grumpus

The lowest setting on a typical automotive torque wrench is too high for most bike parts.

Duragrouch

The coil spring and mechanism in a click-stop torque wrench is steel. If not overstressed and not at (very) elevated temperature, steel does not "creep" or "take a set" at room temperature. Plastics/polymers/elastomers/etc are different, and can take a set. Lead, solder, ice, can also creep at temps below melting point. From wiki:
Steel, at room temperature, no.

Kontact 

Apparently torque wrenches overstress their springs, because every torque wrench maker says to release the tension.

Camilo

There's lots of places to get torque devices (wrench, screwdriver, whatever) in places other than auto parts stores, if what you say is true (which isn't the case where I live..Auto zone has one, fwiw). I only mentioned auto parts stores as an example of many places I personally would check out.

But all I'm doing is that if the OP feels accurate torque is necessary, his first step other than guessing should be to look locally. I have no idea what's available where they live, but I just suggest they look around.

Duragrouch

May be just "old practice", or it may have to do with whatever is the sliding "cam" surface where it overrides the spring force, perhaps that is not steel.

Kontact 

So what was your point? Do you advise against detensioning the wrench between usage or not?

Leisesturm

Sorry people but I completely lost it after only about eight posts and came right here to say: I've never owned a torque wrench. I've built bikes and maintained bikes for 50 years and there isn't anything I can't do to or for a bike, and apart from cross-threading a replacement bottom bracket 8 years ago, that had to be re-tapped by my LBS, I've never broken anything, or had anything fail on me on the road. O.p. scenario is making my sides hurt I am laughing so hard. And the ferocity with which follow on posters are suggesting things like overnight delivery of a new wrench ... oy ... enough ... stop. Please. O.p. torque that nut to 8hm and give it a smidge more, or don't. If 8nm isn't enough, you will know because your crankset will explode, mid-race and you will DNF. Lesson learned. Develop 'the touch' that all good mechanics must have to get to the next level.

choddo

Getting torque wrenches delivered overnight here is a case of going on to amazon and 3 clicks. It’s not like having a viable donor kidney delivered.

Duragrouch

I generally agree, never used a torque wrench... until the left crank arm on a hollowtech II came loose. I wasn't using enough torque, partly perhaps due to the short lever arm on the allen wrench. But I pulled out the microtorque wrench and bits, did it to spec, way easier because a much larger moment arm. And it hasn't come loose since. Way back in the day, I had to replace a freehub body, big 10mm bolt, and my guess was, that torque was critical. I put the long end of the allen wrench inside the hub, put a pipe on the short end, measured out a lever arm, then did my best to apply the proper load to get the target force, and by pulling and not pushing, pulling is easier to compare to lifting a known weight.

Duragrouch

Well, if used a lot, I wonder about the wear of constantly screwing the handle up and down, but probably no worries there, so I guess I'd follow instructions and detension it. I'll have to look at the instructions for my torque wrenches. EDIT: Yeah, it says turn back down to lowest setting when done.

$10, brand frickin' new, 10 years ago. They were always on sale at HF, reg $30, on sale for $10, any size:

FBinNY 

Sometimes "best practice" is unrelated to mechanical considerations.

For example dive computers automatically reset oxygen to 100% at midnight. This is a safety measure done to force divers to set the correct mix before diving, rather than assuming anything.

Likewise, best practice would be to set a torque wrench to zero so one cannot get into trouble by taking the setting for granted.

Not saying that's the logic behind torque wrench shop practice, but offering it as a possibility.

There are countless examples of things done a certain way, but the reasoning behind it being forgotten. Like why "normally open" valves are always left 1/8th turn off from full open.

Duragrouch

(above) Makes sense.

choddo

I want to know why normally open valves are kept 1/8th from open.

Duragrouch

So you don't break it by trying to open it more and just think it's stuck. You open it more, it moves, then reaches its stop, and you know that's the limit.

FBinNY 

Various reasons depending on the application. Where temperature may be a factor it prevents jamming with shrinkage.

But the usual reason is insurance against panic. In an emergency it might be necessary to quickly close the valve, ie. to prevent flooding.

Under stress an operator trying to close the valve might turn it the wrong way. Assuming it's stuck he'll continue, losing precious time before recognizing his mistake.

OTOH if the valve is free to turn in either direction, and he starts out wrong, he'll know it's not stuck, and correct himself after that 1/8th turn.


It can also be an aid for inspection. On many valves you can't see whether they're open or closed. By leaving the valve cracked off, it's easy to verify that it's open with a quick tweak.

