torque measurements

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torque measurements

Postby jamesn184 » Tue Sep 17, 2013 8:34 pm

My BBB torque wrench arrived today so I've set about making sure all my bolts are at the correct torque
But I'm somewhat stuck on the crankset as Sram call for 47-54nm but my wrench only goes up to 14...

what can I do?
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by BNA » Tue Sep 17, 2013 8:38 pm

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Re: torque measurements

Postby Dan » Tue Sep 17, 2013 8:38 pm

Just tighten it almost 4 times ;)

You'll need a larger range torque wrench for that particular application. Or, just lean on a ratchet a bit - I think crankset bolts are at the tougher end of the bolt spectrum.
Or take it to the LBS if you're set on getting the correct torque.
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Re: torque measurements

Postby DoubleSpeeded » Tue Sep 17, 2013 8:53 pm

jamesn184 wrote:My BBB torque wrench arrived today so I've set about making sure all my bolts are at the correct torque
But I'm somewhat stuck on the crankset as Sram call for 47-54nm but my wrench only goes up to 14...

what can I do?



Yeh those little tiny torque wrenches are really for real minor adjustments... for stems, handle bars, brake shoes, cleats on shoes, carbon seatposts etc etc.. Its not designed for tight applications like cranksets etc.

yeh just take it past a LBS, mine does little things like that for a $2 donation for their charity bin

or go past an Automotive mechanic workshop.. they should have one also
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Re: torque measurements

Postby biker jk » Tue Sep 17, 2013 9:18 pm

DoubleSpeeded wrote:
jamesn184 wrote:My BBB torque wrench arrived today so I've set about making sure all my bolts are at the correct torque
But I'm somewhat stuck on the crankset as Sram call for 47-54nm but my wrench only goes up to 14...

what can I do?



Yeh those little tiny torque wrenches are really for real minor adjustments... for stems, handle bars, brake shoes, cleats on shoes, carbon seatposts etc etc.. Its not designed for tight applications like cranksets etc.

yeh just take it past a LBS, mine does little things like that for a $2 donation for their charity bin

or go past an Automotive mechanic workshop.. they should have one also


Shimano crank arm bolts need to be tightened to 12-14NM so those "little tiny torque wrenches" are fine for Shimano cranks. SRAM, Campagnolo are a different story.
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Re: torque measurements

Postby DoogleDave » Tue Sep 17, 2013 9:20 pm

Or you could go buy one of THESE.

I bought one of these along with an appropriate socket (25mm from memory) to fit my lockring tool and I use this all the time to remove and reinstall my cassette (makes cleaning your rear cogs a breeze). Would also suit to do your cranks as well.

If you only intend on doing this once or twice a year then its probably easier to just go to the LBS, but otherwise it is handy to have your own tools at home.

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Re: torque measurements

Postby human909 » Tue Sep 17, 2013 9:42 pm

jamesn184 wrote:My BBB torque wrench arrived today so I've set about making sure all my bolts are at the correct torque
But I'm somewhat stuck on the crankset as Sram call for 47-54nm but my wrench only goes up to 14...

what can I do?


-Tighten using wrench up to 14NM and then tighten by feel using a wrench of similar length until it is 4x tighter.
-Tighten without torque wrench and calculated the toque by length of wrench x force on wrench.
-Tighten it 'bloody tight'


(I always do the second one if I have any concern. I rarely do though.)
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Re: torque measurements

Postby barefoot » Wed Sep 18, 2013 9:49 am

human909 wrote:-Tighten it 'bloody tight'


+1

Small torque wrenches are good for things that you need to be careful on to avoid stripping or crushing. For things where "tight" would be a problem.

For other things... especially when you have a reasonable sized steel bolt going into a steel thread... just do them "tight".

One thing to consider is the size of your tools (said the actress to the bishop... ahem...). Notice how smaller sized spanners and allen keys are shorter? There's a good reason for that. Tools evolved to their typical lengths because that's a comfortable length for doing up normal (steel in steel) fasteners at a reasonable torque.

If a spanner was much longer, then you'd get more leverage, so more torque for a given force... and you'd be at greater risk of stripping a thread by overtightening it. If a spanner was much shorter, then you would have a hard time undoing a reasonably torqued bolt without hurting your hand. Over time you get a feel for what a reasonable torque feels like with a normal hand tool. You need to push firmly, but not so tight that the tool hurts your hand.

That's the danger with socket sets... you use the same handle for small and big bolts, so you lose the natural feedback of a right-length tool.

But, obviously, a mumble thousand dollar carbon fibre bike is not the place to be developing a feel for reasonable torque with hand tools. Just understand that if a bolt has a torque specified that is significantly higher than the range of your torque wrench, then you're safe to just do it tight. If there was a significant risk of stripping or crushing, then they'd have specced a low torque.

tim
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Re: torque measurements

Postby twizzle » Wed Sep 18, 2013 10:38 am

I have a mega-expensive "Warren and Brown" 1-25Nm indicating beam for the small stuff. Needs occasional re-calibration, which isn't a common service.
I use a Park beam for everything else (1-70Nm). Doesn't ever need calibration, although I have had to bend the indicator a couple of times to zero it.
I also have another two W&B's for car use.
All up... about $900 in torque wrenches.

