Tightening torque - question.

omri

Shimano recommends the tightening torque for its ultegra BB to be 35 - 50 Nm. Since to install that BB I need to use this tool how am I suppose to know if I did it tight enough or too much/less ?

By the way is there any correct way of installing bb - should I first tighten the right side - which in this case comes as one with the inner cover, and then the left side ?

Raam

If the frame cracks, you've gone too far.

Just kidding, that's a lot of torque, just don't go mental and you will be fine.

omri

Fine till the first strange clicking noise coming somewhere from there

Melodeon

35-50 Nm = 26-37 lbf-ft = 3.5-5 kgf-m

So, if you can rig a way of applying 26-37 pounds of force at a distance of 1 foot, or 3.5-5 kilograms of force at a distance of 1 meter from the fulcrum (the centre of the bearing in this case), you'll be close enough for government work.
I'd suggest 30 pounds at 1 foot or 4 kilograms at 1 meter would put it nicely in the middle of the recommended torque.

Al Wright

I'd guess the length of the tool is not more than 8 inches (200mm) so it shall take a hefty pull to reach 50 Nm (this is about normal for 5/8 inch or M16 steel bolt). You should be safe enough by pulling it comfortably tight (the pressure of tool edge uncomfortable in your hand)

Keep_Her_Lit

Raam wrote: »

just don't go mental and you will be fine.

I think that's about right. The tool that you linked to doesn't readily facilitate measurement of the applied torque. This suggests that correct installation of the BB is not highly dependent on accurate torque control, otherwise Park Tool would have a lot of unhappy customers.

The designers of the tool will have chosen the length of the handle so that the type of person one might typically expect to find installing a bicycle bottom bracket will apply approximately the correct torque when using the tool in a sensible fashion, i.e. squeezing reasonably hard but not bursting any arteries.

But maybe you’re a 120kg block of solid muscle who can bench press twice your own body weight. That would probably make you an outlier on the statistical distribution of bottom-bracket-installing-persons, leaving you understandably nervous about the prospect of inflicting serious damage on your bike. In that case, if you haven’t already bought the BBT-9 tool, just get the BBT-19 instead, which accepts a 3/8” square drive or a 1” socket. Other tool makers offer a similar tool which takes a 1/2" square drive (in case you already have a 1/2" drive torque wrench but don’t have any AF sockets).

If you’ve already bought the BBT-9 and you have a torque wrench, you could still use your torque wrench to get a “feel” for 35-50Nm by practicing on something else. For example, clamp an old bolt in a vice, set your torque wrench to 42Nm and see how much effort it takes to reach that torque. You should grip the torque wrench along its length at the spot that roughly corresponds to where your hand will be on the BB tool.

Melodeon wrote: »

35-50 Nm = 26-37 lbf-ft = 3.5-5 kgf-m

So, if you can rig a way of applying 26-37 pounds of force at a distance of 1 foot, or 3.5-5 kilograms of force at a distance of 1 meter from the fulcrum (the centre of the bearing in this case), you'll be close enough for government work.
I'd suggest 30 pounds at 1 foot or 4 kilograms at 1 meter would put it nicely in the middle of the recommended torque.

Yes. And this can be done reasonably well with a weighing scales.
1. Grip the BB tool somewhere close to the end of its handle, where it’s designed to be used.
2. Estimate the distance from the centre of your hand to the centre of the BB. Let’s say it’s 25cm.
3. 42.5 Newtons applied at 1m is equivalent to 17.3kg applied at 25cm.
4. Fit the BB, screwing it “home” but not fully tight.
5. Now position the tool on the BB so that its handle is both parallel to the floor and the force being applied to it is vertical (i.e. the bike is upright – get someone to hold it for you if necessary).
6. Stand on the weighing scales and note your weight.
7. Put one hand at the correct position on the handle of the BB tool and leave the other hand free.
8. Now bear down progressively on the BB tool handle until the displayed weight has reduced by approx. 17.3kg.
9. Of course, it will take more than one go, since the BB will rotate as it tightens. So you will need to reposition the tool a few times in order to keep it roughly parallel to the floor.

That’s it. It may sound silly or ridiculously elaborate but it works in a fairly crude kind of way. I’ve used it before to tighten nuts to torques for which I didn’t have a suitable torque wrench. For very high torques, you need to swap the tool around by 180 degrees, so that you are pulling up and therefore adding to rather than subtracting from the displayed weight.

omri

Now that BBT-19 makes sense though already got the tool mentioned in my question. I did that without this complicated yet accurate looking method. I did it as tight as it let me. After that I tightened it bit more which made the handle move few mm at the time. So hopefully there this should be enough and no clicking will happen.

The only thing that made me feel bit confused was that I could install the left cup all the way without the use of the tool. I was obviously able to tighten it more with the tool but not sure if this stay tight for long.

That tool is very very nice to use. Well worth money spent.

Thanks everyone for help.