Just as the title says. A friend of mine cracked her seatpost by applying too much torque and she just got her new one in and is afraid to tighten it down too much.
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Re: What is the correct torque specs for a QR carbon seatpost [carboner]
[ In reply to ]
info needed:
- what model
- what year
- torque wrench available
otherwise, we can't really help.
my '08 caliente says 4nm, which isn't a lot. 10nm feels like a lot.
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC
- what model
- what year
- torque wrench available
otherwise, we can't really help.
my '08 caliente says 4nm, which isn't a lot. 10nm feels like a lot.
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC
Re: What is the correct torque specs for a QR carbon seatpost [carboner]
[ In reply to ]
The right torque is the amount just needed to prevent slipping in all service loads. Seriously...
My typical rant is just specifying torque is meaningless. Unless you have test data to show how that torque becomes tension in the bolt, you might as well pull a number out of a hat and use that. In its easiest form, preload is equal to Fpre=Torque*C, where C is a function of bolt diameter and the state of lubrication (or lack thereof). If dry, you need more torque to get to a required Fpre. If lubed on the threads only you get a lower torque required. Lube on the threads and under the head and you can get an even lower torque to get you to Fpre.
It's not the torque that got her first frame - it's Fpre.
Personally, what I do is just make the seatpost/tube interface as "dirty" as possible. That is, high friction. Why? Friction force is mu*N, mu provided by the interface and N provided by Fpre. By driving up mu, I can lower Fpre, and therefore, reduce my risk of not knowing the proper torque-tension relationship for this interface. I'll torque to the "feels right" level and then just go out and ride. If I hit a big bump and slip, I know I need a little more. Sure it's trial and error, but I'd rather spend a little extra time to avoid cracking my frame.
My typical rant is just specifying torque is meaningless. Unless you have test data to show how that torque becomes tension in the bolt, you might as well pull a number out of a hat and use that. In its easiest form, preload is equal to Fpre=Torque*C, where C is a function of bolt diameter and the state of lubrication (or lack thereof). If dry, you need more torque to get to a required Fpre. If lubed on the threads only you get a lower torque required. Lube on the threads and under the head and you can get an even lower torque to get you to Fpre.
It's not the torque that got her first frame - it's Fpre.
Personally, what I do is just make the seatpost/tube interface as "dirty" as possible. That is, high friction. Why? Friction force is mu*N, mu provided by the interface and N provided by Fpre. By driving up mu, I can lower Fpre, and therefore, reduce my risk of not knowing the proper torque-tension relationship for this interface. I'll torque to the "feels right" level and then just go out and ride. If I hit a big bump and slip, I know I need a little more. Sure it's trial and error, but I'd rather spend a little extra time to avoid cracking my frame.
Re: What is the correct torque specs for a QR carbon seatpost [carboner]
[ In reply to ]
I have an 07 full carbon Lucero, which I broke the front forks off running into a car door coming home late to watch a TDF mountain stage. I also cracked the frame about one inch around a bottle cage holder bolt hole, the top one had come loose and i accidentally kicked the cage and ripped the lower bolt holder out of the frame while carrying 6 boxes of thin mints home from a tri party. It has had a one inch crack for 3 years now and hasnt grown. I frequently destroy wheels by bunny hoping curbs, pot holes and other things when i forget Im not on a mountain bike. I race IM around 170+, but am typically fatter the rest of the year. I bought my Lucero used and have ridden the hell out of it for aboout 5 years now, so I definitely have to tighten my seat to about ten times what's recomended by the mfg. Of course mine is the aero post, but I have stripped the bolts once and mine still has never cracked. I would be willing to bet you had a faulty post. BUT, this is no place to get info about safe torque info about your bike. Go to your LBS, I'm sure they can do it right. I've always wondered if half the carbon damages you hear about (frame, wheels, other) weren't from bad bike racks, getting bumped in a garage, or being mishandled by the road race sag.