If I was starting out on bikes, I would just buy both the Park TW-1 & TW-2. Cheap, foolproof, doesn't require calibration.

All smart mechanics use beam torque wrenches... unless they go certified digital, but that can be mega-bucks.
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Re: torque measurements

Postby ball bearing » Wed Sep 18, 2013 11:33 am

twizzle wrote:I have a mega-expensive "Warren and Brown" 1-25Nm indicating beam for the small stuff. Needs occasional re-calibration, which isn't a common service.
I use a Park beam for everything else (1-70Nm). Doesn't ever need calibration, although I have had to bend the indicator a couple of times to zero it.
I also have another two W&B's for car use.
All up... about $900 in torque wrenches.

If I was starting out on bikes, I would just buy both the Park TW-1 & TW-2. Cheap, foolproof, doesn't require calibration.

All smart mechanics use beam torque wrenches... unless they go certified digital, but that can be mega-bucks.

My W&B split-beam wrenches have never needed calibration. I have three of them. The baby one is for bikes. My Snap-On torque is used for the bigger bike stuff and when I need reverse.

From what I have heard, digital are a royal pain.
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Re: torque measurements

Postby DoubleSpeeded » Wed Sep 18, 2013 6:41 pm

biker jk wrote:
DoubleSpeeded wrote:
jamesn184 wrote:My BBB torque wrench arrived today so I've set about making sure all my bolts are at the correct torque
But I'm somewhat stuck on the crankset as Sram call for 47-54nm but my wrench only goes up to 14...

what can I do?



Yeh those little tiny torque wrenches are really for real minor adjustments... for stems, handle bars, brake shoes, cleats on shoes, carbon seatposts etc etc.. Its not designed for tight applications like cranksets etc.

yeh just take it past a LBS, mine does little things like that for a $2 donation for their charity bin

or go past an Automotive mechanic workshop.. they should have one also


Shimano crank arm bolts need to be tightened to 12-14NM so those "little tiny torque wrenches" are fine for Shimano cranks. SRAM, Campagnolo are a different story.



crankset
? not
crank arm
?
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Re: torque measurements

Postby Duck! » Wed Sep 18, 2013 7:59 pm

DoubleSpeeded wrote:
biker jk wrote:
DoubleSpeeded wrote:

Yeh those little tiny torque wrenches are really for real minor adjustments... for stems, handle bars, brake shoes, cleats on shoes, carbon seatposts etc etc.. Its not designed for tight applications like cranksets etc.

yeh just take it past a LBS, mine does little things like that for a $2 donation for their charity bin

or go past an Automotive mechanic workshop.. they should have one also


Shimano crank arm bolts need to be tightened to 12-14NM so those "little tiny torque wrenches" are fine for Shimano cranks. SRAM, Campagnolo are a different story.



crankset
? not
crank arm
?
SRAM, FSA (some models, not all), Campagnolo & others have a large bolt that holds the crankset together. It required a lot of torque. Shimano (and some other FSA) cranks have the end-bolt which only applies bearing pre-load, and the actual assembly retaining bolts are through the butt of the left crank, clamping it onto the spindle. These are smaller and require less torque, as too much will strip the threads out of the crank.
I had a thought, but it got run over as it crossed my mind.
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Re: torque measurements

Postby jacks1071 » Thu Sep 19, 2013 12:23 am

jamesn184 wrote:My BBB torque wrench arrived today so I've set about making sure all my bolts are at the correct torque
But I'm somewhat stuck on the crankset as Sram call for 47-54nm but my wrench only goes up to 14...

what can I do?


Buy a bigger torque wrench.

I have three of them at home for different torque ranges and another one at work which is used exclusively for cassette installations.
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Re: torque measurements

Postby winstonw » Thu Sep 19, 2013 7:20 am

All bolts apart from 3 on a modern road bike require <20Nm.
The 3 are
bottom bracket bearings to frame
pedals to crank
cassette lockring

I have a W&B and BBB for the small stuff, and don't bother with larger one.
If you can borrow a bigger one, and use it a few times, it's easier to get a feel for the higher torques required like 35-50, than it is for smaller torques. Further if 50Nm is required and you only apply 30Nm it is highly unlikely to become an issue.

I'd suggest you also read up on using loctite or similar where appropriate. I use it on many bolts i.e.
- pedals to cranks because it stops threads from tightening as much as loosening, and disperses load more evenly across both thread surfaces.
- bidon bolts as they are subject to a lot of vibration and with the weight of water bottles, are more prone to loosening.
- derailleur to frame bolts for similar reasons.

-
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Re: torque measurements

Postby ctguru » Wed Oct 23, 2013 9:54 am

I've got 2 different sized torque wrenches that I use for bike work
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