Hey guys. I got some minor problemos. I just got a Carbon Fiber KH seatbase and a GB4 Universal Seatpost. I want to mount the Seatpost and my existing reeder handle.
There is a bump on the seatbase where the seatpost is to be mounted. The flat part of the seat post doesnt have the same curve as the ‘mounting bump’ on the seat base, so it doesnt sit quite flat on the seatbase. Heres a little drawing i made. Please dont insult my Paint skills. haha
So should i play around with some washers to make a flat platform and distribute the load? Should i grind the washers to make them slanted so they sit flat on the curved base? Should i use a piece of innertube in between?
Up front on the seatbase, where handles are mounted, theres a small ridge. Although my reeder handle has enough points of contact to stay flat, this leaves a little valley underneath. Should i do anything to fill in the open space? Heres some lil pics of the ridge:
Do you all use carriage bolts or do it GB4 style? I used carriage bolts in my last CF seat and didnt have any problems although filing the squares holes took a while. A friend showed me today that you can just drill a hole big enough for just the threads, then tighten the nut and let the square part of the bolt bite a square into the CF. Do you think this is a bad idea?
I did this on my cf base. It’s been fine for the last few months.
I think the reeder is fine with the space under it, although I’d place an innertube or other rubber washer-like material between the handle and the base, just to protect the cf.
no big deal at all. what i did was drill a hole the size of the threads then i took a file which has a little square pokey handle thing on the top, you know? well just stick that in the round hole and tap it in a little till the hole becomes square (dont pound it in there, just tap it till the hole starts to square), then stick the carrige bolt in and tap it in with a wood mallet till its snug.
all that advice about using tiny little diamond files to square the hole is tedious and unnecessary.
yes to rubber under the post and the reeder, an old tire tube works good. just get a puntured one and cut it to fit,slightly over laping the medal.
I agree with Jagur that you should make a square “guide” for the carriage bolts. I’m not too sure if you let it bite into the base that it would be healthy. Why risk weakening your base?
When Zack was putting his bolts through his seat, he drill holes big enough for the theads, and hammered the bolt heads in. Later on, some of the bolts came kind of loose and the carbon fibre directly around them broke up a tad. I’m not sure exactly what happened, but I remember thinking “hmmf, I’m glad I filed my holes into squares and took my time when made my seat.”
he must have made the square to big in the beginning then. the key is to make the square by what ever means a little smaller than the 4 sided carrige so it goes in tight.
So did the usage of inner tube let the reeder and seatpost fit snugly to the seatbase? I am considering embarking on a similar project, and more pictures would be nice… Has it been completed yet?
I ended up filing the squares roughly the size of the carriage bolts. The square part of the bolt would start to go in but not all the way. Then I put a nut on each bolt (with a washer of course) and cranked down on it until the bolt was forced into the square and nicely seated.
I fiddled around with a bunch of washer combinations and also put a piece of innertube under the seatpost for good measure.
I got a little washer action going on on the reeder handle too.
I rounded the edges of the seatbase with a big file cause they were a little sharp. Then i glued tubing to the edges and duct taped the tubing also.
Everything went really well:
Those pictures were before i put the duct tape on one side of the tubing and over the heads of the carriage bolts on top of the seatbase.
I put a gemcrest seat cover over the whole thing. It is a pretty tight fit but i dont think i have it situated quite right. I was just so happy to have the seat together that i wanted to ride it and not mess around with positioning of the airpillow thing.
Ive taken it for two real hard rides since i made it. I really like the narrow-ness of it where its between your legs. My old miyata style CF airseat was wider and would rub my thighs. I wore through alot of shorts and bike shorts as a result.
Seat out is nice of course because of the sick tubing job.
It is certainly easier to make an airseat with a Miyata style CF seatbase. But to me its worth the extra work for the narrower KH.
Thanks for all your help, guys. And, Jerry, thanks for your help and good company.
