Advice on torque settings

[Jmph67]

I finally invested in a torque wrench to take the guesswork out of bolt tightening efforts.

After servicing the headset recently I replaced the stem. Attaching the handlebars on the final turn to achieve the torque setting etched on the stem the bolt snapped. Drilling out the bolt is not cost effective. New stem required.

Afterwards I realised that I should have progressively tightened the opposing bolts. Too much lateral pressure , I'm guessing.

Now the question:
Is the stated pressure on the components an absolute limit?

Or should I tighten to less than the stated pressure?

[trailgumby]

Tighten to the stated number but where multiple bolts are involved (eg, stem faceplate, Shimano cranks, stem steerer bolts) do so in increments, evenly across all bolts.

[DoubleSpeeded]

I finally invested in a torque wrench to take the guesswork out of bolt tightening efforts.

After servicing the headset recently I replaced the stem. Attaching the handlebars on the final turn to achieve the torque setting etched on the stem the bolt snapped. Drilling out the bolt is not cost effective. New stem required.

Afterwards I realised that I should have progressively tightened the opposing bolts. Too much lateral pressure , I'm guessing.

Now the question:
Is the stated pressure on the components an absolute limit?

Or should I tighten to less than the stated pressure?

if its carbon its more important

but i normally tighten it slightly less than the specified limit....

[Mulger bill]

Tighten to the stated number but where multiple bolts are involved (eg, stem faceplate, Shimano cranks, stem steerer bolts) do so in increments, evenly across all bolts.

This.

I'm glad I'm not the only one to have pulled this trick.

[winstonw]

it's possible whoever tightened that bolt previously overtightened it, and stressed it.
If I have someone else service my bike these days, I often check critical bolts with a t.wrench before I ride it. rarely have all been tightened to spec...they can be grossly over or under. I rarely see a LBS mechanic use a torque wrench.

the other option is you didn't set the t.wrench to the right torque, or it is right out of calibration. practise using your wrench. and always zero it when finished, to preserve the spring mechanisms.

if the bolt snapped before you tightened any of the other bolts, then bolt failure is not likely due to tightening completely to spec first.

it's also a good idea to put marine grease on all bolts. when tightening bolts, it helps the tension build up more gradually.

[toolonglegs]

Unless you clean and lube the threads then you are probably over tightening them with a torque wrench... that's why I never bother using one.

[sogood]

Unless you clean and lube the threads then you are probably over tightening them with a torque wrench... that's why I never bother using one.

For you, it'll break anyway. So 'torque to spec' leads to no practical difference.

[scirocco]

Unless you clean and lube the threads then you are probably over tightening them with a torque wrench... that's why I never bother using one.

Isn't it the exact opposite?

[jacks1071]

I rarely see a LBS mechanic use a torque wrench.

Think about that statement the next time you let one of those monkey's touch your bike.

[toolonglegs]

Unless you clean and lube the threads then you are probably over tightening them with a torque wrench... that's why I never bother using one.

Isn't it the exact opposite?

Yeah probably... But you get the idea :-p

[Duck!]

I rarely see a LBS mechanic use a torque wrench.

Think about that statement the next time you let one of those monkey's touch your bike.

I do not appreciate being called a monkey, thank you very much!

[jacks1071]

I rarely see a LBS mechanic use a torque wrench.

Think about that statement the next time you let one of those monkey's touch your bike.

I do not appreciate being called a monkey, thank you very much!

Are you saying you're an LBS mechanic and you don't use a torque wrench when working on your customer's bikes?

http://www.cyclingnews.com/features/tor ... o-use-them" onclick="window.open(this.href);return false;

[Duck!]

I am a LBS mechanic, and I do use a torque wrench. I take offence at your implication that by definition, according to your quote, that I am a monkey.

[jacks1071]

I am a LBS mechanic, and I do use a torque wrench. I take offence at your implication that by definition, according to your quote, that I am a monkey.

I'm sorry that you misinterpreted the comment. LBS mechanic's are not by definition monkies, I'm quite sure there is some very good ones and in fact I know a few of them. Any mechanic who works on your bike and doesn't use a torque wrench, then the nicest thing I could call them is a monkey.

Anyway, I thought you were a duck?

[thomashouseman]

Anyway, I thought you were a duck?

[rebilda]

A torque wrench is not a "magic wand". It is really just a tool to prevent some of the Ham fisted mechs out there with 10,000V in the arms and no lights on upstairs, from snapping every bolt they lay a hand on.
Some people have a "Fear" menatlity when tightening bolts and end up over tightening to the point of failure. I've seen people wreck machine parts, even when using a torque wrench, simply because they didnt know how to use them correctly.
An experienced mechanic, would know how the allen key feels when the correct torque is reached, and not over tighten due to experience.

On another note - how is drilling out a broken bolt, not cost effective??
Sorry, i'm not trying to be condecending. I suppose if you had to go out and buy all the tools necessary for the job (including the drill). If the bolt was snapped under load, and doesnt have any loctite on it, it should nearly just tap out using a centre punch and a small hammer (200g...not a club mallet)

[RonK]

Kinda amusing how people bag experienced mechanics for not using a torque wrench, while amateurs tell of using a torque wrench and still breaking bolts anyway.

[winstonw]

I accept some, not all, mechanics might develop a reasonable feel, and get away without using a wrench much of the time.
However, 2 years ago, my ex's sons and 3 of their mates all bought roadies with 105 groupos. all from different LBSs.
I kid you not, that each bike had a mechanical failure within a week due to bolts not being tightened adequately.
In fact, several of the failures were life threatening - bars suddenly came loose when out of the saddle on a busy road, chain jammed during big effort, when FD twisted locking up chainring and chain.
I had at least 3 issues after LBS services before I decided to commit to more of the servicing myself...and I changed LBSs to a guy who is well respected in Brisbane. I take it to him if I feel the frame has been compromised. But I even check torque after he has had it now. It's a small piece of insurance for the piece of mind it gives when descending at speed.

