Tire pressure for Kitfox IV?

[rwaltman]

Getting the plane ready for my first taildragger lesson, after kicking the tires I would like to know what pressure you guys use for a 'stock' Kitfox IV 1200.
( This one: http://www.teamkitfox.com/Forums/album.php?albumid=117 )

When operating from paved runways only?
When operating from grass strips only?
For both?

Thanks,

Roberto Waltman

[Slyfox]

does the tire say anything. I have the 21" nankings and put 8lbs in them. I would say fill them until there is no bulge. Than go fly and have fun.

[Av8r3400]

I run 8-15 psi in my ATV tires in the summer and ~25 psi on skis...

(on my Kitfox IV.)

[Newkid]

Same here.

[Slyfox]

people have their process for checking out their airplane, mine is to have a pressure guage right on the hangar floor right next to the one tire that does go down on mine once in a while. First thing I do when I get to the hangar is check the tire pressure, not give it a smack and think is it ok. Next I don't use a tube, NO WAY. The way I fly, the stem would pop off the tube on just about any type of landing from me. I do beautiful landings I just like to play, you know, wheelies and such, I run down the runway and switch between wheels and just really have a bunch of fun. I hate tubes, won't run them on my fox.

[Dave S]

Roberto,

There are several things to think about for tire pressure - and a whole bunch of choices a person can make, none of which are necessarily wrong.

1) There are limits - a) The tires themselves have upper limits, although I don't think many of us will run pressure to the upper limits of the tires. b) The wheels may have pressure limits for the tires too - I have seen it for a particular rim/tire combination where the rim had a 5 psi limit lower than the tire.

2) Certainly different for standard aircraft tires than for tundra tires - the guys using the tundra tires know best.

3) Some folks, including engineers, think of the tire as part of the shock absorbing system - we can probably figure that one out, but there there is some middle ground a person can arrive at between bouncing like a superball and and going ker-splut...into the muck.

4) Here is another thing to consider - there is a difference in rolling resistance between a tire with high pressure vs low pressure - that translates into rolling resistance - soft tires - more rolling resistance - longer takeoffs and shorter landings - hard tires - the other way around. Just try this - vary the pressure in your tires from 5 psi up to the max inflation pressure in 5 psi increments - then go out and push your plane by hand up and down the tarmac - extra points if the experiment is tried on wet grass or a slight incline. The reality will make itself evident.

5) I don't do riverbed landings so I tend to keep the tires on the hard side (standard aircraft tires and grove gear) - that way I don't look as bad pushing the plane around in and out of the hangar...grass vs tar doesn't seem to matter much - muddy grass - don't know but a little flotation might be a good thing there.

6) Total weight matters too - more weight - harder tires even things out.

7) Normally, tires can take more abuse at higher pressures+wear less; and, tolerate less abuse less at lower pressures while they wear quicker.

Sincerely,

Dave S
KF7 Trigear

[rwaltman]

Thanks for the replies - I'll be using mostly paved runways, (specially at the beginning), so I am leaning into using higher pressure.

Do not need extra cushion because of groundhog holes, etc. and, for some reason, do not like the idea of shearing the stems... (thanks for the warnings, that is something I didn't think of)

Roberto Waltman.

[SkyPirate]

sounds like you hit the ground pretty hard to shear a valve stem,..I flew my model 2 with tubeless carlisle tires around 8 lbs of air pressure,..made allot of really short landings with power ..never once sheared a valve stem,.or popped a bead,...the avantage of a tire designed like the carlisle,..the side walls give allot which is good for off field landings, and helps take out some of the shock on a rough landing,..and if you do have to run lower air pressure( tubeless I wouldn't recommend it) ,..the side wall allows for a bigger foot print on the ground ..floatation,.. now on an air plane that will never see grass or a rough field I'd probably choose a different heavier tire.

Chase

[Av8r3400]

Roberto-- Don't be shy of grass runways. They are very forgiving for a novice tail-wheeler and lots of fun, too.


Chase-- I don't follow you. Joey has (had?) tubes in his tires, that's how he was able to shear a stem. The rim rotated against the low pressure tube and pow. Tubeless, it is impossible to shear a stem from low pressure...

[SkyPirate]

that was my point ..tubeless is better for low pressure tires especially on aircraft for off field landings,. from a dead stop to spinning 25 - 50 mph instantly .no chance of ripping off a valve stem with tubeless. but the bead can break ..good thing they make bead seal every day