rotate the tire on the rim every few years to help with the camber issue. I could see that center wearing out quick running real hard on pavement all the time.
DENNY