digger

I just purchased a Filzer Torque Wrench (TR-1) from MEC.

I have tried it on my Cervelo carbon fiber bike but I think the torque on this wrench is not right.

This bike was purchased new, *just 4 weeks ago*, at my LBS. So the bolts should have been set correctly.

When I set the wrench to 5.2Nm to tighten the bolts on the stem, they required one full turn before the wrench clicked. I seriously doubt that the bike shop set the torque too low.

Out of concern that the wrench is incorrect, I set it at 3Nm, 1.5Nm less than the required 4.5Nm for the seat post bolt. I eventually stopped tightening that bolt after one full turn of the seat post bolt for fear of breaking the frame. Again, I would imagine that the bike shop would have torqued the seat post bolt properly before I bought it. I have been using this bike on the trainer and the post have never slipped,so that is telling me that the bolt is tight enough.

I am not too confident in this wrench. Any suggestions on testing to see if the torque is right?

DaveSSS 

The only practical way to test a click-type torque wrench is against a beam-type. Beam types require no calibration.

Expecting a stem bolt on a bike from a LBS to be properly torqued is foolish, IMO. They are not that likely to have used torque wrench.

I've been wrenching on bikes for 25 years and using carbon parts for over 10 years. I've never used a torque wrench on any M5 or M6 bolt yet. Never had slippage problems or damaged anything yet.

If you can't manage to do a decent job of tightening these bolts without a torque wrench how are you ever going to make an adjustment out on the road? It pays to know what a moderate torque feel like, using a short handled hex wrench or a 4-5-6 Y-style wrench.

FBinNY 

+1 on the above with one minor quibble. It isn't that beam torque wrenches don't need calibration, it's that there's no mechanism to correct calibration errors. They depend on the flex properties of the beam and their accuracy depends on their quality.

The way to calibrate a torque wrench is to engage the drive end to a fixed bolt head, or gently clamp it in a vise with the handle perfectly horizontal. Hang known weights at a known distance and compare either the beam reading or "click point" to you're known torque (weight X distance). It's a straight forward process and easy to do with any degree of mechanical and mathematical skill.

As far as torque specs on bikes, it's more complex than many believe. The ratio of torque to holding power (bolt tension) varies with thread friction among other things, so it's important to know if the torque spec is for a dry or wet thread. Also because there's a difference between static and sliding friction, bolts must be torqued to spec. in a single steady motion, not tightened by degrees. Also the torque to break a bolt loose will always be higher than the torque just applied to tighten it.

Torque wrenches can be very useful where all the manufacturing and procedural specs are carefully adhered to, but otherwise they can be misleading and create as many problems as they solve. They are most useful at high loads but not at all a replacement for good hand feel at the low end of the range.

digger

I have a fairly large beam type, but it is high torque.

No doubt they can "feel" what the proper torque would be. But when working on expensive frames, I would have thought that it standard practice to use a torque wrench as a safety factor.

Well, that's great for you, you have the experience, I'm glad for you. Since, this is my first carbon bike, I bought a low-torque wrench to ensure I do not cause damage.

Ergo, the reason I bought a torque wrench...to learn.

How do you get your head through a standard sized doorway?

digger

I suspect this is the case here. The seat post clamp is plastic, combined with a stainless steel M5 bolt, creating less frction. I do not believe there is grease on the bolt.

The owner of the LBS, where I bought this bike, had shown me how to tighten the seat clamp without a torque wrench. However, being new to carbon and not use to what 4.5Nm feels like, I felt a torque wrench would help.

DaveSSS 

I gave you the facts. Find a small beam type wrench if you think your click type is off. Then get the feel for the proper torques. Everyone has to learn sometime, but relying completely on a torque wrench makes for a poorly trained mechanic.

One of the drawback to click-type wrench is they must be calibrated and if something goes wrong with one, you often find out when you strip threads or break something because of a malfunctioning wrench.

The real fact is that the torques are not as critical as most manufacturers would have you believe. Those 5Nm maximum torques are more for legal protection than anything. Tightening a stem to 6-7Nm should not cause any damage.

I did a real-world test to prove that it was truly difficult to cause damage to a well made carbon steering tube. I took a cutoff scrap of steering tube, and installed a stem on it that had two large M6 clamp bolts. I did not put a compression plug into the steerer. I used a long-handled hex wrench and gave a ridiculous pull to both bolts. I'm amazed that the threads didn't strip. I don't know how much torque was applied, but it was many times what any sane person would do and it caused no damage at all.

