Fixed cup loosening up
 

I have been putting on some good mileage on my new to me Super Course. When I got the bike it had a buggered up crank cotter on the drive side. Someone had taken a punch and really mangled the cotter. I finished the job by banging it out with hammer and punch. I supported the bottom bracket as best I could. In the process the fixed cup came loose from all the hammering. I assume that the threads have been damaged and now when I put the bike to a test(cranking up steep inclines) the fixed cup loosens up. If I use something such as Loctite on the threads will it be able to be removed in the future?

I looked up and found Loctite Blue. Anyone use this, and does it keep things tight?

http://im1.shutterfly.com/media/47a2...D720/ry%3D480/

I never recall using Locktite on FC myself but know some do. You need ot crank a fixed cup pretty tight, hence the name, and if your just using a standard BB tool without a cheater bar you may not have enough UMPH! to do the trick. My tool is over the top modified with a 3/4x3 Aluminum bar stock about 4 feet long. it was free and does the trick.

Or get a threadless "repair" bottom bracket. They are pretty cheap.

http://www.amazon.com/Sunlite-Bottom.../dp/B001642Z48

I'd Locktite it Big ring.

+1....I had a FRENCH fixed cup come loose, even though I tightened it. Quickly found out they need the be really tight!!! Second time I used loctite and a cheater bar on the fixed cup tool.

I'm confused. You didn't mention changing the cranks. You mentioned a cottered crank, and you show us a picture of a cotterless crank.

I replaced the crank with a cotterless. The original steel cottered crank was bent. I kept the original cups and am using a stronglight spindle and a combination Nervar crank, with Stronglight chainrings I had in the parts bin.

This is British thread? I thought the fixed cup on British was left hand thread to prevent this problem?

Yes its left hand thread, but I think with my heavy handed cotter pin removal I may have damaged the threads somewhat on the fixed cup. Or perhaps its just that i cant tighten it enough with my limited tools. I have a BB wrench but with just a slight shoulder on the BB cup its hard to really get a good hold to torque down on it.

Got a sturdy bench vise, Big Chainring ?;)

Use a variation of the Sheldon Brown cup removal trick: a bolt with some washers and nut to keep your wrench from slipping off. You don't need to get the bolt super tight, just snug enough to keep the wrench in place.

OK, I went down to the hardware store and got the Loctite. Dismantled the cranks and BB, cleaned up the threads, and did the job. I'll take it out for a spin in a couple hours, see how it goes. Did the best with what I have. I'm hoping it stays tight.

When I had it apart I saw a flat spot on the threads of the cup. About a 3mm diameter spot where the threads seem flattened. May be a cause of the loosening, I dont know.

The FC on my Gitane loosened up on a ride some time back, I put Loctite on it and has remained fixed. I can't remember which variety of Loctite I used but it did the job.

Loctite won't prevent you from getting it out later on either.....

Joe

Are those pretty good quality? I've always used Shimano UN-53 where I could. A little pricier though.

It depends on which version of Loctite.
RED is a no no!

"Loctite® Threadlocker Red 271™ is designed for the permanent locking and sealing of threaded fasteners. The product cures when confined in the absence of air between close fitting metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and vibration. It is only removable once cured by heating up parts to 500°F (260°C)."

Bill,

Good point ! I should have said BLUE Loctite...it's what I use.

Joe

I used the Loctite Blue. Went for a ride yesterday without any problems. Hopefully this solves the problem.

What did you use to tighten the cup? One crude way is to clamp the cup in a vise and use the frame as a lever. The vise jaws have to be nice and sharp, though.

Fixed cup loosening up
 

I used a Park BB wrench. Leaned into it as hard as i could. I don't have a vise.

In the future, feel free to give me a shout if necessary. I have a vise on my workbench. Might be able to help.

Skip

Will do, thanks Skip.