Deontologist

I adjusted the seat post height on my Time ADHX 3 times.

You can see the evidence of each adjustment on my seatpost.

The latest adjustment was done just this morning and I rode for literally only 5 miles. Nothing. And it appears that the seat clamp collar has already started sawing into the seat post.

Before you ask:

1) Yes, I have a torque wrench (I have 2 torque wrenches, actually)

2) Yes, it's been torqued properly, to just 4 Nm (never slipped, no need to go to 5 Nm especially with use of carbon grip paste)

3) I never had this issue with this seatpost on my old bike--a crappy Canyon Grizl 7

I felt the inside of the seat clamp collar with my finger and I noticed there's a noticible "lip" all the way around the circumference of the seat clamp collar. It appears that this lip has been sawing through my seatpost.

The damage appears to be more than cosmetic -- when I first pulled out the seatpost entirely today to further inspect it, I found loose fibers. So the damage has extended past the clear coat and into the fibers.

Wondering if:

1) Is it safe to ride?

2) Should there be a lip inside the seat clamp collar? Would this be the cause of the issue?

3) What else should I do? Any advice? Thanks

Andrew R Stewart 

Without a photo it's not happening post a shot to the gallery or a third party sharing site and let us know.

The seat post clamps that I have dealt with have a lip that is less than the tube wall thickness if I remember correctly. Some don't have any lip at all. For the lip to be "sawing" through the post means that there's relative movement as sawing is a cutting action. Yet there's no report of slippage. Could the post "damage" be other than abrasion?

1- We don't really know but one likely low cost solution might be to swap out the post for a metal one.
2- As mentioned locating (at the top of the seat tube) lips found on binder clamps is pretty common, For the lip to be "high enough" to contact the post is not at all common and if so I might consider replacing with a binder collar without a lip if possible.
3- provide us with photos, take the bike back to where it was bought, use an Al post. Andy

Deontologist

Duragrouch

You mention "fibers" in damage; Is that seatpost carbon fiber? It doesn't look like it, but it could have a black coating to shield the resin against UV light. If the seatpost is aluminum, the scratches shown should be fine, just periodically check there. Aluminum seatposts are generally made with alloys of aluminum that are less "notch-sensitive", so minor scratches are not critical.

Check that the seatpost clamp (I assume separate from bike, what is known as a "turtleneck"), that the inner "rim" on top (prevents it from slipping down) is larger diameter than the seatpost; The rim should overhang the top of the seat tube, but not touch the seatpost. This may not be the case, the clamp rim touching the seatpost, if the collar was not designed for that bike. My bike uses an external clamp collar, but also a "shim/bushing" between the seatpost and the seat tube; If your bike is designed same and that bushing is missing, the clamp may contact the seatpost.

My guess is that the scratches are from a burr on the top inner edge of the seat tube, or in the slot, scratching into the seatpost like that, especially if rotating the seatpost by the seat when raising or lowering, if it's tight. If seat tube is aluminum, steel, or titanium (really, any metal), easy to deburr the edge if needed. Carbon fiber is a lot more tricky, I'm not an expert, chamfering an edge can remove enough resin to expose carbon fibers. Check with carbon frame experts.

Deontologist

Yes, it's a Canyon VCLS carbon seatpost, definitely full carbon all the way through.

FBinNY 

First of all, I concur with Andy doubting the clamp's lip caused those scratches while you were riding.

The scratches look more like they might have been caused twisting the post against a burr, most likely at the slot in the seat tube.

Check by removing the post and working a finger around until it gets cut.

Meanwhile, to answer your question. ----- Yes, the post is still safe to use.

Duragrouch

If that's the case, I don't think the carbon has been damaged; Zooming way in, it appears the carbon was coated with something to shield it against UV light, which can damage the resin that bonds the carbon fibers, and that coating has been scratched off in those areas, but not worse. Or the coating was applied as "armor" for the carbon fiber. If that area is normally covered by the seat tube, no worries. If that area is exposed to sunlight, probably also not a problem, but if any worries, find out what would be safe to recoat the area, and just dip a toothpick in it to carefully dab over the scratches. You don't want any coating there to be thicker than the surrounding factory coating, and unfortunately, you cannot sand it flush after drying. Black nail polish, using a toothpick, might be good, but you need to check that its solvent is not damaging to the carbon fiber resin. You can often find that by looking up the Material Safety Data Sheet (MSDS) or Safety Data Sheet (SDS) for the material; I just looked up the SDS for White Lighting Chain lube, and it said heptane, but didn't list the actual lube. (Car touchup paint has skyrocketed in price, but brand-x cheap nail polish is still low cost, and I use it for bike touchups, mixing colors if necessary. They even have matte black if you look for it.)

Andrew R Stewart 

Does the frame have a metal insert at the post binder/top of seat tube? Is there wear on that lip that coincides with the post 's indents (and that's what they look to me)? Would just filing off the lip eliminate improper contact? Has the seat tube ID been honed? Andy

Deontologist

It looks to be that the seat clamp collar is way too close to the seat post itself. The inner lip on the seat clamp collar does appear to be touching the seat post itself.

