Bike Rack Retaining Bolt Replacement Knob

I was in such a hurry to beat traffic from the Indy 500 (300,000 people) that I forgot to attach the retaining plate and knob to the bike. Luckily I had used my lock to lock the bike to the spare tire! So I only lost the plate and knob.

I made this knob to put the new bolt through. Originally I wanted to get one where I could put a nut to keep the bolt in the knob, but the only bolts I could find that fit my rack (13mm x1.75 pitch) had to be at least 90mm (3-½") long, and most of the shaft didn't have threads. It wasn't feasible. That said, if you can find a bolt with enough threads that work for you, there's a version where the nut will be hidden once you tighten it on the bolt. My solution was to bury the bolt head in the knob and have a cap that fits over it to hold it in. 

There are a couple different sizes because the first one I made apparently had a larger bolt head. The second time I forgot to use the retaining plate and bolt was after I found that my Jeep had been broken into in a parking garage. I got distracted and forgot to secure it. Again, luckily I had put the lock on the bike and my spare tire, so I didn't lose the bike on the road! I bought a new bolt, but the head was slightly smaller, so the hole in the knob for the bolt head got stripped when there was resistance tightening the bolt on the plate.

The shaft hole has a diameter of 13mm (½") I know a ½" bolt fits, but the threads on my rack used metric.

If you use a bolt with a different size bolt head or shaft and need the hole resized, let me know and I can quickly resize it and post it.

As for the plate, I didn't 3D design one because I'm almost positive that the stresses on it while a bike is mounted and wobbling around during driving would break it. (Confirmed. I designed one and it didn't work). I used an old 3/8"  (9.5 mm) thick plastic cutting board. I marked where the channel on the rack to hold the bike was. Then I used a rotary tool and routed out a ¼" deep channel to fit over the top of the bike's bar. I drilled the ½" hole in the center and it was done.

When I only transport one bike, I use a 1-½" (38 mm) dowel piece so the plate is fairly level when I tighten the retaining bolt.

The square stem piece is separate so that the stress of turning it against the plate won't cause the stem to snap off. Just use some super glue to attach it.

For the version with the nut, put the bolt through the knob and put the nut on. The cutout for the stem will allow a socket or wrench. Then, put some super glue on the stem and fit it over the nut. Alternately, you can put the nut on and use the cutout in the stem as the wrench. twist it and/or the knob to tighten the nut. Put some super glue on the stem before tightening it all the way.