I have a 20 year od Centurion that I have been commuting with the last 4 years.

I thought it would be a good idea to check the bottom bracket as it has never been repacked.

I was wondering if it would be a good idea to replace existing components with a sealed bearing set from Shimano or other.

Would I have to remove/replace the existing fixed cup?

the "windy" wheel

"Fixed cup" might be an apt description for a bottom bracket that's been in place for 20 years.

If it was my commuter I'd definitely replace the BB with a Shimano cartridge if I could find one with the right spindle length.

Is it a direct swap or must I also replace other parts? ( ie remove fixed cup and replace with something else while using the same adjustable cup)

Shimano has the right length and size

The cartridge bottom bracket is one piece. You completely remove the old bottom bracket and plug in the cartridge unit.

Check inventory before you assume you can still get the replacement that you need.

thanks. I checked Harris Cyclery and they have a Shimano 68 by 113mm long but I will call.

That's a pretty common size. You will even have a choice of quality: UN52 or 53 vs. UN72 or 3, the larger number being somehow better (and more expensive). The tough part will be getting off the current drive-side cup; see Sheldon (RIP) on a tool for the job. Be prepared to work hard. Search for tips on installing the cartridge - it's easy, but some steps make it work better.

Also remember that the drive side cup loosens clockwise (toward the front of the bike).

That fixed cup will be hard to remove. 20 years and moisture and lots of thread area and very little wrench flat area adds up to a hard case.

On the other hand, they will all come out with the right persuasion, so do not give up on it.

jim

If you're not sure about how to remove the fixed cup and don't have the proper tools, it might be well worth the couple of bucks to have an LBS do that part of the job. At best, fixed cups can be difficult and 20 years worth of no maintenance won't make it any easier.

If its in good shape why not just regrease it and put it back together. You wont risk damaging something and it will save yourself a few $$ and a potential headache.

My BB went on an old 1980s Motobecane. We had all the right tools to take out the cups, but we just couldn't get that puppy loose. When you are removing the cup, check on the new BB to see which way it threads to avoid confusion or damage to your frame. I eventually threw the frame in the back of the car and went to a bike shop. Best $5 I've spent on biking.

I went with a cartridge BB, and I recommend it. Low maintenance and not much more expensive. Very smooth rotation and you don't have to worry about tightening the cups to get the right resistance. If your BB needs replacing, upgrade. If not, then run it into the ground and then upgrade.

I was on my third unsealed BB. They kept failing in the winter slush.

thanks alot. I checked Sheldon's article and it described in detail how to do the job

That's what I'd do. No sense replacing it unless it's bad.
My LBS sells the 1/4" BB's for $.05 each, so for $1.10 I've got new bearings. Actually, I bought a bag of 100, since the same size is used in the rear hub. To me, it's not worth the hassle inspecting 22 BB's for any imperfection, with my tired old eyes.

If the balls have been used more than ten minutes, then you don't inspect for damage; you just assume they are no longer perfect and replace them.

I've never had any issue with removing the fixed cup using the "vice trick"... using a vice to hold the fixed cup and then turning the frame around the cup. The frame gives you tremendous leverage. But you REALLY want to be sure you're turning the right direction, you need a machinists vice with clean and square jaws, and you want to make sure the vice is grabbing the flats perfectly. You may only get one chance.

I recently went through this upgrade decision and decided to upgrade to a UN54 cartridge. But my existing 3-piece BB was not in very good condition and it would have been more expensive to replace the cups and balls. If everything looks great when you take it apart, I'd be sorely tempted to leave well enough alone and simply regrease and ride. While a cartridge is a bit smoother and relieves you of future repacking maintenance, the 3-pieces have worked quite well for billions of miles for millions of cyclists.

- Mark

+1

If it's a 3-piece bottom bracket, it can be asymmetrical.
https://www.sheldonbrown.com/bbsize.html


A and C can have different lenghts. Modern cartridge bb are symmetrical.

I second that emotion. You have to really want to change the bearings over to a cartridge to justify the work and frustration. IF you get it wrong, it will put you way behind the eight ball.

All things considered, I would change the gease and the bearings and keep it the way it is. Them old bearing cups never hurt nobody. Leave 'em be.

That's been disputed by many experts here.

- Mark

I won't dispute it.
There are asymmetrical bottom brackets by Phil that cost more than the author's bike. He can also add a spacer to move the right side.

I just recommend to take out the axle and measure it or look for the size code.
Here you can find the size codes for Japanese bikes: https://www.sheldonbrown.com/bbsize.html

Yellow Jersey.com carrys the tange BB in the size you'd need. The late Sheldon Browns Harris Cyclery site also carrys the Shimano sealed taper spindle BB.
On removing the fixed cup. If you have a large vise put the flats in the vise and sue the bike as the wrench. Mark Stonich (see bicycle_restoration Yahoo Groups) makes a tool to remove the fixed cup.It's a socket style.
A reputable bike shop should be able to remove it for you as well.
I'm guessing that after 20 years of no service you may have a worn spindle/bearings.
I converted to the sealed BB on my 91 Paramount and on my restored 81 Schwinn Letour Tourist. I highly reccomend the sealed system.

I had a bad BB case once where I tried the vice trick and I shattered the brittle edge of the vice face. Generally, I think it is a great plan though.

On the other hand, good old Sheldon describes (and pictures) on his site a home-made tool made of of a stout bolt, a couple of washers, and a stout nut that works like magic. I have never, ever had that one fail me. Even on the BB that shattered my vice. Oh yeah, get a Jesus bar to really go to town on it. Its fun actually. Man beats steel!!! A friend of mine gave me a couple of frames that he could not get the fixed cups out of. He is no slouch of a mechanic. I had those cups out of there in about 3 minutes. It was so satisfying, I would have done 20 more if I had them.

jim

jim

Incorrect.

If the bike is in really good condition hold onto the old BB so that if you get vintage bike mental disorder you can re install it and brag about being old school. Alternatively you might be able to buy a really good fixed cup bb like shimano 600 ect. off ebay that has seals and install that. I have even read about driling a hole in the BB and using it as an oil port so you would never have to replace the BB (but would have to oil it), now that would impress your friends.

So how do you measure it? Maybe one of the folks who responded "incorrect" can tell me.

When you take one out of the box they generally look like the left spindle is longer. When you install it in the bike, however, the bearing cartridge doesn't go all of the way to the left side of the bottom bracket shell.

I guess that you could install the bottom bracket and measure from the shell to each end of the spindle but I've never cared enough to do that. If, after installing the crankarms, they spin approximately equi-distance from the chainstays that's close enough for me.

The offset is generally fairly small 2-3mm, such the the left side crank is placed further out. The intent is that you could put a 1-2mm spacer on the right side to adjust your chainline.

This practice was more common when the brackets had alloy cups vs the plastic ones.

The Barretts manual that I have has a chart showing the relative offset of the Shimano brackets.

As to the OP's question, you can't go wrong with a cartridge. Less mainteance, easier to setup. You might be suprised at how easy the fixed cup comes off. I had a 20 yo Peugeot and a 30 yo Raleigh that took no more than good sized monkey wrench to remove.