Most cases of carbon breakage are either due to poor quality carbon or to a poor fit of the stem to the bar or steerer. Most stems are precision forged, but get little or no post-forging machining. Ridges along the edges can cause stress concentrations and fractures. I always check stems for smooth burr-free edges before installing and file a small chamfer on any edges that are suspect.

FBinNY 

rather than rely on a torque spec or tool of unknown reliability, why not apply a functional torque logic. You're not dealing with an aircraft engine bolt which might vibrate loose unseen and cause a crash.

It's a bicycle seat clamp whose sole job is to keep the post secured. Tighten it until it feels tight. Check by trying to twist the saddle. If it seems OK ride it. If nothing moves you're in, if the seat moves tighten a bit more. Once the post is secured enough to meet your needs any tighter is needless strain on the parts.

This procedure is not appropriate for a professional mechanic working on other peoples bikes and so a pro would have to develop good consistent hand skills, but for anyone working on their own equipment "good enough" is good enough.

kycycler

As a former aircraft mechanic for major airline I can state unequivocally that the only way to gurantee the accuracy of any torque wrench is to have it tested against a standard at a calibration lab. With that said I have to agree with the statement about the torque of the stem bolts above.

FBinNY 

There is no more accurate way to calibrate torque wrenches than properly conducted deadweight tests.

One of the reasons that regulated industries such as aircraft send their wrenches out for testing has more to do with law than precision. These days government regulators frown on self certification, so by sending the wrenches to a third party they not only get accurate calibration, but third party verification that it was done.

HillRider

I'll try to be a little more tactful but I also disagree with this. For a new mechanic the only reasonable way to learn how the proper torque settings is to use a quantifying (i.e. torque) wrench and see how tight various torque settings feel. After some experience, you can dispense with the wrench and go on feel and past learning. Sheldon Brown used to poo-poo torque wrenches too but he had decades of experience.

There is a "rule" mechanics use; "new mechanics overtighten small fasteners and under tighten big ones." The number of postings we see about loose crank arms and bottom brackets supports this.

operator

He doesn't deserve tact. Any, whatsoever.

Torque wrenches allow anyone, from zero to most experienced to consistently and accurately set bolts to their proper torque. I mean with the carbon spray that digger seems to think everyone is supposed to use on carbon parts, you'd need almost no torque on bolts at all! Why even bother with the wrench?

operator

Realize where DaveSSS is coming from. He's wrenching on his on bikes not for a high volume bike shop that deals with hundreds of repairs a month. Landscape differs dramatically when you're wrenching on the latest CF components.

That static test is representive of nothing, i've done the same thing with a throwaway 1 1/8 carbon fork that retails for ~ $500 - yes it takes more torque than the standard 5nm. So what? Can you guarantee that the part is not going to fail sometime down the road at 7nm? Maybe more?

Why even gamble in such a fashion, when there is a *tool* to allow you to properly set the torque, nearly exactly the same each and every time? Why retro-grouch like this? I don't get it.

digger

Oh stop. I had disproved your claims of your experience by outlining your flip-flopping back and forth in that particular post. You obviously couldn't stick with one straight answer, ergo you did not know the answer.

You, laddie, are a hack. You get your information off the internet and parade yourself here as experienced. You've been discredited.

operator

I've been discredited!

Holy ****! Help me bikeforums

operator

Oh, i'm sorry. This thread isn't on the internet, nor are you asking for information. You, laddie, are a hack by your own standards. Any other genius commentary?

Which shop do you work for in Nova Scotia? Or are you just some random home mechanic who thinks they are the world's greatest $THING. One who can't even determine if a torque wrench is working properly?

I think that carbon spray ought to be used on all your parts before you even *torque* those bolts!

digger

That is what the LBS owner described to me. Do not use a long handled allen key, but rather a Y-type. Snug the bolt into the clamp and turn 1/4. Twist saddle to see if post moves in seat tube. If yes, give 1/8 of a turn, check and repeat until saddle (post) does not move.

However, being a sufferer of C.O.S. (Chronic Overtightening Syndrome) I thought it best to have a torque wrench to ensure I do not overtighten and as Operator states, "Torque wrenches allow anyone, from zero to most experienced to consistently and accurately set bolts to their proper torque." To me, in this case only of course, Operator is correct.

