Seatpost Clamp
10-22-18, 06:39 PM
#1
Junior Member
Thread Starter
Join Date: Jun 2017
Location: Pennsylvania
Posts: 16
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Seatpost Clamp
How long should a seatpost clamp last? I over tightened my original clamp and stripped the aluminum threads, so I bought a Thomson clamp to replace it. From the reviews I had read, it seemed to be a good product. It fit fine and tightened up nicely, but then a couple of months ago I noticed a crack in the clamp itself. I purchased it just under five years ago, but over this time I only rode the bike 284 times before I noticed the crack. Unfortunately for me, the warranty was only three years. For the price I paid, I hoped it would have lasted a lot longer. I thought that once it is tightened, it should just sit there pretty much forever. It shouldn't fatigue like a spoke, so why would it crack? What kind of life do other riders get from their seatpost clamps?
10-22-18, 08:16 PM
#2
Senior Member
Join Date: Sep 2015
Location: Massachusetts
Posts: 763
Bikes: S-Works Stumpjumper HT Disc, Fuji Absolute, Kona Jake the Snake, '85 Cannondale SR900
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 219 Post(s)
Liked 217 Times
in
142 Posts
How long should a seatpost clamp last? I over tightened my original clamp and stripped the aluminum threads, so I bought a Thomson clamp to replace it. From the reviews I had read, it seemed to be a good product. It fit fine and tightened up nicely, but then a couple of months ago I noticed a crack in the clamp itself. I purchased it just under five years ago, but over this time I only rode the bike 284 times before I noticed the crack. Unfortunately for me, the warranty was only three years. For the price I paid, I hoped it would have lasted a lot longer. I thought that once it is tightened, it should just sit there pretty much forever. It shouldn't fatigue like a spoke, so why would it crack? What kind of life do other riders get from their seatpost clamps?
Cause that’s all i can think of that would do that, and anyway, I agree with you, I’m surprised a quality clamp would do that.
I’ve never had a post clamp that cost, like, anything at all, and although I’ve had one or two crack on dozens of bikes over the years I just figured they were old and abused so yeah, they eventually fail. But usually I’ve had an issue with the bolt, not the body of the clamp.
10-22-18, 08:20 PM
#3
Non omnino gravis
Send a pic to Thomson, see what they say. I think a seatpost clamp, other than any internal threading for the bolt, should pretty much last forever.
__________________
10-22-18, 09:02 PM
#4
Senior Member
I sheared off a couple of 5mm machine screws when I adjusted the height. I'm using a stainless steel hose clamp right now. However, if I'd had the torque wrench with me to properly tighten the seat post collar clamp, that wouldn't have happened.
10-22-18, 09:02 PM
#5
Generally bewildered
Join Date: Aug 2015
Location: Eastern PA, USA
Posts: 3,037
Bikes: 2014 Trek Domane 6.9, 1999 LeMond Zurich, 1978 Schwinn Superior
Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 1152 Post(s)
Liked 341 Times
in
251 Posts
Yeah, and for 20-30 bucks, I'd think that they'd replace it. Be sure to get back to the forum to let us know how their warranty and customer service was.
10-23-18, 05:24 AM
#6
Advocatus Diaboli
Join Date: Feb 2015
Location: Wherever I am
Posts: 8,635
Bikes: Merlin Cyrene, Nashbar steel CX
Mentioned: 14 Post(s)
Tagged: 1 Thread(s)
Quoted: 4733 Post(s)
Liked 1,532 Times
in
1,003 Posts
People swear by or at Thompson from what I've read. There've seemingly been a good amount of stories about their stems cracking as well.
10-23-18, 06:06 AM
#7
- Soli Deo Gloria -
Join Date: Aug 2015
Location: Northwest Georgia
Posts: 14,779
Bikes: 2018 Rodriguez Custom Fixed Gear, 2017 Niner RLT 9 RDO, 2015 Bianchi Pista, 2002 Fuji Robaix
Mentioned: 235 Post(s)
Tagged: 0 Thread(s)
Quoted: 6844 Post(s)
Liked 736 Times
in
469 Posts
Is it possible that this was over tightened?
Was it torqued or tightened by hand?
-Tim-
Was it torqued or tightened by hand?
-Tim-
10-23-18, 09:28 AM
#8
Banned
Some have wisely added a steel barrel nut, and so it,
1) has steel threading into steel..
& 2) the round nut barrel shape self aligns to the bolt, as the clamp is tightened ..
...
1) has steel threading into steel..
& 2) the round nut barrel shape self aligns to the bolt, as the clamp is tightened ..
...
Last edited by fietsbob; 10-23-18 at 09:33 AM.
10-23-18, 11:10 AM
#10
Senior Member
Join Date: Mar 2011
Posts: 3,094
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1034 Post(s)
Liked 1,290 Times
in
743 Posts
Stop hamfisting it when you tighten the clamp. Use one of these: https://www.amazon.com/CDI-Torque-TL...ue+key+bicycle
10-23-18, 11:27 AM
#11
Senior Member
This design is a pretty safe bet. I've used Salsa clamps of this style for years and had trouble-free function and zero failures.
