Measuring Torque

[Mr Pig]

So, in order to work on a bike then we need to buy torque wrenches Mr Pig.?

No, but it's a good idea.

I usually don't use one myself when doing stuff to the bike, but I've been working on machines professionally for over twenty years. However, I'll still use one on important fasteners, at least until I get the measure of how tight they should be.

I'm sure that the country is full of bikes that have rounded bolts, worn out or sheered parts, stripped threads and goodness knows what other damage due to fasteners being either too loose or too tight. It can be potentially very dangerous obviously. This is the work of people who think they know what 'tight' means.

People like you or I have at least half a chance of getting it right but for most people, a torque wrench is a very good investment. If nothing else it will teach them a great deal about what 'tight' actually means.

 

[jimboalee]

The only time I use a torque wrench is on cylinder head studs.

Bicycles don't have cylinder heads, so a torque wrench is not in my toolbox.

 

[Twenty Inch]

The OP was asking about carbon bikes, where torque is a little more important than on my steel clunker. Too much force on the clunker, and I have a rounded-off allen bolt. Too much force on the carbon bike, and I have a frame-fatal fracture. I think if I had a carbon frame I'd go out and spend £40 on a torque wrench too.

 

[byegad]

Agree that a torque wrench is a boon to alloy and carbon components. I bought one on Amazon for under £20 with enough range low to high for all my cycle needs.
It came with a calibration certificate and solved a continually slackening Alloy nip bolt on my old MTB. (now sold)

 

[DaveP]

Well opinions seem divided here upon the need for a torque wrench I sit firmly on the “you need one” side of the fence (look at figures stamped on Shimano lock ring spacers for example).

Parker tools http://www.parktool.com/repair/howtos/torque.pdf have a whole list of items that should be torqued up and the figures to what they should be tightened up to, why go to all this bother if a torque wrench is not needed?

Any component that relies upon mechanical properties to remain "tight" has an optimum point (tension and loading) to which it is tightened, not enough and it may loosen, too much may result in sheer.

Material composition and environment (i.e. vibration) will come into play also with some components having features such as Nyloc inserts or materials such as Loctite applied.

 

[barq]

One significant advantage of having a torque wrench is that it can help warranty claims. Some manufacturers/distributors tend to blame incorrect installation for failures (and a fair bit of the time they'd have a point). Telling them you used a torque wrench and quoting their recommended limits seems to simply claims.

On the whole people buying a complete bike from a good LBS probably don't need a torque wrench because you have some sort of reference point to begin with. I only splashed out on torque wrenches when it came to my first complete bike build.

 

[skwerl]

The only time I use a torque wrench is on cylinder head studs.

Exactly. And the reason being that most people will under-tighten them or be too variable between bolts and cause loss of compression or warp the head.
I can only see a torque wrench being useful for high-torque applications. Bikes don't have any of those.

A torque wrench for a seat-clamp? Come on.

 

[jimboalee]

The torque values for bike components is so low, lubrication on the thread and surface finish of the threads can have a large ( in % terms ) influence on the resultant torque applied.

To get the correct Nm, the threads need to be polished and lubed with copper filled grease.
Usually, cyclists just pick up the bolt, finger tighten it into the thread and give it the torque wrench. No inspection of the theads and no lube.

Then they wonder why the stud corrodes in the thread or the bolt works loose.

 

[DaveP]

To get the correct Nm, the threads need to be polished and lubed with copper filled grease.

Ever used Dry film assembly lubricants such as ROCOL Moly Spray Jim?

 

[jimboalee]

I usually give the threads a couple of laps of PTFE tape and wind them in with a Stilson.

No, I use NGK Anti seize compound.

No, I use Castrol Moly Grease.

No, I use Loctite Threadlocker and cure it with a blowtorch.

No, I use Weldtite Lithium Bicycle grease.

 

[DaveP]

I usually give the threads a couple of laps of PTFE tape and wind them in with a Stilson.

No, I use NGK Anti seize compound.

No, I use Castrol Moly Grease.

No, I use Loctite Threadlocker and cure it with a blowtorch.

No, I use Weldtite Lithium Bicycle grease.

 

[Mortiroloboy]

Word of warning. Most car torque wrenches don't go down low enough to cover most of the fittings on a bike. Just in case you thought a car one would do the job, it won't.

Did you get a refund?

 

[Mortiroloboy]

Torque wrenches are a perfectly good way of spending money on something for your toolbox that you don't need.All bolts need tightening till they are tight. I don't need a £60 spanner to tell me that

 

[Mr Pig]

[/color]Did you get a refund?

Have a car one anyway, for fixing cars?

 

[02GF74]

Parker tools http://www.parktool.com/repair/howtos/torque.pdf have a whole list of items that should be torqued up and the figures to what they should be tightened up to, why go to all this bother if a torque wrench is not needed?

Why indeed. I've never used a torque wrench on my bike, and do it by feel. I don't have one that goes low enough.

In that time I have not stripped any threads, snapped any bolts nor rounded off any allen heads. Only issue I can remember is a cassette locking ring coming loose. So I nipped it up.

Any component that relies upon mechanical properties to remain "tight" has an optimum point (tension and loading) to which it is tightened, not enough and it may loosen, too much may result in sheer.

That is correct.

... but back to the carbon fibre post. I have one in my road bike and despite tightening the seatpost clamp, it still kept on slipping - up to the point where I could see the surface of the post starting to damage. I suppose a wider clamp to spread the pressue may have worked but my solution was to fit a sort piece of copper pipe (central heating stuff) inside the post and that solved it. Ok, so I gained a bit of weight but still had the blinginess of CF!