pennpaul

The stock seatpost clamp on my Fuji Team Road bike is weak. For as long as I've owned this bike, the stock (can't remember anymore) Ritchey seatpost has always slipped. The post will twist side to side, and/or slide down.

I even got as desperate as wrapping the post in one layer of adhesive aluminum tape used for ductwork. Even with that extra layer between the post and the clamp/seat tube, the post still slips.

I want to add this bike back into my stable, but not with this clamp. Are there aftermarket clamps that will fit this bike and actually work? I'm not sure what type of specs I should be looking for, and no, I'm not a weight weeny so the clamp can be robust.

Thanks,
Paul

dedhed

Sounds like you have the wrong size seatpost

Sy Reene

A clamp either clamps, or it doesn't clamp because the bolt threads are stripped. What would make a clamp "weak"?

pennpaul

Found the bike specs on BikePedia. This seat post is the original, has the right size stamped on it, and measures around 27.17mm for most of its length using my calipers just like a different "27.2mm" seatpost I have on my gravel bike.

Not stripped, but the clamp is smaller than the clamp on my other bike that doesn't let that seatpost slip and slide. Now that I know the size I'm going to do some more googling.

CargoDane

I may be stating the obvious: But if one of your other clamps fits on this (test it), buy one of those or one with the same measurements.
A seatpost clamp that made the seatpost slip on any of my bikes would last 15 minutes before I tossed it in the bin and found something else. We know the tech works, so it has to be a matter of sizing and/or lack of strength. It doesn't look like it's some weak ultralight CF clamp with a titanium bolt, so it has to be the sizing.

dedhed

Carbon post? using carbon paste?

CargoDane

Too big would make it not clamp properly, unless it flexed enough when tigthened down.

Edit:
Come to think of it, maybe the seatpost is too small a diameter for the bike. That would certainly do it.

Trakhak

The "DO NOT OVERTIGHTEN" warning on the clamp could be a blanket message regarding potential over-torqueing by ham-handed mechanics or could mean "by the time we discovered that the bolt/nut threads tend to strip in this particular clamp design, we'd manufactured too many to throw them all away, so we added a warning label that suggests it's your fault if it strips."

dsbrantjr

Put the post in, tighten the clamp to the specified torque, and take a photo of the rear of the seat tube, showing the clamp and the slot in the seat tube. You ARE torqueing it to the specified amount, right?

Koyote

And if using the appropriate torque doesn't do it, use some carbon paste.

mpetry912 

I am going to dunk my entire bike into a huge vat of Carbon Paste. I read on the internet that it's good.

the comment above about the gap in the clamp is good. If the tube gap is mashed together, you will never get enough bite on it.

it's also possible that the tube is not round. A good clear picture would be helpful, with the post inserted and tightened.

A shim is a possibility. you might also try using a center punch below your insertion line to create some interference. Make some "dimples" about 1/2 inch below the insertion line.

I have a wonderful Stein Knurling tool that is perfect for solving problems like this. But first it's helpful to understand what the problem is.

Mark Petry
Bainbridge Island, WA

grizzly59

How can you have the proper size seatpost if you can wrap it with duct tape and it still fits in the seat tube? Maybe your seat tube is bigger than the specs say it is, Tegrity Farms was supplying the frame shop.

CargoDane

I somehow missed that part of his post!

Quote:

I even got as desperate as wrapping the post in one layer of adhesive aluminum tape used for ductwork. Even with that extra layer between the post and the clamp/seat tube, the post still slips.

Yes, that is certainly proof-positive that the seatpost is too small for the seat tube.

Bigbus

When the clamp is tightened properly, check the gap in the seat tube. I've seen instances where the gap is closed and the seat post is still loose. If that's the case, find a larger seat post or create more gap. Good luck

pennpaul

Let me track down some solvent to clean up the seatpost and the seat tube and then I'll torque it up and take a picture.

The seatpost is correct (27.2mm) according to the specs for this bike. If the seat tube is too big, then what can I do? The next commercially available seatpost is 28.6mm. I can't imagine that one layer of adhesive foil added 1.4mm in diameter.

CargoDane

Well, open the seat clamp (and remove it) and see how close the seat tube actually is. 28.6mm is a mere 1.4mm bigger in diameter, which means your seatpost only has to be 0.7 mm more all around.
That would probably explain why it continued to slip, and why you could fit a piece of tape around it.

