Tire Review - Specialty Tire "Air Trac"

[jimboe]

Hi Everyone,

It's about time I contributed something to this site that I have been so dependent on for so long. I just put some new tires on my Champ and wanted to share some of what I learned as I did the research, installation and first tests.

I’ve had the Champ for close to 10 years and it had re-capped 7.00-6, 6-ply Condor tires. The outside corners wore out so a few weeks ago I decided to flip them around and wear the other corners out, but when I checked the tubes one had a fold that appeared to be a weak spot and I didn’t want to re-use it.

I had read from more than one tire manufacturer NOT to re-use tubes because they may stretch enough that folds are common. I’m a motorcyclist and didn’t take the advice seriously until I saw the fold in the tube.

I decided to start fresh with new tires and tubes because the old tires were about done anyway. I liked the larger diameter of the 7.00-6 for grass and dirt strips I frequent, but they weighed 13 lbs each and I wanted to save weight. I asked a few people I trust for advice (thanks Paul) about my airplane and they suggested staying with the larger tires.

I looked at specs for Michelin “Aviators” and Goodyear “Flight Special II” for a benchmark. Wow! Those tires are expensive. I looked at lower cost tires like Condors and Specialty Tires.

I found that most 7.00 & 8.00 tires were 6-ply and had max load capacities of 1,900 lbs or more, which seemed like overkill for a Champ. I also saw that the recommended pressure for those tires ranged from 35 to 55 psi. I remembered looking at old forum postings where plenty of people were putting 15 psi in their Champ and Chief tires. I had never put more than 25 psi in my Condor re-caps and they were on the harsh side when rolling on rough ground. I didn’t want a tire that was designed to hold 50 psi because I figured it would have a harsher ride and putting a lot less air in it might be bad.

I called Specialty Tires of America and told the rep I wanted a larger diameter, light-weight tire for a Champ flown on a mix of pavement, dirt and grass. He suggested either the “Air Trac” or “Air Hawk” in 8.00-6, 4-ply. Each weigh 10 lbs and the recommended pressure is 23 psi, and they have the same rubber compound. The difference between them is the profile and tread pattern. The “Air Trac” has a rounder profile and is “ideal for soft field applications.” The “Air Hawk” is a more common “square shoulder tire.”

I looked at the wear pattern on my old tires and it seemed like a rounder profile would make a wider footprint and potentially wear longer on a Champ with oleo shocks compared to the square Condors wearing at the outside corner. I decided to try the rounder profiled “Air Tracs.”

I found them only at Dresser ($162 ea), Aircraft Spruce ($165), Wag-Aero ($161), and Aircraft Supply ($144). I called Chief, but they don’t sell the 4-ply Air Tracs.

I also bit the bullet and ordered two 7.00-8.00 x 6 Michelin Airstop tubes for $72 apiece. They are made with butyl rubber that is supposed to hold air longer. I have hub covers and have to unscrew them every time I check the tire pressure so I wanted tubes that didn’t leak much (I was tempted to put those airless wheelbarrow tires on the Champ, but the plastic hubs didn’t strong enough for my landings).

The price for tires and tubes was substantial, but I remembered that a decent rear tire for my KTM 690 Enduro is about $150 and those only last 2,000 miles. Then again, the KTM has the same horsepower as a stock 7AC and can fly pretty far without wings, but the landings are not as predictable.

I took some measurements and photos as I changed the tires. The new 8.00-6, 4-ply Air Trac weighed 9 lbs which was 4 lbs less than the worn out re-capped Condor 7.00-6, 6-ply.

Both the worn out Condor re-cap and the new Air Trac were a little over 18” diameter.

I field tested the Air Tracs on pavement, dirt and grass strips and they worked nicely over bumps, gopher holes, doing S-turns on alternating wheels, landing in a turn, dropping and greasing onto the runways. One feature I really liked was they were well balanced, unlike the old tires which had me stabbing the brakes after take-offs to stop the wheel shudder.

I'll try to remember to post a long-term report about how they wear.

I posted pictures of the Champ with the new tires, of the Condor and Air Trac side-by-side, and of my old tube with the fold at my Dropbox link below.

https://www.dropbox.com/s/jbekrng6l2wbo ... c.JPG?dl=0

Hope some of you find this info helpful.

Jim

[bob turner]

You lucky guy! I run 8:00x4s, and tubes are not available. I am still using tubes marked "1958". I run them at 25 psi. Tires are now over $300 each.