Replacing the cranks. Apparently they can be pretty finicky about how tight they are.
Torque wrench, how critical
- Thread starter Soltydog
- Start date
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Replacing the cranks. Apparently they can be pretty finicky about how tight they are.
mr messy
Veteran
- Location
- Sunny? Glasgow, the friendly city...
Generally tightening torques and assembly procedures are derived from the manufacturer's research and development in design of their products unless the product is generic and therefore designed to meet set existing criteria. Why waste time and money on calculations and instructions if not deemed important?
subaqua
What’s the point
- Location
- Leytonstone
really ?
Don't quote me on it, I'm no bike mechanic, but I've read a few horror stories. Mostly cracking from over tightening them.
MacB
Lover of things that come in 3's
- Location
- Farnborough, Hampshire
I used to be very much in the tighten by feel camp and then I decided to get a couple of torque wrenches for peace of mind with my adjustable dropouts. I bought the two Park Tools beam ones but in hindsight I could probably have got by with just the larger one. My non-scientific tests have shown me that my nipping up for things like stems, seatpost clamps and the like were about spot on. However my tightening at the higher values was well short of where it could be.
As soon as a part requires over about 20nm I was underdoing things, over 30nm and I was way short. I'm thinking things like square taper BBs and cranks, lockrings and I can go to 30nm on the bolts for my adjustable dropouts. When going to 50nm, even with the larger wrench, I was still shocked by just how much force was involved.
But that's just me and with a non-mechanical background, others that are used to this sort of thing may never have made my sorts of errors.
As soon as a part requires over about 20nm I was underdoing things, over 30nm and I was way short. I'm thinking things like square taper BBs and cranks, lockrings and I can go to 30nm on the bolts for my adjustable dropouts. When going to 50nm, even with the larger wrench, I was still shocked by just how much force was involved.
But that's just me and with a non-mechanical background, others that are used to this sort of thing may never have made my sorts of errors.
black'n'yellow
Guest
MacB
Lover of things that come in 3's
- Location
- Farnborough, Hampshire
if nothing ever fell off or came loose, then they were not errors....
my middle sons cranks fell off
fortunately no harm was done but I felt terrible
Zakalwe
Well-Known Member
- Location
- Barnsbury, London
Bit heartbreaking if you over tighten the stem into your carbon steerer tube and crack it, or perhaps worse - the seat tube from over tightening the clamp. You can all play billy willy waver, I do it by feel as much as you like - I'll remove any doubt and use an inexpensive tool to ensure I hit the torque I intend to, every time, no matter how many times I adjust things.
subaqua
What’s the point
- Location
- Leytonstone
therein lies the rub an inexpensive i.e. cheap torque wrench will lose its calibration very quickly so it then turns into a lottery again. not an issue if you can get it calibrated regularly for nothing if it goes off with some of the torque wrenches and torque spanners we use in work, but for joe public its not generally viable. I stopped sending it a long time ago and just use it as a bar
Zakalwe
Well-Known Member
- Location
- Barnsbury, London
Comparatively cheap, as in a £2000 frame is worth getting a £50-100 torque wrench to use on it. If you look after your tools properly and release the tension when you aren't using it then it won't need constant recalibration and the only thing that will happen is actual torque will be less than advertised when it loses spring tension, which is still preferable to believing some mystical power will tell your brain when your hand reaches 12Nm. Suggesting its better to not bother is bizarre. Torque wrench > cheaper torque wrench >>> The Force.
mr messy
Veteran
- Location
- Sunny? Glasgow, the friendly city...
Have an experienced older friend that swears his elbow gives out at 50 lb/ft.... 
subaqua
What’s the point
- Location
- Leytonstone
learn what it feels like. a bit like no having to constantly look at a speedo to know when you are doing a certain speed. its not difficult really
Zakalwe
Well-Known Member
- Location
- Barnsbury, London
Cracking advice to spread that is.
"Basically, if you crack something you've gone too far, and if something comes loose during your ride you didn't go far enough. It's the best way to learn, trust me! I'm an expert."
I suppose you're one I those guys who can tell exactly how fast 77mph by feel alone, or can cut a shelf to exactly 4'8" without measuring.
You know, the guys who get all the speeding tickets and have to buy more wood after cocking up the shel measurements.
"Basically, if you crack something you've gone too far, and if something comes loose during your ride you didn't go far enough. It's the best way to learn, trust me! I'm an expert."
I suppose you're one I those guys who can tell exactly how fast 77mph by feel alone, or can cut a shelf to exactly 4'8" without measuring.
You know, the guys who get all the speeding tickets and have to buy more wood after cocking up the shel measurements.
deanE
Senior Member
- Location
- Falmouth, Cornwall
I suppose someone is going to suggest reading instruction leaflets next.
subaqua
What’s the point
- Location
- Leytonstone
ermmm no 14 years without a ticket, and yes fairly easy to cut a shelf to length without a tape. its all down to experience. sadly swome people just don't want to learn by feel just blindly follow a tool . as i said before ham fisted spanner manglers.
a bit like holding a car on the clutch, i don't have a tool for that - its all about feel. try it sometime you will be surprised. same as stripping insulation off a copper cable- the by the book way is to set wire strippers to a specific depth. i don't know any electricians who use wire strippers . 99% use side cutters or the cutting blade on a pair of linesmans pliers. its all about the feel.
