....Kinport bumper question....

i just recevied a Kinport handle and bumper,the bumper is alot more flexy than the handle.is it made out of the same plastic?

also,can someone who has the Kinport rear bumper and a old Jap made Miyata bumper see if the holes line up.mine dont.the holes are in closer twords the seatpost on the Miyata,making the holes on the Kinport unable to reach my already drilled holes.

The rear bumper is much thinner which might make it alot more flexible. I have one installed on a new Miyata so I can’t give you a comparison of the hole line up with a Japanese Miyata. Can you just drill it out a bit or file it? Or is it a HUGE mismatch?

Both the handle and bumper are made from UHMW. I don’t have an old seat base but I do have an old bumper … just not handy at the moment. I remember measuring the hole spacing and found a slight difference between the old and new Miyata handles and bumpers but my intention was to oversize the holes in the Kinport bumper so it would fit regardless.

I haven’t tried installing the handles or bumpers on a CF seat base. Is is possible that the large radius between the base and flange that’s around the edge is affecting the way it fits?

UHMW doesn’t sand or file well but it’s easy to trim with a sharp knife. Unfortunately, some trimology (technical term) might have to be applied to make it fit.

Steve Howard

the differance isnt that the holes are closer together or farther apart side to side (like the old & new handles.)

the problem im having with the bumpers is that the holes are in farther,so far that elongating the hole in the K-bumper isnt possible because there isnt enough material.i would have to drill 2 more holes 1cm behind the holes i have to make it fit.

see the eyes in this seat looking thing ive created?[:-> pretend those are the holes and the [ is the bumper.the holes on the older Miyata bumpers are in farther (to the right twords the - )

yes i need a camera

I can’t belive i actually understood that :slight_smile: :astonished:

I have no idea what your talking about, that just looks like a new kinda smiley to me [:-> something on the lines of a guy with a bad flat top and a pointey tongue…

This is just another reason to stay away from Miyata seats.

oh come on C-nuts ,unispin got it…

the flat top [ is the bumper,the >smile is the handle,the - is the seat bracket and the : eyes are the holes.

i say stay away from Miyata seats too,but i bought mine over a year ago when they were good quality. only now when im trying to mantain it with newer after market products am i finding all the tiny little changes that happened to them in China.(all the after maket items are modeled from the new M-seats) I got the Barnes seat reinforcer plate to work but the holes were a little off there aswell.basicly all the holes in the newer M-seats are slightly off from the old ones and when you go and try putting anything but OEM stuff on them all the little tolerances add up.

This happened to a friend of mine. He had his CF base drilled out for the old miyata hadle, but then it broke. He got the kinport, so on the next ride, he was there with the piece. I had a 10 mm wrench and he had a pair of vise grips. Between the two of us, we managed to bend the U - bolt just enough to squeeze it through the handle, and then bolt it on.

I d’ont think i would ever use this technique under those conditions, because it damaged the threads, but with the right tools, it’s a good option.

Otherwise, i d’ont think (aside from cutting the handle) there is any other way. If i were you, i’d put it in a vise, and gently bend the U-bolt by very small increments untill you can get it to fit in.
Oh, and i understood your diagram. VEry excellent indeed!!

Just my experience,


im talking about the rear bumper though :thinking: the handle goes on fairly easy.

hopefully Harper can still produce the pic’s of the old and new bumpers side by side like he hinted at in a PM.

i couldnt just bent the bolts to fix my prob,its a full cm off target.the bolt would be almost sideways then.

If you have a carbon fiber base, drilling additional holes for the new bumper is not a problem. I’ve got lots of extra holes drilled in some of my CF seat bases. The CF base is strong enough that it isn’t going to weaken the strength of the seat.

I’ve done some checking between old and new bumpers and there is a difference between them - as Jagur already knows. I’ve added a couple pictures in this gallery that shows the situation very well:


When I first came up with the bumpers I tried them on both old and new seat bases and they fit either one. I didn’t, however, try a bumper on a CF seat base drilled for the old bumper. The dimensions for both the Kinport handle and bumper came from the new Chinese parts. This is regrettable. My only suggestion at this point is to re-drill the CF base. I’m very sorry about this.

Steve Howard

Yahoo! I’m off the hook! Thanks, Steve.

aah,so im not crazy after all.i have alot of extra holes in my CF plate too John,looks like i’ll have 2 more soon.maybe i’ll just make some long slots :wink:

i think it would be cool if after market items like handles and bumpers came with the same "U-cut, U-drill style as the CF plate does.just a thought.

could i see a shot of this picture http://www.unicyclist.com/gallery/CNC-handle/aao with the bumpers flipped over,i think the pocket that cups the seat base may be narrower on the new China ones also.

ive been doing alot of urban seat drags down stairs and stuff,otherwise i would never wear out a bumper.

drilling a couple of new holes is better than not having an after market rear bumper at all.no apology needed.

Sure. Here is the original


Here it is flipped over



ho ho,thats very funny Harper,not.

i mean flip the bumpers over so i can see the other side,not just the reverse. :roll_eyes: you crazy!

I don’t think this has been established.