Re: What is the correct torque specs for a QR carbon seatpost [totallyspoked]
[ In reply to ]
totallyspoked wrote:
BUT, this is no place to get info about safe torque info about your bike. Go to your LBS, I'm sure they can do it right.
Re: What is the correct torque specs for a QR carbon seatpost [tigermilk]
[ In reply to ]
no guessing necessary, it's stamped on the seat binder hardware: 4nm
use carbon assembly paste to improve the friction of the post and binding hardware.
My typical rant is just specifying torque is meaningless. Unless you have test data to show how that torque becomes tension in the bolt, you might as well pull a number out of a hat and use that. In its easiest form, preload is equal to Fpre=Torque*C, where C is a function of bolt diameter and the state of lubrication (or lack thereof). If dry, you need more torque to get to a required Fpre. If lubed on the threads only you get a lower torque required. Lube on the threads and under the head and you can get an even lower torque to get you to Fpre.
It's not the torque that got her first frame - it's Fpre.
Personally, what I do is just make the seatpost/tube interface as "dirty" as possible. That is, high friction. Why? Friction force is mu*N, mu provided by the interface and N provided by Fpre. By driving up mu, I can lower Fpre, and therefore, reduce my risk of not knowing the proper torque-tension relationship for this interface. I'll torque to the "feels right" level and then just go out and ride. If I hit a big bump and slip, I know I need a little more. Sure it's trial and error, but I'd rather spend a little extra time to avoid cracking my frame.
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC
use carbon assembly paste to improve the friction of the post and binding hardware.
tigermilk wrote:
The right torque is the amount just needed to prevent slipping in all service loads. Seriously... My typical rant is just specifying torque is meaningless. Unless you have test data to show how that torque becomes tension in the bolt, you might as well pull a number out of a hat and use that. In its easiest form, preload is equal to Fpre=Torque*C, where C is a function of bolt diameter and the state of lubrication (or lack thereof). If dry, you need more torque to get to a required Fpre. If lubed on the threads only you get a lower torque required. Lube on the threads and under the head and you can get an even lower torque to get you to Fpre.
It's not the torque that got her first frame - it's Fpre.
Personally, what I do is just make the seatpost/tube interface as "dirty" as possible. That is, high friction. Why? Friction force is mu*N, mu provided by the interface and N provided by Fpre. By driving up mu, I can lower Fpre, and therefore, reduce my risk of not knowing the proper torque-tension relationship for this interface. I'll torque to the "feels right" level and then just go out and ride. If I hit a big bump and slip, I know I need a little more. Sure it's trial and error, but I'd rather spend a little extra time to avoid cracking my frame.
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC
Re: What is the correct torque specs for a QR carbon seatpost [cwg_at_opc]
[ In reply to ]
Re-read my post and see where 4 N-m just may not give you all you need to know...
Hint, 4 N-m doesn't fully define the procedure. There are a couple of key bits of information missing.
Hint, 4 N-m doesn't fully define the procedure. There are a couple of key bits of information missing.
Re: What is the correct torque specs for a QR carbon seatpost [tigermilk]
[ In reply to ]
i did read, and i'm not disagreeing with your technical acumen; 4nm dry bolt(s) hold my post fine.
your procedures and specs may be overkill here though.
would you agree that a torque wrench would be advised in this application(dry bolts)?
Hint, 4 N-m doesn't fully define the procedure. There are a couple of key bits of information missing.
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC
your procedures and specs may be overkill here though.
would you agree that a torque wrench would be advised in this application(dry bolts)?
tigermilk wrote:
Re-read my post and see where 4 N-m just may not give you all you need to know... Hint, 4 N-m doesn't fully define the procedure. There are a couple of key bits of information missing.
