Imagine this: Your chain is hanging down like a wizard's sleeve and you want to tighten it. You lay out your tool kit, hit your favourite music on Spotify and whistle along to it.
You slip the wrench onto the nut. But it won't budge. It's ok, let's pull harder, you say. But it still won't move. Not even a micrometer.
So you now have to contort yourself all over the bike to get better lever. It still doesn't move. It felt like the nut might as well had been welded on.
Now, as sweat pours off your brow, you resort to hammering on the shaft of the wrench. Nope. Nothing's happening. So you stand on the wrench. The nut suddenly began to move and your foot slips off it as you almost hit the ground, and all sorts of swear words known and unimaginable are heard by your neighbours.
Is this another of my writer's imagination gone wild? Unfortunately, no. It just happened to me this morning.
What cause it?
The answer is simple: The so-called mechanics in most workshops, except for a very few, have a love affair with the pneumatic impact wrench, or more popularly called the air gun.
19mm nut? Air gun. 14mm bolt? Air gun. The lazy buggers would even use it on 10mm bolts. I sometimes wonder if they use the gun on their partners, too, FFS.
They simply do not understand that different bolts and nuts for different applications have different tightening torques. For example, the the rear axle nut is usually requires between 90 to 110 Nm, depending on the size of the bolt, which usually also depends on the size of the bike. The 14mm bolt holding the rear brake caliper bracket of a Yamaha Ysuku needs just 39 Nm. And yet they'd KLAK KLAK KLAK KLAK KLAK on these fasteners unscrupulously.
Thus a 15 minute chain tightening job became 1 hour... And that's without breaking a bolt or nut!
I've experienced a bike's rear axle bearing breaking during a ride, which resulted in the bike riding sideways like a crab too, because the nut was overtightened with a pneumatic wrench!
So, what's the solution?
My first solution is to frequent a workshop that observe correct workshop practices, such as using a torque wrench. (There are two I usually go to).
Secondly, if you don't fancy so, buy yourself a good torque wrench. They aren't so expensive. Only caveat is you need to take good care of it.
So, if I visited a workshop due to an emergency or other situations and they used the pneumatic wrench, I'd loosen the fasteners and retighten them to the correct torques.
Tips on using the torque wrench
1. CLICK or KLAK ONLY ONCE. I repeat: ONLY ONCE. Clicking once means you have reached the desired tightening torque. Clicking more than once means you are introducing more than the desired torque. I learned this directly from a German engineer while working for Mercedes, who gave me an effing in front of everyone on the workshop floor which I will never forget. Checking this with other qualified engineers confirmed this.
2. DO NOT drop or throw the wrench around. You may damage the internal clutch and it will have different torque readings after that.
3. DO NOT use it to loosen fasteners from the beginning as you may damage its internal clutch. You ought to use a normal wrench to first loosen a fastener, then continue with the torque wrench if you so wish because it has a built-in ratchet.
4. Set the torque back in the lowest setting and store the wrench to maintain the spring's strength.
5. Store it in the case that it came in.