Bicycle Mechanics - Replace Bottom Bracket; Sealed vs Unsealed

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

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 (http://sheldonbrown.com/tooltips/bbcups.html) (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

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.

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.

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

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.

- Mark

+1

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

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

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

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.

Modern cartridge bb are symmetrical.

That's been disputed by many experts here.

- Mark

That's been disputed by many experts here.

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: http://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

Modern cartridge bb are symmetrical.

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.

Modern cartridge bb are symmetrical.

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.

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.

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.

The left side is not very important, it's the right side that matters. It should be longer for the older cranksets.
I would measure the distance from the end of the right side (excluding the threads for a nut if they exist) to the bottom bracket shell when the bottom bracket is installed. The small arrow on the picture.

Then compare this distance with the cartridge manufacturer info.
http://www.yst-corp.com.tw/new/images/pro/cartridge-cad.jpg
Then you can calculate the width of a spacer to move the cartridge to the right. Usually, 1 or 2mm.

If you don't want to use a spacer, the width of bb should be longer. But then the left pedal will be too far.

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.

I just went downstairs and measured my Klein. It has an Ultegra octalink bottom bracket (with metal left side spacer) and a 2mm spacer to move the chainline to the right. FSA Energy crank. With the spacer in place the right crankarm is 15mm from the chainstay and the left crankarm is 13mm. If I removed the spacer I guess that the opposite would be true.

I hate taking measurements and working with facts.

In any case, repacking is certainly easy enough and I've done it lots, but it sounded like you wanted to put a new one in. Despite my earlier warnings, literally the only tough part is getting that DS cup out. For ease of install, nothing beats the cartridge.

Incorrect.
Give as many examples as you can of $20 asymmetrical bottom brackets
1)
2)
3)
4)
5)

that can replace, for example, the bottom bracket that goes with the typical vintage crankset
Double Sugino Super Maxy:
Size Code - 3T , sheel width - 68, D Length Overall - 123, A Length Left End - 32, B Length Middle - 52, C Length Right End - 39
http://www.sheldonbrown.com/images/spindle.jpg

FSA Energy crank.
It's not a retro crank at all, it's symmetrical.

It's not a retro crank at all, it's symmetrical.

I never said it was. I was reporting what's on my bike.

I could make the argument that, since it's on my bike, it's retro's crank.

On this question of symnetric cartridge BB's, its been debated over and over here without a good conclusion.

Nobody (even Shimano) seems to publish any data on what that critical distance is between the right side BB shell face and spindle end for their cartridges. Instead, they publish overall spindle length which is not what is critical to chainline. Barnetts appears to publish some "relative chainlines" (e.g., 1.0, 2.0, 3.0 mm) that can be used to compare betweeen BB's, but no absolute ones. Perhaps these are centering offsets - I can't tell. If they are, then except for the short spindle lengths (107mm), all current cartridge BB's are not symmetric. Just the fact that this relative chanline varies from 0.0 to 9.0 mm (for the 127.5 mm) strongly suggests to me that there is a variable degree of asymmetry that increases with spindle length. Sheldon Brown gives some "equivalent symmetric" cartridge spindle lengths that give what length of spindle you should get in a symmetric BB to replace various spindes in 3-piece BB's, but that doesn't seem very useful to me if the BB's are not symmetric.

It appears the usual way to handle this is trial-and-error. I'm about to replace a asymmetric 115.7 mm 3K spindle 3-piece with a 115 UN54 and I'll have another trial-and-error result shortly.

- Mark

www.biketoolsetc.com (http://www.biketoolsetc.com) sells cheap Taiwanese YST threaded cartridge bottom brackets in different sizes.
Here you can see dimensions for them:
http://www.yst-corp.com.tw/new/cartridge_bb01.html
At least, they have steel cups, not plastic ones as Shimano.

I think you can send a message to biketoolsetc asking to measure the actual bb. They seem to be good guys.

