Flexible seat failure

Yesterday, Mike who is better at hopping than riding had a go on my Wilder MUni. He jumped over some mags with a plank balanced on them. I was pleased to see how impressive his hops were, even though he wasn’t riding away from them. As I was riding home I was surprised by how flexy the Kris Holm Velo saddle felt. Upon closer inspection Mike had snapped the seat in the middle. There was no metal plate, and Mike’s jackhammer/pogo style learner hopping was too much for the flexible plastic. I’d say it was a combination of bad design and bad technique. I have heard of a method to fix this problem with a brace thing, but I have another temporary solution : to build an Air-saddle. I have to wake up early tomorrow to drill out holes for the Reeder handle. Also I am wondering about what bumpers fit on carbon fibre bases, and if most people use them or what. I am considering getting a Kinport rear bumper.

broken kh velo seat.jpg

The Miyata rear bumper is more leg-friendly than the Kinport, but you can trim the Kinport somewhat. If you wear Cordura riding shorts, that helps a lot with the Kinport, which is much cheaper to obtain than a Miyata.

You should definitely use a rear bumper. WIth a Reeder handle, the front bumper is not desirable.

In addition, recent developments suggest using a couple thicknesses of thick DH inner tube between the seat adapter and your CF base to help spread out the stress areas that exist at the edges of the adapter.

I recently rebuilt mine and have pics, but haven’t posted any yet. Here’s one, though, that shows the rubber insert on the adapter. You should also use one on the Reeder handle - CF interface.

This shows the insert for the Reeder handle.

Thanks for the replies and the advice U-turn. That picture looks like a Wilder rails adapter, the Kinport one has no brake mount. I get the idea conveyed by the pictures though. I already intended to use some inner tube rubber after seeing the broken CF seat, is one layer of rubber not enough for protection? I want it to cushion the edges but not be enough to flex when I pull on it. I will consider getting the leg-friendly Miyata bumper (maybe someone has a spare one), or else I could get that kinport one because at least they make it in black. I just had an idea that I could temporarily strap some innertube rubber to the back of the seat for the meanwhile. I should be finished the rest of the airseat today, and I haven’t even ordered a bumper yet. It will be hard not to split the leather if I don’t have protection.

I had a go yesterday on my Airseat with a long seatpost. It felt amazing to ride up a gutter, and I could feel the unicycle compress at both ends! I was also impressed that my Thomson seatpost defeated my pipe cutter last night. I’ll have to hacksaw it because the pipe-cutter blade kept getting stuck, and would not delve deep enough.

Does anyone know if the dust from drilling/sanding carbon fibre seats is hazardous? I read something on the net about carbon fibre dust being dangerous to breath if the fibres are so many microns across or long, but I wouldn’t have a clue as to how many microns each fibre is. I have been drilling in the Polytech workshop, and I was wearing breathing and eye protection, but Todd behind me reckoned I poisoned him with my fumes. The tutor thought it would only be dangerous if you inhaled it all the time (and wasn’t going to supply me with a dust mask). It’s fun to drill the Carbon fibre seat base, I am glad the holes line up well enough so far after I did it myself.

The extra layer of rubber is heavier, to be sure. I just figured it would round out the stress edges more. There doesn’t appear to be any flex anywhere in the seat or handle.

You could drill a hole on the back edge and install a rubber “foot” about 1" in diameter, sticking straight out the back. Even better would be one on each back corner as well. This temporary fix would not affect the saddle strength and would help immensely with UPD damage. Get the feet at the local hardware store.

For the best protection, though, especially off-road in rocks and the like, the back bumper would be ideal. The back bumper would cover up any holes you have drilled, in the CF or in the leather.

Maybe your buddies at uni.com.nz would have a couple of Miyata seat seconds kicking around that you could buy the back bumper off of.

If you have any concerns at all about fibers simply wear breathing protection. It’s not worth a lifetime of respiratory problems to mess with.

Good luck with the rest of your project, Rowan!