10-23-18, 01:33 PM
#12
Senior Member
Join Date: Jul 2007
Posts: 1,039
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
It's hard for me to tell in the photo, but is the Thomson clamp all the way down on the seat tube? Tightening it if it wasn't completely in place might have caused it to crack.
10-23-18, 02:13 PM
#13
Banned
may not be seen from above , but as described , they (seller) say:
- Utilizes the Thomson Seatpost bolt, washer, and barrel nut combination that has proven strong over the years
10-23-18, 03:05 PM
#14
Senior Member
Join Date: Jul 2007
Posts: 1,039
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
The Thomson website says the recommended torque for their collar is 2.8 Nm. I wonder if that's lower than most.
Last edited by Pendergast; 10-23-18 at 03:18 PM.
10-23-18, 05:14 PM
#15
Junior Member
Thread Starter
Join Date: Jun 2017
Location: Pennsylvania
Posts: 16
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
The Thomson clamp has a shoulder machined into it so it sits on the top of the seat tube. I purchased and used a torque wrench when I installed this clamp, so it wasn't over-tightened. I probably adjusted the (aluminum) seatpost 3 or 4 times since I originally installed the clamp. I mailed the cracked clamp back to Thomson a few months ago along with a letter telling when I purchased it, and the number of rides it was on. I told them knew it was out of warranty and I suggested that they examine the clamp to find out why it failed. I thought maybe they would have contacted me to explain why it failed, or even replaced it under a good will gesture, but I never heard from them. So much for (good) customer service. I guess I've purchased my last Thomson product.
10-23-18, 05:38 PM
#16
Senior Member
Join Date: Oct 2005
Location: SW Ohio
Posts: 3,682
Bikes: Puch Marco Polo, Saint Tropez, Masi Gran Criterium
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 1163 Post(s)
Liked 442 Times
in
315 Posts
The Thomson clamp has a shoulder machined into it so it sits on the top of the seat tube. I purchased and used a torque wrench when I installed this clamp, so it wasn't over-tightened. I probably adjusted the (aluminum) seatpost 3 or 4 times since I originally installed the clamp. I mailed the cracked clamp back to Thomson a few months ago along with a letter telling when I purchased it, and the number of rides it was on. I told them knew it was out of warranty and I suggested that they examine the clamp to find out why it failed. I thought maybe they would have contacted me to explain why it failed, or even replaced it under a good will gesture, but I never heard from them. So much for (good) customer service. I guess I've purchased my last Thomson product.
10-23-18, 05:53 PM
#17
Junior Member
Thread Starter
Join Date: Jun 2017
Location: Pennsylvania
Posts: 16
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
It's a titanium frame (lynskey) with a FSA SL-280 seatpost. The clamp size is 31.8, and the seatpost measures 27.1mm. There is a collar inside the seat tube with serrations to grip the seatpost. It is a snug fit, and the seatpost never slipped. I also have over 3" of extra seatpost length before I get to the minimum insertion depth so there is no rocking motion.
10-23-18, 06:31 PM
#18
Senior Member
i've never even thought about torque numbers for seatpost clamps. I'd probably be paying more attention to that if carbon was involved. A couple of mine are marked 5 Nm, but most of mine aren't marked. I've never damaged one. I do use a torque key for some things.
The Thomson website says the recommended torque for their collar is 2.8 Nm. I wonder if that's lower than most.
10-24-18, 10:36 AM
#19
Senior Member
Join Date: Oct 2005
Location: SW Ohio
Posts: 3,682
Bikes: Puch Marco Polo, Saint Tropez, Masi Gran Criterium
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 1163 Post(s)
Liked 442 Times
in
315 Posts
It's a titanium frame (lynskey) with a FSA SL-280 seatpost. The clamp size is 31.8, and the seatpost measures 27.1mm. There is a collar inside the seat tube with serrations to grip the seatpost. It is a snug fit, and the seatpost never slipped. I also have over 3" of extra seatpost length before I get to the minimum insertion depth so there is no rocking motion.
i have a sleeved titanium frame with a Ritchey carbon post and I’m having all kinds of issues with creaking and movement. I have a pretty Hope seat collar with a fine thread aluminum bolt & just last night snapped the bolt while attempting to stop the creaking noise. I’ve now broken 2 bolts in a row.
The depth of the collar increases clamping force, I would think. The Thomson one looks a little shallow...
There are 2 bolt ones from China that actually look pretty nice - Fourier brand?
10-24-18, 11:36 AM
#20
Senior Member
Join Date: Sep 2014
Location: Norman, OK
Posts: 837
Bikes: Casati Laser, Colnago Tecnos, Ciöcc Exige, Black Mountain Cycles Road
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 129 Post(s)
Liked 177 Times
in
78 Posts
I've never broken a clamp like that, nor have I heard of any of my friends breaking one. I have stripped out the threads.
Currently using a Miche clamp with no issues (carbon frame, alloy seatpost, installed with torque wrench: 5nm).
Sorry about the giant picture.
Currently using a Miche clamp with no issues (carbon frame, alloy seatpost, installed with torque wrench: 5nm).
Sorry about the giant picture.
