woodcraft

Bummer. I just check some (w/pre-set 5kn key) & they're fine.

the only thing I have trouble with is a stupid 1 bolt seatpost.

rydabent

On the new plastic (CF) bikes a torque wrench should probably be used. Anyone that says he can accurately tighten nuts and bolts without one is nuts, and should be avoided.

drlogik 

Back in the day when I worked in shops none had a torque wrench. This was before carbon and aluminum bikes though. Tightening by feel was common and we got "pretty good" at it over the years but it takes literally hundreds of fasteners to get that consistent "feel" for most folks. However, with today's high-priced carbon and aluminum bikes or other high priced components I think it's un-wise to not use a torque wrench if you work in a shop. If the mechanic jacks a fastener up then the customer's safety could hang in the balance.

I use a torque wrench on many of the fasteners on my own bikes, steel or aluminum. I don't own a carbon bike. If I did I'd use a torque wrench on probably every fastener. As far as fasteners I try to find the factory spec on whether to torque a lubed fastener or a dry fastener. It makes a huge difference.

If one torques a lubed fastener to spec when it needs to be dry then the likelihood of over-tightening is heightened. BTW, all three of my torque wrenches are really high quality not cheap $30 dollar torque wrenches.

Once torqued properly to spec I don't see the need to re-torque unless there is a reason. Even then I'd recommend torquing to 1 or 2 NM's less than spec to see if the fastener moves. If it does then tighten to spec.

DrIsotope

Yeah, riding the plastic-fantastic is still something I'm getting used to. CF bikes regularly make noises that my steel and alloy bikes never made. I'm a 200lb guy riding a 17lb bike, so I'm keeping a constant eye on everything.

Within the span of 4-5 rides, the seatpost will usually start making some intermittent noises, so I know it's time to check the torque. If the stem or headset are at all loose, the bike lets you know right away-- that first gnarly creak from riding over a railroad track or expansion joint is terrifying. Just another of the prices I guess some of us are willing to pay to go that little bit faster.

Retro Grouch 

I've heard that but the torque from the non-drive pedal has to transfer to the drive side crank. Why shouldn't it be the same either side?

Racing Dan

How much is "quite a bit". Im betting they are way better than guessing by hand.

Slash5

I wish they had done it at 12 ft lbs and 35 ft lbs too. 5 Nm isn't too bad, it's so low that it's barely tight.
I know when I installed a RaceFace crank, I would never have tightened the spindle bolt enough without a torque wrench.

andr0id

You should definitely torque to the top end of the spec as many manufacturers specify a value that is below the correct preload for the size of the bolt.

For example, an M5 needs a 5.5 Nm preload to not loosen by itself, but you often see this in use on stems with a 5 Nm max specified.

MePoocho

The majority of vehicle assembly / manufacturing facilities using a line build process will torque all hardware with calibrated air motors at each station. The QC group will swap the air motors (impact wrenches) daily and reverify the ones that were picked up. This way each process has their individual air motors set for the exact function they preform and they are colored/identified for that stage of the line.

That is not quite feasible at most shops or home levels. But what is available is a good click torque wrench. It should come with a certification document. If the wrench is not dropped or used as a hammer it will remain accurate for a very long time. Now, to maintain good longevity always, always unwind the spring tension..... other words zero out the setting. If it is 'directional' do not use it as a breaker bar to loosen the lug nuts on your 4x4 truck.

I'm a believer that all hardware does not need to be 'torqued'. Good technicians over the years know the 'feel' of a 6mm bolt or a 10mm axle nut in all various hardware. But there are some items that beg to be torqued. And I feel that it is arrogant to disregard the design specifications 'cause when two hairs on my arm pop up it's torqued.

It is just not hard or expensive to have a good quality torque wrench safely tucked away. Hey,, that cool set of Italian spandex riding duds you wear probably cost more. And as to lawyers and the such... I'd rather testify that I regularly use one even if it has not been recently recently certified. At least it shows responsibility and good intent.

Step up guys,,, you are not working on plumbing fixtures.

ThermionicScott 

Yep. A beam-type torque wrench good enough for our purposes is ~$20. It's not gonna break the bank. I prefer beam-type since you can watch the torque approach the desired values, rather than waiting blindly for a click.

MePoocho

ThermoicScott,,,,,,, Thank you,,, you are spot on the subject. Using a click wrench I 'sneak-up' on the torque value. That way I can sense what going on with the metals and hardware. Not scientific, but makes me feel better and no surprises.

I'm new to the bike world... what does RUSA #7498 mean? Sorry if I should already know.....

Bike Gremlin

Right side crank transmits torque directly to the chainrings.
The left side one does that through the axle. So it stresses the crank-axle connection when doing so - a lot more than the right hand side crank does.

When standing on the pedals, they being parallel to the ground, or when standing on one pedal - those are the situations when the torque on the crank-axle interface is the same for right and left crank.

