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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 10-24-08, 12:37 AM   #1
banjo_mole 
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Completely virgin to bottom brackets:

Greetings, All!

I've been riding a Univega (Maxima Sport) for a while now, but I've decided I want to replace the bottom bracket on it.

... Or the axle housing. Whatever. Don't heckle me.

You know. The thing the cranks attach to. The bottom bracket.

I know NOTHING about bottom bracket sizing/installation/etc.

In that, I suppose it's sort of silly for me to be window shopping for them, but I saw this one:

http://velo-orange.com/irdbobrwistc.html

and decided it, or something like it, would be neat. I dunno.

I am lost like a puppy in the jungle.

Could someone explain to me how this all works, and/or what I need to know to select/install one?

Thanks.

-Nick Skaggs
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Old 10-24-08, 01:12 AM   #2
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Does it come off? It seems that it would pretty much be welded there or something but I'm a cruiser rider.

Are you trying to replace the bearings and races or even the entire crank with a stronger/lighter assembly? Or do you want to build a single speed or maybe even a fixie?

You see, I'm confused too as most of us tend to want the bracket to remain on (repaired mine twice then had it braced to take my weight)

I can't really see where it bolts on if it does based on this picture.

PS I don't know if they are still at it but this picture came from an organization in San Francisco that rescued dumpster bikes call Garbage Bikes. It looks very nice. I rescued the link from an internet dumpster restorer called GOOGLE.

(I'm never sure about THAT outfit)

If search actually works well today (does God play Wagner real loud when he frowns on our search engine?) I would try some form of bracket repair. bottom bracket or crank removal as a general introduction as they have been discussed quite a lot and ought to be there. If that either doesn't help or it doesn't work we'll see that you get figured out.

If you can expand your question some if need be I think were getting close to and don't fret. Welcome to Bike Forums, we are out of maps but the restrooms are clean or your membership is free.

That's right. I forget it already is. Well, it's free-er.
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Old 10-24-08, 01:14 AM   #3
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First you'll need to buy a couple of specialty tools. The first is a crank puller and the second the spline socket for the new BB. You'd also need whichever tools are needed to remove your present BB depending on what your present setup is. So it's at least two tools and maybe as many as 4 tools depending.

Now all of this is fine but is your present BB making noises, suffering from bearing slop or in some other way offending you when you ride? If not then leave it alone.

As always go to www.parktool.com/repair and hover your mouse over the part of the bike diagram you're looking at working on. In this case the BB area and read up on the options and use the options presented to determine which setup you have and how to do the work.
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Old 10-24-08, 01:16 AM   #4
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Rollfast, you're confusing the bottom bracket with the bottom bracket shell. The shell is part of the frame and is welded so that's not going anywhere soon. The BB itself is the axle for the cranks and the bearings they run in be it the separate components that rely on the shell for alignment or the one piece screw in assemblies.
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Old 10-24-08, 01:45 AM   #5
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Quote:
Originally Posted by banjo_mole View Post
I've been riding a Univega ..I've decided I want to replace the bottom bracket on it.
...Could someone explain to me how this all works, and/or what I need to know to select/install one?
BCRider covered the tools pretty well, but apart from that you also need to know that kind of axle you've got, judging by a quick search it'll be square taper and not one of the different splined ones, unless you're also looking to replace your cranks. You need the length of the axle and the width of the bottom bracket shell. Even with that info getting the chain line where you want it can be a bit of a gamble.

But the big question is: why do you want to change it?

Unless the current one has failed in some way the performance you stand to gain by switching to a better BB is really very, very small. For the average(majority) rider the BB is one of the most unobtrusive components on the bike. There are plenty of components to replace that'll have bigger impact on riding than switching out a functional BB for another. And it won't do much for bling value either.
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Old 10-24-08, 07:43 AM   #6
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FYI, since it rotates with the cranks, I think we should be calling it a spindle not an axle.
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Old 10-24-08, 08:34 AM   #7
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do some reading on sheldon brown
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Old 10-24-08, 10:00 AM   #8
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[QUOTE=dabac;7723782]
But the big question is: why do you want to change it?
QUOTE]


Well, I've been slowly (but steadily) replacing parts on my bicycle in my mind, to make it more suitable for very long distance touring, and I thought that possibly a "sealed" or very low-maintainence bottom bracket might be suitable for touring. Don't they make ones that are completely sealed inside themselves?

