Yay carbon! (not so much..)

[Clean39T]

Well, there’s $100 down the drain.

https://uploads.tapatalk-cdn.com/20171219/c30dbb025091395556bec3e1a23fac73.jpg

Tightened using a Bontrager 5nm 4mm torque wrench until one click. Didn’t hear a crack or any creaking, but noticed this when pulling the post to load it in the car just now.

Either I’m just unlucky (had the same thing happen to an Oval post earlier in the year), or this is the Furies telling me to chuck in all this modern crap for a nice heavy vintage scoot. If it’s the latter, I wish they’d have spoken up a month ago - I’ve got two ultralight carbon wunderbikes in the works w carbon tubs...

[AngryScientist]

that's just some minor indentations in the carbon. i'd have no problem continuing to ride that post, personally.

[Clean39T]

that's just some minor indentations in the carbon. i'd have no problem continuing to ride that post, personally.


But that vertical crack...

It’s in the seattube obviously for now, but is that going to eventually split straight up further and leave me stranded with a broken post?

[Big Dan]

A broken seatpost while riding is not nice.

:eek:

[saab2000]

that's just some minor indentations in the carbon. i'd have no problem continuing to ride that post, personally.

It's cracked. Not riding that post.

[AngryScientist]

But that vertical crack...

It’s in the seattube obviously for now, but is that going to eventually split straight up further and leave me stranded with a broken post?

i highly doubt that is a vertical crack, i think there must be some small, sharp protrusion in your seat tube that caused that scrape as you pulled the post out. similar to the "z" pattern often seen on seatposts from wiggling them out.

unless the pictures are deceiving me, and it really is a crack, but i dont think so...

[Clean39T]

i highly doubt that is a vertical crack, i think there must be some small, sharp protrusion in your seat tube that caused that scrape as you pulled the post out. similar to the "z" pattern often seen on seatposts from wiggling them out.

unless the pictures are deceiving me, and it really is a crack, but i dont think so...


Nope, it’s a crack.

I’ve got no choice but to ride it while on my vacation (assuming I get more riding opportunities), so I’ll just keep an eye on it I guess.

I’m thinking I need to spring for a real torque wrench now. But even then, I’ve heard many aren’t accurate anyway.

[AngryScientist]

surprised to hear that. damn. time for a nice alloy post! and by alloy - i mean titanium alloy.

[72gmc]

A bit of Nitto S-83 will fix that crack.

[Clean39T]

surprised to hear that. damn. time for a nice alloy post! and by alloy - i mean titanium alloy.


Exactly.

[batman1425]

Two different carbon posts cracking in the same way in the same frame? Points to a frame problem to me, along with the indentations you are seeing at the clamp interface. Looks to be clear pressure points and a non-round frame at the clamp. I'd address that possible issue if this is a multiple post in one frame failure mode.

[Clean39T]

A bit of Nitto S-83 will fix that crack.


Or a topical application of Thomson Masterpiece - oh wait, just sold mine...goddammit! This Deda has the perfect setback for this frame for me too. So much frustrating.

[NHAero]

And we're saving like 50 grams over a Thomson post when we go with carbon? Haven't yet seen a cracked Thomson, but maybe others have.

[54ny77]

have no fear, fiber fix is here!

https://images-na.ssl-images-amazon.com/images/I/816XheQ1gdL._SY550_.jpg


:p

p.s. was that a taillight clamp that caused the crunch?

[AngryScientist]

A bit of Nitto S-83 will fix that crack.

i just took delivery of one of these. they are indeed lovely.

https://scontent-ort2-1.cdninstagram.com/t51.2885-15/e35/25006918_1551142668300640_3902453340079915008_n.jp g

[sailorboy]

So was it creaking while you were seated pedaling or any other indication besides you noticed it visually?

yea, i've never had a frame do that to a post, even if you over-tightened slightly. shouldn't happen.

[AngryScientist]

by the way, i agree with the sentiment that you should check that seat tube to make sure nothing abnormal is going on.

[Clean39T]

So was it creaking while you were seated pedaling or any other indication besides you noticed it visually?



yea, i've never had a frame do that to a post, even if you over-tightened slightly. shouldn't happen.


