CSI seatpost size?

[stephenyi]

According to past Serotta catalogs, the CSI is supposed to accept a 27.2 seatpost. I bought my CSI used and the previous owner had a 26.6 Thomson seatpost installed with a shim (yes, weird size).

Well, I finally purchased a 27.2 Thomson seatpost and to my surprise, it will not fit. I also tried a spare 26.8 seatpost and it still seems a bit loose. Were any CSI's made to fit 27.0 seatposts?

[mandasol]

The CSI I had was spec'd to fit a 27.2, but it was one of the tightest fitting seatposts of any bike I've ever had. It fit but it was really tight. Will your 27.2 seatpost not even go in?

[stephenyi]

The CSI I had was spec'd to fit a 27.2, but it was one of the tightest fitting seatposts of any bike I've ever had. It fit but it was really tight. Will your 27.2 seatpost not even go in?

No, it doesn't fit at all. I wonder if it was originally meant for a 27.2 but in the years spent with the 26.6 seatpost (with shim) have caused the seat tube to tighten up even further. I could try to force it the 27.2 seatpost in but I'm afraid of damaging the frame.

[Ahneida Ride]

Does the back of the seat post cluster have a slot....

You can carefully spread that slot, by inserting a screw driver and
tapping it in slowly and carefully. Use a big screwdriver with a nice
sharp edge.

That will fix the problem.

Uh.... I learned this from a rather knowledgeable entity.

I used it on an old DeRosa, fixed the tight seat post issue in 60 seconds.

[stephenyi]

Does the back of the seat post cluster have a slot....

You can carefully spread that slot, by inserting a screw driver and
tapping it in slowly and carefully. Use a big screwdriver with a nice
sharp edge.

That will fix the problem.

Uh.... I learned this from a rather knowledgeable entity.

I used it on an old DeRosa, fixed the tight seat post issue in 60 seconds.

Yes, there is a slot. Thanks for your tip. I will try it out tonight.

[guyintense]

Chances are the 26.6 post and shim combo was a little undersized and the previous owner over torqued the bolt. I've had good luck lightly taping a hardwood wedge into the seat tube slot until the 27.2 post slid in. Remove the bolt first of course. Sometimes I have had to ream the seat tube, not something I would recommend to the faint of heart.
Here's a good article about that:
http://poehali.net/content/b00007/07_Seat_Tube_milling.pdf

[David Kirk]

I would urge you to spread the slot in a different fashion. Take the bolt out and screw it in from the 'wrong' side. Put a penny in the slot and carefully tighten the bolts against the penny. This will allow you spread the slot in a controlled fashion without risk of damaging the paint or metal with a screwdriver.

Frankly I doubt it will solve your problem but it is possible that the binder got bent in some by using too small a post in the past or just plan cranking the **** out of it for no good reason. If this is the case then it might work.

What year/era is the frame?


dave

[victoryfactory]

Dave;
I know that trick works on quill stems where one side of the clamp is
threaded, but is a CSI seat lug clamp threaded on one side?
If so,
I would add that when you have the slot expanded, insert the post to
the desired height before you undo the penny gizmo.
You may be able to avoid scraping up the post if the clamping is still
a little too tight.

VF

[stephenyi]

What year/era is the frame?


I believe the CSI frame was built around 1996. Serial number is CS 58L 169.

[stephenyi]

Thanks for all the tips, everyone. I will give the penny trick a try tonight.

[David Kirk]

I believe the CSI frame was built around 1996. Serial number is CS 58L 169.

I'm 99.9% sure that your frame would use a 27.2 post if built in that era. I assume you bought it used?

dave

[stephenyi]

That did the trick and it only cost me a penny!

http://i210.photobucket.com/albums/bb198/stephenyi/bikestuff/penny.jpg

[weisan]

I would urge you to spread the slot in a different fashion. Take the bolt out and screw it in from the 'wrong' side. Put a penny in the slot and carefully tighten the bolts against the penny. This will allow you spread the slot in a controlled fashion without risk of damaging the paint or metal with a screwdriver.

nice trick, Dave-pal. One to put in the magic hat. :banana:

[David Kirk]

That did the trick and it only cost me a penny!

http://i210.photobucket.com/albums/bb198/stephenyi/bikestuff/penny.jpg

Money very well spent. Enjoy the ride.


Dave

[guyintense]

As usual, Dave gives the best advice. My system works well for me but I imagine pennys are more plentiful than hardwood wedges.

[dave thompson]

As usual, Dave gives the best advice. My system works well for me but I imagine pennys are more plentiful than hardwood wedges.
You can try www.hardwoodwedge.com they have wedges in all seatpost sizings. :D