Another cautionary tale on rear sprocket bolts

[TallTom]

After this happened I came in and found a few threads on it. But I will add another one since none are new.

Routine replacement of rear sprocket. Crank off the bolts no problems. Torque spec calls for 43 lb/ft. of torque.

So I tighten them in stages. 20 then 30 then final value. 3 of these stripped before taking full torque. 3 took full torque.

There is nothing that says these are not re-useable. But as this and several other threads here show, 43 lb/ of torque doesn't seem to be very desirable.

I have a new set on order.

Good thing I'm not in a hurry.

 

[IG.]

I don't think you are supposed to use multiple stages. I think that's a no-no because on the follow up stages you have to overcome static friction as opposed to rolling resistance. This way, you may end up under tightening.

Also, never use 12-sided wrench on high torque applications - only 6-sided wrench, and depending on wrench quality make sure it fits snugly. Lower quality wrenches may be bigger by 0.1 mm or so and this could make a difference.

I also hope you were tightening when the wheel was ON the bike, otherwise it is inevitable that you apply effort slightly at an angle and with a lot of effort it's easy to round such relatively small nut because the wheel can easily move and suddenly change an angle. Don't ask me how I know.

If you did everything right, then I would be as upset as you are.

 

[RedBusarider]

I don't think you are supposed to use multiple stages. I think that's a no-no because on the follow up stages you have to overcome static friction as opposed to rolling resistance. This way, you may end up under tightening.

Also, never use 12-sided wrench on high torque applications - only 6-sided wrench, and depending on wrench quality make sure it fits snugly. Lower quality wrenches may be bigger by 0.1 mm or so and this could make a difference.

I also hope you were tightening when the wheel was ON the bike, otherwise it is inevitable that you apply effort slightly at an angle and with a lot of effort it's easy to round such relatively small nut because the wheel can easily move and suddenly change an angle. Don't ask me how I know.

If you did everything right, then I would be as upset as you are.

While I agree with you for the most part - there is something that doesn't really seem like a common thing to do.

So you think you should finger tighten the nuts to the sprocket and then re-install the rear wheel and then finish when on the bike.
I wouldn't think at that point you would want the chain on the sprocket and so it would be in the way somewhat and could scratch
your wheel up. So I think most would attach the nuts and torque them off the bike. I haven't looked at the service manual to confirm this,
but I don't remember them saying to torque on the bike.

Now with all that said I do agree that someone could easily apply "effort slightly at an angle".

So now that this has been brought to my attention if/when I change my rear sprocket I might use my tire changer
to hold it in place and make sure the torque wrench is parallel to the sprocket etc.

Seems to me that this might also be a good place to use a little lock tight as nuts coming off a sprocket in motion
can't be a good thing. But no mention of lock tight that I have seen. Wait - maybe they are clinch nuts, no?

 

[Nastee]

Notice he said Bolts not the nuts in title. I Torqued new sprocket & nuts on last night & was a little concerned with the spec so I got out a second wrench to make sure. Wheel was not on the bike no problems. I don't think Tall Tom is rounding nuts off or tilting the socket; but that the bolts are stretching then stripping thread or shearing after multiple use. 43fpd doesn't sound like much till you start tightening.