Seatpost Issue

[saab2000]

My seatpost slips.

On my lugged steel Croll I currently have installed an old el cheapo Specialized labeled aluminum seatpost. It has lots of setback and this is why it is installed.

The problem is that it may be ever so slightly less than 27.2 mm. I checked on my calipers and it seems to be a weak 27.2, though it is hard for me to tell.

The seatpost slips about .5 to 1.0 mm per ride. Another issue, and perhaps resulting from the possible slightly small seatpost, is that the clamp comes together when tightening the post. This should not be the case and as a result, the bolt bends a bit and I have broken a couple without having used excessive force.

My question is the following: what can I do about this? I am prepared to get a Campy Ti seatpost for this bike. Is it likely to be the size advertised? Will it seize in the frame?

The bike is built of 531 and has a fairly standard seatpost binder bolt built on.

This question is aimed largerly at the people here who know lugged bikes, namely the e-Richies of the world or the Kirk Pacentis of the world or the David Kirks of the world.

What can I do here to prevent the post from slipping and is there anything to do about the fact that the binder bolt bends a bit and breaks? Is a newer post, Campagnolo, Thomson, or Salsa, likely to help the problem? I have heard that some seatposts are ever so slightly smaller than advertised and that this can cause problems.

Any tips?

[soulspinner]

I have a Campy ti post you can have if you want it, a little scratched up(they seem easy to scratch) but only used one season, just pay the postage. I have gone to Thomson as I need less setback. All I have to do is find it. Its in one of those bike boxes somewhere....

[saab2000]

Send me a private message....... sounds like we might have a deal.

Still, I would love to hear if this will be a solution. Has anyone else ever had this problem?

[Frank]

Send me a private message....... sounds like we might have a deal.

Still, I would love to hear if this will be a solution. Has anyone else ever had this problem?

to add just a bit of size to it. Not sure how much that actually adds or how much of a difference it would make for you.

[Too Tall]

I agree with Frank.

[Michael Katz]

Are you greasing the seat post? Major contributor to slippage. Contrary to conventional "wisdom", there is no need to grease a seat post. Just remove it once a month as part of routine maintenance or after riding in the rain, wipe it down, wipe out the seat tube, put it back in dry and you should be fine. Also, when you wash your bike don't spray the hose at the seat post collar. No less a luminary than Tom Kellogg shared this "uncoventional wisdom" with me on a visit to his shop. I've followed it for the last 2 years with steel and Ti frames without any issues of galling, corrosion, rust etc. It is also very easy to overtighten the clamp. I use a torque wrench and keep the torque between 40 - 50 inch ponds depending on the post/frame combination. No slippage at all even with my 190 pond carcass pounding over rough roads.

[Todd Owen]

I had the same issue a couple years ago and the problem was an undersized seat post . once I got a nother post the problem stopped. if you tighten the frame too much with the smaller post you can end up snapping the bolt. get a new post!

[saab2000]

I am halfway tempted to get a Thomson Masterpiece Setback and try a saddle with longer rails to achieve the same setback. The Thomson is grooved and probably less likely to slip.

[cpg]

If none of the aforementioned solutions pan out, you may want to consider having the seat tube slot widened. You're getting close to bottoming out and in the picture it looks as if the binder ears aren't in line with each other due to the undersized post. Sometimes this causes the seat lug binder area to stretch out of shape. Good luck. This can easily be fixed.

Curt

[Dave]

Your picture shows that the clamp has been stretched from repeated overtightening. As long as the ears don't touch, at least the clamp is applying some force, but the crooked surfaces contacting the clamp bolt are causing bolt failure. You might try spreading the ears apart a bit and see if you can get a coke can shim (or stainless steel) at least half way around the post, as it's inserted into the frame. This might be enough to keep it in place.

If there's more than the .004 inch coke can shim clearance, you may have to invest in some real shim stock in the .006-.008 inch range. Try www.mcmaster.com.

[David Kirk]

It looks like they clamp of the frame is stretched pretty good but it's hard to say for sure in the photo. When you loosen the clamp does the post flop around at all in the frame? It should slide in and out smoothly without any real play in the fit.

A 27.2mm post is a nominal size. Meaning that it is meant to fit into a 27.2 hole not that the post itself should measure 27.2. Most 27.2 posts measure somewhere about 27.15 - 27.16.

Dave

[Ken Robb]

I have a bike that I bought on eBay. When I got it I could not insert the seat post it came with. I thought it must be a 27mm tube so I bought a 27mm post. It went in but would slip as you described and I too broke a bolt. Hmmmmmmmm; I tried another 27.2 post and it went in bur VERY tight. I miked them all and found the kind of variation that D. Kirk mentioned. I finally decided that the shop that shipped the frame tightened the collar on the shipping plug which was smaller than the post that came with the bike. This compressed the space between the ears on the collar and prevented the post from going in. Some delicate twist-prying with a flat screwdriver and now all the 27.2 posts work fine. Anyone want a very slightly used 27mm post?

[Too Tall]

Saab-bro I'm pasting my big old pile of seatpost setback numbers just incase you decide to exercise your credit card.

Seatpost Setbacks:
The Dura Ace post has 20mm
Moots Ti has 19
Moots layback seatpost (Ti): 19mm setback in 27.2 and 16mm on 28.6
Campagnolo posts have 25
Thomson's have 16
Syncros Derived 0-29mm
Race Face Evolve 25
Ritchey's 20mm
Salsa Shaft 23mm
Easton 23mm
FSA SL-220 has a whopping 35mm

[saab2000]

TooTallissimmo,

You are awesome! I am on the verge of getting a Thomson Setback post. But I like the Campy Ti better and it has more setback. Is the 16 you quote for the Thomson Setback?

[chrisroph]

Saabisimo--You know that the current crop of Campy posts have notches for the angle adjustment so if the tip of the saddle is not at the proper height while the post settles in one of the notches you are sol? The first post I had in my majestic was a campy ti. I couldn't get the angle right so I dumped the post fast. Its wearing an AC. How is your Eddy?

[saab2000]

Christoph,

I have not ridden the Eddy since I was in Minneapolis a couple weeks ago. Bummer.

Anyway, I realise that there is some risk with the notched Campy, but I once had a Record carbon in this bike and it was alright, so I know it will work if I get the Ti version with a Flite saddle. Putting the carbon in the bike was probably not a good idea, but it did not break the post. I might have to try to shim the existing one 'til I can get something else.

[chrisroph]

I'd go for the setback thomson if it has enough setback for you. Those things are slick, strong and easy to adjust.

[saab2000]

I think I may have the problem solved.

I took the bolt all the way out and sure enough, there was a fair amount of slop. Then I took out the post and took a large screwdriver and wedged it into the clamp and forced the two sides apart far enough to be parallel. Now there was a LOT of slop when I put the post back in.

I cut three little strips from an aluminum can and slid them into the crack and now there is a lot less slop and when the bolt is tightened the two sides don't touch.... cool. I will still try for a better post. This one is a real cheapy, but has the setback.

The reason I never tried the aluminum can shim is that I never expected that there would be that much play between the post and the frame. I probably could get another little shim in there.

I will try to ride tonight to see if this is the solution, but if it is it will have sure been cheaper than a new seatpost.

I would love that Thomson...... just not enough setback for this frame and this saddle.

[Ken Robb]

if it's still that loose perhaps a 27.4 post is the answer?