I have the Robart landing gear for the GP GeeBee. While the gear is a snap to install, the stock wheels will not fit. Robart says to use robart wheels, well they generally are too soft, and will probably deflect and catch the fork of the gear. I am not so sure that adding their backer-rod filler would help. What other narrow hard wheels are available out there?

You can use Robart foam inserts inside Robart tires to make them harder and prevent the tires from deflecting or rolling over on their rims.

From what I have seen, they use a caulking foam rod that you cut to length. I have tried this and it is not much improvement. On their 4 inch wheels, the rubber in relation to their rim size leads to a very tall sidewall. It would be much better to have a low profile, hard tire.

What is the width of the fork?

Yak

[link=http://www.hobby-lobby.com/wheels.htm]Kavan Wheels[/link] and [link=http://www.towerhobbies.com/listings/cat-cat-q.html]Williams Brothers Smooth Contour Wheels[/link] are narrow. Williams Brothers wheels are also hard.

I had thought about the Williams Brother's wheels. That is what I will probably go with. I am not sure what the width of the fork is, but the stock tire just does rub, so I am guessing it is about an inch and an eighth wide. I like Kavan wheels, but I am not sure of the width, since they are kind of squarish wheels.
Wouldn't you know it, the Williams Brothers are backordered..

I ordered a set of gear from Robart this morning ... $145! Tower has them listed for $129, but they aren't in stock. Where did you get yours, JeffH? How much, if you don't mind me asking?

I picked up a GP GeeBee this weekend at the WRAM show. Got an excellent deal. I'm VERY excited about this project! YS-120 will be used.

MIne came from a LHS. They were right around Towers Price. IMHO, they are over priced, but the stock gear is useless.

I am putting an OS 160 Gemini Twin in mine.