Difference between 4.5 & 5NM?

tomsimmonds

Hi,

I have a Roubaix SL4 s-works and as its new i thought i may as well get a torque wrench to ensure i don't crack and carbon. I want to get the ritchy 5nm torque key however on stem and handlebars it says 4.5nm. Is the 5nm tourqe key going to be suitable?

Thanks

Tom

nicklouse

Well if it says 4.5 and you set it to 5 any problems will be yours.

DiscoBoy

I can't think of any reason for them making it 4.5Nm other than to wiggle out of as many warranty claims as possible.

5Nm will almost certainly be fine, but of course they won't warrant it.

tomsimmonds

would it be better to go for the 4nm version instead or would that be too low?

most bolts seem to be 5nm

Dales1

0.5 of a NM is only a nominal amount of torque.

If I didn't have an adjustable torque wrench, I would happily set it to 4 NM. Then, for peace of mind, I would try my very best to twist the stem and to twist the bars, to make sure they were secure.

I usually set my torques a fraction under the quoted value, on carbon, to avoid damage. If it should then slip (unlikely) I can always apply the extra 0.5 NM if necessary.

Dales.

Terrytibbs

Torque wrenches will have an degree of tolerance. 0.5 is only a minimal amount and the wrench is probably 0.1-0.5 out anyway.

From my experience, 5nm is all you need on a stem and bar, even carbon. Most manufacturers are around 5nm. But as someone has stated, it's likely there to stop people from over tightening too much. I image they expect if a user sets their torque wrench to 4.5nm, then they shouldn't tighten it past 5nm. But on the other hand it has to be tight enough.

I'd personally, set it to 3, see how much effort it takes to get it to 4. Then set it 4 and do it until it clicks. Finally, set it 5nm and do it a touch more but don't let it click.

At least you've got a torque wrench so you can do this. The problem is when people don't have one and do it too loose for being scared to break anything or just over tighten it because they don't have a clue.

Sawilson

Hi Tom, just slightly bemused that you go to the expense of buying a a S-works frame and then falter about spending less than £50 to get the correct tool to ensure it is the correct tightness and the warranty will be intact.
Websters of Leicester have an M tool torque wrench on offer at £36 at the moment.
As stated before they are not always as accurate as you think, but if you have followed the instructions you will always have the peace of mind that you have somewhere to turn turn case of failure, be it the frame manufacturer, or the torque wrench maker, somebody will be liable but not you.
It's called covering your backside.
Great choice of frame by the way.

tomsimmonds

i think I'm going to go ahead with the m-tools wrench looks pretty decent for the money.

thanks

Tom

dgunthor

don't worry about it, most people massively overtighten stuff anyway so if you *only* tighten it to 5Nm that's still a lot less than most will have overcranked it

i doubt a 5Nm tool is particularly accurate anyway

gazman428

I never use a torque wrench, just gently nip it till it doesnt move imo.

but on applications where I do use them ie stretch bolts in engines etc, if I can't get the desired setting I work on percentages. Ie 0.5 is 10% off your recomended torque and on something as brittle as carbon I wouldnt chance it. On ally or steel I wouldnt hesitate.
you also have to factor in any error in the calibration of the tool, which could arguably be as high as 10% so before you know it your miles over the 4.5nm

slowbike

Sawilson wrote:

Hi Tom, just slightly bemused that you go to the expense of buying a a S-works frame and then falter about spending less than £50 to get the correct tool to ensure it is the correct tightness and the warranty will be intact.
Websters of Leicester have an M tool torque wrench on offer at £36 at the moment.
As stated before they are not always as accurate as you think, but if you have followed the instructions you will always have the peace of mind that you have somewhere to turn turn case of failure, be it the frame manufacturer, or the torque wrench maker, somebody will be liable but not you.
It's called covering your backside.
Great choice of frame by the way.

In my mind - £50 on a torque wrench that isn't accurate isn't very helpful anyway.

I have a 5Nm turnkey that I use for setting anything that requires a small torque setting on my bike - it won't be 100% accurate, but in terms of acceptable error it'll be close enough (for Jazz) ...
Unfortunately I don't (currently) have any means of testing it's calibration - but I may think of something ...

