Tire Pressure

gusc · Post by **gusc** » Mon Jul 24, 2006 00:17

What do most of you use for tire pressure in your 1220 GW Champ? I always used the rule of thumb of 1 psi for each 100 lbs of weight but these 8:00x6, 6 ply tires are extreme overkill for this airplane.

When I got mine it had 20 psi so I decreased it to 12.5 psi but haven't flown it yet.

I know 20 psi is way too much and noticed that it was pretty bouncy. My Stinson only used 24 psi and it had a GW of 2400 lbs!

Paul Agaliotis · Post by **Paul Agaliotis** » Mon Jul 24, 2006 00:20

I use 30 +/- 2psi.
Paul

Post by **joea** » Mon Jul 24, 2006 00:50

Gus,

Hard or soft runway? Makes a very real difference.

I fly off of a hard runway and usually run 14-15 psi on my 7.00X6 tires. Too much more and its "skiddish" on higher pressures.

Soft runways you can reduce pressure a bit but do not get too low.

Paul, you might try taking yours below 20 and see how it works. I found that mine was a lot more stable with less air in the main tires up to a point. What sized tires are you running up front?

Joe a

MikeB · Post by **MikeB** » Mon Jul 24, 2006 08:34

I have 8:00 X 6 and use about 20 psi and seems to handle well on both hard and turf. It seems the manual calls for around 16 psi on 6 inch tires.
Might try dropping it a bit and see if there's any difference, but then why mess with it if it works, I guess.

Jon B. · Post by **Jon B.** » Mon Jul 24, 2006 13:01

'57B wears Goodyear 8.50 tires these days. I keep them around 12 or so psi. I started with 16, just to get the bead 'stuck' to the rim. I don't want to spin the tire on the wheel and rip the valve stem off.

The 7.00s were originally at 20 psi but that was too hard. I backed them off to around 14-15 and that seemed fine. I used the "footprint" in the dirt to see if the tread was flat on the ground, and reduced the pressure 'til the whole surface was leaving a track.

Jon B.

Ron Babos · Post by **Ron Babos** » Mon Jul 24, 2006 16:24

Jon: 700/6, I start at 16 and feels about right. More too stiff and less than 10 the Cleveland hyraulics would probably sheer the valve stem. Sick of always having to top them up and considering using nitrogen as it's molecule is larger and won't seep through the rubber as easy. With air I start at 16 and about a month they are down to 12 psi.
Ron

Paul Agaliotis · Post by **Paul Agaliotis** » Mon Jul 24, 2006 18:14

Joe,
I have the 6.00x6 tires installed. At the lower presures it just wears out tires. The oleo gear is soft enough to absorb all the bumps. If the gear was stiff like a Cub or Tcraft the lower presure is needed.
In the past I,ve used from 8 to 32 psi and don,t see a problem or advantage with any presure.
Paul

gusc · Post by **gusc** » Mon Jul 24, 2006 21:30

Thanks for all the responses, more than I expected.

I always thought that the larger the tire the less pressure should be used, don't know for sure where I got this info but it makes sense.

I don't understand why anyone would put 6 ply tires on a 1220 lb airplane?

I think I'll compromise and go back to 15 psi, I kinda had the feeling that 12.5 was too low. The weight of the heavy tires might make them move on the wheel.

Jon B. · Post by **Jon B.** » Tue Jul 25, 2006 10:16

Paul Agaliotis wrote:Joe,
I have the 6.00x6 tires installed. At the lower presures it just wears out tires. The oleo gear is soft enough to absorb all the bumps. If the gear was stiff like a Cub or Tcraft the lower presure is needed.
In the past I,ve used from 8 to 32 psi and don,t see a problem or advantage with any presure.
Paul

Paul:

I have the marvelous No-Bounce (or long-stroke) gear on '57B. They're great for landing but not so great for taxiing. I like softer tires for that purpose. Also, on take-off from less-than-smooth 'strips" the softer tires are nice before the wings start supporting some weight and the gear legs uncompress.

I only operate off pavement if there's no alternative. Champs and grass (dirt, gravel, sand or snow) are made for each other!

Jon B.