ScottCommutes

Just speaking from ordinary life experience, coiled steel springs don't last forever when constantly loaded. I'm thinking of the springs pulling against a garage door, or the suspension springs in a car.

Regardless of the actual physical reason, if accuracy is important it makes sense to store a spring in its most comfortable state.

Trakhak

From what I remember reading somewhere, what wears springs out is cycling them through a range of motion. Whether the springs are under compression or tension or neither apparently doesn't matter.

So, at least theoretically, changing a spring from a state of tension or compression to its most relaxed state as a matter of course (and then, of course, loading it again later, when it's back in service) would result in the spring wearing out faster than if you were to leave it as is.

FBinNY 

If cycled within its working limits a spring will last nearly forever. Storing it loaded or unloaded doesn't make a difference. If that werent true, your car would slowly lower sitting in your driveway.

Springs don't change their constant (get weaker)unless distorted significantly. Otherwise they have 2 failure modes.

If stretched or compressed beyond their yield limit they won't return to their original length. A typical example is a bathroom scale that no longer zeros out after an extremely heavy person uses it. However, the constant is unchanged, so you can reset zero and continue using it. Old cars and trucks with a history of being overloaded sag for this reason.

The other mode is fatigue, whereby repetitive flexing beyond the fatigue threshold causes stress cracking and ultimately, collapse.

Trakhak

This reminds me of a long-gone car of mine, a 1960 Plymouth Golden Fury, bought in 1977 from the original owner, in Brooklyn. The engine mount arrangement was apparently a one-off design: big hinges in front, big horizontal coil spring in back.

Unfortunately, the first time I hit a good-sized pothole, the coil spring let the engine sag enough for the fan blades to slice into the radiator. Over the next couple of years, I went through three radiators. Finally sold it to a friend for a dollar.

I've wondered ever since whether there might have been a workaround for the punctured-radiator problem.

Maybe something using bike inner tubes.

Further off topic:

Earliest bike inner tube hack was towing a friend on his motorcycle to a repair shop in 1974.

Latest: 2 hours ago, 24 x 2.00 tube stretched over the end of the bathroom sink drainpipe, secured with a Fernco coupler, and fed down the pipe that connects to the main waste pipe, bypassing a leaking section that would require tearing out a lot of Sheetrock to access.

Should last forever. As the French say (more elegantly, no doubt): nothing endures like the provisional.

FBinNY 

Don't know your particulars, but a SOP fix for sagging or weak coil springs was (still is?) to fit a study rubber balloon into the spring, and inflate it firm enough to add some lift. The coils braced the sides, and you ended up with a poor man's tunable, air ride suspension.

Duragrouch

Also known as Air-Lift (tm), I used them on a wagon I used to own. Not because the springs sagged, but going to and from college and fully loaded, I wanted a level ride. I didn't want air shocks as the mounting points for them are small compared to the spring bases top and bottom. Worked fabulously. I ran separate air lines for each to improve roll stiffness, and I ran the air lines forward inside the lower trailing arm to the forward pivot, then a short jump to where I put the schrader valve, held in an existing frame hole, that way not a huge lengthening/shortening of running the line to the body just above the axle, as indicated in the instructions. The air bags were red flexible plastic, not as stretchy as rubber but far more durable and didn't need that much stretch. Oh, and ordered from the Sears catalog, back when there was a Sears and a catalog.

Duragrouch

Or as I heard it, "There's nothing quite as permanent as a GOOD temporary fix."

I dunno about that year Fury, but in the years just prior, according to wiki:

grumpus

Years ago I cut a small slot in a water pipe while fixing the floor - I clamped a bit of old radiator hose over the cut, meaning to go back later with some solder ...

Camilo

Great! There's no need for any torque wrenches ever because you don't need one! I'll rest easy .

FBinNY 

There's no need to get sarcastic. While there may be some jobs where close adhesion to torque specs is important, the reality is that most jobs are far more forgiving, and torquing by "calibrated hands" is fine.

We might also note that there are two types of published torque specs. Some may be critical with limited margin for error, while most are simply a way of offering guidance, since things like "hand tight" don't make the grade anymore.

There's also a cultural difference. For decades, mechanics learned hands on from more experienced mechanics, with knowledge passing from generation to generation this way.

Some time back, along with the creation of the internet, how we learn changed, and folks needed to communicate info like how tight is right in different ways, not dependent on the old one to one method.

So, I suspect we have s cultural divide based on when and how each of us learned. I, for one, am not invested in how anyone does any job, as long as they do it well.