Nope, noticed it only when pulling the post.

Maybe it’s the Thomson clamp - secretly designed to overtighten and crack wimpy carbon posts ;)

The only reason I even tightened this to one click instead of my usual undertighten is because it slipped and I didn’t have carbon paste with me. Still, the spec is 5nm, so if you tighten it to that, why the crack?

[Clean39T]

i just took delivery of one of these. they are indeed lovely.



https://scontent-ort2-1.cdninstagram.com/t51.2885-15/e35/25006918_1551142668300640_3902453340079915008_n.jp g


They are. I had one on a steel rig earlier in the year myself..

[Clean39T]

And we're saving like 50 grams over a Thomson post when we go with carbon? Haven't yet seen a cracked Thomson, but maybe others have.


Not even 50g - a Masterpiece w lighter hardware isn’t much heavier if at all than a carbon post. I got the post to match the stem and to try for some extra flex/dampening.

[djg21]

Or a topical application of Thomson Masterpiece - oh wait, just sold mine...goddammit! This Deda has the perfect setback for this frame for me too. So much frustrating.

Agree. What’s the point of a carbon post? IME, all they do is slip and/or crack. I prefer the Thomson’s, which are light, durable, and with the knurling, never slip in a seat tube.

[Cicli]

Agree. What’s the point of a carbon post? IME, all they do is slip and/or crack. I prefer the Thomson’s, which are light, durable, and with the knurling, never slip in a seat tube.

Thomsons are a bit undersized sometimes. They can slip. I have seen them cracked as well.
I do like Thomson stuff though. Works well, looks good.

[Clean39T]

Two different carbon posts cracking in the same way in the same frame? Points to a frame problem to me, along with the indentations you are seeing at the clamp interface. Looks to be clear pressure points and a non-round frame at the clamp. I'd address that possible issue if this is a multiple post in one frame failure mode.


The first one was a different frame, but same torque wrench.

[batman1425]

According to the thomsons instructions for the clamp, 2.8Nm is the recommended torque, and they even suggest a specific orientation for the clamp when used with a carbon post or frame. Seems you may be drastically over-torquing at 5Nm using this particular clamp.

https://www.bikethomson.com/wp-content/uploads/2015/10/CollarInst.pdf

In general, in my experience the torque ratings on parts are not targets to reach but ceilings not to exceed. I generally use the lowest possible torque that achieves a solid slip free interface. I try to avoid going to the max if possible. Assembly paste helps with this.

[R3awak3n]

you know what the worst seatpost clamp I ever had was?

the thomson one, what a piece of garbage... 2.8nm is not nearly enough to make stuff not slip. I even torqued mine to 5, 6 and still slipped. Its just poor design, just like a lot of thomsons products.

also when manufacturer says X amount of NM, it is the MAX recommended, not what you should torque to exactly

[Imaking20]

Carbon posts CAN be a lot lighter. Carbon paste is also helpful if you're worried about slippage.

I say try a different clamp. I've got a few in different sizes and have 2 Deda posts in 31.6 if you need another. Ive even got matching Deda SL stuff :)

[54ny77]

i've had tremendous luck with a reasonable slathering of carbon paste and campagnolo seat clamps.

not the most elegant, necessarily, but incredibly effective on alu & carbon seat tubes in my experience. nice & wide, distributes clamping force. i've rarely torqued it down to spec, always grips aplenty just a tad back of spec.

[Clean39T]

Carbon posts CAN be a lot lighter. Carbon paste is also helpful if you're worried about slippage.



I say try a different clamp. I've got a few in different sizes and have 2 Deda posts in 31.6 if you need another. Ive even got matching Deda SL stuff :)


Appreciate that. I’ve got a POB 25 setback - it’s a 27.2. Honestly not sure if I’m keeping the bike at this point (unrelated to the post). Someone else may be fine using the post if they have a lower (2+ cm) saddle height - I’d disclose it of course. And I’ve got a Salsa collar that is taller and probably a better clamper.