However, many of you, being more experienced than Operator, seem to be saying to me that a torque wrench is not necessarily a wise choice? Other factors come into play here? Ok, perhaps I should return this thing before I do evil (and become like Operator) and check into those beam-type torque wrenchs at Park Tools (I'll probably have to take out a second mortgage on the house though). :-)

I wonder if they sell that carbon spray as well......?

digger

There is no end to the entertainment!

EDIT: I am some random home mechanic and I KNOW I am the worlds greatest thang.

digger

Interesting, and it makes sense that some safety margin is put into these torque specs. My issue is with the seat post clamp, not the stem bolts really. I am not going to tighten it any further with this wrench until I learn some more.

operator

What is certain is that you have neither wrenched at a shop for pay, nor assembled any bike from the crappiest loss-leader at a low end commuter shop to a $15k pinarello. I hope one day you realize your ignorance long enough to actually learn something from people who are being paid to turn a wrench, those that are legally liable for the work that they do.

CCrew

Operator is correct. And a decent torque wrench is a precision tool, not one to be dropped on the floor or just thrown around loosely.

I'll tell you like I was told, and I grew up with a father that owned a precision machine shop: : "There's no such thing as a calibrated elbow" which is why you use the proper tool. Since all his work was MIL-SPEC, all tools like that had to be sent out to be calibrated.

DRietz

Warning. I am hijacking this thread.

How much torque do I use with a titanium seat post and a saddle with carbon rails? I assume to just tighten it until the saddle can't move, obviously...

mechBgon

I'd also suggest lubricating the threads of the bolts, and the contact surfaces of the bolts' heads, so that the torque you do apply is not being excessively consumed by friction just to turn the bolt.

One of my co-workers gave a great explaination for why he prefers beam-type or dial-type torque wrenches to clickers (besides having to set and re-zero them): you can see what's going on, by watching the dial or the scale. You're not just waiting in limbo for a click that may or may not come. If you're not happy with your clicker, return it and get one of the alternatives, such as the Park Tool-branded mini-beam model or its equivalent.

I can also remark that a reality check never hurts. At our shop, we discovered that the "official" torque spec for our bikes with quill-style stems was producing marginal results... it was possible to hold the front wheel between one's knees and spin the stem in the fork. With one hand. That's at the torque specified by both Major Bike Company "T" and by Sutherlands.

In the end, I was only satisfied after exceeding the official torque by about 30% and using carbon "grit paste" assembly compound on the quill and wedge. They would've stayed put under normal riding, but a sudden reaction to, say, having the front wheel drop over the edge of the MUP's pavement, might've resulted in a spun stem.

cia dog

Have a torque wrench calibrated at a certified test center will cost about $150, more then you paid for the wrench! So the only practical way to certify it is at home. It's a little weird but it works for far less money then sending in.

Step1
Mark the center point of the wrench head on the back of the torque wrench. Use a a pencil or marker.

Step 2
Measure from the center point to the point at which you apply the most pressure when using the wrench. Write down this measurement as "Distance 1" either in inches (if your wrench measures in inch pounds) or feet (if your wrench measures in foot pounds).

Step 3
Clamp the wrench bit in a vise horizontally. Using string, hang a 20-pound weight from the handle of the wrench.

Step 4
Move the weight along the handle of the wrench until it measures exactly 40 foot pounds or 480 inch pounds. Measure the distance from the center point on the head of the wrench to the string and write this measurement down as "Distance 2."

Step 5
Divide "Distance 2" by "Distance 1" with the calculator to find the calibration ratio. This ratio is the difference between the the settings on your wrench and the actual force needed to acquire a "click" at that setting.

Step 6
Set your torque wrench for a specific application by multiplying the required torque of the bolt by the calibration ratio. For example, if a bolt requires 43 foot/pounds of torque and the calibration ratio is 1.124, multiply 43 times 1.124 and set your wrench to 48.3 foot/pounds.

BUT, and I mean a BIG BUT, really on a bike it's not all that critical and more then likely the wrench is calibrated from the factory + or - 4% which is more then accurate enough for what your doing.

digger

Correct.

That's why I'm here.

If you do work at a bike shop, they must pay through the nose for insurance to cover the liability issues I have proven that you create. As I said before, you must own a shop, no one would keep you on for long.

digger

Who said anything about throwing it around? Of course Operator is correct; the right tool for the job. I'm just pullin' his strings, he's easy to set off.

This torque wrench was bought new, so I can only assume it was properly calibrated and had asked if it could be checked.