Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 05-23-12, 10:35 PM   #1
Hill-Pumper
Senior Member
Thread Starter
 
Hill-Pumper's Avatar
 
Join Date: Jun 2008
Location: In Oregon looking for more hills to ride
Bikes: 2016 Niner RLT Steel, 2015 GT Grade Carbon 105, 2014 NS Bikes Eccentric, 2013 Norco Sight Killer B-1
Posts: 830
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Slipping seatpost fix.

I have a problem with my seatpost slipping down. The bike is carbon with a carbon post. The post looks like there may be an aluminum insert, but I don't want to tighten any harder then I have already for fear of crushing the post. My thoughts are to replace the seatpost with a Thompson Elite, and then upgrading the collar to a Salsa Lip-Lock. I was hoping that might fix the problem, but was hoping for some input here.
Hill-Pumper is offline   Reply With Quote
Old 05-23-12, 10:38 PM   #2
Shimagnolo
Senior Member
 
Shimagnolo's Avatar
 
Join Date: May 2008
Location: Zang's Spur, CO
Bikes:
Posts: 7,501
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 132 Post(s)
http://www.competitivecyclist.com/pr...aste-3321.html

It feels gritty when you smear it between your fingers.
It has fixed slipping seatposts, *and* a slipping headlight mount for me.
Shimagnolo is online now   Reply With Quote
Old 05-23-12, 11:09 PM   #3
catonec 
Senior Member
 
catonec's Avatar
 
Join Date: Apr 2009
Location: burlington VT.
Bikes:
Posts: 2,472
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
you need to buy a torque wrench. since you own a carbon frame you should already have one. this way you can tighten everything correctly/securely without the chance of doing damage.
__________________
2010 Kestrel RT900SL, 800k carbon, chorus/record, speedplay, zonda
1997 Trek ZX6000, 6061w/manitou spyder, xt/xtr, time atac
catonec is offline   Reply With Quote
Old 05-23-12, 11:54 PM   #4
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
did the post come with the bike?
DannoXYZ is offline   Reply With Quote
Old 05-24-12, 07:07 AM   #5
dsbrantjr
Senior Member
 
dsbrantjr's Avatar
 
Join Date: Sep 2010
Location: Roswell, GA
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Posts: 4,584
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 59 Post(s)
+1 on the torque wrench, they are available inexpensively from Harbor Freight, Northern Tool and others. A must on carbon components.
+1 on the carbon assembly paste.
dsbrantjr is online now   Reply With Quote
Old 05-24-12, 08:41 AM   #6
Hill-Pumper
Senior Member
Thread Starter
 
Hill-Pumper's Avatar
 
Join Date: Jun 2008
Location: In Oregon looking for more hills to ride
Bikes: 2016 Niner RLT Steel, 2015 GT Grade Carbon 105, 2014 NS Bikes Eccentric, 2013 Norco Sight Killer B-1
Posts: 830
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
I have a torque wrench,so I have that covered. The post is the one that came with the bike. I was placing an order today, so I will add assembly paste to the rest of what I am getting. Thanks everyone!
Hill-Pumper is offline   Reply With Quote
Old 05-24-12, 09:46 AM   #7
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 29,662
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 218 Post(s)
Carbon assembly paste, or if you have a friend who does auto you can beg a smear of coarse lapping compound.

Either will improve traction preventing slippage at lower clamping force. Lapping compound is basically grit in a grease base. The grit bites into both the post and frame providing a mechanical interlock. It's the same principal as why you use sand to improve traction on an icy road.

Carbon paste varies from brand to brand. Some are very similar to lapping compound, others use softer, non-cutting media with high friction properties.

If you use a grit base product, be sure not to move the post unless you've fully loosened the clamp, otherwise you'll leave scratches in the post. I also suggest you avoid inserting the post beyond the desired depth to avoid marring the visible area.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline   Reply With Quote
Old 05-24-12, 11:01 AM   #8
ultraman6970
Senior Member
 
Join Date: Dec 2005
Bikes:
Posts: 7,860
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
coarse lapping compound??? good to know... thanks!
ultraman6970 is offline   Reply With Quote
Old 05-24-12, 11:22 AM   #9
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 29,662
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 218 Post(s)
Quote:
Originally Posted by ultraman6970 View Post
coarse lapping compound??? good to know... thanks!
I suspect that some of the assembly pastes are simply that repackaged, though they may be slightly different.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline   Reply With Quote
Old 05-24-12, 11:35 AM   #10
ultraman6970
Senior Member
 
Join Date: Dec 2005
Bikes:
Posts: 7,860
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I did not know about this product, found some in the internet and i thought the same thing, the purpose in mechanical industry is different but pretty much is the same product with a different label, as you say maybe just plain repackaged.

Quote:
Originally Posted by FBinNY View Post
I suspect that some of the assembly pastes are simply that repackaged, though they may be slightly different.
ultraman6970 is offline   Reply With Quote
Old 05-24-12, 11:53 AM   #11
GeoKrpan
George Krpan
 
Join Date: Jan 2007
Location: Westlake Village, California
Bikes:
Posts: 1,689
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
How good is the fit of the seatpost? Does it wobble in the frame before you tighten the binder screw?

