Yes I read the gentlemans post GB and I only was suggesting "avoiding the temptation" a simple trap that messes up lots of people.

Gphil OK so now we know we are not dealing with piano wire axles/gear but the straight machined and nutted axles. Just happened to have replaced recently a new set of Dubro 4" Big Wheels (a balloon type) on my 50cc Katana and I used Dubro 1-1'4inch long by 5/32 spring steel axles. What confused things a bit was when you mentioned adjustable axles, I know of no straight nutted axle that is in some way adjustable.

At 1-1/4 if you use any spacers and or a wheel collor the the they are a little tight. Since I always solder a washer and use no collors it is a perfect length with no problems. Also the 5/32 axles are what the wheel is drilled with. If you use this wheel and I do not know if this is the 4 incher you are talking about but perhaps you would be better off going to the 3/16 X 2 inch if you intend to use wheel collors.

Now I am guessing your airplane is some sort of 40/60 sized stick and the four inchers may be overkill. And contrary to popular beleif GB and I do occassionaly agree sometimes and the four inchers are quite heavy compared to some other so indeed CG of course as any other change needs to be corrected back to your previously established position for flight. Of course as you noted you already know to do that.

I think actually the three inchers would be the ideal for you to try. Oh by the way I love Dubro big wheel balloon smoothies even though they are heavy for any given size, There're may favorites.

John