Tension Wrenches

Originally Posted by Captain Nemo

i use mine on parts that take load...or the bike cant move without, calipers wheels bars stuff like that, ancilliaries like levers controls bodywork and stuff just use common sense, summat like finger tight +1/4 or 1/2 turn with the spanner maybe, you can get a feel for how tight stuff is after awhile

I've had a torque wrench for about 30 years. I only ever used it to evenly tighten cylinder head bolts and some of the internal engine bolts on cars.

When I got the SV and read on here about the cheese bolts I decided to use it for anything it would measure. It measures in lbft so I have to convert the NM to lbft prior to using it. Now I have a damn phobia about not using it! I suppose I should get the calibration checked at some time as well. It's probably way out by now.

Originally Posted by John Burt

Don't forget that on the SV the chain tensio wil increase (free play decrease) as you re-tighten the wheel spindle.

Ooh - Why's that?

I use torque wrenches when ever I work on a bike, purely because I like the idea that the machine under me is not about to fall appart due to incorrect, under or over torqued nuts and bolts. As I am not a mechanic, but did study engineering, I will continue to use the torque settings defined in manuals such as Haynes when reassembling my bikes.

I have 3 torque wrenches, large, medium and small, to cover everything (in theory) I'll come accross.

Originally Posted by Kinvig

Ooh - Why's that?

That's cos the natural tightening of the nut moves the nut in a clockwise direction ... which, as the nut bites on the swingarm washer, will naturally cause a slight left-to-right movement - this movement is transferred to the axle, which in turn has the effect of moving the rear wheel back by a few millimetres and moving the rear wheel back will cause the chain tension to increase therefore. Does that sound about right?

[timwilky]

Difficult one this. I have 30 plus years spannering experience. Have worked in R&D for vehicle manufacturers, and for a number of racing teams.

I always use a torque wrench. Mine I have calibrated. However I still use "feel".

For those of an engineering background you will remember those graphs you used to plot of stress/strain


You need to ensure that your applied torque leaves the fasteners at that optimum point at the end of the elastic range etc. Usually you can feel that you have gone past the optimum. That being the case back off and replace the fasteners before damage

[embee]

I'm with Rictus/Timwilky etc on this.

Use one whenever you can, but also use your brain. As above, I've been in engine design/development for near 30yrs and if an engine builder didn't use a calibrated torque wrench I'd sack them. Why? If something fails and you don't know what torque was used.............

General fastener torque figures are usually for "dry" threads as someone said, these days assembly processes use dry fasteners because oiling attracts dirt and can cause problems with Health and Safety and in cars can even cause issues with evaporative loss certification.

In the outside world where we all usually oil/grease threads I tend to reduce the quoted figures by around 10% as a starting point, but also rely on feel.

It's good practice to gradually work up to a specified torque especially on unknown fasteners in places you haven't tried before. For example I find the quoted figures feel worryingly high on SV caliper fixing bolts, and I set the wrench about 25% low and go to that for the first shot, and step it up a bit at a time until it feels right. At least I know what it's been done up to.

If you're just starting into spannering, a good exercise is to get hold of a few odd nuts and bolts and try tightening them until something fails, then you get an idea of what yield feels like.