Do I really need a torque wrench for cranks and BB?
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Do I really need a torque wrench for cranks and BB?
Postby adaml » Fri Jan 11, 2013 3:15 pm
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Re: Do I really need a torque wrench for cranks and BB?
Postby il padrone » Fri Jan 11, 2013 3:29 pm
Try not to overdue it with extender bars. Good solid pressure on a conventional wrench or 12" shifter should be more than enough.
"An unjustified and unethical imposition on a healthy activity."
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Re: Do I really need a torque wrench for cranks and BB?
Postby mitzikatzi » Fri Jan 11, 2013 3:44 pm
The "crank bolts". I have a 8mm allen key about 200mm long. I read somewhere that this will only allow about the correct torque to be applied (provided you don't go silly). Again don't "whale" on it. You can force the soft alloy arms onto the steel shaft of the bottom bracket. Check the bolts after a couple of short rides.
If you don't know how to do bolts up by feel you might be better off with a torque wrench.
Some say do not apply any "lube" to the shaft before installing the crank arms.
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Re: Do I really need a torque wrench for cranks and BB?
Postby il padrone » Fri Jan 11, 2013 3:47 pm
"An unjustified and unethical imposition on a healthy activity."
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Re: Do I really need a torque wrench for cranks and BB?
Postby rustychisel » Fri Jan 11, 2013 5:46 pm
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Re: Do I really need a torque wrench for cranks and BB?
Postby Mustang » Fri Jan 11, 2013 6:06 pm
70 years young.
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Re: Do I really need a torque wrench for cranks and BB?
Postby grantw » Fri Jan 11, 2013 7:09 pm
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Re: Do I really need a torque wrench for cranks and BB?
Postby il padrone » Fri Jan 11, 2013 7:21 pm
Before the advent of mass-market carbon frames and parts, torque wrenches were virtually unheard of.
"An unjustified and unethical imposition on a healthy activity."
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Re: Do I really need a torque wrench for cranks and BB?
Postby grantw » Fri Jan 11, 2013 9:50 pm
torque wrench = more leverage
therefore substitute long piece of pipe on wrench + heave as hard as I can to fit BB
as opposed to
torque wrench = specified torque applied.
Right tool for the job = win
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Re: Do I really need a torque wrench for cranks and BB?
Postby wqlava1 » Fri Jan 11, 2013 9:52 pm
As someone who has had a $15 K-Mart 0-150lb torque wrench for 34 years for my early cars, and a theoretically better Warren & Brown 0-80lb clicker for 30 years for my motorbike, I naturally look out for the right torques and they are there and have been specified. My deeper interest in bikes has only been the last 7-8 years, but I have readily found sources of the cassette, BB and crank torques (the only ones that I have really needed to use regularly). For example in Barnett's manual, an early version of which I found years ago scanned on some Russian site.il padrone wrote:Been working on my own bikes for over 30 years. I have lots of specific bike tools. But I've never owned or used a torque wrench. All my bikes are steel or alloy... no carbon. Have not had any 'oops' moment for many a long year.
Before the advent of mass-market carbon frames and parts, torque wrenches were virtually unheard of.
Those 3 are all around 30-40 ft/lb, which is a comfortable pull but by no means needs any cheater bar for people of normal strength with common tools. A 200mm allen key on your crank bolts needs just about 30kg assuming that you will only be able to get the force applied a cm or 2 from the end - which is quite likely at the limit of comfort! A long handle exerting pressure on a plastic BB end nut may well strip it (and the lightweight metal for the UN55 BB is not noticeably stronger than the plastic they had for the UN54), and likewise if you ever tighten the weak-looking lockring on an aluminium freehub, you wonder which one would strip first (I do, anyway).
But if you just pull on all 3 pretty firmly and have worked out what about 30-40lb/ft feels like, you will probably be fine.....
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Re: Do I really need a torque wrench for cranks and BB?
Postby Mulger bill » Fri Jan 11, 2013 10:53 pm
Isn't the handedness of BB and pedal threads that way for a reason?
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Re: Do I really need a torque wrench for cranks and BB?
Postby wqlava1 » Fri Jan 11, 2013 11:15 pm
Mulger bill wrote:I don't use a torque wrench on pedals, crank tapers or BBs, I just tighten to snug then add a fraction more, never had a problem.
Isn't the handedness of BB and pedal threads that way for a reason?
I think the handedness is for safety, to avoid them self-undoing when the older type BBs with loose bearings run out of lubricant and lock up, and the rider keeps pedalling.
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Re: Do I really need a torque wrench for cranks and BB?
Postby RonK » Fri Jan 11, 2013 11:43 pm
Much more important with the UN55 is the sequence of assembly and tightening. You need to screw in the bb nearly all the way home, then start the left side cup, return and fully tighten the right side, then the left side. Use plenty of grease.
BTW, if you don't like the plastic left side nut, you can buy an aluminium replacement. Just make sure you order the correct size according to the bb shell width.
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Re: Do I really need a torque wrench for cranks and BB?
Postby ball bearing » Sat Jan 12, 2013 10:41 am
I think that most bike mechanics who insist that their tighten-up and back off a bit is good enough is anywhere near accurate would be surprised how far off their bush-mechanic skills are when it comes to proper torque of components.