It may be my eyes playing tricks on me, but BB's similar to these:
http://velo-orange.com/grcrubobr.html
http://velo-orange.com/irdbobrwistc.html

look like they're completely sealed of, almost like one big piece that just threads into the bottom bracket, whereas the ones I've disassembled seem more like a collection of bearings and cups.
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Old 10-24-08, 12:49 PM   #9
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Properly maintained, the cup & cone types are perfectly fine and you can adjust them to a gnats whisker!
Personally, I wouldn't think about swapping in a new cartridge type to replace a good C&C type. That's something you do IF/WHEN the C&C type goes bad.

Also to change it out, you need the tools to remove the C&C type and ADDITIONAL tools to install the cartridge type.
Just buy the first set of tools (all you really need is the crank puller and a bit of ingenuity if you already have some hand tools), $2-3 worth of 1/4" ball bearings and a bit of grease and you can overhaul your current one.
The 2nd time you service it, it'll be a relatively quick job.
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Old 10-24-08, 01:42 PM   #10
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Quote:
Originally Posted by banjo_mole View Post

Could someone explain to me how this all works, and/or what I need to know to select/install one?
Interesting question, since I just acquired a different Univega, and am also thinking about this upgrade just to see what it would be like ...

First, other than the "I'm upgrading and have made it to the bottom bracket" step, here are some things to consider / pointers on tools, etc.: (and, the suggestions above to look at Park Tools' site is a good one)

? Does the existing BB spin smoothly and quietly? Has it ever, or recently, been maintained?
To answer the smooth/quiet question, get the chain off of the chainrings (take rear wheel out of frame so you can get chain off of CRs). Spin the cranks ... smooth? noisy? If rough, and/or if you don't know if the BB has been serviced, think about opening it up.

Tools: probably a hex wrench to pull the caps out of the cranks. A big (maybe about 17mm) wrench to loosen/remove the bolts holding the cranks onto the spindle. An appropriate crank puller and wrench to operate it to pull the cranks. A lockring spanner, or some approximation thereof (back in the days of blacksmith bike repair, a punch and a ball pein hammer) to loosen/remove the lockring on the left (non-drive) side. A pin spanner to remove the left side cup. [ penetrating oil or special penetrants like Kroil or other chemicals may help loosen threads if things are tight ] If you want to make the replacement, going from cup-and-cone/bearings to the "unit" approach, you'll need a wrench to get the right side cup out, too, or fuss with a bench vise or some other approach.

Once the cranks are off and the left-side cup is out, you'll be able to extract the spindle and the ball bearings. There may be a "crud guard" plastic or metal cylinder in there to block/****** the passage of rust and grit to the bearings -- if so, pull it out too. If the bearings are in retainer cages, notice which way the cage is oriented when you take them out, and remember it for putting it back together. Wipe all the grease off -- reaching through the BB shell to the right side cup, which can stay in the bike if you aren't replacing it. Look at the balls, the cups, and the contact surfaces on the spindle. If things are scratched, balls have pits or are missing/broken, you should replace the parts -- or change to the sealed bearing unit. The spindle may be marked to tell how long it is -- you will want to know that, because your new spindle needs to match (especially if you have a triple chainring setup). New ball bearings (loose) are pretty cheap; you probably won't be buying the ceramic ones, but consider getting ones made to the Campagnolo quality requirements for roundness if you stay with balls.

This would be a very good time, if you haven't before, to apply a frame-saving treatment to the inside of the tubes (if they're steel). Boeshield T-9 (may be available at Sears) or Weigle's Framesaver -- turn the frame upside down and spray down the insides, and into the chain stays.

Reassembly is the reverse of the dis-assembly; take your time playing with the tightness of the cups on the bearings (they will loosen up just a bit). Longer end of the spindle is the chainring end. You won't need the crank puller when it comes to tightening things up.