Dan Burkhart 

Fair point, but in my experience, both direct and from what I read, left crank loosening happens with much greater frequency than right cranks, so it's as good an explanation as I've heard.

Sy Reene

Even better.. I've seen folks pretend they can tell if the tire being reinflated on a group ride (after a flat) is at the appropriate psi by a finger flick and the resulting sound.. Quite the tire connoisseur to know the appropriate pitch by tire brand by rider weight...

rydabent

Plus the beam never goes out of spec.

Another thing to consider is that if you have more than one bolt or nut to tighten on an assy with more than one, with the beam I can tighten say all all 5 in stages with the beam wrench. It can prevent warping.

Kimmo

That depends not just on the accuracy of the tool, but also how much experience you're going to disregard in favour of the dumb tool.

There's generally a fairly wide window of acceptable fastener tension, even on high-end carbon stuff, unless the part in question is crazy minimal, poorly designed, or just flogged out with the threads close to stripping.

I prefer to do as much as I can with the one set of L-shaped allen keys, the type of tool I've used on tens of thousands of fasteners, which gives me the most feedback on what's happening at the threads. As mentioned, torque ratings are inherently sketchy due to variations in friction, which can be felt.

I don't use a torque wrench on my plastic bikes, and I have more faith in them as a result. I pretty much only use a torque wrench for high-torque fasteners without a hard stop, like Campy's UltraTorque crank bolt; this sort of fastener is doing a job like a cylinder head bolt, where fastener torque is critical, and thread prep and the right grease are necessary.

Arrowana

I decided to test my skills at work today. I got 4.2Nm when shooting for 5Nm. My manager got 8Nm.

I'm quite the fan of my Topeak D-Torq DX. It gives a reading of where it currently is like a beam-type, and gives a beep when you hit the desired torque.

TimothyH

I'm going to use that on my next group ride. "Here, let me check your pressure." "No, you are good."



-Tim-

70sSanO

After reading through this, no crank arm is tightened to 5nm, so whatever is being testing is to a low torque.

So for "aluminum/steel," does anyone really torque chainring bolts, rear derailleur to hanger, derailleur cable bolts, brake cable nuts, front derailleur bolt, seatpost bolt, etc? I probably should torque the stem bolts.

I do torque crank arms and cassette lockrings, but not the small stuff.

John

Kimmo

40Nm is crazy for those. Half that is plenty, unless you're trying to prevent an aluminium freehub body from getting notched, but that probably won't work anyway.

Bike Gremlin

This works for me too. For final tightening I use the long part of the L as a lever, with just a thumb and the index finger as leverage. Since the length of the "L" depends on wrench size, which usually corresponds with the bolt (and the thread) size - I get it just about perfectly tight, without over tightening, or stripping threads.

For wrenches and similar tools, I hold the tool as near to the bolt as the hand would go - and that gets it right. No bolts loosening, no threads stripped.

Racing Dan

All this talk about accuracy and validated tools. Im betting a little ingenuity would let us verify our own tools. 5Nm (5n at 1m) is the same as 10n1/2m or 20n1/4m. 20n is ~2kg.

Now stic a bolt in a vice, with the head to one side, stick a matching socket on the wrench and stick the wrench on the bolt with the handle parallel to the floor. Hang a 2kg weight 25cm from the center of the socket. Adjust the wrench so that it just breaks with the weight as specified. > now you know where to set the wrench to get 5nm even if it out of adjustment.

andr0id

Out of curiosity, I checked my Syntace F109 stem when I got home. I use these whenever possible.
The bars are held on with 4 M5 Ti bolts and a pair of Ti M5 bolts secure it to the steering tube.

They all specify the max torque as 6Nm. So shoot for a toque that is greater than the preload and less than the max on the part. If the mfg has a max < the preload, it is a poorly designed part. Mechanical engineers should know better.

Common preloads for Bicycle sized bolts

M5 = 5.49 Nm (stems and handlebars )
M4 = 2.74 Nm ( water bottle cages and small accessory brackets )
M8 = 22.62 Nm ( some crank bolts )



https://www.tribology-abc.com/calculators/e3_6a.htm

In general, a bolt tightened to the preload should not vibrate loose.

Here's a great site with pretty clear information on how fasteners work.

A Tutorial on the Basics of Bolted Joints

andr0id

And if you use certified weights and jigs, etc... You're got your own PME lab.

If you don't abuse stuff, it will stay calibrated a long time. The Navy made us send in torque wrenches every 90 days.
I took my Craftsman in a few year ago to a local calibration shop after bicycle and auto use at home for 10+ years and they said it was still dead on. (Still charged me $25 anyway!)

Down use it as a breaker bar, take off the tension when you're storing it, don't drop it. Pretty easy rules to follow.

andr0id

It's the equivalent of an M30. 40Nm is actually pretty low.
Probably because they're usually Al and they don't want you to break it.