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC
Re: What is the correct torque specs for a QR carbon seatpost [cwg_at_opc]
[ In reply to ]
cwg_at_opc wrote:
i did read, and i'm not disagreeing with your technical acumen; 4nm dry bolt(s) hold my post fine. your procedures and specs may be overkill here though.
would you agree that a torque wrench would be advised in this application(dry bolts)?
tigermilk wrote:
Re-read my post and see where 4 N-m just may not give you all you need to know... Hint, 4 N-m doesn't fully define the procedure. There are a couple of key bits of information missing.
Torque wrench for this application? I would ask the vendor (assuming the clamp, seat post, and bolt are all OEM and in an as-received state) the proper procedure so I know how the joint should function. But personally I would lube it to reduce the scatter (well lubed threads/heads do wonders for reducing scatter), apply some torque, try to twist the seat, and if it moves apply a little more. Take for a test ride and make sure it doesn't slip. I'd prefer to creep up on it for carbon bits. Now if it were all metal parts? Crank the crap out of it and hope I don't shear the bolt.
Re: What is the correct torque specs for a QR carbon seatpost [tigermilk]
[ In reply to ]
this brings up an interesting assumption: manufacturers give specs on their parts knowing that not all LBS wrenches and home/end-users are NOT aerospace engineers like yourself - my bike did not come with a manual and i can't download one from their website, so i can't verify, but for pro-wrenches out there, do you lube threads/heads as TM has suggested, or do you just turn the wrench until the part doesn't move, or turn to the specified torque and stop?
your procedures and specs may be overkill here though.
would you agree that a torque wrench would be advised in this application(dry bolts)?
Hint, 4 N-m doesn't fully define the procedure. There are a couple of key bits of information missing.
Problem with the dry assumption is how do you know it's dry? Just a small amount of lube makes a ton of difference. And is that 4 N-m above running torque or absolute? If that bolt has been cycled a few times you can expect wear particles to develop in the threads, increasing running torque, dropping nut factor, reducing preload, etc. Also, dry surfaces have unbelievable scatter associated with them (I've seen +/-30-40% in preload in tests I've done on NAS fasteners with various dry/lube conditions and even higher in JPL data).
Torque wrench for this application? I would ask the vendor (assuming the clamp, seat post, and bolt are all OEM and in an as-received state) the proper procedure so I know how the joint should function. But personally I would lube it to reduce the scatter (well lubed threads/heads do wonders for reducing scatter), apply some torque, try to twist the seat, and if it moves apply a little more. Take for a test ride and make sure it doesn't slip. I'd prefer to creep up on it for carbon bits. Now if it were all metal parts? Crank the crap out of it and hope I don't shear the bolt.
(real precise here, but the parts are metal, so...)
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC
tigermilk wrote:
cwg_at_opc wrote:
i did read, and i'm not disagreeing with your technical acumen; 4nm dry bolt(s) hold my post fine. your procedures and specs may be overkill here though.
would you agree that a torque wrench would be advised in this application(dry bolts)?
tigermilk wrote:
Re-read my post and see where 4 N-m just may not give you all you need to know... Hint, 4 N-m doesn't fully define the procedure. There are a couple of key bits of information missing.
Problem with the dry assumption is how do you know it's dry? Just a small amount of lube makes a ton of difference. And is that 4 N-m above running torque or absolute? If that bolt has been cycled a few times you can expect wear particles to develop in the threads, increasing running torque, dropping nut factor, reducing preload, etc. Also, dry surfaces have unbelievable scatter associated with them (I've seen +/-30-40% in preload in tests I've done on NAS fasteners with various dry/lube conditions and even higher in JPL data).
Torque wrench for this application? I would ask the vendor (assuming the clamp, seat post, and bolt are all OEM and in an as-received state) the proper procedure so I know how the joint should function. But personally I would lube it to reduce the scatter (well lubed threads/heads do wonders for reducing scatter), apply some torque, try to twist the seat, and if it moves apply a little more. Take for a test ride and make sure it doesn't slip. I'd prefer to creep up on it for carbon bits. Now if it were all metal parts? Crank the crap out of it and hope I don't shear the bolt.
