BB torque?
 

Hi, I have bought a BB tool in order to open, clean and regrease (LX M661 cranks).
How important is the exact torque when reinstalling? Or is "tight, you know, tight but not too tight..." good enough? Or should I take it to my LBS for the final tightening?

Thanks for any advice :)

First...There really is nothing to regrease on your bottom bracket. The cups have pressed in bearing cartridges. The bottom bracket axle is a part of the drive side crank arm and is an interference fit with the bearings in the cups. The preload adjustment is very slight and is made by installing the non-driveside crank with its retention cap. The whole shebang is locked into place with the two bolts that secure the non-driveside crank to the axle. The only maintenance one typically performs on this type of BB is to wipe down the axle and perhaps put a very thin coat of grease on it to prevent it from corroding to the inner diameter of the bearings, replace the cups and bearings entirely, and make sure the setup is properly tightened.


Second...Take the money you would pay the shop and buy a torque wrench. Amazon.com has good prices on products made by Pittsburgh Pro...and while not the best wrench available they are certainly a good product at a great price point. Paying the shop receives a one shot single benefit....purchasing a tool that can be used for other things (working on a car perhaps) is a continual benefit.

Also, the chance of a shop using a torque wrench to install a bottom bracket is pretty unlikely...it would suck to pay someone for a job you could easily do yourself.

Just sayin.

-j

hollowtech bb's are torqued to around 40nm, shimano cartridge type around 50 that said I have never used a torque wrench when installing either of those types. I have a 1/4 inch drive click type that i use for the cap screws(pinch bolts) in the non drive side crank and on all the other cap screws on my carbon bike, I also have a 3/8 drive pole t/wrench which rarely gets used. Based on my own experience (depending on your tool/wrench size) 40nm takes a bit of effort so up to you whether you feel the need to get it checked

Google is having trouble finding a LX M661 crank.
Exactly what is it that you have, and what are you trying to fix?

There's a LX FC-T661 crankset. That's outboard (cartridge) bearings HT II.
Not much there to "open, clean and regrease".
Wipe with cloth, ride until it dies.
Buy new BB bearings. Install. Repeat.

There's an SLX crank. Also HT II. Treat as above.

It's POSSIBLE to replace the bearings ONLY, and keep the bearing cups. But not many bother.

It's also possible to gently pry the seals out and add more grease, which some claim improves bearing life under poor conditions.
Not many bother with that either.

The generation before that used a square taper axle in a sleeve holding cartridge bearings.
Notthing there either to sensibly "open, clean and regrease".
Treat as above.

Only BB standard where "open, clean and regrease" really makes sense is with cup & cone type BBs.

Yes sorry, I must have have made a wrong notation about the crank part number.
LX FC-661 would be the one I have; LX Triple, Hollowtech.

I'm not trying to fix anything, just take apart, clean, check BB bearings and replace if necessary. I've toured with this crank about 10K kms.
As you gather this is my first experience opening a Hollowtech BB.

edit: Maybe I should just leave it alone?

Unless your cranks are loose then there is nothing to really service on these types of bottom brackets except replacing the cups and bearings. While it is possible to remove the bearings from the cups it will require some special tools like a collet and slide hammer....for the price of the cups and bearings most people just replace them together as the manufacturer intended. Just ride them until they start to fail and then replace the cups/bearings with new ones.

I highly recommend using a torque wrench on the bolts on the non-driveside crank arm.

-j

Thanks guys!

Pittsburgh Pro AKA Harbor Freight They are often on sale for $10 with a coupon and IMO are a good value. I have two and both check out within spec on the torque checker at work.

Note that some "click style" torque wrenches (particularly the inexpensive ones) only work on right-hand-threaded fasteners. For BB cups and pedals, you need one that can measure torque in both directions. Inexpensive beam-style torque wrenches require a little more skill to use, but work both directions and are less work to keep in calibration.

First, the Pittsburgh pro click type torque wrenches sold on amazon.com can be switched from right hand to left hand just like a ratchet wrench. No worries there.

Second, I have both beam and click types in 1/4 inch, 3/8 inch, and 1/2 inch drive...and while I agree the beam type are generally easier to keep in calibration, they are a pain in the arse to use for applications like securing a bottom bracket, square taper crank arm retention bolts, etc. The way one must hold the floating handle of a beam type wrench makes it difficult for the user to use/read accurately in anything but low to moderate torque situations. As soon as you have to add some muscle to that floating handle things can get wonky. Click type torque wrenches are much easier to use in these applications.

-j

If that's true then they've changed the design within the last couple years. The two PP wrenches I have let you switch the ratchet direction, but the torque "click" only works in the clockwise direction. You'll break the wrench or the fastener waiting for the click in the counter-clockwise direction.

I guess it depends on your workshop. I've never had any difficulty using a beam-type for BB work. Just put the frame in the workstand, grab the rear dropout with one hand and the torque wrench with the other and squeeze them towards each other. My face is right in front of the beam gauge when I do it this way. Cassette lockrings are more challenging since I like to set the wheel on the ground for stability. In that case I just tell myself that bending over double to read the gauge is a good hamstring stretch :)

But your point is valid that clickers are almost always quicker and easier. I have both types and which I use depends on the application. But the beam-types are the ones I really trust.