I have four torque wrenches going from my tiny Warren & Brown one to my big Snap-on.
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Re: Do I really need a torque wrench for cranks and BB?
Postby Mulger bill » Sat Jan 12, 2013 10:52 am
Absolutely. The main reason I got mine tho' it has paid for itself over most of the rest of the fleet too.ball bearing wrote:I reckon that a torque wrench is an essential tool for bikes, especially if you work on dual suspensions.
Still not sure whether it's needed for cassette lockrings...
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Re: Do I really need a torque wrench for cranks and BB?
Postby ball bearing » Sat Jan 12, 2013 10:56 am
I guess it is a individual thing - I find that doing up the lockring to 40Nm is usually the only surefire way of eliminating play and saving the hub threads at the same time.Mulger bill wrote:ball bearing wrote: Still not sure whether it's needed for cassette lockrings...
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Re: Do I really need a torque wrench for cranks and BB?
Postby rkelsen » Sat Jan 12, 2013 11:38 am
That's flippin' awesome! The plastic LH cup always looks a bit off, and they're too easy to strip as well. This is going straight to the pool room... or maybe my just Bookmarks list...RonK wrote:BTW, if you don't like the plastic left side nut, you can buy an aluminium replacement.
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Re: Do I really need a torque wrench for cranks and BB?
Postby il padrone » Sat Jan 12, 2013 7:52 pm
OP said nothing about his dual suspension requirementsball bearing wrote:I reckon that a torque wrench is an essential tool for bikes, especially if you work on dual suspensions.
"An unjustified and unethical imposition on a healthy activity."
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Re: Do I really need a torque wrench for cranks and BB?
Postby ball bearing » Sat Jan 12, 2013 10:05 pm
Says he who never owned or used a torque wrench. ; )il padrone wrote:OP said nothing about his dual suspension requirementsball bearing wrote:I reckon that a torque wrench is an essential tool for bikes, especially if you work on dual suspensions.
Doesn't hurt anything to have the right tool - and if you have it you might as well use it on the BB and other assorted bits. Hell, I even know people who think a workstand is an unnecessary tool and they hang their bikes from an old inner tube. Hey, if it works it works - I know how I like to do things, I'm happy that you know what works for you.
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Re: Do I really need a torque wrench for cranks and BB?
Postby wqlava1 » Sat Jan 12, 2013 10:28 pm
If you have a look at the price, its USD20 plus postage from the UK (must sell mostly to the US). I buy UN55 BBs from Bike24, usually once I have a need for a couple of hundred dollars' worth of stuff, for approx $18 or $19, with the 20 euros postage spread over all the items. It's not worth getting the aluminium one unless you will definitely be pulling the BB in and out on a regular basis, and even then you'd wait to see if you could save the supplied cup.rkelsen wrote:That's flippin' awesome! The plastic LH cup always looks a bit off, and they're too easy to strip as well. This is going straight to the pool room... or maybe my just Bookmarks list...RonK wrote:BTW, if you don't like the plastic left side nut, you can buy an aluminium replacement.
What usually wrecks a cup for me is when it has accumulated crap in the castellations/grooves of the cup and I don't take time to clean them out perfectly to let the tool seat fully, or when I don't position the frame optimally and use my best engaging tool on a comfortable long 1/2" drive extension so as to apply force exactly around the BB. Any angle on the tool is fatal for the cup.
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Re: Do I really need a torque wrench for cranks and BB?
Postby wqlava1 » Sat Jan 12, 2013 10:35 pm
Yes, but this thread has been going a while, we have elicited a variety of flavours of good advice based on different experience, and it has wandered in a few related directions. I just think back a few days to a thread about a failed fork that I started. Early on, it got some good technical commentary (including from your good self), then the conversation broadened, whilst still staying vaguely related. It's how people are, and it's how the forum is commonly used, and maybe it's what some people find appealing.il padrone wrote:OP said nothing about his dual suspension requirementsball bearing wrote:I reckon that a torque wrench is an essential tool for bikes, especially if you work on dual suspensions.
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Re: Do I really need a torque wrench for cranks and BB?
Postby dontazame » Sun Jan 13, 2013 12:32 am
I find 40nm for cassettes hard to guess (with the nm jump and using bigger tools) and its where using a torque wrench gives me the most peace of mind.I find that doing up the lockring to 40Nm is usually the only surefire way of eliminating play and saving the hub threads at the same time
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Re: Do I really need a torque wrench for cranks and BB?
Postby il padrone » Sun Jan 13, 2013 12:49 am
"An unjustified and unethical imposition on a healthy activity."
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Re: Do I really need a torque wrench for cranks and BB?
Postby alex » Sun Jan 13, 2013 5:11 am
you wouldnt have found an EFTPOS terminal for much of that time in those shops either, guess they are useless too!il padrone wrote:I'd say that during the 70s, 80s and for much of the 90s if you'd have walked into a LBS workshop you'd have been hard-pressed to find a torque wrench.
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Re: Do I really need a torque wrench for cranks and BB?
Postby il padrone » Sun Jan 13, 2013 9:18 am
Same could not be said for EFTPOS.
"An unjustified and unethical imposition on a healthy activity."
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