(real precise here, but the parts are metal, so...)
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC
Re: What is the correct torque specs for a QR carbon seatpost [carboner]
[ In reply to ]
Be careful! I over torqued mine and f-ed up the FRAME. Expensive fix. Now I have a P2C
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Re: What is the correct torque specs for a QR carbon seatpost [cwg_at_opc]
[ In reply to ]
Any hints on just getting the seatpost to stop squeeking? My Cd0.1 seatpost doesn't slip (I am just past the advised torque, at 5Nm, with no lube on the threads), but it sure does make a lot of noise. I just want it to be silent......
Has anyone tried things like putting a single thickness of electrical tape on the seatpost (right where the clamp intersects)? Or possibly the carbon assembly paste? Again, I don't have a slippage problem.....just a noise problem!
Thanks,
Chris
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Has anyone tried things like putting a single thickness of electrical tape on the seatpost (right where the clamp intersects)? Or possibly the carbon assembly paste? Again, I don't have a slippage problem.....just a noise problem!
Thanks,
Chris
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Road: Colnago C50
Cross: Ridley X-Fire
Tri:Trek SC 9.8
Re: What is the correct torque specs for a QR carbon seatpost [chris8382]
[ In reply to ]
Hey Chris,
Did you ever get a fix here? Mine creaks with assembly paste and seems to move (flex) a lot more than my other bikes.
Cheers!
Did you ever get a fix here? Mine creaks with assembly paste and seems to move (flex) a lot more than my other bikes.
Cheers!
Re: What is the correct torque specs for a QR carbon seatpost [carboner]
[ In reply to ]
So this is what is has come down to: needing torque specs to tighten a seatpost..........
God help us..............
**All of these words finding themselves together were greatly astonished and delighted for assuredly, they had never met before**
God help us..............
**All of these words finding themselves together were greatly astonished and delighted for assuredly, they had never met before**
Re: What is the correct torque specs for a QR carbon seatpost [ktm520]
[ In reply to ]
Nope.....never got a response, but I have fixed the problem. Just tightened the bolts a bit more and now I have no noise at all.
I don't notice at all the flexing that you describe. I have my seatpost out pretty far (or at least what I consider to be far), and don't notice anything different from my other bikes (but may be I am just not sensitive to this type of thing).
Chris
_______________________________
Road: Colnago C50
Cross: Ridley X-Fire
Tri:Trek SC 9.8
I don't notice at all the flexing that you describe. I have my seatpost out pretty far (or at least what I consider to be far), and don't notice anything different from my other bikes (but may be I am just not sensitive to this type of thing).
Chris
_______________________________
Road: Colnago C50
Cross: Ridley X-Fire
Tri:Trek SC 9.8
Re: What is the correct torque specs for a QR carbon seatpost [Mojozenmaster]
[ In reply to ]
Lol I thought the same thing.
My laces are loose , should I use a overhand square knot or a becketts bend knot to tie them and how tight should i make them ?
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My laces are loose , should I use a overhand square knot or a becketts bend knot to tie them and how tight should i make them ?
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Re: What is the correct torque specs for a QR carbon seatpost [bmanners]
[ In reply to ]
http://www.netknots.com/...better_bow_knot.html
My laces are loose , should I use a overhand square knot or a becketts bend knot to tie them and how tight should i make them ?
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC
bmanners wrote:
Lol I thought the same thing. My laces are loose , should I use a overhand square knot or a becketts bend knot to tie them and how tight should i make them ?
"...I try not to ever ride as slow as 20mph. ;) ... And even more than that, I don't race with a speedometer. My computer is set up to show Power // Cadence // Time. I don't actually ever know how fast I'm going. I only know that if I'm in 53/11, and it takes more than 100rpm to hit my target watts, it's time to coast." - Jordan Rapp on '09 IMC