Finding and replacing the BB on my 1990 Muddy Fox
 

My 1990 Muddy Fox has it's original BB. I had it repacked in the spring and it will start making sound with in a few miles of riding it. So it is time to find a new BB for it, ideally one of the modern ones that is all sealed. I measured the shell, to the best of my ability, the chainset. Here is a picture of me measuring it, notice the red circle, I wasn't able to get all the way to the edge:(

http://bikeforums.net/attachment.php...hmentid=425165

According to Sheldon Brown's web site, the Exage 400LX Triple has a length of 121 and is square. I have found the Shimano BB-ES25 Cartridge Bottom Bracket, but it is Octalink V2 spline, not square, so I would need a new crank.

1. Does anyone know of a BB that will work with my existing crankset?
2. What is involved in replacing this? Is it something I can easily to myself?

You need to measure your existing spindle to see how long it is, and make sure that it is is the same length on both sides. Conventional bottom bracket spindles are often longer on one side than they are on the other. The longer side is usually the drive side.

Take the spindle off the bike (make sure that you keep track of which end goes where), and measure from one end to the other end, not including the threaded parts if the spindle has threaded studs that nuts screw onto to secure the crank arms.

Measure from the ball bearing journal to each end to see if the spindle is symmetrical. If it's not symmetrical, and the long end goes on the drive side, figure out the different in length, and add that difference to the overall length of the spindle to get the approximate length of the spindle for the replacement bottom bracket.

Now you can go shopping for a square taper bottom bracket to replace your old bottom bracket. If you shop for a cartridge bottom bracket, be aware that the common relatively inexpensive bottom brackets (less than $50) will probably be heavier than your old conventional bottom bracket, AND it will not last as long as your old bottom bracket went before it needs replacement.

When you repacked your old bottom bracket, did you replace the ball bearings and inspect the races? Conventional bottom brackets last forever if you replace the ball bearings and repack with fresh grease on a regular basis. Noises are usually due to improper adjustment, damaged races due to inadequate maintenance, inadequate cleaning, or improper or incorrect grease, or not enough grease.

Get yourself a Shimano UN55 bottom bracket. The 73 mm bottom bracket shell by 122.5 axle length should work just fine. Here is a link to the cartridge bottom bracket. It is a square taper so that you can keep your original crankset. When you pull out the old axle it will have the length stamped on it.

For question number 2, you certainly can do it yourself if you have the right tools and are somewhat mechanically inclined. The Park Tool website will walk you through it, plus YouTube has many videos of the procedure. Sometimes though it is just easier for a shop to do it if you haven't done it before.

Whether the bearings were replaced was my first question. Have you always owned this bike? Do you know for sure it is the OEM BB?


A few MTBs back then had a 73mm shell with English threading rather than the more typical 68mm shell.

According to my '93ish Quality Bike parts catalog, the BB for that 400LX (actually 500/400/300LX) crank came in either 122.5 or 127.5mm and a shell of either 68 or 73mm.
Check with Harris Cyclery or Niagara Cycle Supply

I, personally, didn't repack the bottom bracket, my LBS did. They have tightened it a number of times and each time I would ride about 2 miles and it would make sounds again and there is a lot of play in it, as well. I am assuming that it is just simply warn out.

The history is that I stopped riding it back around 2001 and only returned to cycling last year. I had the bike overhauled by one LBS last spring. It didn't take long for the bottom bracket to make noise and become loose. I rode all of last season that way, well over 1000 miles.

This spring I took it to another shop to get some drops put on it, they repacked it, too. Same thing, by the end of the first real ride it was loose and making noise. Twice they tightened it and both times within miles it was back to being loose.

Moved from C & V Appraisals (since the OP isn't seeking a valuation).

Sounds to me like the people at the shops you've gone to don't know what they are doing.

I'd wager that the people who worked on your bike were born after cartridge bottom brackets were introduced and they don;t work on them much, and they don't know how to inspect, clean, lubricate, and adjust a bottom bracket properly. Did they change the bearings? I guessing that they didn't lubricate the bearings properly, and they probably did not adjust the bottom bracket properly when they were done. I'm guessing that they left it too loose, and did not replace the ball bearings.

Niagara Cycle has a crap-ton of square-taper sealed-cartridge bottom bracket sets that will work. See Components - Drive Train - Bottom Bracket - Bottom Bracket 3 piece - Square Taper - Niagara Cycle. You could also check eBay.

Best bet here is the Shimano UN-54 or UN-55. Make sure you choose the 73mm shell width and not the 68mm, which will likely be too short, given your photograph above.

Park Tool has appropriate bottom bracket installation tools for the above.

Combined with your Chesini advice in the other thread, I'm voting BG as the BB Queen of 2014.

I would tend to agree with you except the first shop that worked on it has one of the highest reputations in town, with prices to go along with it. I trust both shops and really tend to believe that it is just very old parts that have warn down over the years. Now if I had regularly maintained the bottom bracket and had it repacked on a regular basis, then I might start believing both shops didn't know what they where doing, but I have let this bike site and site, then last year and this I put around 1600 miles on it with this issue. I think the real issue is the rider, not the mechanics on this one:)