Failing to unscrew BB - what now?

Question

I have an external bearing BB, that I need replaced (It is quite badly rusted). I opt to do the repair myself. The bike is a Specialized Hardrock, the crank arms are SR Suntour.

Having removed the crank arms, I proceed to unscrew the plastic sealing rings of the BB. I removed the non drive side one. However, with all my strength, and a 30cm arm wrench I fail to produce any progress on the drive side cup. I am trying to turn the cup clockwise.

What is going on here? Am I doing something wrong? If I go to my LBS, is it probable that they will have a larger wrench?

Answer 1

I tried both techniques proposed here, but to no avail (I might have damaged the BB with the hammering).

The LBS had the tool for the job - experience. The guys put the wrench in a vice, calculated the direction to unscrew carefully, then put the frame on and just unscrewed the damn thing. The frame was providing large leverage.

Answer 2

You could try hammering your wrench, see photo 4b of http://www.bikeradar.com/gear/article/workshop-replacing-shimano-truvativ-or-fsa-bottom-brackets-27046/ (or search for "Cheat 3:")

Or, as it also says, a longer cheater bar if your tool allows (see the photo above the "Cheat"s, though that's the tool for internal cartridge brackets).

Either way, try and make sure that the tool can't slip off the bracket (e.g. use a bolt though the bracket holding large washers overlapping the tool), and that even if it does, your knuckles won't hit anything.

(When you say "wrench", you are using a tool designed for the bracket cup, not a pipe wrench or similar, yes?)

But yes, there's a good chance LBS will have stronger tools if you can't shift it.

Answer 3

I would try and use differential heating, or one of the other methods suggested by Sheldon Brown's.

I had very good luck with cooling the components, but in your case the aluminum is outside, so you have to heat the whole thing. You can adapt my experience as follows.

Because heating too much will definitely ruin the paintwork, I suggest that you use some sort of large container (I'd say 40 cm long, but it depends precisely on the frame geometry).

• 0 - gather all wrenches/pipes/friends/vice/explosives you are planning to use to uscrew. Keep them at arm's reach.
• 0.1 - [optional] I usually hammer energically the part that is stuck, perpendicular to the screwing direction. In your case this would be along the BB axis. Should you do so, put the frame on a flat surface, making sure only the non drive side of the BB touches. Then, making sure it touches wholly, hammer the cup 5-6 times. This is (supposedly) meant to break oxide bounds in the threads.
• 1 - put the frame inside the container, making sure the BB is fully under the container edges. Removing the front wheel and/or placing the container on a small chair/box will help.
• 2 - now put hot water in it, until BB is about 1cm under.
• 2.1 [optional] I don't think the mass of the frame will be able to cool the hot water too much, but it really depends on the volume ratio between frame and water. If you think the water has been cooled significantly in contact with the frame (and the container) you might change it.
• 2.2 [optional] Depending on whether you had success or not, you might want to put the stuck cup in contact with an ice bag without the latter touching the aluminum.
• 3 - Take the thing out of the water and rapidly apply unscrewing force.

I'd go with 0,1,2,3. If you don't have success try adding the optional steps. In 1 you will find additional ideas (e.g. using ammonia, soaking in ice - I had a hard times with pedals vs cranks before learning to let them sit overnight in the freezer!). I have never tried most of them though.