exRunner

Do you have any idea how that is done? Because if you did you would realize how wrong you are. Bolt stretch either requires specific conditions and very special equipment, or specially designed fastners and a lot time. It is very limited in industry.

DMF 

Yeah, we know that (or at least I do). But it is far more accurate than using a torque wrench. Fastener torque is merely an easy way of approximating stretch. Even with highly accurate wrenches the actual results can vary widely. If clamping force is critical, it's best to measure stretch directly.

PlatyPius

I have one. It's full of Snap-On, Matco, and Mac tools, too.

Of course, I didn't BUY the tools when I was a bike mechanic.....

DMF 

aha!

mike047

I worked in Naval Aviation for 13 years and NEVER used a torque wrench on ANYTHING.

DMF 

So, uh, how did you determine whether a bolt was tight enough (or not)?

Don't aircraft manufacturers provide specs for clamping force?

ScottNotBombs

I used a matco torque wrench when I first put on my carbon fiber bars and stem, but after that just guessed... The only time I've used it on my car is for flywheel and pressure plate, but only because it spins at 7,500 rpm. The experienced mechanics at the shop I go to rarely use torque wrenches..

mike047

If I remember correctly[ I served from 64-77] I never saw a torque wrench while I was in the service. I am sure that intermediate level engine work required its use. The line maintenance that I did never specified ones use. I removed skin panel and parts of spar and turtle back supports on fighter planes during my work but never torqued the fasteners and was not required to do so. I was a final safety of flight QC in my electronics area and was never required/asked about torque on fasteners we removed and replaced. It may have and likely has changed.

I use a torque wrench on my bikes and one is a park and the other is a BlackHawk, more than sufficient for my use.

nahh

If it's tight enough not to slip, and not too tight to break or bind, you're good. Park Tools torque wrenches get you in that ballpark just fine.

Sometimes people forget we're talking about bicycles, they don't fly or go super fast. You pedal them. it's quite simple.

mechBgon

Yeah, I was working on a Shimano XT M760 crank today. The sticker on the left arm says to torque the bolts to 10-15 Nm. How's THAT for a range. And this is for mating two precisely-made parts made by the same manufacturer, not Brand X stem on Brand Y steer tube and Brand Z handlebar. The shop's new owner is into having things torqued with a torque wrench, and I'm paid by the hour, so hey... bust out the Snap-On TQFR50 and *clink* them thangs a couple 1-2 cycles But I can do them fine by elbow too.

Yeah, I think the OP should be sentenced to having an actual bike shop of his own

Nessism

I have three different Snap-On torque wrenches, in-lb dial type, ft-lb dial type. and one of those large split beam type, and I don't use any of them on my bikes.

Booger1

Bolt stretch can vary widely with just the difference in the lube used,oil,moly,grease,nothing.

Any reasonable torque wrench is fine for using on a bike,but there are better ways.

In my line of work,I measure bolt stretch everyday,so I might know something about it,maybe.....

It's so special,you'll need a $10.00 mic from Harbour Freight for some bolts.If you have blind holes you'll need gun drilled bolts and $10.00 depth gauge from Harbour Freight.Even this would be far more accurite than the best torque wrench.But all of this has nothing to do with bicycles....

mtnbke

It depends on what you're talking about...

If you're talking about a split beam torque wrench, the kind that Precision Instruments make, and are also sold under the Snap-On label, well, those are very durable and extremely resistant to abuse, including getting dropped.

However, if you're talking about a cheapie open beam, or whats refereed to as a micrometer torque wrench, like what Park's best torque wrenches are, and what the Pedros's wrench is, well those are EXTREMELY sensitive to being dropped and can't be used reliably if they have been dropped, even from only about a foot up. Those type of micrometer torque wrenches are usually only accurate to around 4% of the top of their scale, aren't accurate at ALL in the first 20% of their range, and the calibrated spring is completely susceptible to being really far off if its been dropped or if it hasn't been returned to its minimum setting after EVERY single use. For this reason people who wrench for a living hate these things. It costs over $50 to get NIST traceable calibration, and its a complete pain to have to dial 'em down after every use.

If you think that torque wrenches aren't used constantly in aviation or in precision manufacturing, you're nuts. For crying out loud, even your lug nuts on a crappy old beater car should be torqued to a specific torque, lest you warp your rotors.

Where torque wrenches are critical is the exact areas in cycling where you need precision accuracy, on soft aluminum, and magnesium alloys, and carbon fibers. Heck, a Park torque wrench either the cheapie open beam type or the micrometer type isn't all that accurate to begin with, and if its been in a shop where the wrench hasn't been dialed down after every use, or its been dropped, well, I guess its better than nothing. However, a precision tool it ain't.

There is a reason that the Snap-On Torque-O-Meter, made by Precision Instruments, has been the torque wrench of choice for mechanics for years. Its accurate to 2% of the entire upper 80% of its range, not just the top of the scale. There is a reason that mechanics reach for a split beam torque wrench when they want a 'click' style wrench, either the Snap-On, or the Precision Instruments (who makes 'em for Snap-On). There is a reason that every motorcycle or car junkie knows these are the best wrenches in the business.

Snap-On acquired CDI, to make their wrenches in house, and it wasn't but a couple of years later that Snap-On was calling back to Precision Instruments asking if they could reestablish the relationship.

Precision Instruments (and the Snap-On non-CDI ones made by Precision) are the standard. They invented the torsion bar dial torque wrench, the split beam torque wrench, and are the standard for torque wrenches. Proto, S&K, CDI, all make pretty good torque wrenches.

