Tightening things correctly

Red_Logic

It says on my frame that things need to be tightened to say 8Nm, how do you do this?
Is there any way that it can be done just using normal wrenchs?
Thanks for any replies...

tallmansix

If the tightening force is say 5Nm, thIs means that if you had a 1 meter long spanner tightening the said nut, you would need a 5N force applied. On earth that is 0.5kg of weight applied.

If I reduce the spanner to a tenth of it's length, say 10cm, then the force required will be 50N or 5kg

To tighten a 5Nm nut with a typical 5cm Allen key requires 10kg

Therefore it can be done roughly without a torque wrench or such.

Wirral_paul

Much easier however to just spend £25 or so on the correct tool at B&Q or Halfords however.

Bozman

You just use common sense, i'm chopping and changing bits all the time and i've yet to have a problem, i've never cracked or sheared a thing........... by saying this, the next time i tighten my seatpost it will crack. A blessing - it's a Dorico!

mikenetic

A torque wrench is a decent investment, especially if you're doing work on Carbon bikes. I have two, a small one for stem/steerer/seatpost work, and a Park Tools beam one for high torque items like BB cups, lockrings etc.

I know that on most bolts I'm reasonably close when I tighten things by hand, but it's nice to have the reassurance, IMO.

Red_Logic

Thanks, I think il use a torque wrench, il try to borrow one or take it to my LBS. They cant charge more than a fiver for tightening a few things.

Yossie

Just buy one - take it to the LBS four times (easy to do if you're messing with stem/seat height) if they charge you a fiver a pop then there you go, you've paid it for it already.

Also think about thetime you waste getting there, explaining what you want, hanging around while they do it yada yada yada

Torque wrenches also make you look PRO at home if any burds wander into your garage looking for Chardonnay/alcopops.

Wirral_paul

I also have 2. A 1/4" one will do most jobs on the bike other than crank bolts and cassette lock rings

http://www.machinemart.co.uk/shop/product/details/040210674?da=1&TC=GS-040210674

thescouselander

Just a small warning on torque wrenches - they can be miles out, even the expensive ones. I remember years ago, as a trainee engineer, doing a study for a major automotive parts company who were suffering from a lot of failed wheel studs on parts they were supplying. It got quite complicated but in essence a number of things affected bolt torque including technique and accuracy of the torque wrench - it is very hard to get both of these things correct and it's even worse when you're talking the low torque settings we use on our bikes.

Also, an uncalibrated wrench out of the packet can be more than 50% out. Even the calibrated ones need recalibrating regularly. I'm not saying don't use a torque wrench but ideally you should have a good idea how much to tighten things anyway as its not a fool proof tool.

Red_Logic

ok thanks everyone, i think il just take to my LBS when im ready....im sure they can do it right

sungod

what is it that needs tightening?

if there's, say, 8nM printed on something that's typically the maximum, not what you need to tighten to

my stem has a maximum of 13nM on the steerer clamp, but it gets tightened until it is secure, which is around 5-6nM

i do use a torque wrench but it's mainly for speed and repeatability, many components are doable by feel, for instance a stem barclamp is tight enough when the bars don't rotate under force