I'm having problems attaching a Schwinn child/pet trailer to my RadRunner after using it for several years on a conventional bike.
The coupler (photo 1) won't sit flat because of a bolt located just above the axle. Another coupler (photo 2) fit the axle ok, but didn't have enough space for my trailer arm. A third coupler that misses the bolt above the axle (photo 3) is recessed, so there isn't enough room for the stock axle nut to attach.
I tried to find a conventional nut to attach to the axle and the threads on the ones that were the right size weren't compatible.
My next thought may be to take some metal tubing to connect to another coupler that is too small to attach directly to the trailer hitch. I looked exhaustively fo r another coupler that's slightly larger and fits the axle but to no avail. My thought was to get a smaller-sized tube, attach it to the coupler and attach the other end to the trailer arm and use washers to account for the difference in size between the tube and the trailer arm.
Does anyone have a better solution? Thanks.
Here's what I ended up doing: I used a small piece of pipe to attach to the coupler and to the bike trailer. It works fine.
My mount was recessed as well. I had a friend mill it down. See pic.
My trailer has the angle bracket like your third picture. I bought a nut that does not have the flange, and used a washer that was small enough to fit in the hole.
"It is best to attach the trailer to your bike frame or seatpost but please do not attach it to the axle."
I had the same issue and contacted rad for options. THEY RECOMMENDED TO NOT ATTACH A TRAILER TO THE REAR WHEEL. Here is the response I got:
"Please do not attach a trailer to your rear axle. We do not recommend attaching anything to your rear axle and we do not offer any other nut aside from the stock one that you already have. Attaching a trailer to your rear wheel axle can damage the motor and possibly cause an accident because the rear axle is not designed to hold trailers. The good news is that your RadRunner has plenty of other areas where you may attach a trailer for your doggie. As I mentioned in my email please look into some of the Rad Owners Groups online where you may find some tips on attaching a trailer to your Runner. It is best to attach the trailer to your bike frame or seatpost but please do not attach it to the axle."
Interesting. They told me something similar but different. Didn't say a word about attaching it to something other than the axle. And said don't do it, but if you do, check with the online forums and a mechanic. But we don't recommend it.
"Unfortunately, Rad does not recommend this modification or add on to our bikes due to the extra strain it can add to the motor, motor mounts, and wiring.
As for adding a trailer to your bike, or any third-party component, I would encourage you to seek the expertise of a professional bicycle mechanic. Generally, we cannot recommend any parts that we haven't tested for safety and compatibility with our bikes (and determined to be compatible and safe). You may also be able to check online forums for Rad Power Bikes to see if any other customers have had success adding these kinds of parts to their bikes, though we still recommend consulting with a professional mechanic."
FYI, Rad would never recommend attaching anything to the axle for legal reasons anymore than they would endorse riding with no hands or even 1 hand.
"For safety reasons please come to a full stop, dismount your bicycle then take a drink of water" " Reaching down for a water bottle could cause a loss of control " "Do not use hair dryer in shower" etc etc.
Anyway, millions of trailers including Burley ( The biggest name in trailers for children) attach to the axle. Perfectly safe when done correctly.
I attached a burley to my RadCity 5+. I went with the axle method by removing the Rad axle nut and replacing it with a M12-1.25 hex coupling nut available as part FBAPM60029-1 from www.clipsandfasteners.com, faying up the burley steel hitch (part 960116) to the outboard face of the coupling nut, and attaching/securing the burley steel hitch with a hex flange bolt M12-1.25 (fine thread) x 20mm long available from www.mcmaster.com as their part number 95735A114. Cart is 35 pounds and dog is 60 pounds. No issues to report. Tows like a dream on asphalt, but I keep PAS at 1 and sometimes 2 and speed at 10mph or less. Haven't tried higher speeds or rough terrain. Two photo's attached.
I think another reason is that the rear axle is not replaceable. If you strip the threads or bend the axle or anything, you have to buy a new wheel. Rad is afraid you would claim a warranty defect and try to get a new wheel. Maybe also for that reason, they don't want anyone messing with the rear axle.
I connected my trailer to the rack of my Mini ST2. No modification of anything but I used the old fashion Burley mount. See https://www.radowners.com/index.php?topic=1630.msg8158#msg8158