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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 01-24-07, 08:28 AM   #1
benk0
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Integrated seatpost binder in aluminum frame - slipping seatpost.

I'm guestimating how much torque to put into the binder bolt which is integrated into an aluminum frame (Pista Concept) to keep the seatpost from moving and to also keep those threads in check.

Starting low and working up, I'm at what I would consider "pretty tight" using a Park folding allen and it slipped a bit... is there a trick other than torqueing the crap out of that bolt? I used assembly grease putting the seatpost in.

Thanks.
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Old 01-24-07, 08:33 AM   #2
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grease the bolt, too - any time you've got threads, grease is going to help them get tight enough to hold.

get it snug, firm, and tight, but don't go nuts on it. grease is the trick - for many things.
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Old 01-24-07, 08:34 AM   #3
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If it's slipping and the post it the right size it's not tight enough but be very careful as you can trash the fame by tightening too much.

torque is easy to estimate within 10-20% though
-Look up the recommended torque.
-convert to inch*lbs
-divide by the length of your wrench
-find something that weighs that much
-pick it up with three fingers.
-put the same amount of force it took to hold the item on the end of the wrench.
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Old 01-24-07, 08:48 AM   #4
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That happened to me. Had to tighten the crap out of the seatpost binder, and the seat still wound up slipping. Turns out the seatpost was too small. They come in 0.2 mm increments, you might need to get a larger sized seatpost.
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Old 01-24-07, 09:19 AM   #5
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beer can shim
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Old 01-24-07, 09:20 AM   #6
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stripped my integrated seatpost clamp that way. i was sad.

anybody tried helicoil on the steapost binder (aluminum frame)?
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Old 01-24-07, 09:22 AM   #7
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So the frame calls for a 27.2 and that's what I have... but I should try and find a 27.4?
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Old 01-24-07, 09:23 AM   #8
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I always thought it was hard to judge proper torque with a folding allen wrench set. I assume yours looks something like this:

What might feel like a lot of torque on one of these may feel pretty loose on a longer wrench. It's hard to tell.

If that fails, your seatpost may be a little small for its size. Besides getting a better-toleranced seatpost, you might try one of the new friction compounds offered by a few manufacturers (like FSA and Ritchey). Ritchey's looks something like this, and it's supposed to reduce the amount of torque necessary to keep a part from slipping:


You'll have to pardon me if that's what you meant by 'assembly grease'.
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Old 01-24-07, 09:28 AM   #9
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Quote:
Originally Posted by keevohn
I always thought it was hard to judge proper torque with a folding allen wrench set. I assume yours looks something like this:

What might feel like a lot of torque on one of these may feel pretty loose on a longer wrench. It's hard to tell.
That is because you are feeling force not torque. If you can't convert by feel DO THE MATH it's worth 15s to not trash a component or the frame.
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Old 01-24-07, 09:47 AM   #10
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for posterity:
torque is force times radial distance. if you have a wrench with a 3" handle and apply fifteen pounds of force, you are exerting 15*.25 foot-pounds of torque (3.75 ft-lbs). if you have a 6" handle and apply the same force, you're applying more torque: 15*.5 ft-lbs (7.5 ft-lbs).

for a practical example of this effect, try to push open a heavy door from near the hinges, and then try again out near the handle. close to the hinges (less radial distance) it requires more force to open it. the further out you go, the less force it requires to get the same effect.
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Old 01-24-07, 09:52 AM   #11
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Quote:
Originally Posted by queerpunk
for posterity:
torque is force times radial distance.
technically, it's the cross product of force and distance. but with a wrench you you're applying almost all the force in the angular direction, so it simplifies to force times radius.

/physics ******
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Old 01-24-07, 11:03 AM   #12
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Ok, I'm not a bicycle guru, but I'll tell you a bit about fasteners.

When it comes to torqueing a threaded fastener, just like virtually everything else in this world, MORE is NOT better. Learn moderation. Apply it in your daily life. Every bolt has a torque setting that provides the proper tension in the bolt to provide maximum clamping force (primarily based on material and cross sectional area). Torqueing further DOES NOT provide any more clamping force. It may be harder to turn, but it is not holding your part any tighter. It is only incresing your chances of stripping threads, or failing the bolt. Determine the manufacturer's recommended torque and use it, it is given for a reason.

And as far as greasing the threads - also not a good idea unless recommended by the manufacturer. As mentioned above it will not provide you any more clamping force to simply torque the bolt more. In addition to risking damaging something, lubricants on the thread will make torque readings inaccurate if you are trying to do the proper thing and torque your bolt correctly.

Mac
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Old 01-24-07, 11:14 AM   #13
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every manufacturer and mechanic i've ever read or talked to or heard about recommends greasing threads. greasing threads eases the thread interfacing, reduces the chances of stripping, and allows for snugness (not necessarily overtorquing) where ungreased parts might shake themselves loose. furthermore it prevents parts from rusting together.
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Old 01-24-07, 05:00 PM   #14
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you need a bigger post.
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Old 01-24-07, 05:42 PM   #15
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Quote:
Originally Posted by dirtyphotons
stripped my integrated seatpost clamp that way. i was sad.

anybody tried helicoil on the steapost binder (aluminum frame)?

juyst drill it and get a standard old school seat binder bolt boy o boy do I like my seat collar on my brass knuckle even more know
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Old 01-24-07, 05:57 PM   #16
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Is the seat post carbon? If not try to rough it up a little with some coarse sand paper below the binder bolt height and reinstall. DO NOT TRY THIS WITH CARBON.
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Old 01-24-07, 05:59 PM   #17
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Solution (to my issue).

This technique was recommended to me by my LBS mechanic.

Seatpost out. We measured the seattube collar with a digital caliper and it was 27.35 (ie. a 27.4 post woundn't and didn't work). She said she sees things like this all the time where tolerances are off because of uneven or miscalculated expansion or contraction of tubing when assembling frames... mine was made in Taiwan... probably very quickly and in mass quantities so it makes sense.

With the seat post out, I tightened the binder bolt to close the diameter of the collar then I took my seatpost out to the shed and with a slotted screwdriver and a hammer, put several small notches where the binder collar grabs the post. Reinserting the post after doing these two operations already made it nice and snug. I tightened the binder bolt down to where I felt it should be and beat it up around town through some construction zones and up and down some curbs and no slipping whatsoever.

I wouldn't suggest this if you care what your seatpost looks like inside the seattube or if you ever plan to resell it. Mine is a cheap Kalloy generic post... so I don't care, obviously.
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Old 01-24-07, 08:08 PM   #18
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Quote:
Originally Posted by Retem
juyst drill it and get a standard old school seat binder bolt boy o boy do I like my seat collar on my brass knuckle even more know
awesome, the best solution is always the simplest. thanks!
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