Seatpost Binder Bolt Torque Setting?

[jberenyi]

I have a classic Italian steel frame bike with a Campy style chrome moly seatpost binder bolt. The seatpost is aluminum and I'm curious what others have torqued their binder bolts to. I set mine to 80 inch lbs and I used Tacx carbon setting compound to prevent galvanic corrosion and help with slippage. It's hard to find a comparable range for these bolts on the net.

[Peter P.]

36-60 in-lbs. for Campagnolo, per the Sutherland's Manual.

[jberenyi]

36-60 in-lbs. for Campagnolo, per the Sutherland's Manual.

Ouch! I wonder if I should back it off?

[avalonracing]

Skinny Italian bike racers have built in torque meters in their arms. They are set to a max of 5nm.

[jberenyi]

The aerospace engineer in me says too low for chrome moly so here is what the calcs say and I even went 10% low on the yield strength of chrome moly (4140). Oh, and don't forget that if you grease or oil the bolt to reduce that value by 30-40% or you just may snap that puppy like I did :D


Nominal Thread Diameter: 6 mm
Thread Pitch: 1 mm
Yield Strength of Bolt Material: 750 MPa
Percentage of Yield to be used.: 75 %
Nut Factor Used: 0.179

Results

Torque Value 12.1570 Nm
Preload Value 11319.3954 N

Additional Information

Basic Thread Pitch Diameter 5.3505 mm
Basic Thread Minor Diameter 4.7731 mm
Stress Diameter of Thread 5.0618 mm
Stress Area of Thread 20.1234 mm²

Torque Value Conversions

Torque Value 12.1570 Nm
Torque Value 12157.0306 Nmm
Torque Value 1.2397 Kg-m
Torque Value 8.9666 Lbf-ft
Torque Value 107.5988 Lbf-in
Torque Value 1721.5804 Oz-in

Preload Value Conversions

Preload Value 11319.3954 N
Preload Value 1154.2571 Kgf
Preload Value 2544.6001 Lbf

Nut Factor Details

Selected Coating/Finish: As received steel
Minimum Nut Factor: 0.00000
Mean Nut Factor: 0.17900
Maximum Nut Factor: 0.00000
Selected Nut Factor: 0.179

[cpg]

Back when aluminum posts and campy binder bolts were the norm, NOBODY even talked about the torque setting. Tightenen it enough so it won't slip when you're riding it. If you over torque it the only bad thing that will happen is the bolt will break. Given your line of work this might be difficult advice to take but here it goes- Stop overthinking this one. Good luck and put the torque wrench back in the drawer.

Curt

[jberenyi]

Back when aluminum posts and campy binder bolts were the norm, NOBODY even talked about the torque setting. Tightenen it enough so it won't slip when you're riding it. If you over torque it the only bad thing that will happen is the bolt will break. Given your line of work this might be difficult advice to take but here it goes- Stop overthinking this one. Good luck and put the torque wrench back in the drawer.

Curt


Good one Curt...LOL. The only reason I had to over think this one is because I was having some slippage issues but thanks for the advice.

[cpg]

Slippage? Why didn't you say so? Here's where you can pull out some measuring tools. Measure the post OD and seat tube ID. Depending on the age of the frame, how accurately it was originally reamed and the design of the seat lug, the typical frames of yore built around the campy binder bolt have suffered from the seat tube stretching. This leads to the ears getting closer and often the campy bolt bottoms out. So no matter how tight you make the bolt it's not really clamping. So there you go mister/ms. engineer. Bust out the measuring tools and your highly educated analytical mind. Report back with your findings. Extra points for white paper format.

[benb]

CPG,

You just gotta understand it is really really frustrating to an engineer when you buy a simple tube of metal/CF for $100+ to attach a seat to a frame and this company with all their high tech marketing can't even dot their I's and cross their T's to the point of providing meaningful torque specs.

jberenyi's reaction is so understandable. If they're charging such premium prices & using exotic materials they ought to be able to provide good specs.

How long did it take to do those calculations? If someone does it for free in their spare time the bike company can afford to include it with the part.

[cpg]

CPG,

You just gotta understand it is really really frustrating to an engineer when you buy a simple tube of metal/CF for $100+ to attach a seat to a frame and this company with all their high tech marketing can't even dot their I's and cross their T's to the point of providing meaningful torque specs.

jberenyi's reaction is so understandable. If they're charging such premium prices & using exotic materials they ought to be able to provide good specs.

