Hey Doug, I could do that, the only problem is all tire manufacturers seem to be different. Even though they say there tire is 21'' it may be a little more or a little less or it may be 8'' wide or it may be a little more or a little less. I was hoping someone has already done this and I could find out what brand actually fits or doesn't fit. I'm 61 yrs. old with a bad back and just want to get as much cushioning as possible without adding rear suspension. If I add rear suspension I should add suspension to the side car and I don't want to do that. I like basic and simple. Thanks for your input. Anyone with the name Doug must have good advice!.............................................. Signed Doug