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C-40 seatpost size...(14 posts)

C-40 seatpost size...rib-eye
Sep 9, 2001 6:13 AM
I can't find this spec anywhere. If it was on the stock post, it's worn off at this point. The only reference I've seen was a 27.2 and I KNOW this isn't correct. This is a '01 60cm C40 B-stay.

Thanks.
28.0mm....C-40
Sep 9, 2001 6:29 AM
It's an oddball size, probably intended to keep people using the Colnago post supplied with the frame. A .015 inch shim wrapped around a 27.2mm post would make this common size useable on a C-40.

I asume that you're looking for a straight-up design, in an effort to experiment with a more forward KOP.

Be sure that the saddle that you are using is not part of the problem. Different brands position the rails differently. I'm using the Colnago Hoskar on my C-40. I have plenty of forward travel available, but my C-40 is also a 55cm, which has a 74 degree seat tube angle.

I wouldn't worry too much about your KOP being 1cm behind the pedal spindle, unless you feel that you're pedaling at a slow cadence and applying too much torque.
re: post sizerib-eye
Sep 9, 2001 6:54 AM
Thanks for the post size. Every bike I've got (5) use different sized posts! I'm using a Koobi saddle, so I'll check the rail position. I'm concerned about the KOPS issue only because of possible knee strain by an exaggerated out of position setup. But, it doesn't sound as if I'm outside the range of an acceptable set up. I did a 40 miler a couple of days ago and afterwards did feel a few twinges in my knees. BUT, I also had been off my bike for 2 months recovering from a broken clavicle (mtn biking), so it may have just been a little reclamation...

Thanks again. All this info has been very helpful.
other bike set-up....C-40
Sep 9, 2001 7:51 AM
Since you have several other bikes, you could compare the KOP on your Colnago to one the others (which I would assume suit you).

I'm not familiar with the Koobi saddle, but it sounds like a mountain bike model. I know the SDG line of saddles, which are geared toward the mountain bike crowd, have the rails positioned for lots of rearward movement. I've got one SDG that I like, but can't use it on some frames, because it won't go far enough forward.
question for youCT1
Sep 9, 2001 7:54 AM
I just got a C40 frame and the 28.0 mm post is REALLLLLY tight. What's up with that?? I'm not sure I want to shove the darned thing 'in' for fear that it will jam.

Any suggestions?
Thanks JohnG
question for yourib-eye
Sep 9, 2001 8:22 AM
Yes, the post to tube tolerance is minute. I does seem like a little variance here would cause one frame/post to be manageable while another not. I've moved mine around quite a bit while sizing and at times it does initally feel like it's "stuck". I just use an exaggerated side to side wiggle while moving it up/down. I've heard that using lube on CF to CF is not recommended. The first few cm of the post appear to be shaved/sanded; I assume to assist with insertion. PERHAPS a little more sanding with fine grit would help with the initial insert.

However, as this frame is totally new to me as well, take all of this for what it's worth. Perhaps more experienced CF riders can assist as well.
mine was tight too.....C-40
Sep 9, 2001 3:05 PM
I also found the post to be a lot longer than necessary, so I cut at least an inch off the length, which helped. Roll up a sheet of 120 grit sandpaper to about the size of the inside of the seat tube, and run it up and down a few times, there may be some burrs or stray epoxy resin holding it up.
mine was tight too.....CT1
Sep 10, 2001 7:25 PM
Thanks.... it looks like I should sand down the post slightly.

ride hard
JohnG
where can I find a shim?rib-eye
Sep 9, 2001 10:27 AM
It well could be the saddle, but I'd hate to have to change it. It took me years to find one that fits as well as this Koobi. Is there a source for manufactured shims?
maybe local auto supply...C-40
Sep 9, 2001 2:59 PM
or try mcmaster.com, a large industrial supply house. Brass, aluminum and stainless steel are common shim materials. Stainless steel would be ideal. Some bike catalogs may list seatpost bushings, but these are usually a lot thicker, to make up large differences in diameter.

mcmaster.com also has a lot stainless steel socket head cap screws that are great for stems, water bottle brackets and seat post clamps.
where can I find a shim?Ken
Sep 9, 2001 5:04 PM
I think you'll find shims on the following link.
http://cambriabike.com/seatposts/seatpost.htm
Ken
where can I find a shim?peloton
Sep 9, 2001 5:08 PM
Try Tamer bicycle components. They make some nice aluminum shims in a wide variety of sizes. I think they have a website, or you could talk to your shop.
Thanks for the feedback....nmrib-eye
Sep 9, 2001 6:14 PM
measuring diametersSamDC
Sep 10, 2001 11:54 AM
As a suggestions to everyone, I think owning a pair of calipers would be ideal for almost all bicyclists. They're relatively cheap (read: not as expensive as one would think). I would recommend buying machine shop quality rather than scientific rated calipers (scientific ones are much more accurate and precise and much more $$$). Also, if you can, get a digital one that converts between metric and English (mechanic ones cannot switch between systems the last time I checked); it's more convenient than having to wip out the calculater everytime you have to do a conversion and it's easier to read.