That makes sense, I didn't think of the added drag of a side car compared to that of a trailer.it pulls the sidecar ok, as you would expect from a motorcycle fitted with a motor that would work well in a D9 Cat, but first gear is way too tall for the kind of slow maneuvering I would like to have (without abusing the clutch as much as I am now). I’ve been on two or three wheels for over 30 years and this is my 5th or 6th sidecar outfit.
I don’t (and would never) tow a trailer with a bike but I don’t think the comparison covers the extra wind drag a sidecar presents, which is huge. The benefits of lower gearing are usually better gas mileage, cooler running and a longer clutch life.
I have been researching this for many hours and have sent out a few email enquiries but I don’t like the chances of solving this without some serious engineering unfortunately.
Another option is to lace a smaller rim on the rear and/or install a lower profile car-type tire, the latter having the added benefits of more traction and much longer life. I would probably go this route before paying for one-off machine-work. I just thought that someone would have done this already...