[rebilda]

I accept some, not all, mechanics might develop a reasonable feel.

Beleve me. I have known plenty of Experienced mechanical Technicians who would fall into the "10,000V at the arms and no light on upstairs" catagory.
That term came form one of my Geman Colleages who has spent a fair amount of time on jobs in the USA.

However! there is NO excuse for leaving a bolt loose!!

In my line of work, a loose screw has the potential to cause $50K - $100K damage to a printing press.

[jacks1071]

Kinda amusing how people bag experienced mechanics for not using a torque wrench, while amateurs tell of using a torque wrench and still breaking bolts anyway.

I had a customer recently put 40Nm into the alloy cone on the end of his wheels instead of onto the cassette lock ring. I guess nothing is fool proof.

[winstonw]

However! there is NO excuse for leaving a bolt loose!!

In my line of work, a loose screw has the potential to cause $50K - $100K damage to a printing press.

I think a problem for many LBS mechanics is they are continually interrupted, and no matter how good their "feel" is, if they lose track of what they've done, bolts get overlooked. The only surefire way to work effectively on bicycles day in day out, is to have a check list that requires ticking when a bolt (or several) have been "finalized", as is the convention in many fields. However, I suspect most in the industry would see that as admission 'their elevator doesn't go to the top floor'!

[RonK]

Kinda amusing how people bag experienced mechanics for not using a torque wrench, while amateurs tell of using a torque wrench and still breaking bolts anyway.

I had a customer recently put 40Nm into the alloy cone on the end of his wheels instead of onto the cassette lock ring. I guess nothing is fool proof.

God forbid that any of these amateurs ever encounter torque-to-yield bolts. What ever will they do then...

[rebilda]

However! there is NO excuse for leaving a bolt loose!!

In my line of work, a loose screw has the potential to cause $50K - $100K damage to a printing press.

I think a problem for many LBS mechanics is they are continually interrupted, and no matter how good their "feel" is, if they lose track of what they've done, bolts get overlooked. The only surefire way to work effectively on bicycles day in day out, is to have a check list that requires ticking when a bolt (or several) have been "finalized", as is the convention in many fields. However, I suspect most in the industry would see that as admission 'their elevator doesn't go to the top floor'!

A Bicycle isn't all that complicated TBH.....
But in saying that, I did have a well respected local Bike Mechanic call me, after I picked my bike up from a repair once, asking me to double check the tension on my crank bolts. Ok, I knew he had been getting smashed in the workshop and obviously had the thought in his head that he couldn't remember tensioning those bolts. I have had the same feeling and gone back to a customer to double check a bolt before. I know I always run through what I have done and act on any suspicions that I've missed something.
I was glad he called. It means that he thinks about what he does and is concerned about the quality of his work.

(BTW - the bolts were tight.)

[toolonglegs]

However! there is NO excuse for leaving a bolt loose!!

In my line of work, a loose screw has the potential to cause $50K - $100K damage to a printing press.

I think a problem for many LBS mechanics is they are continually interrupted, and no matter how good their "feel" is, if they lose track of what they've done, bolts get overlooked. The only surefire way to work effectively on bicycles day in day out, is to have a check list that requires ticking when a bolt (or several) have been "finalized", as is the convention in many fields. However, I suspect most in the industry would see that as admission 'their elevator doesn't go to the top floor'!

There's how many bolts on a bicycle?, there's only about 30 on my CX bike, it really isn't that complicated... There's is never an excuse for leaving a bolt loose.
As a mechanic ( motorbikes ) in a previous life, I can tell you that I got the "feel"... The only time I would use a torque wrench was on things like cranks, heads and cams etc.
Thats why I freak watching someone crank up a stem bolt etc with a cheap torque wrench ... But then again some people are butchers no matter the quality of tools in hand.
PS I should add that if I was working on modern velos all day like Duck, no matter how good I thought my feel was I would use a torque wrench on flimsy carbon tabs etc... If for anything, just to cover my arse when the cracks appear.

[ironhanglider]

However! there is NO excuse for leaving a bolt loose!!

In my line of work, a loose screw has the potential to cause $50K - $100K damage to a printing press.

I think a problem for many LBS mechanics is they are continually interrupted, and no matter how good their "feel" is, if they lose track of what they've done, bolts get overlooked. The only surefire way to work effectively on bicycles day in day out, is to have a check list that requires ticking when a bolt (or several) have been "finalized", as is the convention in many fields. However, I suspect most in the industry would see that as admission 'their elevator doesn't go to the top floor'!

There's how many bolts on a bicycle?, there's only about 30 on my CX bike, it really isn't that complicated... There's is never an excuse for leaving a bolt loose.
As a mechanic ( motorbikes ) in a previous life, I can tell you that I got the "feel"... The only time I would use a torque wrench was on things like cranks, heads and cams etc.
Thats why I freak watching someone crank up a stem bolt etc with a cheap torque wrench ... But then again some people are butchers no matter the quality of tools in hand.
PS I should add that if I was working on modern velos all day like Duck, no matter how good I thought my feel was I would use a torque wrench on flimsy carbon tabs etc... If for anything, just to cover my arse when the cracks appear.

Hmm winstonw knows mechanics with a few screws loose, and now we learn that TLL used to be a plumber.

Ancora Imparo.

Cheers,

Cameron