Tire size comparison - photos

[Battson]

Before I starting my build, one thing I always spent a lot of time thinking about was which tire size to purchase. As most of us know, the choice is a trade-off between weight, airspeed, and rough field capability.... oh, and maybe aesthetics too.

To help with this decision, one thing I really wanted to see was a visual comparison, to help understand what all the different numbers meant in real life. That proved hard to find. So I thought I would drop all mine into this thread, so it can become "Googleable".

If you wanted to add your own photos or information, that would be great.



Main landing gear:

Michellen Aviation 8.00 x 600 x 6ply compared to 26" x 10" x 6ply Goodyear (actually only ~23" tall when inflated)


Note the Goodyear tires are taller and narrower when inflated on a rim, about 23" tall.



31" AK Bushwheel compared to 26" x 10" x 6ply Goodyear






Tailwheel:

Bearhawk Tailwheels 10" tailwheel compared to Bearhawk Tailwheels "Tundra tailwheel" 4.00 x 4 (12" tall and 4")




With the weight of the aircraft resting on the tires, the axles sit quite a bit lower.

[Bdflies]

Thanks for the pics! Great to see each, in comparison to the others. Having flown your plane on each of these tires, what are your impressions of each set? I've heard that the 26" Goodyears are really stiff and don't provide much cushion effect over the smaller tires. Are the 31’s firm enough to provide good feedback?

Bill

[Battson]

How they feel to land on
I would say I got roughly the same amount of improvement at each tire change. Going from 8.00s to 26"s was a noticable increase in cushioning, and going to the 31"s was about the same again.

On a smooth grass surface, if the 8.00 gave you 100% feel for the ground you're on, then the 26"s would be about 50%, and the 31s would be about 0% feeling.
To put that another way, I can land the 31s on smooth grass and the rolling noise is the only way I know I've touched the ground, I can't feel the firm springiness of the main suspension whatsoever. Whereas with the 26s I got some feel of the suspension springing, even with my best landings. With the 8.00s the suspension travelling was very obvious.

It was easy to bounce a landing on 8.00s if I was not careful. There's no way to bounce with 31s unless you really slam the plane down - I mean really screw things up. Again, the 26s were about half way between the two.

Versitility off airport
Each set is a meaningful step up. But this is mostly about safety factor, shock absorbsion, and pilot confidence. The 26" are probably the biggest step over the 8.00s, they open up most places a Bearhawk can land. The 31s probably open up another 5% or 10% (max!) of landing places compared to the 26"ers, and that's both soft surfaces and hard rocky places, so about 5% more beaches and 5% more riverbeds. Not much. Whereas with the 8.00s you have to be quite selective about where you land, so the 26"s are the biggest improvement there.

The steering / braking with the treaded 8.00s is totally different, compared to a bald tire. The treaded tire is very hard to skid, whereas the smooth tire will skid without warning. They take some getting used to. I think most aircraft owners with smooth tires have either given themselves a scare on wet grass, or they are going to in future! The tire size isn't the predominant factor, it's the tread.

Weight and balance
The weight of the 31s and 26s isn't greatly different, because each uses a different thickness of rubber for construction. Both heavier model tires make a small but noticeable difference to the forward CG location at light weights. This becomes obvious when trimming the aircraft for a low speed landing.

Installation
All tires larger than 8.00 (including an 8.50) really demand double puck brakes. You can't brake-steer safely on a windy day without them.

The Goodyear 26" tires require one spacer on each side (about 1/4" thick from memory). Otherwise they rub on the brake caliper and get damaged. This is no extra work if you plan ahead, and spacers aren't expensive.

The 31" tires require substantial modifications to the gear leg fairings. Perhaps only two hour's work if done during the initial build - but on a finished plane, it takes about two days work to retro-fit so as everything looks as good as new, depending on your covering system.

[tailwind]

Thanks for the review. I enjoyed reading about your observations when flying the different tire sizes. I currently have 8:50s on and will need a new set in the next 50 hrs.

[jaredyates]

Going the other direction, here is the Goodyear 26 with a 800x6:
. IMG_0956.JPG
And here is a not-as-well-framed shot of the Goodyear with a 600x6. The photo makes the 600x6 look a little bigger than it is, but compare the sidewall dimension:
IMG_8296.JPG