Is this possible?

I recently got a topeak ridecase for my iphone 5s and it's a great system, but requires a threadless stem cap to install the mount the cleanest way (otherwise it has a handlebar mount adapter)



As you can see it replaces the stem cap and bolt - works great on my rumblefish but not so much on my `84 road bike which is the bike I intend to use this with the most on long rides so I don't have to pull over and stop to pull my phone out when I get lost

I've seen the profile designs and origin8 adapters but it looks like the bolt system for them goes through a permanently attached stem cap?

Any ideas?

looks like the stem cap is not attached, so just unscrew and use the stemcap on your adapter

https://www.excelsports.com/main.asp?...jor=1&minor=22

One possible way is a quill to threadless adapter to replace your stem: https://www.nashbar.com/bikes/Product...45_-1___202442
You will need a new threadless stem to use it.

right, but the bolt still looks to run all the way through the adapter from the stem cap down to the quill anchor pivot. This topeak mount bolts to the star nut near the top of the cap, are there no 1" to 1 1/8" adapters which have a normal cap design? I do not believe I can remove the bolt from this topeak mount to run the longer bolt through it, it is not only used to tighten it to the stem, but also holds the angle of the mount tight / that bolt doesn't seem to want to come out.

I can't believe the bolt in the Topeak adapter is welded in place. It has to be removable and can be replaced with a longer one. Any 1" quill to 1-1/8" threadless adapter has to have a tightening wedge and the longer bolt that accompanies it.

no, probably not welded, but it does seem to be internally retained, probably with e-clips.

Remove them.