There shouldn't be and aren't any burrs inside this frame--it's all carbon, no metal inserts for a seat post, and it's a Time, supposedly one of the best quality frames inside and out. Supposedly made by wrapping braided carbon around a solid wax mandrel... Shouldn't really be any stray fibers or burrs or anything inside the frame, unless something seriously went wrong during production.

I took the bike to my LBS and they said they think it's the lip on the collar, too, and they took to filing the lip down and painting it black again.

I'm surprised as this issue has never occurred on any other bike I've owned, and I've been running carbon seatposts for a long time.

​​​

Kontact 

Is that the original seatpost? Seems a little undersized.

FBinNY 

It would have helped if you included that photo with the original set.

Nobody here is psychic, and can only base our opinions on the info you provide, and/or the photos included.

It's good that filing the lip solved the immediate issue, but I have to wonder if that's the original clamp, or why the lip exceeds the wall thickness of the seat tube.

Take a good look at how the clamp is closed almost entirely on itself. That implies that either the post is undersized as Kontact mentioned or that the seat tube OD, wall thickness, and clamp don't match correctly.

A sub spec wall thickness would account for the lip rubbing and the clamp closing as far as it does. That's not a crisis, and can be addressed, but shouldn't be ignored.

Duragrouch

(above) I agree with everything FBinNY said. The clamp collar looks all wrong. Way too close on the seatpost, and in the clamp slot. If the collar is not wrong, I would suspect a bushing between the seatpost and seat tube (like on all Dahon folders) is missing. Did you buy this bike new, or used?

WAIT: Dumb question: Maybe with that carbon frame, the collar is *supposed* to take the bending load, rather than the top of the carbon seat tube? Maybe the close fit around the seatpost is a safety measure to prevent crushing the seat tube? That appears to perhaps be a more complex "system" then we may know. I'd ask Time about it.

FBinNY 

Sorry, but no, that couldn't be true.

If the collar clamps to the post, it cannot compress the seat tube against the post. So, you'd have the post and collar free to rotate in the frame.

This is precisely why the lip on collars is always such that it cannot ever touch the post.

Duragrouch

You're right of course. Why I didn't see that, I don't know. Sincere thanks for the correction.

That collar looks tailor made for that bike, or the frame designed around it. It just doesn't seem like Time would make an error like that, to where someone has to open up the collar with a file.

EDIT: From Time website: "Seatpost Clamp: Proprietary ADHX Alloy"

cranky old road 

Would like to see a picture of the frame with the collar off. Parts page image 05 looks like there should be a metal insert slotted to the side.

https://shop.timebicycles.com/produc...ice-parts-adhx

Kontact 

I see carbon slotted on the side sticking up, the collar and the bolt. What metal insert?

As I asked earlier, is this post the right diameter? The clamp is behaving like it has to close more than necessary to lock the post.

Deontologist

Yes, the post is just a bog standard Canyon 27.2mm although I wouldn't put it past canyon to sell an incorrectly dimensioned seat post

cranky old road 

I've never had experience with a slotted carbon seat tube, figured it must be metal. Surprised that it is safe to clamp directly on slotted carbon. My inexperience with "modern" technology.

Deontologist

I posted about this issue on the Time owners group and I immediately found 2 other people with identical issues on the same bike (ADHX) ... seatpost collar notching the seatpost itself ...

FBinNY 

So there's a design/construction defect affecting these bikes.

Bear with me while I explain. The lip at the top of the clamp should NEVER come into contact the post. It's purpose is 2-fold
1- cosmetic, to hide the top of the seat tube.
2- convenience, to locate the clamp and prevent it from being pushed lower on the tube.

By design the clamp's lip depth must be less than the wall of the seat tube. This endures that it clamps the tube and NOT the post. Should the clamp touch the post, that would prevent it closing against the seat tube and cinching the post to the frame.

Also, like all clamps, the ears cannot close to touch each other because that would prevent clamping the frame effectively.

Based on the photo, and description, I suspect that the seat tube wall is thinner than spec and the OD is undersized.

While the post itself may also be undersized, that alone would not cause the lip to touch.

Fixing it involves 2 things.

1- confirm that the post measures fully 27.2mm and is a snug running fit in the frame before clamping.
2- build up the tube to spec wall thickness/OD. This could be as simple as one or two turns of cloth surgical tape under the clamp. Or more turns of a thinner tape.

The clamp should fit snugly on the built up tube with the opening being 2-3mm, leaving room to tighten without the ears touching. (note, if you fixed it right, there will be a visible gap between the clamp and post all the way around).

Good luck,
FB

PS. feel free to PM me so we can arrange payment of my consulting fee.

Crankycrank

Did they come up with any solutions? I would contact Time as they may offer some advice or new parts if this is a known problem.

Kontact 

Among 27.2 posts you will see some variation in diameter. It would be interesting to see if a different post leaves more gap at the bolt. More gap is likely to also dig into the post less.

Duragrouch

With the cost of that frame, and sounds like fairly new, I wouldn't try to MacGyver (improvise) a solution, but make sure of your facts and then contact Time. Perhaps coordinate with other users online, and write a common letter together to Time.

Kontact 

All bikes with carbon seat tubes are slotted if they have round seat posts.