[mas]

I have a question about bolt torque. I've read that you should always use grease on a bolt to make sure the proper torque is achieved when tightening. I've also read that a greased bolt will be "tighter" at a certain torque level than a dry bolt and some torque specs refer to a dry bolt only.

My Marzocchi manual says I should tighten the crown bolts to 11nm torque...should I grease the bolts or not? I didn't see a reference to whether or not I should grease them in the manual. Thanks...

 

[Brian HCM#1]

I always use grease on all bolts, including rotor bolts. No only does it help get a more accurate torque measurment, but it makes it easier when you have to remove it.

 

[D_D]

The only way to get it consistant is to grease the bolt, press fit etc.

 

[mas]

That's what I always thought, then I did some searching on Google groups and found this:

http://groups.google.com/groups?q=torque+bolt+dry&start=30&hl=en&lr=&ie=UTF-8&oe=UTF-8&selm=36d1e455.1003613@news.sgi.net&rnum=39

It's a dirtbike newsgroup, but I think the same thing might apply to bicycles. It was strange to me how much I had to tighten the bolt to match the spec'ed torque once I lubed it...kinda makes me nervous considering which bolts they are.

 

[johnbryanpeters]

From too many years as a manufacturing engineer, my take is that the only correct answer is fugidunno.

Nominal specifications that you'll find in handbooks are generally for lubricated threads.

Any thread that uses a sealant like LocTite (rotor bolts, for instance) should NOT be lubricated.

When in doubt,

a) Read the manual. If it doesn't say lube, don't lube.

b) If that fails, call or write the manufacturer.

c) Hope they did their homework. Depending on the details of any particular design, proper torque varies tremendously from nominals.

d) If all else fails, get torque from a fastener handbook, use lubrication, and pray to the mechanical gods.

J