Jose Mandez

A Tale of Two Bottom Brackets
by Jose "Work Smarter, Not Harder" Mandez

I purchased a 1988 Trek 520 from a local man about a month ago. He was no longer physically able to ride it comfortably, and I've always wanted one, plus the price was right. Anyhow, after a few weeks of riding it as a commuter bike, I noticed that the cranks had a lot of side to side play when I grabbed them by hand. I thought maybe the problem was loose crank bolts, so I tightened the bolts. Still, the play was there. At this point, the problem seemed to be with the bottom bracket (BB), so I figured now was as good of a time as any to replace the old packed bearing BB with an after market sealed BB. (I had the same problem with my old Trek 400 a year and a half ago and put in a new after-market BB, which is still going strong over 6,000 miles later).

The first step in getting the bottom bracket off (actually, this was when I was still checking the crank bolts and was hoping that the BB was still good) was getting the crankbolt dust covers off. These were the kind of dust covers that actually screw in to the crank threads, not the kind that just slide in and are held in by friction. I got the non-drive dust cover out just fine, but I found that the drive side dust cover had the Allen head of it stripped out, so I couldn't turn the dust cover off with an Allen wrench. I tried punching a few nails into the plastic dust cover and somehow turn it clockwise with tools, but I was unsuccessful. Finally, I managed to get the dust cover off destructively, but I realized, much to my dismay, that the plastic threads of the dust cover were permanently stuck inside the crank threads on the drive side, which were now effectively stripped.

I searched the internet for several tips for loosening a stripped out crank, all of which did not work for my case:

1. Try riding the bike around with the crankbolts loose--the crank will work itself off. I took the crankbolts completely off and rode it 38 miles on my indoor trainer. I stayed in good riding shape that weekend, but my crankarm was no closer to coming off.l.

2. Pour hot boiling water on the crank; (the crank is aluminum and will expand 37 jillion times more than steel will when heated and some other scientific sounding mumbo-jumbo) and then hit the crank with a hammer (or hit a 2"x4" held right next to the crank with a hammer) to work it off. I used up some of my winter supply of propane and destroyed several pieces of wood with my hammer in the process, but my crank wasn't any closer to coming off. (Another source recommended heating the crankarm with a propane torch...oh, sure, just let me get out the propane torch that I keep in my bedroom right next to my industrial-sized jackhammer).

3. Pour 3 in 1 oil down into the crankbolt, let it sit for a few hours, then hit the crank with a hammer. This is where I probably made a mistake--I used a dry chain lubricant to pour into the crankbolt...this actually seemed to gum up and actually secure the crank tighter in place, as it no longer had side-to-side play as it did before. I tried again with motor oil, but the crank was still stuck.

4. I tried holding a lighter to the crank threads with the bike tipped to its side, hoping that the heat would melt the plastic threads of the dust cover and that I would be able to then wipe the melted plastic off of the metal crank threads; then I would simply be able to use my crankbolt extractor as usual. This did not work--the plastic threads were stuck in there.

My cousin, a very practical and frugal man, suggested using JB Weld to put a nut inside of the crankarm, then threading a bolt through it to push the crankarm off of the BB spindle. This sounded like an exercise in frustration to me, since I've never had much like with JB Weld and other similar products.

Finally, almost in desparation, I went to my local bike shop (LBS). I called before going (they're 30 miles away) and they said that their mechanics were very busy but that they might be able to get it off today if they got it off after a few minutes of trying, but that otherwise it would be a few weeks before they could get to it.

When I got to the LBS after a very long (and boring) trip by car, I got very little positive input from the mechanics other than a general coveting of my 520. They told me that it would take about 10 days for them to get to it, and that they would have to cut it off--they were going to charge me $60 for what would take about an hour of their time. I told them "no thanks" and stuck my bike in the back of my Honda and drove off.

On the way home, I stopped by a Sears in a local mall to buy some power tools. My plan was to buy the best drill and the best set of drill bits they had and just drill holes into the crankarm/BB until it fell apart. However, before doing this, I had one last hare-brained scheme that I might be able to pull off.

I'd messed with similar BBs on bikes of this era before, and I knew that it was possible to twist the BB cups off of both sides and simple pull the BB spindle out through one side, since these are not sealed units. I'd had trouble getting the fixed cup off the drive side in times past--the last time I messed with one, I had to get the best grip possible with a pair of vise grips and muscle it off. The fixed cups had two flats, but I didn't have a wrench that would fit them in the past--my 32 mm was too small. However, I'd bought a 36mm/40mm bicycle wrench from the bike shop that day (this is the kind of wrench that is very thin, with narrow flats). According to noted bicycle authority Sheldon Brown, the flats of the fixed cup are just too narrow to get a good grip with any sort of wrench; he recommeded the fixed cup off with a bolt/nut combination coming in from the other side. I can't help but believe that Mr. Brown was referring to a traditional sort of wrench when he wrote this advice back in the 80's (the Lord only knows what he meant, since Mr. Brown is now dead), because I found that the flats of the 40mm end of the bicycle wrench fit the fixed cup perfectly, and I was able to screw the fixed cup off. (When doing this, remember that the fixed cup is reverse threaded; thus, you will turn the ring clockwise in order to loosen it).

I was nearly ecstatic; all I had to do was take the crank off the non-drive side (which was not stripped) and pull the BB through the drive side, still attached to the crank. I ended up not buying power tools from Sears that day (not worth buying now that my mission can be accomplished without them--I rarely need power tools anyway).

When I got home, I was able to get the crankarm off the non-drive side with a crank-bolt extractor, thread off the BB cups from both sides, and pull the BB out (still attached to the crank). I'd already had an after-market BB and a set of crankarms that I'd purchased ready to put on. I simply took the chainrings off of the old crankarm and put them on the new one, then cleaned out the BB shell, greased it, put the new BB in, then attached the crankarms, and then the pedals.

In retrospect, I'm rather amazed that my LBS did not think of doing this. It could be that they work so much on modern bicycles in which the bottom brackets are one-piece that they are not used to old school BBs in which the spindle can be pulled out through one side. It is fortunate that my crank wasn't stuck on a sealed BB, because then it probably would have required power tools to remove.

The tool of the day is my ParkTool 40mm bicycle wrench...a $15 tool that saved me from $60 of labor or $100 of power tools . I hope that this post might help someone else who runs in to a similar problem as this. (I will try to post some pictures of my repair process within a few days, which some might find helpful...right now they are on my IPod, and it and I are not getting along at the moment).

Pedalling hard against the wind,

Jose

p.s. If anyone needs pictures of any part of this process, send me a private message and I will try to get the pictures to you.