Better Carbon Fork Plugs?
#1
Full Member
Thread Starter
Join Date: Mar 2018
Location: Los Angeles
Posts: 463
Bikes: 02 Litespeed Ultimate, 84 & 85 Raleigh Grand Prix, '84 Raleigh Prestige, 85 Raleigh 555 RSL, '20 Raleigh Tamland, 38 Raleigh, 85 Landshark "Raleigh", '84 Marinoni Levi's Raleigh, SB4484, SB7979, Raleigh SSCXWC, 87 Raleigh USA 531 Prototype
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 202 Post(s)
Liked 147 Times
in
79 Posts
Better Carbon Fork Plugs?
I have now tightened a guy's FSA Carbon Fork Plug for him multiple times, and it lasts about a week before I have to do it again due to the tension bolt backing off. This is the only time I have seen this type of repetitive situation. Is this something that these things are known for? Is there a preferred plug that holds better? Thanks.
#2
Senior Member
Join Date: Oct 2017
Location: Chapel Hill NC
Posts: 1,683
Bikes: 2000 Litespeed Vortex Chorus 10, 1995 DeBernardi Cromor S/S
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 645 Post(s)
Liked 797 Times
in
446 Posts
I have now tightened a guy's FSA Carbon Fork Plug for him multiple times, and it lasts about a week before I have to do it again due to the tension bolt backing off. This is the only time I have seen this type of repetitive situation. Is this something that these things are known for? Is there a preferred plug that holds better? Thanks.
#3
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,073
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4201 Post(s)
Liked 3,857 Times
in
2,305 Posts
There are a few differing designs of compression plugs (not including a basic star nut which is not to be used in a carbon steerer). One is glued in the steerer and tends to be fork specific. The two types taht are secured with an expanding section differ in what bolt does what job. The one bolt versions use the stem cap's draw bolt to both drive the expanding portion of the plug tight inside the steerer and also pull the stem cap down to preload the bearings. One bolt two jobs, often not the best choice. Style two has the expanding plug done by a hollow bolt at the top of the plug. The stem cap's draw bolt is then threaded into this hollow plug bolt. One step tightens the plug the second step/bolt preloads the bearings. Much easier to work with.
Either type of expanding plug usually needs to differentiate between the friction the wedges and "brake shoes" have and that of the bolt so applying grease to the proper surfaces allows better tightening and future removal. Carbon steerers have a max amount of plug tightening allowed before the steerer is at risk of fracture. Balancing all these factors is important to having the plug do it's two jobs, only one of which is needed after the stem is pinched in place. If the plug is coming loose and you can't understand and fix that then you owe the rider to find someone who can. His health and safety depends on his fork/stem remaining a solid item Andy
Either type of expanding plug usually needs to differentiate between the friction the wedges and "brake shoes" have and that of the bolt so applying grease to the proper surfaces allows better tightening and future removal. Carbon steerers have a max amount of plug tightening allowed before the steerer is at risk of fracture. Balancing all these factors is important to having the plug do it's two jobs, only one of which is needed after the stem is pinched in place. If the plug is coming loose and you can't understand and fix that then you owe the rider to find someone who can. His health and safety depends on his fork/stem remaining a solid item Andy
__________________
AndrewRStewart
AndrewRStewart
Likes For Andrew R Stewart:
#4
LR÷P=HR
Join Date: Sep 2019
Location: SF Bay Area
Posts: 2,180
Bikes: 1981 Holdsworth Special, 1993 C-dale MT3000 & 1996 F700CAD3, 2018 Cervelo R3 & 2022 R5, JustGo Runt, Ridley Oval, Kickr Bike 8-)
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 867 Post(s)
Liked 1,204 Times
in
693 Posts
A carbon steerer requires an expanding plug. This expanding plug helps stop the stem crushing the carbon steerer and provides traction to preload the headset bearings.
Do check that the plug is inside the stems clamp. Having the plug too low in the steerer, will stop it supporting the stem clamp.
Oh and don’t forget to use the correct torque on both the plugs expander and the stem clamp bolts.
Barry
PPS: Carbon Assembly Paste is your friend. The grit in the paste helps stop bits moving around. After all, with a carbon steerer you can’t just lean on the wrench !
#5
Full Member
Thread Starter
Join Date: Mar 2018
Location: Los Angeles
Posts: 463
Bikes: 02 Litespeed Ultimate, 84 & 85 Raleigh Grand Prix, '84 Raleigh Prestige, 85 Raleigh 555 RSL, '20 Raleigh Tamland, 38 Raleigh, 85 Landshark "Raleigh", '84 Marinoni Levi's Raleigh, SB4484, SB7979, Raleigh SSCXWC, 87 Raleigh USA 531 Prototype
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 202 Post(s)
Liked 147 Times
in
79 Posts
A metal steerer can use a star type plug to provide enough traction to preload the headset bearings.
