Have been running 8.50s on my 180. alignment is good/equal both sides.
Since I'm here in N Cal, mostly on asphalt, ABWs would just be eaten alive. Thought I'd be a smart ass and jump on some 29" Goodyear retreads from Desser. They're heavy, and treaded. Running at 25 psi. Have experienced some directional control and occasional crow hopping.

Back on 8.50s no problem. I'll prob try again at lower pressure next time.

Anybody have similar experience?




Thanx,
Dave

26" Goodyear "Blimp" tires from Desser, smooth, 8.50 tubes, no loss in cruise speed. 16psi, lower if you bead lock the tire with sheetmetal screws after drilling through the hubcap screw holes.

Do you check tire pressures before each flight?
Different pressures can obviously cause directional problems.
At minimum - stand a good distance out in front of your plane and see if you can see a tire difference
often most visible out at the wing tips.

Is it possible that the tire swap procedure could have induced some alignment error?
Maybe look at/in the gear box area for "effects" of heavier tires - crow hops. Shot in the dark there.

How many landings?
A second person/pilot might see something during those busy seconds.

Hope you have the 29s balanced on their own wheels.
Do they shake just after lift-off so that you needed the brakes to stop them?

Is "crow hopping" is a euphemism for Pilot Induced Oscillation?


Hoping for the best

Chris C

Don't think there's any change in alignment between tire swaps as axle remains in same place. Recently rechecked when I took off of floats and installed gear. Skid plates and all for procedure. Obviously, radius changes/enlarges with larger tires. 6" rims on 8.50s, 10" wheels on 29s. Brand new tires, only a few landings on them.

Balancing is an interesting point. They are 60lb each (wheel/tire/tube) May run over to tire shop and see if we can't balance them.

Negative on the pilot induced oscillation, but feels like R tire just wants to head off in another direction causing the minor crow hop. Have experienced that as well as an out of alignment aircraft. Makes me appreciate an aircraft alignment that is true. Learned how to do that from Tom the Landing Gear Works guy. Spot on! Great guy if you ever need to learn how to do it and need a collection of shims.

I'm thinking I will go forth with a balanced tire, deflate to 20psi.... see how that goes. I did assemble with some Barge Cement to keep the tires from rotating on the wheels at lower pressure. May just be too much directional tread....

Thanx for the ideas!

abnranger-

I experience the same issue going from 8.5x6 to 10's.... In my view the toe is more exaggerated on the larger tire, because of the contact patch of the tire is greater. If I'm right or wrong it is a real effect. I've aligned my gear 4-5 times. Right now with 8.5x6 its perfect. But with the larger tires I need to tweak it before its comfortable to fly.

gunny

First thing I'd look at is the tires themselves. Why treaded? On the 10 inch tires I've run, we always bought new tires and had them buffed down to be almost treadless. No tread will definitely help with directional control issues.

I never really trust retreads either.....personal preference. Retreads are always HEAVY, as you noted in your posts. I spoke to a Goodyear rep once and asked why Goodyear doesn't offer retreads for GA tires. He said they do many thousands of retreads a year, but only on airliner type tires. He said the cost to do a proper retread and the increase in weight just didn't make sense to Goodyear for retreading small tires. He did say there was really nothing bad about retreads, properly done, except weight.

Gunny may have hit the nail on the head as well, though. The combination of a bigger contact patch and a treaded tire might be what's causing the issues. That is all going to be amplified by the spring gear on a Cessna, and it can get pretty exciting at times.

Since you are familiar with gear alignment on these things, if you're planning on running these tires regularly, I'd re-align the gear with the big tires. In my experience, gear alignment can be a significant PITA, but getting that gear alignment right is really essential on spring gear Cessnas.

But, again, I'd consider getting a new set of tires and have them buffed, or get the retreads buffed for that matter, to get rid of most or all the tread.

MTV

Did you align them toe-out, like Cessna suggests, or toe-in, which actually increases directional stability?

Any chance your landing gear moved in the gear box after being weighted and unweighted a couple times?

I really don't see wheel balance being a contributing factor to directional stability. I'd re-check the alignment. Get ahold of E. Wolf if you see him...he's a freaking guru when it comes to alignment. He's fixed a lot of airplanes that the "experts" swore were perfectly aligned, including the N3N on the field.

FWIW, my IA prefers spot-on, rather than toe-in or toe-out. He just says "it works better".

Cary

I fixed my first post.

With tailwheels, a slight toe-out will exacerbate directional instability...if the airplane is veering right, the right tire will start scrubbing and creating more drag, while the left tire comes into line with the direction of the caddywhompus aircraft down the runway and creates less, making the problem worse.

A slight toe-in reverses this. With toe-in, an airplane veering right will increase drag on the left tire and decrease drag on the right, which acts as a self-correction.

I don't recall how much toe-in is optimum...it's not a lot, but it makes a very noticeable difference.

The best solution of course is to just stay off pavement...then it doesn't matter how you're aligned.

All great ideas. As much as I can figure, I'm about half a degree in, equal on both sides. Don't believe alignment's changed. I'll run again on lower pressure, see if that makes a difference. If not.... They'er up for sale.

I've always had good luck w/ Desser retreads. I think they make a good product, never had any issues w/ about ten sets over the years. They do put a little extra tread on them. Just wanted tread due to mostly asphalt landings around here. Maybe I'll just break down and by the ABW 29" or 31"s. Quick enough to switch back and forth as needed.

Yes, and Evan is the guru around here for that. Very knowledgeable!

Thanx fellas!

Really in these airplane's the only value tread offers is landings on wet asphalt, to help prevent hydro planing.

Almost everything else about tread on tires is negative in my opinion....again, on this type plane.

MTV

Speaking of Hydroplaning:
A film similar to this, (if not the same), was included in my first ground school class given at Palo Alto Ca. High evening aviation class circa late 60s.

Big - low psi - "Smoothies" might want to remember this when stuck with a paved rainy day Wx alternate.


https://www.youtube.com/watch?v=TFOoFkYGqL8 #tires #hydroplaning

Wannabe
Chris C

wannabe wrote:Speaking of Hydroplaning:
A film similar to this, (if not the same), was included in my first ground school class given at Palo Alto Ca. High evening aviation class circa late 60s.

Big - low psi - "Smoothies" might want to remember this when stuck with a paved rainy day Wx alternate.


https://www.youtube.com/watch?v=TFOoFkYGqL8 #tires #hydroplaning

Wannabe
Chris C

Hydroplaning involves a minimizing of traction between tire and asphalt. In a 185, it's actually kinda nice not to have much traction between the tires and asphalt at times.......especially on long, wide runways.

Big difference between an airliner and a 185.

MTV