Now, even if it worked at the clamp height to "pad it", the end of the seatpost will wobble a little, slightly grinding at your seat tube continuously.

Try a 28.6mm seatpost. It is probably the correct size - or maybe even a bigger one is needed, depending on how much "slop" there is now.

Edit: just in case you think it's "too much because a foil wrap dealt with it": Any seatpost clamp will be able to pinch your seat tube more than the diameter of the (correctly sized) seatpost. If I tigthen my seatpost clamps without a seatpost in it, I am pretty sure I will have the top of the seattube collapse or at least be misformed.

It is certainly your seatpost being too small.

CargoDane

Keep in mind that if you force your seat tube into submission now, you might permanently deform the tube, so when you try a bigger one that should fit, it may not due to the seattube not being round enough anymore (can be fixed, though).

dedhed

Where are you getting that information? Seatpost generally go by every .2mm.

https://bike.bikegremlin.com/3114/se...zes-standards/

grizzly59

You may crack the seat tube if you repeatedly tighten the clamp down on a seatpost that is too small. Maybe look around for something called a seat post shim. Amazon has a bunch. None of my bikes have ever had this problem, I have nil experience with this. Best of luck.

bikemike73 

I would buy micro calipers. About 15.00 , and measure the seat tube. And the measure the seat post again.

See how much difference there is.

You might find out you need a new, larger, seat post.

djb

One of my bikes seatpost collar has been like this a few times, but probably because it wasn't seated down properly and improperly tightened (ive over tightened abd snapped collar bolts before)

seat post collars can be had for less than 10 bucks new, so why not just replace it.

kinda odd that you can fit aluminum tape around post though

Fairly certain that all my bikes have seatposts that fit in with no clearance for tape.

bought bike used?

Iride01 

Are you the original owner of the bike? No telling what a previous owner may have done. Some get excited to use a reamer after reading articles about reaming seat tubes. Especially if power tool involved.

If a bigger seat post fits without having to pound it in, then use that.

mack_turtle

I had a seatpost that would slip constantly. I tried different clamps and that gritty "carbon assembly paste." in the end, the seatpost was worn in the middle and slightly smaller than 27.2mm. replacing the seatpost with something that fit more tightly in the frame solved the problem instantly.

furthermore, a friend of mine purchased a mass-producted titanium seatpost from a popular brand and has a similar problem. He made the company replace the post twice after measuring each new post using at least two different digital calipers. each post was just small enough from the labeled 27.2mm that it could not be clamped tight enough to stay put. he later got a refund and bought a ti seatpost from Eriksen and never looked back.

IME, problems like these are usually because the seatpost is undersized by just enough that they slip, so the solution is to replace the seatpost.

ClydeClydeson

Actually, there are features of the clamp that can affect its function - the main ones are the bottom of the bore on which the head of the bolt sits, and the condition of the threads on the bolt or the barrel shaped 'nut'. If the surface of the clamp is not flat against the underside of the head of the bolt, the torque from your allen key will not be properly turned into the linear clamping force you need. Same for damaged or otherwise less-than-perfect threads on the bolt or nut. You lose loads of torque in damaged threads and so you get insufficient clamping force. THe other fun feature of poor threads is that the excessive force you put into it will eventually cause the bolt to snap.

THe easiest solution is to order a new clamp. The size you need is normally stamped into the inside of the clamp - it will be some number like 34.9. A new clamp will have a new fresh flat bored surface under the bolt, and perfect new bolt and nut.

79pmooney

+1 and my first thought. There should be room for (say) a sheet of thin cardboard between the inside faces of the clamp at the bolt when tight. If not, file or sand or put in a vise and saw with two blades on a hacksaw those insides and try again. Or get another clamp. (I learned about the 2-blade trick from a framebuilder. This happens on steel frames as well.)

Edit: Another approach that has been done. Clamp as you have been doing but add another smaller clamp to the seapost itself and it slid down to contact seatpost or clamp top.

Second edit: You have calipers. Try measuring the seattube inside. (Take a bunch of measurements, Inside diameters are tough to get accurately and tubes may well not be round after welding.) The mickey mouse fix if the tube is too large for the seatpost, sheet aluminum shims. I used DIet Coke can shims on my namesake for around 15 years running an MTB seatpost n my 27.2 seattube.