Captgrumps · Post by **Captgrumps** » Tue Jul 25, 2006 11:54

Air pressure for J-3 Cub tires (8:00x4)is recommended to be 16#. On low pressure tires it is difficult to determine air pressure by looking at the or kicking tem. If pressures gets too low--and you land on hard surface, the common faulit is tearing the valve stems with tire slip on the rim.. I had a Cessna 185 with 8:00x6 and ran them at 24/25# and that was with gross weight of 3300#.
Example the Cessna 150 with 6:00x6's run about 21#. With the large softer tires you need to watch air pressure--not so much for weight problems but the formentioned valve stem and tire slipping problems. This is also a problem for high presssure tail wheel tires (i.e. 10:00 SC) on Stearmans, Fairchilds and etc.
I have replaced many Cub tubes and tail wheel tubes over the years for people that wanted estetics rather the performance and those too lazy to check tail wheel tire presssure becuase those tires were fairly rigid and always looked OK.
BTW--the original Aeronca Chief and Chanp manuals says the recommended tire pressure of a 6:00x6 (2 ply) tire is 13-15 PSI.

Doug

Paul Agaliotis · Post by **Paul Agaliotis** » Tue Jul 25, 2006 18:26

Jon,
Some of the No-Bounce gear use a Belville washer set up rather than a spring for taxi. The washers are much stiffer than the spring and not a good choice for off field work.
I have the long stroke oleo on my L16 and the later No-Bounce gear will not interchange.
I agree with Doug on the tail wheel presures. I was using an 8.00SC and ran about 90psi to keep from pulling the stem out. At the time the tubes cost more than the tire.
Paul

Jody Wittmeyer · Post by **Jody Wittmeyer** » Thu Jul 27, 2006 22:02

14-16 works very well on 6.00 X6

Nathan K. Hammond · Post by **Nathan K. Hammond** » Thu Jul 27, 2006 23:05

I ran my 600x6's at 30psi for a little while. Made it great when pushing it out of the hangar and up the hill. But it did make every little bump noticeable. I got kind of worried about causing damage on the fittings and what not, so dropped them down to around 20psi for a good balance of cushion and ability to move around.

nkh

Jon B. · Post by **Jon B.** » Tue Aug 01, 2006 13:40

Here's some anecdotal 'evidence' regarding tire inflation.

I have the aforementioned 8.50 Goodyear tires on '57B, inflated to approximately 12-14 psi. Last week, I attended the annual SuperCub.org fly-in at New Holstein, Wisconsin. One of the things we did was a short-field competition (bragging rights only; no prizes) for landing and take-off.

Now, with only 90hp, I was hardly a threat in the take-off portion but, I figured I may be able to give them a run in the landing department. My best take-off was 295 feet; just me in the front seat and a lot of air in the gas tanks. The winner used 130 feet!

My shortest landing was 180 feet, six inches. Unfortunately, the six inches was in front of the line, so I 'scratched'. The others were 205 and 208 feet. The guy who won landed in 151, and had two more within just a few feet more; very consistent! Had I hit the line, I'd have easily had second place. Second and third were 203 and 204 feet, respectively. Coulda, woulda shoulda...

I made my approaches rather steep, (nearly) power off and about 40-45 mph. I have Cleveland wheels and single-puck, hydraulic disc brakes, the same models as the lighter Cessnas. At touch-down, I had the brakes applied, hard! At that speed, angle and power steeing, the nose is high and so is the descent rate. The No-Bounce gear gets exercised pretty hard. I continued braking hard 'til the tail refused to stay down (I had my tool kit, flight bag and a quart or two of oil in the baggage bin), then backed off, pumping them 'til I stopped. In a couple of practice runs, I slid the tires on the (grass) runway.

Afterward, I carefully checked for tire spin and found them to be quite nicely where they belong. The valves are still sticking straight out, with no angle to indicate tire movement. I doubt that I can be any more aggresive and still re-use the Champ afterward. I'm no longer going to worry about spinning the tires on the rims.

Jon B.

Post by **joea** » Tue Aug 01, 2006 14:05

Jon,

Good to know. If you are worried about tire spinning on the wheels, you can always paint some markers on the tire/rim to keep an eye on it.

Joe