[AngryScientist]

timely...

https://forums.thepaceline.net/showthread.php?t=215164

https://forums.thepaceline.net/attachment.php?attachmentid=1697951519&stc=1&d=1513718023

[zap]

According to the thomsons instructions for the clamp, 2.8Nm is the recommended torque, and they even suggest a specific orientation for the clamp when used with a carbon post or frame. Seems you may be drastically over-torquing at 5Nm using this particular clamp.

https://www.bikethomson.com/wp-content/uploads/2015/10/CollarInst.pdf

In general, in my experience the torque ratings on parts are not targets to reach but ceilings not to exceed. I generally use the lowest possible torque that achieves a solid slip free interface. I try to avoid going to the max if possible. Assembly paste helps with this.

Agreed. 5nm is way to much for a Thomson clamp.

[NHAero]

FWIW, our mountain bike ride Sunday was halted by a member's Lynskey Ti setback seatpost cracking at the weld.

[Clean39T]

Agreed. 5nm is way to much for a Thomson clamp.


I thought the spec was on the post, not the clamp?

Learn something new everyday I guess..

[zap]

In this case you have to look at the specs for both components.......go lower than the lowest value (in this case the Thomson clamp) and see if it holds.

[R3awak3n]

exactly, spec is always the lowest number. Not only you cracked the post but you could have also cracked the clamp (but its a piece of garbage so you would have actually been luckier if that was the case :) sorry I really dislike that clamp, I returned mine the next day)

[bmeryman]

I like a lot of Thomson's lineup, but I too have returned one of their seatpost collars. My go-to right now is the basic Dimension one. It comes in black and silver, it's light, and there aren't any small parts to lose.

I'll also echo the sentiments of others and say to check the seattube and see if maybe there's an inconsistency that's causing it to clamp unevenly. Sometimes paint can build up on the inside of the lip.

Good luck!

[AngryScientist]

salsa liplock. best clamp i've used.

https://static.shoplightspeed.com/shops/614778/files/006188734/800x1024x2/salsa-salsa-lip-lock-seat-collar-306-black.jpg

[54ny77]

this.

super intuitive, right?

ahhh, not really, esp. if you're not swapping bars out often and dialed into the what's what on how to do that.

and even then, lowest value may still be too high. happened to me on an easton high zoot carbon bar and fancy ritchey carbon stem. sounded like rice crispies at one point, despite being below spec. i said f that, ditched it all for alu stem and bar. now i don't worry about it.

aluminum bars & stems are what's for dinner. ;)

In this case you have to look at the specs for both components.......go lower than the lowest value (in this case the Thomson clamp) and see if it holds.

[sales guy]

I thought the spec was on the post, not the clamp?

Learn something new everyday I guess..

Actually, it's both. Both have their own specs. If the clamp is less, you need to base it on the clamp. If the clamp is more, base it on the post.

5nm is high for the clamp. It's a solid enough clamp that it wouldn't fail. but it's high.

[dem]

I've ridden a cracked carbon seatpost 5000 miles before, crack never propagated - road only, but I'm pretty light on my bike.

That being said, the Thompson clamp is less than ideal for carbon seatposts - ideally you want something taller and something with a pivoting bolt/clamp interface - more "wrapping" and less "pinching"

I like these cheap ones, you can pick 'em up for $20 on eBay or similar.
https://cdn6.bigcommerce.com/s-tqfdy/products/705/images/2461/FWB_Carbon_Seatpost_Collar_Parent_01__60177.144961 7721.1280.1280.jpg?c=2

[Clean39T]

salsa liplock. best clamp i've used.



https://static.shoplightspeed.com/shops/614778/files/006188734/800x1024x2/salsa-salsa-lip-lock-seat-collar-306-black.jpg


Salt in my wound.

That’s the clamp Temeyone gave me with the frame - and I swapped it out for the Thomson because I liked the machined look..

But I can see now that the problem with the Thomson is it’s shortness, leading to the top pinching instead of the whole thing squeezing.

[charliedid]

How much post was exposed?

My *guess* is that it cracked due to flex force. Happened to me a couple times before...

[cadence90]

https://www.totalcycling.com/Images/Models/Full/18962.Jpg
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[R3awak3n]

https://www.totalcycling.com/Images/Models/Full/18962.Jpg
.
.

yes, these are excellent!