I'm not interested in anyone else being liable - I just want the parts fitted correctly and safely on my bike.

slowbike

gazman428 wrote:

I never use a torque wrench, just gently nip it till it doesnt move imo.

but on applications where I do use them ie stretch bolts in engines etc, if I can't get the desired setting I work on percentages. Ie 0.5 is 10% off your recomended torque and on something as brittle as carbon I wouldnt chance it. On ally or steel I wouldnt hesitate.
you also have to factor in any error in the calibration of the tool, which could arguably be as high as 10% so before you know it your miles over the 4.5nm

Hmmm - are you sure Carbon is brittle ... I've been bending carbon for a good few years before I got into bikes - there's no way I'd describe it as brittle!

southdownswolf

Slowbike wrote:

gazman428 wrote:

I never use a torque wrench, just gently nip it till it doesnt move imo.

but on applications where I do use them ie stretch bolts in engines etc, if I can't get the desired setting I work on percentages. Ie 0.5 is 10% off your recomended torque and on something as brittle as carbon I wouldnt chance it. On ally or steel I wouldnt hesitate.
you also have to factor in any error in the calibration of the tool, which could arguably be as high as 10% so before you know it your miles over the 4.5nm

Hmmm - are you sure Carbon is brittle ... I've been bending carbon for a good few years before I got into bikes - there's no way I'd describe it as brittle!

Of course carbon is brittle. It also melts if you leave it out in the rain. :twisted:

gazman428

Slowbike wrote:

gazman428 wrote:

I never use a torque wrench, just gently nip it till it doesnt move imo.

but on applications where I do use them ie stretch bolts in engines etc, if I can't get the desired setting I work on percentages. Ie 0.5 is 10% off your recomended torque and on something as brittle as carbon I wouldnt chance it. On ally or steel I wouldnt hesitate.
you also have to factor in any error in the calibration of the tool, which could arguably be as high as 10% so before you know it your miles over the 4.5nm

Hmmm - are you sure Carbon is brittle ... I've been bending carbon for a good few years before I got into bikes - there's no way I'd describe it as brittle!

Really? I stand corrected then, im only going off the parts that I've destroyed on mtbs and racing motorbikes. It just seems to explode and be unfixable, or tear or crack at load mounting points.

BenderRodriguez

To be honest, blindly relying on any torque set via a torque wrench can be a path to disaster. Torque values as set by a wrench are only 'right' under a very specific set of conditions, most of which relate to the friction that needs to be overcome. For example, the specified setting could relate to a clean dry thread, or one that has been lubricated with light oil and then left to drain for an hour. If the user then puts grease on the threads (a common practice with stem bolts) and tries to set the torque to the same value, the bolt will be over-tightened due to the reduction in friction and may even snap or strip the threads.

Take care!

lesfirth

BenderRodriguez wrote:

To be honest, blindly relying on any torque set via a torque wrench can be a path to disaster. Torque values as set by a wrench are only 'right' under a very specific set of conditions, most of which relate to the friction that needs to be overcome. For example, the specified setting could relate to a clean dry thread, or one that has been lubricated with light oil and then left to drain for an hour. If the user then puts grease on the threads (a common practice with stem bolts) and tries to set the torque to the same value, the bolt will be over-tightened due to the reduction in friction and may even snap or strip the threads.

Take care!

AAARRRGG! Please don't start this again. Check out "why do we grease bolts thread". You can see how long you can stay awake reading it.

slowbike

gazman428 wrote:

Slowbike wrote:

gazman428 wrote:

I never use a torque wrench, just gently nip it till it doesnt move imo.

but on applications where I do use them ie stretch bolts in engines etc, if I can't get the desired setting I work on percentages. Ie 0.5 is 10% off your recomended torque and on something as brittle as carbon I wouldnt chance it. On ally or steel I wouldnt hesitate.
you also have to factor in any error in the calibration of the tool, which could arguably be as high as 10% so before you know it your miles over the 4.5nm

Hmmm - are you sure Carbon is brittle ... I've been bending carbon for a good few years before I got into bikes - there's no way I'd describe it as brittle!

Really? I stand corrected then, im only going off the parts that I've destroyed on mtbs and racing motorbikes. It just seems to explode and be unfixable, or tear or crack at load mounting points.

Masts, bow sprits and tiller extensions - all regularly bent and returned back to shape when the load removed - sometimes you bend it too far though - then it breaks .... Pretty much like everything else. Carbon is flexible - to a degree ....

PhunkyPhil

This thread made me laugh. If your worried about having the correct torque values then why not get a wrench which will allow you to tighten the bolts to the correct values