The question "which ABW should I get" has been answered, a lot. I never did see a poll and the search drew a blank...

It would be really interesting to know how many people are actually using which sort of tire off-airport.

So the question is about off airport landings into basically unimproved locations. Different kinds of location might need a different tire, but the question is more about what pilots are actually using. You can pick a few options if you've used more than one.

I don't need no "stinking tires" (when on a beautiful backcountry lagoon of floats) !

850s

Hey how come I can't seem to respond to polls? what am I doing wrong?

Hey I don't see 5.0 on there! Don't hate on my nosewheel!

I've been to quite a few real off airport locations with 800s on my Luscombe. They were far from ideal and there were several times I was lucky I didn't break a wheel. I have zero experience with bushwheels but I see some 29s in my future.

piperpainter wrote:Hey I don't see 5.0 on there! Don't hate on my nosewheel!

Hey Z, if I edited this Poll, would I lose all the responses so far?

whee wrote:I've been to quite a few real off airport locations with 800s on my Luscombe. They were far from ideal and there were several times I was lucky I didn't break a wheel. I have zero experience with bushwheels but I see some 29s in my future.

Whee - thanks for the heads up, I've been looking and the 8.00's on my BH and thinking:
Hmmmmm.... I wonder whether it's a good idea.... hmmmm...... maybe if I was really careful....
Sounds like 8.50's would be a smarter move.

I am proposing a universal formula which may deduce some reasoning.

Gross_weight / (overall_tire_height x tire_width) = big_tire factor

On my bird:

#1 Scout with a Gross of 2150 LBS fitted with 31136.R (31") tires would have a "big _tire_factor" of (5.3)
Example 2150 / (31 x 13 ) = (5.3) big_tire_factor

#2 Scout with a Gross of 2150 LBS fitted with 8.5 tires would have a "big _tire_factor" of (42.1)
Example 2150 / (8.5 x 6 ) = (42.1) big_tire_factor

The smaller "big_tire_factor" means my airframe relation to tires is getting smaller. Less airframe and more tire to deal with.

21/800x6 (Not listed in poll) on Grove tubeless wheels

I like your formula 8GCBC. My Citabria on 31136.Rs give me a big tire factor of 4.09 @ my gw of 1650. I really like my 31s.
David

A1Skinner wrote:I like your formula 8GCBC. My Citabria on 31136.Rs give me a big tire factor of 4.09 @ my gw of 1650. I really like my 31s.
David

Yes! We have correlated data together! Your comparison shows me that your tires are really LARGE. Which is totally cool! My 31136.Rs, as mentioned, are 5.33 @ 2150GW. You beat me by a "big_tire_factor" of -1.24.

But what you really want is the lbs/inch^2 on the tire, which means you need the surface area of the tire that is in ground contact. The width of the tire would give you that, but the height doesn't really. And the width you use isn't really the tire width...850x6 tires are on 6" wheels...but so are 31" bushwheels...and the 850 is a lot wider than a 600x6 tire.

The inflation pressure of the tire can have a big impact on the amount of surface are of the tire on the ground as well, so that's another factor that makes it hard to calculate effective tire footprint.

In the end, I don't know if there is a good way to shorthand a big tire number. But I do know I like big tires. And I know that the 850s on my PA-22 are amazingly soft compared to the 600s that were on there before.

I've been flying a super cub on 35's lately. It all depends where your landing, I landed in the river bar the other day and was glad to have the 35's...

Troy, the taller the tire is, the bigger your footprint is, so taller does = bigger footprint, same as wider = bigger footprint.

A1Skinner wrote:Troy, the taller the tire is, the bigger your footprint is, so taller does = bigger footprint, same as wider = bigger footprint.

True, but as Troy pointed out, 29 inch Bushwheels inflated to 4 psi have a substantially larger footprint than the same tires at 12 psi.

MTV

Yes, agreed 100%

And less GW = less PSI in tires that I fly.

Radius vs GW will always matter too.

8GCBC wrote:Gross_weight / (overall_tire_height x tire_width) = big_tire factor...........
#1 Scout with a Gross of 2150 LBS fitted with 31136.R (31") tires would have a "big _tire_factor" of (5.3)
Example 2150 / (31 x 13 ) = (5.3) big_tire_factor
#2 Scout with a Gross of 2150 LBS fitted with 8.5 tires would have a "big _tire_factor" of (42.1)
Example 2150 / (8.5 x 6 ) = (42.1) big_tire_factor
..........

Your idea's good, but you're comparing apples to oranges. You need a big-ass set of calipers to measure the actual OD & width of the mounted tire, so you can use actual dimensions, not arbitrary numbers (such as the 8.5 on airplane #2) from the size designation. You also need to extrapolate tire contact area somehow by using tire pressure and weight of airplane. Contact area and weight per sq inch would give an indication of how much flotation they'd provide, but you'd also need to factor in diameter and it's effect on being able to roll over obstacles. A small diameter fat tire might be better in sand while a large diameter skinny tire might be better in rocks, In short, I don't think this is something that can effectively be compared using math.
I use math to compare airplane performance potential by comparing a combination of power loading (weight / horsepower) and wing loading (weight / wing area). This is apples to apples but can't take into account different airfoils, liftier flaps, etc or pilot technique and skill.

I recommend 65's for this location

Bigger is better!!!