I have solved this issue by buying a seatpost 0.2mm larger than the original. For example, if the original seatpost is 27.2mm, get a 27.4mm seatpost.

Thomson makes a 27.4mm seatpost.
GeoKrpan is offline   Reply With Quote
Old 05-24-12, 11:59 AM   #12
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 29,662
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 218 Post(s)
Quote:
Originally Posted by GeoKrpan View Post
How good is the fit of the seatpost? Does it wobble in the frame before you tighten the binder screw?

I have solved this issue by buying a seatpost 0.2mm larger than the original. For example, if the original seatpost is 27.2mm, get a 27.4mm seatpost.

Thomson makes a 27.4mm seatpost.
This would only make sense if the frame was oversize. The ID of seat tubes below the slotted area is fixed and should match the published spec with a tolerance of only +.25mm. For example, a frame taking a 27.2 post should have an ID of 27.25mm and no more. The tune below the slot has no capacity to expand and therefore it would be nearly impossible to jam the next size post in there.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline   Reply With Quote
Old 05-24-12, 12:29 PM   #13
GeoKrpan
George Krpan
 
Join Date: Jan 2007
Location: Westlake Village, California
Bikes:
Posts: 1,689
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Quote:
Originally Posted by FBinNY View Post
This would only make sense if the frame was oversize. The ID of seat tubes below the slotted area is fixed and should match the published spec with a tolerance of only +.25mm. For example, a frame taking a 27.2 post should have an ID of 27.25mm and no more. The tune below the slot has no capacity to expand and therefore it would be nearly impossible to jam the next size post in there.
Manufacturing defects can and do happen.

I have never seen a bike with a 27.4 seatpost. I think that Thomson, and others, make a 27.4 seatpost for exactly this reason.
GeoKrpan is offline   Reply With Quote
Old 05-24-12, 12:39 PM   #14
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 29,662
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 218 Post(s)
Quote:
Originally Posted by GeoKrpan View Post
Manufacturing defects can and do happen.

I have never seen a bike with a 27.4 seatpost. I think that Thomson, and others, make a 27.4 seatpost for exactly this reason.
27.4 was a fairly common size many years ago. It's for light gauge steel frames, such as some made by Reynolds. Of course it can also be used in cases where seat tubes are reamed oversized by people who don't know better. OS seat tube defects are very rare because the ID is rarely touched by the builder. The dimension is as provided when the raw tubing comes from the mill, and normally not touched later except to deburr the slot.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline   Reply With Quote
Old 05-24-12, 04:11 PM   #15
GeoKrpan
George Krpan
 
Join Date: Jan 2007
Location: Westlake Village, California
Bikes:
Posts: 1,689
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Quote:
Originally Posted by FBinNY View Post
27.4 was a fairly common size many years ago. It's for light gauge steel frames, such as some made by Reynolds. Of course it can also be used in cases where seat tubes are reamed oversized by people who don't know better. OS seat tube defects are very rare because the ID is rarely touched by the builder. The dimension is as provided when the raw tubing comes from the mill, and normally not touched later except to deburr the slot.
Yet, I have had instances where the nominal size of the seat tube and seatpost are the same and the seatpost wobbles.
Fixed by going 0.2mm bigger on the seatpost.

0.2mm = 0.007 874 015 748 inch

Last edited by GeoKrpan; 05-24-12 at 04:55 PM.
GeoKrpan is offline   Reply With Quote
Old 05-24-12, 05:00 PM   #16
hueyhoolihan
Senior Member
 
Join Date: Dec 2010
Location: Above ground, Walnut Creek, Ca
Bikes: 7⃥ 9 road bikes
Posts: 6,401
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
metal posts in metal seattubes weren't perfect either. it's remarkable that an expoxy coated post (some with plastic decals on them no less) made of carbon in a carbon seattube can withstand the torque necessary to keep it in place at all!
hueyhoolihan is offline   Reply With Quote
Old 05-24-12, 06:31 PM   #17
JTGraphics
Senior Member
 
JTGraphics's Avatar
 
Join Date: Dec 2006
Location: So Cal
Bikes:
Posts: 2,673
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I would never use Valve Lapping compound on my Carbon Fiber parts.
Carbon assembly paste comprises tiny plastic balls suspended in a grease. The compound is designed to increase friction.
Valve lapping compound is an abrasive grid made for cutting metal and finer grit will polish by the same process.
__________________
It may not be fancy but it gets me were I need to go.
http://www.jtgraphics.net/cyclist_bicycles.htm

Last edited by JTGraphics; 05-24-12 at 07:46 PM.
JTGraphics is offline   Reply With Quote
Old 05-24-12, 07:26 PM   #18
jeepseahawk
[IMG]http://i4.photobucke
 
jeepseahawk's Avatar
 
Join Date: Apr 2011
Location: Inland Empire, CA
Bikes:
Posts: 739
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I used carbon paste and it still slipped a little, read somewhere to sand inside of seat tube lightly, that with carbon paste worked well.
jeepseahawk is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 09:16 PM.