[sales guy]

I've ridden a cracked carbon seatpost 5000 miles before, crack never propagated - road only, but I'm pretty light on my bike.

That being said, the Thompson clamp is less than ideal for carbon seatposts - ideally you want something taller and something with a pivoting bolt/clamp interface - more "wrapping" and less "pinching"



Actually, the Thomson was designed around the Masterpiece and some carbon seatposts that were tested. It does wrap. Not as much as the Campagnolo one. And the bolt pivots. Actually, the Thomson one is the only one where the bolt aligns straight. All the other clamps, they are drilled straight when loose. So when it tightens, the bolt actually goes crooked and puts uneven pressure on the frame and post. As well as can damage the clamp or break the bolt. The Thomson clamp has an 4 degree offset. So when it's tightened, that offset goes to 0. Which puts less pressure on the clamp, frame, bolt and post. It was designed really well. I've never had an issue with them.

[R3awak3n]

Actually, the Thomson was designed around the Masterpiece and some carbon seatposts that were tested. It does wrap. Not as much as the Campagnolo one. And the bolt pivots. Actually, the Thomson one is the only one where the bolt aligns straight. All the other clamps, they are drilled straight when loose. So when it tightens, the bolt actually goes crooked and puts uneven pressure on the frame and post. As well as can damage the clamp or break the bolt. The Thomson clamp has an 4 degree offset. So when it's tightened, that offset goes to 0. Which puts less pressure on the clamp, frame, bolt and post. It was designed really well. I've never had an issue with them.

really? its the worst clamp on the market.

1- Expensive
2- Doesn't look great
3- bolt WAY too small
4- slips all day long because not enough torque since the bolt is too small

[Cicli]

really? its the worst clamp on the market.

1- Expensive
2- Doesn't look great
3- bolt WAY too small
4- slips all day long because not enough torque since the bolt is too small

We get it. You dont like them.

They work well in my expierence though.

[R3awak3n]

We get it. You dont like them.

They work well in my expierence though.

haha. I am sorry for being repetitive. I needed a clamp, bought a thomson and took it on a ride with some friends. My post kept slipping, it ruined my ride and ruined my knee. No matter how much I torqued the thing, slippage. After stoping to adjust (after 20 times) I just dealt with it. My knee was killing me after 30 miles.

This was a steel post on a steel frame.

[sales guy]

really? its the worst clamp on the market.

1- Expensive
2- Doesn't look great
3- bolt WAY too small
4- slips all day long because not enough torque since the bolt is too small

haha. I am sorry for being repetitive. I needed a clamp, bought a thomson and took it on a ride with some friends. My post kept slipping, it ruined my ride and ruined my knee. No matter how much I torqued the thing, slippage. After stoping to adjust (after 20 times) I just dealt with it. My knee was killing me after 30 miles.

This was a steel post on a steel frame.

I've never had one slip. And i'm not a small guy. Even on a mountain bike, never had an issue. Never a broken clamp or bolt either. And I like the looks of them. And i've never had a carbon or any other post damaged by one.

Ever think maybe your post was slightly undersized as to why it slipped so much? Pretty common thing.

As Cicli said, to each their own. And for you you don't like them.

[oldpotatoe]

But that vertical crack...

It’s in the seattube obviously for now, but is that going to eventually split straight up further and leave me stranded with a broken post?

Which frame is it going in? One with a collar? Often it's a good idea to turn a collar around 180 degrees with carbon posts, when tightening the 'hole' stays a little rounder..if it has 'ears', no collar, carbon posts on that a bad idea. More than a few early gen Campag carbon posts cracked because of collar orientation or no collar frames..

[zap]

edit

I've never had one slip. And i'm not a small guy. Even on a mountain bike, never had an issue. Never a broken clamp or bolt either. And I like the looks of them. And i've never had a carbon or any other post damaged by one.


I too never had an issue with Thomson clamps. With Carbon posts.

[El Chaba]

The Campy collars are really nice, but I like the Miche collars even better. They are carefully designed to spread the load, so there is no need to rotate the collar 180 deg...

[Climb01742]

There are lots of variables at play: seatpost diameter, seattube diameter, and clamp design and whether it's to spec, along with all the other stuff being to spec. Not surprising it's one area of a frame that has high PIA potential.