Sealed bearings are so much better wherever you can puut them, that it should become a natural 'bias' when you are getting parts. This goes for BB's, wheels and headsets. Sometimes a sealed bearing headset that will filt a particular bike is difficult to find or too expensive, then you can go with ball bearilngs in retainers or loose ball units. But generally lean towards sealed bearings. bk

[QUOTE=Barabaika;6153229At least, they have steel cups, not plastic ones as Shimano.[/QUOTE]

It seems to me that calling that nylon spacer thing a cup is a misnomer. It's only purpose is to prevent the bottom bracket cartridge from tipping inside the frame's bottom bracket shell. Since the bearings don't touch it calling it a cup doesn't sound right to me.

The same's true of integrated headsets. The bearings never touch the stops that are formed inside the headtube. Calling the stops "cups" has confused a lot of people about the durability of integrated headset frames.

I've replaced more than a few bottom brackets, mostly for older cranks. Symmetry is just plain not a critical issue most of the time. If it becomes one, there are ways to deal with it, including spacers on the threaded end of the cartridge bottom bracket. I don't see any reason for debate, controversy or fretting over this issue.

Hey,

How do you think of this bottom bracket? It came from 20-something Centurion. I think I have the same question as the original poster. Is it ... good? I mean I can research, but this thing has nearly no marking.

http://i23.photobucket.com/albums/b357/Tomo_Ishi/KC280060.jpg

This has 73mm [fixed] length and 120-something axle length. And, it's asymmetrical.

Does this one count as a retro BB?

T

P.S. I replaced it with a Hollow Axle system. Fed up with crank getting loose.

-- Fixed the Typo. Thanks Buzz. --

730mm? that's almost 29 inches:D

You should worry about a new cartridge bottom bracket only if you plan to use your current crankset; and many of the old cranksets are very nice.

When you change both the bb and the crankset, there are no problems.

Your axle should have a size code. There is a table here: http://www.sheldonbrown.com/bbsize.html
If it's 120+ mm, it can be 3S or 3T. But you can measure it yourself, it's more precise.

Hey,

I see marking "7NL" on it. I see it is for an ISO/British BB. Pretty neat. I'm keeping it for the eventual retro-conversion. Do you think it is OK to plug this into 68mm? I mean you can tighten the ring-nut, right?

T

ive just put in a brand new sealed shimano un-72 and after 2 months ive never had so many problems with a bb. even on my old loose ball if something went wrong i could fix it myself. with sealed they are great until they arent, then i have to replace it...frustrating....

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 suppose this really means that unless you are going to replace the balls EVERY 10 minutes, they will never be prefect - so just grease them and retighten and go!! Or am I missing something in my reading of your comentary??

I suppose this really means that unless you are going to replace the balls EVERY 10 minutes, they will never be prefect - so just grease them and retighten and go!! Or am I missing something in my reading of your comentary??

He means that the balls are cheap, so as a general rule, you replace with any significant time in service rather han re-use. And you always replace as a set because when you buy a bag of the balls, those within a batch will have tighter ball-to-ball tolerances than a mix of balls from different batches.

- Mark

Can someone explain what advantage a cartridge bottom bracket has over a traditional bb (especially a sealed one) other than that it requires no skill to adjust? I'm not trolling i'm just asking a serious question. I have a couple of bikes with cartridge bottom brackets that need replacement. It really bothers me that I have to spend what amounts to a large percentage of the cost of the whole bike to replace the bottom bracket, instead of spending 20 minutes and a dollar or two on bearings to re-build. I find it very frustrating. I've heard the longevity of sealed cartridges touted before, but the bikes i have that need replacements have nowhere near the miles on them a regular bottom bracket if adjusted correctly could take in stride. I feel the same way about my one set of wheels with sealed hub bearings. What gives? am i just having bad luck?