How long did it take to do those calculations? If someone does it for free in their spare time the bike company can afford to include it with the part.


I hear you. You do know that I was joking around right? Here's my straight talk about it. Sufficient or insufficient torque most likely isn't the issue here. The place to start is the seat post OD and seat tube ID. Then check to see if the seat tube slot appears to be collapsing. Then check to see if the bolt is bottoming out. Unfortunately, no calucalations will be needed with that approach. That's another joke.

[jberenyi]

Thanks guys for all the input. The Italian steel lugged frame is new old stock and judging by the way the seatpost slides in with a beautiful slip fit (after the following alterations were made) I imagine all is okay. I believe the issue with slipping was with the paint left inside the first inch or so of the frame tube. I have since removed the paint layers with paint remover gel and grit blasted the aluminum seatpost up to my insertion area. Prior to grit blast the aluminum seatpost had a very shiny clear coat on it that would make a fly break his leg if he landed on it. As an added effort I also used Tacx carbon paste. The final measure was to include the proper torque value. Thus the intent of this thread. :D

[benb]

I hear you. You do know that I was joking around right? Here's my straight talk about it. Sufficient or insufficient torque most likely isn't the issue here. The place to start is the seat post OD and seat tube ID. Then check to see if the seat tube slot appears to be collapsing. Then check to see if the bolt is bottoming out. Unfortunately, no calucalations will be needed with that approach. That's another joke.

Yah... well it is even more of a joke that companies can't build their tubes to tolerances that actually work.

Tube inside/outside diameters & fasteners should be pretty basic when they're doing all this carbon whizbang nanotube this and that!

[cpg]

Yah... well it is even more of a joke that companies can't build their tubes to tolerances that actually work.

Tube inside/outside diameters & fasteners should be pretty basic when they're doing all this carbon whizbang nanotube this and that!


To which companies are you referring?

[cpg]

[QUOTE=jberenyi]Thanks guys for all the input. The Italian steel lugged frame is new old stock and judging by the way the seatpost slides in with a beautiful slip fit (after the following alterations were made) I imagine all is okay. I believe the issue with slipping was with the paint left inside the first inch or so of the frame tube. I have since removed the paint layers with paint remover gel and grit blasted the aluminum seatpost up to my insertion area. Prior to grit blast the aluminum seatpost had a very shiny clear coat on it that would make a fly break his leg if he landed on it. As an added effort I also used Tacx carbon paste. The final measure was to include the proper torque value. Thus the intent of this thread. :D[/QUOTE

For giggles, what kind of aluminum seat post is clear coated? Remember that where you blasted off the clear coat you most likely took of the annodization too. Usually not a big deal unless you leave the post in for a long time without relubing. You shouldn't have to do the blast bit if the fit is good.

[jvp]

Somewhat related, on my old bianchi trackbike I could not get a 26.8mm seatpost I bought for it to tighten sufficiently, yet a 27.0 would not fit. I tried another different brand (sugino) 26.8 seatpost and it tightened up fine.

[jberenyi]

[QUOTE=jberenyi]Thanks guys for all the input. The Italian steel lugged frame is new old stock and judging by the way the seatpost slides in with a beautiful slip fit (after the following alterations were made) I imagine all is okay. I believe the issue with slipping was with the paint left inside the first inch or so of the frame tube. I have since removed the paint layers with paint remover gel and grit blasted the aluminum seatpost up to my insertion area. Prior to grit blast the aluminum seatpost had a very shiny clear coat on it that would make a fly break his leg if he landed on it. As an added effort I also used Tacx carbon paste. The final measure was to include the proper torque value. Thus the intent of this thread. :D[/QUOTE

For giggles, what kind of aluminum seat post is clear coated? Remember that where you blasted off the clear coat you most likely took of the annodization too. Usually not a big deal unless you leave the post in for a long time without relubing. You shouldn't have to do the blast bit if the fit is good.

The seatpost is a clear coated Specialized 27.0mm bought on this forum. I only removed enough to what is inserted so the rest is protected. Of the part that is inserted the Tacx takes care of with respect to the oxidation and galvanic action problems that can occur over time.