What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Tire Pressure

Tire pressures

Have had good luck with 45 mains & 40 nose. Some run less on the nose to reduce shimmy but risk flats due to tire to rim slip &/or tube scuffing.
 
Timely post Bob! I'm doing some taxi test and am having some shimmy issues. Looks like I need to boost the tire pressure!
 
Tire pressure

I run 42 all the way around on the 6A and 10. 20 on the Luscombe.
 
No such thing as "proper" tire pressure. Some prefer more, some prefer less. In general, I prefer as little pressure as practical. In my experience, excess pressure just wears out the center tread faster. I look for the pressure that gives the most even tire wear. IMO, 40 is on the high side in an RV. But you don't want so little that you risk rolling the tire off the rim. There's a wide margin of usable PSI.
 
No such thing as "proper" tire pressure. Some prefer more, some prefer less. In general, I prefer as little pressure as practical. In my experience, excess pressure just wears out the center tread faster. I look for the pressure that gives the most even tire wear. IMO, 40 is on the high side in an RV. But you don't want so little that you risk rolling the tire off the rim. There's a wide margin of usable PSI.

Just because its "experimental" doesn't mean there aren't recommended or "proper" tire pressures. Sure you can choose to run whatever you like but folks smarter than me have already figured most of this stuff out so I go with it.

Articles/FAQ from desser

Link to "Standard tire pressure chart".

More than you ever wanted to know about tires
 
The majority are running tires way too soft.

Listen to Walt, read the chart. 500x5 6 ply = 50 psi unloaded
 
Isn't that max. Pressure?

So says the chart. I'm suggesting the higher pressure is what you should use, for several reasons.

Standard landing gear design assumes 3.8G limit energy. Put another way, it assumes we are not perfect pilots all the time. When you land hard the tire gets squashed more than you might think. For example, plug the numbers for an RV7 leg set into Neal Willford's excellent design spreadsheet and you'll find that a hard landing deflects the tire almost a whole inch more at 35 psi than at 50 psi. (At 35 psi it's well over three inches of deflection.) There are two effects. The tire is rolling, so the tire sidewall and tube are in a near "run flat" condition, which is very stressful. And, unless you run your wheelpants higher than most you're probably looking at some damage to the underside or the mounts.

Second, lower inflation pressure means that even when just motoring around the airport at 1G the sidewall flex is working the tube against the inside of the tire.

Third, lower pressure allows a point load like a pavement edge to protrude further into the tire.

Fourth, the tire heats more at low pressure.

Last, it's a lot easier to push the airplane in and out of the hangar.

With a 500-5 6 ply you're not overinflated at 50 psi unloaded, or about 52 psi with airplane weight. The trick will be finding a spec for minimum pressure.
 
So says the chart. I'm suggesting the higher pressure is what you should use, for several reasons. ...
That might be good and all ... But I'm sure that Van's had a very good reason for setting the pressure at 25 psi instead of 50 psi.

I'm doing some taxi test and am having some shimmy issues. Looks like I need to boost the tire pressure!
That may make it worse not better...
 
Van's recommendation for a 25 lb pressure on the mains was to produce a scrubbing action against pavement in order to reduce oscillation shimmy. I run max pressures to make the tires run more on center because they will tend to run on the outside due to the angle of the gearlegs. I always run max preddure on the nosegear also for the same reasons. Max pressures are 45 for mains and 72 lbs for the lamb tire on the nose.
 
That might be good and all ... But I'm sure that Van's had a very good reason for setting the pressure at 25 psi instead of 50 psi.

You're referring to a paragraph in the build manual where they have you assemble the wheel and do a few trial inflations?
 
My RV9A manual says to inflate the mains to 25 lbs. and deflate several times to make sure wrinkles are removed but says nothing about a going to a higher pressure. The nose wheel is inflated to 60 lbs to seat the bead then deflated and re-inflated to 30-35 lbs. that's where I got a basis for my tire pressure. Since a lot of folks are running much higher pressure I increased he mains to 35 and went with the higher pressure Vans recommends for the nose which is 35 lbs. it's easier for me to remember just one tire pressure. I'm not saying I'm right or wrong, it's just what I'm doing and am getting very good tire wear and have never had any shimmy.
 
Back
Top