What makes a "good" bottom bracket?

[pizzayum]

I am in the process of my first build, and I am curious what bottom bracket I should get. I will be getting a sram red crank.

what is the difference between this:

http://www.ebay.com/itm/J-L-BB-68mm-73- ... qydabUxcBw

a 24 dollar bottom bracket, and something like this:

http://www.jensonusa.com/!kX4u67sdbeT3n ... oC0g_w_wcB

Is it simply the quality of the machining and the weight? Is quality/feel all down to the bearings?

[rbrtwyn]

A lot of it is the company behind the product. SRAM will be there to support you. The other one? I don't know, unless you are based in Taiwan it might be hard.

[prendrefeu]

There are four factors at play for Bottom Brackets:

1. Weight of the cups (ignore if bearings go directly in frame). Not all bottom bracket bearing cups weigh the same. If you want to go light, go light here. If you research you may find some GXP-compatible bottom brackets hovering around 68g (w/ bearings) while others are 150g+ (w/ bearings)
2. Bearing type (minor weight consideration). Steel bearings, by most accounts, last longer than ceramic ones. Ceramic, however, will roll better and therefore offer less watts loss in the mechanical process of turning the cranks->chain->cog->wheel. If you favor reliable/longer lasting over performance, go steel. If you want performance, go ceramic.
3. Weight of bearings: given the same size of bearing (of which a person is limited to their crank/bottom bracket size), most steel bearins will weigh the same. Hybrid ceramic bearings will be slightly lighter, full ceramic will be the lightest. The difference in weight will be a few grams (typically 4-6g per bearing).
4. Quality of bearings & lube used - this is often the most important, as a quality 'steel' bearing can perform better than a low-quality 'ceramic' bearing, but a high quality ceramic bearing will out perform the high quality steel bearing. Bearing quality is a factor of the precision on the balls (look up the rating systems to see how they differ) and the lube used between the balls in the bearings. More often than not high-quality balls will be matched with high-quality lube.

The SRAM Blackbox GXP Ceramic bottom bracket is expensive because of the quality of bearings that are being used (mfg by CeramicSpeed)... those are some really top quality bearings.
The J&L is cheaper and uses lower quality bearings.


BTW - make sure your bottom bracket is GXP compatible: the spindle goes from 24mm diameter on the driveside to 22mm diameter on the non-driveside.

Good luck!

[pizzayum]

There are four factors at play for Bottom Brackets:

1. Weight of the cups (ignore if bearings go directly in frame). Not all bottom bracket bearing cups weigh the same. If you want to go light, go light here. If you research you may find some GXP-compatible bottom brackets hovering around 68g (w/ bearings) while others are 150g+ (w/ bearings)
2. Bearing type (minor weight consideration). Steel bearings, by most accounts, last longer than ceramic ones. Ceramic, however, will roll better and therefore offer less watts loss in the mechanical process of turning the cranks->chain->cog->wheel. If you favor reliable/longer lasting over performance, go steel. If you want performance, go ceramic.
3. Weight of bearings: given the same size of bearing (of which a person is limited to their crank/bottom bracket size), most steel bearins will weigh the same. Hybrid ceramic bearings will be slightly lighter, full ceramic will be the lightest. The difference in weight will be a few grams (typically 4-6g per bearing).
4. Quality of bearings & lube used - this is often the most important, as a quality 'steel' bearing can perform better than a low-quality 'ceramic' bearing, but a high quality ceramic bearing will out perform the high quality steel bearing. Bearing quality is a factor of the precision on the balls (look up the rating systems to see how they differ) and the lube used between the balls in the bearings. More often than not high-quality balls will be matched with high-quality lube.

The SRAM Blackbox GXP Ceramic bottom bracket is expensive because of the quality of bearings that are being used (mfg by CeramicSpeed)... those are some really top quality bearings.
The J&L is cheaper and uses lower quality bearings.


BTW - make sure your bottom bracket is GXP compatible: the spindle goes from 24mm diameter on the driveside to 22mm diameter on the non-driveside.

Good luck!

Thank you for comments! I'll definitely keep them in mind when I finally make the purchase.

On a side note, I dig your current build. How much weight did sanding off the paint of the cranks save?

[bikerjulio]

There is nothing wrong with "made in Taiwan". For me it's a mark of quality. I strongly suspect that the official SRAM/TruVativ BB's are also Taiwan made. As are a great many bicycle components.

[goodboyr]

You missed the most important factor....quality of install. The best bb installed incorrectly becomes the worst bb. That means correct tools, loctite, activator and following mfg instruction.

[Calnago]

Have to agree on the "quality of install" part, and making sure everything is perfectly aligned. It was pretty hard to mess up with threaded bottom brackets. Not so anymore.

[fromtrektocolnago]

i never gave much thought to bottom brackets until recently. they always seemed to work and their were better areas of the bike such as group set , wheels or frame geometry to worry about. Now we have press fit and bb 30 so i'd now answer , 'one that doesn't squeak'. So happy we still have english threaded bikes out there.

[bikerjulio]

OP, both your links showed threaded BB's. Are we to assume that you have the good sense to have a frame with threads?

[breezerboy]

I would recommend something like the wheels manufacturing bb as this uses true 24mm and 22mm bearings that fit the GXP axle. SRAM actually use a 7/8" bearing (22.2mm) that is a sloppy fit on the axle. Another reason I don't like SRAM, when they can't even make their own cranks and BBs fit together properly.

[prendrefeu]

Re: Installation...

Genuinely it's very difficult to mess up the GXP system. First, it's threaded. Second the preload is built-in. Third, the bottom bracket has different sides to match the changing diameter. I have yet to see a GXP installation go wrong.

@breezerboy

Really.

Thank you for comments! I'll definitely keep them in mind when I finally make the purchase.

On a side note, I dig your current build. How much weight did sanding off the paint of the cranks save?

Thanks! Off the top of my head it saved a bit over 5g. I'll be setting up another set of GXP Exogram cranks again for a new build, I'll note the before & after this time around.

[breezerboy]

@breezerboy

Really.

Yes, really, just measure one and you'll see for yourself. You've never noticed what appears to be bearing play until the crank bolt is seriously torqued?
SRAM/Truvative BBs used to use 22.05mm bearing until sometime 2012 when they swapped to the cheaper 7/8" bearings, so it depends on what year your BB is. Early ones lasted fine, newer are Cr@p.
This has been widely known, or at least to those that take note of tolerances, for years. Just see http://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=102151 post 4 onwards for more details.

[prendrefeu]

See bike, I use a different bottom bracket.

As far as the OP is concerned, that ceramic bottom bracket that was linked is not of the "cheap" variety.

[bm0p700f]

Ceramic bb's if they are any good will last longer than a steel one. If they are not any good they won't roll better.

A good bb is one that lasts.

Wheels manufacturing parts are excellent.

Edit i hate my tablet

[pizzayum]

OP, both your links showed threaded BB's. Are we to assume that you have the good sense to have a frame with threads?

Yes, I have a BSA frame.