Bicycle Mechanics - 2 Random questions:

Two random questions for you all-
1. When a seatpost is specified as a 250mm post, or 300mm, or what-have-you, is that length the *usable* length? Or total length from bottom of post to top of clamp? (Bearing in mind that XXmm must remain buried in seat tube for strength) If I had one handly, I'd just measure it, but I'm at work and would like to order a new one!

2. WARNING- this next question smacks of OCD... So please, bear with me. ;-) I'm using a clamp adapter to put my braze on FD onto a frame w/o FD bosses. I've never used one of these clamp adapters before. Do folks typically put anything in between the clamp and frame to protect the frame surface? Will the clamp destroy the paint over time? Call it OCD, but if I can protect the beautiful paint job on my frame, I'd like to. :rolleyes:

THANKS!
Bob

1. total length
2. no protection, and yes, you can usually see where the clamp was installed on the DT later. Was your paint air hardened or forced dry? Also, older frames usually have a DT stop to keep the clamp from slipping down the DT. Does yours have one?

edited for lack of reading comprehension :rolleyes:

This is an FD clamp,not DT shifters. There will be no stop on the seat tube.

Thanks!
My bike does not have a stop, and it was painted by the factory (Specialized) so I have no idea how it was dried. Are factory finishes usually baked on? Would I be absurd to want to protect the finish under the clamp?

2. WARNING- this next question smacks of OCD... So please, bear with me. ;-) I'm using a clamp adapter to put my braze on FD onto a frame w/o FD bosses. I've never used one of these clamp adapters before. Do folks typically put anything in between the clamp and frame to protect the frame surface? Will the clamp destroy the paint over time? Call it OCD, but if I can protect the beautiful paint job on my frame, I'd like to. :rolleyes:
I personally put a thin loop of electrical tape between the frame and the derailer, since the clamp can damage the paint slightly. I have a black frame, so it looks great, and works great too.

I personally put a thin loop of electrical tape between the frame and the derailer, since the clamp can damage the paint slightly. I have a black frame, so it looks great, and works great too.


Phew... I'm glad I'm not the only one. Thanks moxfyre! Do you experience any slippage problems with this solution?
Is there a 12 step program for people like us?

Phew... I'm glad I'm not the only one. Thanks moxfyre! Do you experience any slippage problems with this solution?
Is there a 12 step program for people like us?

Nope, I'm happy to report that I've had no slippage in about 2 years of this setup! I'm afraid this disease is incurable ;)

Is there a 12 step program for people like us?

Yeah. Buy 11 more bikes.

Yeah. Buy 11 more bikes.
:beer: The disease is its own cure!

Yeah, I've used electrical tape too. On another frame that the clamp was a little big for, I used a couple of layers of rubber padding to effectively thicken the seat tube. I wouldn't recommend that for indexed shifting, but it worked fine in that case since I was using friction-shifting barends on that build.

Brush Plasti-Dip on the inner surface of the clamp, let it dry and then bolt it on. Dr. Deltron gave me that tip.

Actually the impression the clamp makes in the seat tube paint is an advantage. When you remove the fd for the bike's annual overhaul, the mark lets you know exactly where to replace it. It saves lots of agrivation once you get the fd adjusted right the first time.

Actually the impression the clamp makes in the seat tube paint is an advantage. When you remove the fd for the bike's annual overhaul, the mark lets you know exactly where to replace it. It saves lots of agrivation once you get the fd adjusted right the first time.

Eh... I doubt it.

First of all, the damage to the paint often doesn't occur at the edges of the clamp, but somewhere in the middle, due to slight imperfections in the clamp surface. So the clamp marks are of practically no value in locating the clamp position.

And secondly, the clamp will leave permanent marks on the electrical tape as well. I don't see why those would be any worse/better for positioning.

And thirdly, I don't ever remove my FD unless it's busted. If it's really dirty I might scrub it with a toothbrush and simply green while on the bike. But perhaps that's just me.

First of all, the damage to the paint often doesn't occur at the edges of the clamp, but somewhere in the middle, due to slight imperfections in the clamp surface. So the clamp marks are of practically no value in locating the clamp position.

And secondly, the clamp will leave permanent marks on the electrical tape as well. I don't see why those would be any worse/better for positioning.
Mine seem to leave an exact negative image of the clamp's inner surface in the paint so it's easy to position it exactly the way it came off. The problem with electrical tape is it can shift or peel so it's not as reliable an index.

And thirdly, I don't ever remove my FD unless it's busted. If it's really dirty I might scrub it with a toothbrush and simply green while on the bike. But perhaps that's just me.
I do remove the fd to clean and relube it off the bike. However, for a braze-on fd with an adapter clamp, I usually leave the clamp in place and only remove the derailleur body.

Mine seem to leave an exact negative image of the clamp's inner surface in the paint so it's easy to position it exactly the way it came off. The problem with electrical tape is it can shift or peel so it's not as reliable an index.
Gotcha. The clamp I use is the $4 clamp from Nashbar (http://www.nashbar.com/profile.cfm?category=600083&subcategory=60001038&brand=&sku=2189&storetype=&estoreid=&pagename=Shop%20by%20Subcat%3A%20Component%20Accessories). It works very very well, but the inner surface has obviously not been machined to a high tolerance.

I don't think electrical tape will shift at all while it's been clamped by the derailer, though.

In any case, to each his own!

Well thanks again all for the replies. You've answered my question!