Park and Pedros do not...

mtnbke

It probably was a micrometer style 'click' wrench, one that hadn't been calibrated since it left the factory, and your friend or his shop probably didn't even realize that they had to dial it down back to the minimum setting after EVERY use lest it become inaccurate. Heck, you can buy a cheap Harbor Freight torque wrench for less than $20. If you believed that it was an accurate measure of torquing you'd be a fool...

mtnbke

Its crap like this that gives the internet a bad name. Fine you were a load toad, or you got pilots coffee at the officer's club, or you were a porter, or a tactical officer, but if you're implying that you worked Naval Aviaion and worked on airframes, AND didn't use a torque wrench you're full of crap.

Like I said, in the military the torque wrenches that meet mil spec have to have their calibration checked new from the factory, before they can enter the rotation. The wrenches are tested against a bench tester constantly during the calibration cycle, and these two to four hundred dollar wrenches probably have thousands of dollars of calibration and controls spend on 'em during their life cycle.

PlatyPius

Dude, you sound like a shill for either Snap-On or Precision Instruments. Not hard to imagine either, since you live in Wisconsin; home of Snap-On, and not too far from Precision....

mtnbke

The context is why you would buy a Park or Pedros torque wrench for nearly a hundred bucks, when you could get a good Precision Instruments split beam, or something equivalent for only a couple of bucks more...

More accurate, resistant to abuse, doesn't have to be turned down, and actually accurately does its job across its range (which Park and Pedro's wrenches won't do).

mechBgon

If a part is marked for a torque range of 10-15Nm, what would you torque it to, and why?

If a part is only marked with a MAXIMUM torque spec, e.g. 5Nm, what would you torque it to, and why?

If parts are from two different manufacturers, and they have conflicting torque requirements (e.g. brand X stem and brand Y handlebar), whose spec will you use?

Would you grease the bolts/fittings or leave them as-is? What grease? Would you grease under the head, or just the threads, or both, or neither? Ti in aluminum, stainless in aluminum, stainless in cromoly, zinc-plated in cromoly, black-oxide... etc etc.


These are some factors I face on a daily basis as an LBS mechanic. It's far from a black-&-white, right-&-wrong field. Aircraft? Spacecraft? Nuclear reactors? Even a car? Ok, your stuff's all been engineered by one company, not slapped together from off-the-shelf parts sourced from all over the world, so get out your torque wrench and follow the service manual. Bikes, however... yeah. Use your torque wrench if you like, but use your common sense as well.

mechBgon

I'm curious: know of any split-beams that go down to, say, 20 inch-pounds? I have to agree that the adjustment system on my Snap-On split-beam is awesome, but its range is too high for small stuff.

Nessism

This thread cracks me up, I though this was a bicycle forum, not about military aircraft.

About 95% of all bicycle related fasteners DO NOT need a torque wrench on them. The ones that can benefit from a torque wrench, some bottom brackets or crank bolts, can be safely tightened with a a cheap beam type wrench that holds it's accuracy plenty good enough for a bicycle.

Don't turn a mole hill into a monster.

mike047

I was an Aviation Electronics Tech. Educated by the Navy for almost a year at NAS Memphis. I did not specify that I was an airframe mechanic. My work involved occasionally removing structural pieces to access electronic components for repair. I worked on airplanes for 7 combat tours during VN, when you probably weren't born. Your statement about me being full of crap is a hubristic attempt to justify your position and is inaccurate. My statement is accurate for the time period that I served and regardless of your infantile rant is ACCURATE.

When you have spent 13 years in my service shoes, you may then assail my statement and character, until then your are the one that is full of crap.

DMF 

Simple question: What good is 2% accuracy when the spec range is 50% of the mean value?


Btw, a calibration test is quick, simple, and free. Lock the drive in a bench vice and hang a known weight at mid-grip.

mtnbke

I bet your lace up and build wheels by 'feel' too, huh? You'd be suprised how many components on a bike have to be torque'd to a particular spec to avoid becoming problematic. For starters many cranks for square spindle bottom brackets have to be torque'd to a particular spec or they'll loosen and deform the crank arm, creating a chronic problem of loosening. Half the problem with the ubiquitous problem of FSA cranks chronically coming loose may be related to torque, or not, I don't know, maybe those are just crappy cranks.

I've never met anyone yet that could accurately guage 'tight' in terms of inch/lbs or foot/pound increments. Essentially there is a right way to do things and then the sloppy and lazy way and ultimately less safe way.

DaveSSS 

mtnbke...

I use a torque wrench for any bolt requiring a relatively high level of torque. The particular bolt that you mentioned would be one to torque because it's critical to the crank's function, just like the Campy UT fixing bolt I mentioned.

The FSA cranks that you referenced use a modest torque in an attempt to preload the crank bearings and still hold the left arm in place without a pinch bolt like Shimano uses. The design is flawed and doomed to problems. FSA has redesigned some of their cranks, using the same 6mm bearing width that Campy uses to create some room for a wave washer to preload the bearings, also like Campy does. Then the crank arm can be tightend much tighter and against a shoulder, I would presume since it is not regulating the bearing preload.

What I really intended to refer to is small stem and seatpost bolts, or any other M5 or M6 bolt on the bike. A good mechanic should not need a torque wrench for those. If you can't tighten those small bolts without one, how would you ever make adjustments out on the road? On a Campy UT equipped bike, the bolts I mentioned are the only ones needing a torque wrench, IMO.

Nessism

Yes, those are crappy cranks that came loose regardless of torque.

Regarding sloppy and lazy, that has nothing to do with not using a torque wrench. Give me a savvy mechanic that doesn't use a torque wrench over a hack that does.