Can someone explain what advantage a cartridge bottom bracket has over a traditional bb (especially a sealed one) other than that it requires no skill to adjust? I'm not trolling i'm just asking a serious question. I have a couple of bikes with cartridge bottom brackets that need replacement. It really bothers me that I have to spend what amounts to a large percentage of the cost of the whole bike to replace the bottom bracket, instead of spending 20 minutes and a dollar or two on bearings to re-build. I find it very frustrating. I've heard the longevity of sealed cartridges touted before, but the bikes i have that need replacements have nowhere near the miles on them a regular bottom bracket if adjusted correctly could take in stride. I feel the same way about my one set of wheels with sealed hub bearings. What gives? am i just having bad luck?

The line is that a cartridge BB will last much longer, be smoother over it's lifetime, be much more weather resistant, and be easier to install and adjust. I have no direct experience, but that's what the line is.

I don't think the cost angle is as grim as you're depicting. I just put a new UN54 cartridge in my old Trek for $20. This seemed pretty reasonble to me.

- Mark

Can someone explain what advantage a cartridge bottom bracket has over a traditional bb (especially a sealed one) other than that it requires no skill to adjust?
Traditional cup-and-cone bbs are not sealed.
In two words: they easily collect sand and grime, and begin to creak.
You have to repack them with new grease very often.

Hey,

I know there are people who chooses to use BMX (3 piece) BB for MTBs and Roads. Why do they do that? They are not sealed right?

T

The left side is not very important, it's the right side that matters. It should be longer for the older cranksets.
I would measure the distance from the end of the right side (excluding the threads for a nut if they exist) to the bottom bracket shell when the bottom bracket is installed. The small arrow on the picture.

Then compare this distance with the cartridge manufacturer info.
http://www.yst-corp.com.tw/new/images/pro/cartridge-cad.jpg
Then you can calculate the width of a spacer to move the cartridge to the right. Usually, 1 or 2mm.

If you don't want to use a spacer, the width of bb should be longer. But then the left pedal will be too far.


Cool!! I learned something from all of this..

The line is that a cartridge BB will last much longer, be smoother over it's lifetime, be much more weather resistant, and be easier to install and adjust. I have no direct experience, but that's what the line is.

I don't think the cost angle is as grim as you're depicting. I just put a new UN54 cartridge in my old Trek for $20. This seemed pretty reasonble to me.

- Mark

I've had exactly the opposite experience, like i mentioned. The couple of cartridge bottom brackets i've had have been complete toast after far too few miles IMHO. What do you mean by adjust, in any meaningful way I understand most of them are non-adjustable.

Actually, it is exactly as grim as i am depicting. For example, i have a bridgestone MB-5 I purchased for $12 even if i decided to use a cheap $20 bottom bracket (which would then be the cheesiest part on the bike) it will still be 166% of the cost of the bike. Or, take for example my Inbred which i purchased for $200, the cheapest bottom brackets in a quality range that would match the rest of the components cost from 20%-25% of the cost of the bike. That doesn't seem reasonable to me.


Traditional cup-and-cone bbs are not sealed.
In two words: they easily collect sand and grime, and begin to creak.
You have to repack them with new grease very often.

Nicer ones were, i have several. It doesn't take much to add a seal to something. I will grant that it's not the same type of seal some cartridge bb's use but they are sealed nonetheless. My experience with cartridge bottom brackets leads me to believe that they collect grime just as easily [which is to say that neither collects much under normal circumstances] only they can't be repacked when they do. Could you define very often? even the most fastidious bike snobs probably wouldn't do it more than a couple times a year unless they are riding through deep water all the time. Figure it takes 20 minutes each time, so maybe an hour or two a year spent working on the bottom bracket?

Actually, it is exactly as grim as i am depicting. For example, i have a bridgestone MB-5 I purchased for $12 even if i decided to use a cheap $20 bottom bracket (which would then be the cheesiest part on the bike) it will still be 166% of the cost of the bike.

I'd stay away from cartridges too if I had your experiences. But your rationale for declaring the cost of a cartridge BB "unreasonable" is just plain silly - bar tape is 150% of the cost of a $12 bike, so I guess bar tape is unreasonable in cost too. I had someone give me their old Trek 400, so I guess even the cost of $0.25 ferrule will be unreasonble by comparison.

- Mark