I've been researching the bigger tires since before I bought my RV-8. Very happy I found this thread.

If you want to go bigger yet I put a set of 21" on my RV4. No wheel pants then of course.

What size are you using on the rear ?

I am close to install the whell pants on my 7. I intent to land on gravel/grass strips later and understand that a larger tire (like the 380) should help in that regard. On the other side i hate to throw stuff away and the installed stock tires do look perfect. So my questions to the guys who switched to larger tires: Is it really a noticable improvement during TO/landing on grass/dirt strips?
Kay

I?d say it?s a noticeable improvement for soft field stuff. The grass strip I was once on was really soft and it helped a lot. If the grass you intend to visit isn?t really soft I wouldn?t bother with the 380?s. After I switched to the 380?s I developed a slight shimmy at around 30kts.

This is a good thread:
http://www.vansairforce.com/communit...v-6+bush+plane

It was a noticeable improvement for me in rough/soft field ops. But it made the gear legs on my RV-7 shake like a paint mixer on landing starting around 30 knots, until I slowed to below 20. I tried balancing (repeatedly) and even another set of tires. The wood gear leg stiffeners offered for sale occasionally on this forum killed off about 99% of that. As is often pointed out, every RV is different. YMMV.

They shake because they can be up to 1/2" out of round NEW. All aircraft tires are this way, even jet tires. My neighbor who flies/maintains a Falcon 900 changed the nosegear tires on his jet and it shimmied bad even after perfectly balancing them. He chucked them on his lathe, saw they were out-of-round and Goodyear sent him a new set of tires. He checked the replacements and they were minimally out of round. No shimmy.

The out-of-roundness is from where the plies overlap. That also forces the tire to have a localized stiff spot as the overlap patch is run over which also causes shimmy/oscillation.

Boy, I'll say. I've cut a tire open just to look. The overlap was ugly, though that was a sample of 1. My current set (Desser Aero Classic) is ok. Worst one was less than 1/4" out of round after sitting inflated overnight. Last set was noticeably worse, which was why I changed them. Were the Falcon tires tubeless? Wondering if that makes a difference on construction. Or radial, but I assume that's getting exotic for an aircraft application.

I've observed this too. Surprising to me. One would think they would manufacture tires that were more round. Seems like you would stagger the ply overlaps at various clock positions around the tire.