IF you're thinking of changing the BB assembly, you will need to know the length of the current spindle to order the replacement, so you would need to at the very least pull the cranks to measure it (millimeters) and place your order, or, if you can handle some downtime for the bike, just take it all apart down there, measure the spindle and wait for your order to arrive in the mail.

hope this helps some. It is really not a hard job to do, and the care and feeding and re-greasing every year or so is not a big deal if you're already taking other things apart to service them. Still, the idea of the no-maintenance sealed bearings -- well, they do have to be replaced from time to time -- is enticing.
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Old 10-24-08, 02:10 PM   #11
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Just make sure you get the right sized bearings, Its not a hard job, But the big thing is, make sure you go sealed.
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Old 10-24-08, 02:17 PM   #12
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Why?
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Old 10-24-08, 09:30 PM   #13
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Quote:
Originally Posted by pacificaslim View Post
FYI, since it rotates with the cranks, I think we should be calling it a spindle not an axle.
Good point. Or the crank shaft.

Mind we already have some terms we misuse in the bicycle lingo so what's another on the pile?
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Old 10-27-08, 02:34 AM   #14
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Originally Posted by BCRider View Post
Rollfast, you're confusing the bottom bracket with the bottom bracket shell. The shell is part of the frame and is welded so that's not going anywhere soon. The BB itself is the axle for the cranks and the bearings they run in be it the separate components that rely on the shell for alignment or the one piece screw in assemblies.
Hey, thanks!

I didn't know there was a tool either, just a big wrench...

I knew somebody would know...
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Old 10-27-08, 05:36 AM   #15
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Quote:
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.. I've been slowly (but steadily) replacing parts on my bicycle in my mind, to make it more suitable for very long distance touring....
Unless you plan to ride through water deep enough to submerge the BB, or simply can't be bothered to give it 20 minutes of TLC on a yearly basis a cup & cone BB will easily stand up to long distance touring too.

Quote:
Originally Posted by banjo_mole View Post
.. . and I thought that possibly a "sealed" or very low-maintainence bottom bracket might be suitable for touring.
So it is, but so is your your current design, with minimal maintenance.

Quote:
Originally Posted by banjo_mole View Post
.. . Don't they make ones that are completely sealed inside themselves?
There's nothing like a complete seal. In the beginning you have a pretty good seal, but there will always be some friction between the lip of the seal and the axle which'll eventually compromise the seal.

Quote:
Originally Posted by banjo_mole View Post
.. look like they're completely sealed of, almost like one big piece that just threads into the bottom bracket...
The biggest advantage of those is at the assembly stage, you've got 2 pieces to insert, with no adjustment available as compared to a minimum of 7 parts + adjustment for the old version. A huge time saver during assembly. But out on the road the advantage is quite marginal.
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Old 10-27-08, 07:54 AM   #16
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Personally, I would replace a C&C style with a sealed BB only if the cups and cones are worn. Yes, a sealed BB takes less maintenance, but they are also more of a disposable part (i.e. once it fails you just throw it out and buy another) while a C&C style just needs to be greased and parts replaced.

Tips for window shopping:
1) Measure your BB shell to determine BB size.
2) Measure spindle length to get the correct size.
3) Buy the correct threading for the shell. Is it English, Italian, or European?
4) Buy a BB that is a decent quality. Nothing effects the smoothness and quietness of your cranking like a well made BB.
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Old 10-27-08, 05:35 PM   #17
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Quote:
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Personally, I would replace a C&C style with a sealed BB only if the cups and cones are worn. Yes, a sealed BB takes less maintenance, but they are also more of a disposable part (i.e. once it fails you just throw it out and buy another) while a C&C style just needs to be greased and parts replaced.
You make a good point, and it gets me thinking that in this case, maybe I should stick with the kind of bottom bracket I have now.

I'll grease it up if it starts giving me problems, I do suppose it functions fine.
I'll take a better look at it once I buy a crank puller. (Currently at the top of my "need to buy" list.)
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