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New Bottom Bracket Bearings

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New Bottom Bracket Bearings

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Old 11-08-18, 08:51 AM
  #1  
mikebian 
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New Bottom Bracket Bearings

Neither of the cranksets on my tandem are spinning smoothly and I am thinking of replacing the bearings. The bike only has about 10,000 miles on it but recent trips through Morocco and Israel where we encountered dust and sand storms may have something to do with it, although I know it shouldn't. At any rate, I am trying to figure out what to buy and that's where I run into trouble. The BBs on the bike now are FSA Mega Exo BB-7000, which seem to be tandem specific. 68mm in front and 73mm in back.

Any advice on replacements? Do I need tandem specific BBs? Can I just replace the bearings? I guess I would need a special tool to remove the bearings from the BB cups. Not sure which bearings to buy either.

Thanks

Mike
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Old 11-08-18, 09:30 AM
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Originally Posted by mikebian View Post
Neither of the cranksets on my tandem are spinning smoothly and I am thinking of replacing the bearings... Can I just replace the bearings?
While possible, it's quite unusual to replace the bearings only. If that's what you want to do, I can't offer much help. These guys tend to receive good reviews on bearings only:https://www.endurobearings.com/

The common procedure is to replace bearings incl bearing cups.

Originally Posted by mikebian View Post
At any rate, I am trying to figure out what to buy and that's where I run into trouble. Any advice on replacements? Not sure which bearings to buy either.
Look for a (FSA) bottom bracket, for a 24 mm spindle, English thread, 68/73 mm. Last time, I got an aftermarket bottom bracket set from BBB. It hasn't seen much use yet, but appears to be doing fine so far.

Originally Posted by mikebian View Post
The BBs on the bike now are FSA Mega Exo BB-7000, which seem to be tandem specific.
Can't see anything to suggest they're tandem-specific.

Originally Posted by mikebian View Post
68mm in front and 73mm in back.
Not a problem, you set that by adding or removing spacers/washers, which are included in the kit if you buy new bottom brackets.

Originally Posted by mikebian View Post
I guess I would need a special tool to remove the bearings from the BB cups.
Can't help you there, sorry. This kind of tool will remove/install BB cups:https://www.chainreactioncycles.com/...ol&cat=product
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Old 11-09-18, 10:37 AM
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You have lots of options from FSA, Shimano, Chris King, Wheels Mfg, BBInfinite, Race Face, Hope, and others. The key interfaces are the frame and the spindle.
Frame width: 68mm or 73mm
Type: BSA, English, 1.37
Spindle: 24mm, RaceFace EXI , Shimano Hollowtech II , FSA MegaExo
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Old 11-09-18, 09:39 PM
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Most bearings are standard and are available from many vendors. The bearing number can be found on the side of the bearing, most commonly on the seal. You might need a good magnifying glass and/or light to read the number. Google the number or search on a bearing sight such as vxb bearings https://www.vxb.com

there are many variants available so don’t let that confuse you, the number is the bearing size and the variants encompass things like materials, hardness, seal, etc. determine that your bearings are standard and available, then determine if you need any tools like a bearing press to replace the bearing. I believe FSA sells a replacement tools for some of their bottom brackets.

once you determine that you can get and can replace the bearings, look for some variant you are comfortable with. Most bearings are for many thousand rpm operation so smooth is important. Bikes operate at several orders of magnitude slower and don’t need the refinement, but do take more impact. I have found little difference between a $4 bearing and an $80 bearing in a bottom bracket.

if your bearings are standard, and tools available if needed, you can replace your bearings at a fraction of the cost.

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Old 11-10-18, 01:21 PM
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Originally Posted by mikebian View Post
Neither of the cranksets on my tandem are spinning smoothly and I am thinking of replacing the bearings. The bike only has about 10,000 miles on it but recent trips through Morocco and Israel where we encountered dust and sand storms may have something to do with it, although I know it shouldn't. At any rate, I am trying to figure out what to buy and that's where I run into trouble. The BBs on the bike now are FSA Mega Exo BB-7000, which seem to be tandem specific. 68mm in front and 73mm in back.

Any advice on replacements? Do I need tandem specific BBs? Can I just replace the bearings? I guess I would need a special tool to remove the bearings from the BB cups. Not sure which bearings to buy either.
Sounds like you've had pretty got service out of original bearings, which are the same as on our tandem. I already have replacement external bearings (same ones) on hand but old ones still running smooth at almost 10,000 miles. But with no trips to exotic places with sand storms.
Not tandem-specific.
Just noted yours are not spinning smoothly. Time for replacement, it would seem. I have never considered just replacing the individual bearings on external bearing sets. Or on cartridge bearing hubs, etc.
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Old 11-10-18, 03:06 PM
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Thanks all. I bought 2 new Shimano BBs. Should get them in a few days.

The old ones feel smooth, but very stiff, which is why I wanted to replace them. I have similar BBs on another of my tandems and they move very nicely. And these ones used to move nicely.

Alcanbrad: New BBs aren't that expensive so I just bought whole new ones. Just for kicks, I'll play with the old ones and see if I can get the bearings out. I did get the numbers from the seal (243775-2RS01) and searched for them. Results are questionable. A lot of cheap ceramic ones out there, but from what I have read, these cheap ones are just trouble. And the pictures of the others make me wonder if they are correct and it wasn't that much more to just buy a whole new BB and know it's good.
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Old 11-14-18, 09:41 PM
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UPDATE: I wound up not having to replace either BB. When I pulled the existing BBs out and examined them closely, I noticed two issues:
  • Dirt/sand had gotten under the outer plastic cap that clicks into the actual bearing. This was what was making the scratchy sounds as the axle spun.
  • There is a rubber seal that sits behind the bearing that is supposed to sit in a small groove in the housing. On two of the bearings, the seal came out of the groove and was pushed up against the bearing itself causing friction and making them feel stiff when I tried to spin them. I probably caused this by not carefully inserting the cranks at one point.
Anyway, I cleaned everything, carefully placed the seals, put it all back together and it all seems great now.

Thanks for everyone's responses.

Mike
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Old 11-15-18, 11:26 AM
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Great news, and yes, bottom brackets costs are typically low enough to not be worthwhile to service.

Be sure and lube the bearings. Light grease will minimize any losses.
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