[DRietz]

I've never had one slip. And i'm not a small guy. Even on a mountain bike, never had an issue. Never a broken clamp or bolt either. And I like the looks of them. And i've never had a carbon or any other post damaged by one.

Ever think maybe your post was slightly undersized as to why it slipped so much? Pretty common thing.

As Cicli said, to each their own. And for you you don't like them.

I’m with this guy.

And a steel post on a steel frame? Who rides steel seatposts anymore?

[cadence90]

The Campy collars are really nice, but I like the Miche collars even better. They are carefully designed to spread the load, so there is no need to rotate the collar 180 deg...
Really? Is "over-foppish" a word in English? (Not directed towards you at all, but rather towards Miche.)

Because I have never seen a Campagnolo seatpost clamp come with the instructions, "Rotate clamp 180° so that the clamping bolt faces forward, and forward only, otherwise all warranties, etc. will be immediately invalidated, blah blah blah...". We know that Campagnolo certainly would do so. And yet, this same design, with no instructions to rotate 180°, has been around for quite awhile.

Has anyone ever done an actual study on this "rotate the Campagnolo collar 180°" thing? It feels extremely phony, really forced, and veramente troppa sprezzatura to me, much like seeing two different water bottles used in those too-cool-for-school photo shoots, etc. :rolleyes:

The Campagnolo clamp, installed with the two triangle-indicated marks aligned with the seat tube notch, and so locating the bolt asymmetrically off center from that notch but still facing rear-ward, just as intended, has worked perfectly fine for many cyclists for years now, on seatposts of all materials. The alignment marks are very logical, simple, and work perfectly well.

There really is no need to over-complicate things, which the Miche clamp seems to do.

https://www.totalcycling.com/Images/Models/Full/18962.Jpg

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[54ny77]

If the post isn't 100% locked down (no movement whatsoever) with the Campy clamp bolt in the back (i.e., logo facing forward), chances are something's jacked up with either the seat tube or seat post diameter (manufacturing goof).

I've actually had that happen. Tried a combo of sanding down the paint just a tad at the seat tube lip (it may have been uneven application) as well as a new model of the same post. That, plus carbon paste did the trick.

I realize that's a sample size of 1, but I use campy clamps on all but 1 bike because they work so well. Not the prettiest, but very effective. The location of the clamp's offset "slot" is the secret sauce. It has solid material where the seat tube slot is). By the way that design also tends to keep less gunk from building up in the seat tube slot, which is good side benefit if your bike sees a lot of wet roads.



Because I have never seen a Campagnolo seatpost clamp come with the instructions, "Rotate clamp 180° so that the clamping bolt faces forward, and forward only, otherwise all warranties, etc. will be immediately invalidated, blah blah blah...". We know that Campagnolo certainly would do so. And yet, this same design, with no instructions to rotate 180°, has been around for quite awhile.

Has anyone ever done an actual study on this "rotate the Campagnolo collar 180°" thing? It feels extremely phony, really forced, and veramente troppa sprezzatura to me, much like seeing two different water bottles used in those too-cool-for-school photo shoots, etc. :rolleyes:

The Campagnolo clamp, installed with the two triangle-indicated marks aligned with the seat tube notch, and so locating the bolt asymmetrically off center from that notch but still facing rear-ward, just as intended, has worked perfectly fine for many cyclists for years now, on seatposts of all materials. The alignment marks are very logical, simple, and work perfectly well.

https://www.totalcycling.com/Images/Models/Full/18962.Jpg

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[Clean39T]

Everyone just chill. We’re talking clamps here...

The frame is perfect and the tolerances spot-on, but the post is slippery-smooth. Not a great combo with a pinchy clamp.

[sales guy]

The Campy collars are really nice, but I like the Miche collars even better. They are carefully designed to spread the load, so there is no need to rotate the collar 180 deg...

The Miche clamps are nice. BUT the bolts, short and since they don't have an exit point you have to be careful when putting a longer bolt in. We use them on our steel frame with 27.2 posts.

[Clean39T]

After further inspection, it’s gouged, not cracked. So it should still get used by someone at some point...just not me...both my bikes now have integrated seat masts :)