A carbon steerer requires an expanding plug. This expanding plug helps stop the stem crushing the carbon steerer and provides traction to preload the headset bearings.
Do check that the plug is inside the stems clamp. Having the plug too low in the steerer, will stop it supporting the stem clamp.
A carbon steerer requires an expanding plug. This expanding plug helps stop the stem crushing the carbon steerer and provides traction to preload the headset bearings.
Do check that the plug is inside the stems clamp. Having the plug too low in the steerer, will stop it supporting the stem clamp.
#6
Senior Member
Is it the style you have to secure with a larger allen? Usually 8mm allen to tighten the plug, and the cap uses the normal 5mm. I always find those loose for some reason. I have a Hope brand one that has always worked for me.
Likes For wesmamyke:
#7
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,073
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4201 Post(s)
Liked 3,857 Times
in
2,305 Posts
I think the reason why the two bolts for the two functions plugs can sometimes loosen is that once in place and the stem cap draw bolt is in installed most riders (and shops) don't remove that cap and bolt after initial use to re torque the plug's bolt and take up the small, but there, slight compression that a carbon steerer sometimes have. Andy
__________________
AndrewRStewart
AndrewRStewart
#8
Newbie
It is widely believed that carbon paste is a bad idea in carbon steerers...the expanding plug should be done properly and torqued to the set specifications for both stem bolts (5-6 N-m) and preload (take out all the play, but no more). Make absolutely certain that your expanding plug fills all the space under the stem...for this reason, it is obvious that the minimum expander length must be 40mm (the most common stem clamp height). Generally should be a little more and should be (as well as can be done) somewhat centered under the stem clamp. It is good practice to use at least a 50mm expander...I tend to use 70mm or 100mm expanders for confidence...they weigh very little and I don't have to worry if I juggle my stem height a little.
A metal steerer can use a star type plug to provide enough traction to preload the headset bearings.
A carbon steerer requires an expanding plug. This expanding plug helps stop the stem crushing the carbon steerer and provides traction to preload the headset bearings.
Do check that the plug is inside the stems clamp. Having the plug too low in the steerer, will stop it supporting the stem clamp.
Oh and don’t forget to use the correct torque on both the plugs expander and the stem clamp bolts.
Barry
PPS: Carbon Assembly Paste is your friend. The grit in the paste helps stop bits moving around. After all, with a carbon steerer you can’t just lean on the wrench !
A carbon steerer requires an expanding plug. This expanding plug helps stop the stem crushing the carbon steerer and provides traction to preload the headset bearings.
Do check that the plug is inside the stems clamp. Having the plug too low in the steerer, will stop it supporting the stem clamp.
Oh and don’t forget to use the correct torque on both the plugs expander and the stem clamp bolts.
Barry
PPS: Carbon Assembly Paste is your friend. The grit in the paste helps stop bits moving around. After all, with a carbon steerer you can’t just lean on the wrench !
#9
Newbie
I think the reason why the two bolts for the two functions plugs can sometimes loosen is that once in place and the stem cap draw bolt is in installed most riders (and shops) don't remove that cap and bolt after initial use to re torque the plug's bolt and take up the small, but there, slight compression that a carbon steerer sometimes have. Andy
The very last thing that you should do is slack off the stem clamp bolts, tighten up the top cap until you just barely feel friction on the steerer, then re-tighten the stem clamp. I do find this works best with snug fitting spacers (I use the Wheels Mfg aluminum alloy spacers...they are individually precision machined).
#10
Newbie
One last thing that I forgot to mention, along the lines of universal solution.
High quality, reasonably affordable and light compression plugs are available in lengths greater than 50mm. You can place these, leave them where they are and move spacers around knowing that you are covering the 40mm where your stem is clamped and not fretting.
The two that I use are:
High quality, reasonably affordable and light compression plugs are available in lengths greater than 50mm. You can place these, leave them where they are and move spacers around knowing that you are covering the 40mm where your stem is clamped and not fretting.
The two that I use are:
Origin8 Fusion Expander Compression Plug - 90mm
Deda Elementi Expander Bung - 70mm
#13
Newbie
Check out this article
A tech bulletin from Trek regarding carbon assembly paste
A tech bulletin from Trek regarding carbon assembly paste
#14
Newbie
As a notable example...I just opened up a Cannondale carbon steerer and found this:
This was not only much smaller than the stem compression zone, it was mounted offset (about 20mm lower than shown here)...providing little support for the steerer tube.
This was not only much smaller than the stem compression zone, it was mounted offset (about 20mm lower than shown here)...providing little support for the steerer tube.
Last edited by shmuelyosef; 12-13-22 at 07:09 PM. Reason: grammar