Ask the expert: bottom brackets

BR_Gregor

Hello,
Next week I'm starting a thread (it'll be in the BikeRadar Office sub-forum; I'll post a link below) in which you'll be able to speak to our technical editor James Huang (aka Angry Asian) – you may have read some of his reviews or his AngryAsian column on the main site. The thread will be called: Ask the Expert.

James has been with us for more than ten years and is an absolute AUTHORITY on all things bike, and in particular, the subject of bottom brackets (be kind now...). He's travelled the world examining all manner of bikes, inspected many bike factories, attended pretty much every bike show, has contacts throughout the industry, has reviewed everything and you can put him to the test, or get him to answer your query.

If anyone has a question on bottom brackets or something similar (we'll run more sessions on other areas depending on how this works out), please feel free to ask him and he'll reply to everyone. Hopefully he can pass on some good advice.

As it'll be a forum thread he won't be answering instantaneously but as he gets a chance each day. So fear not, as he'll be answering stuff all week in case you do wish to question him.

Cheers,
Gregor
Communities and OYB Editor

Chunkers1980

Does he know if Cody will ever ride his bike?

Angus Young

Good idea. Though I suspect you'll get lots of questions about squeaking.

rockmonkeysc

Why the hell do manufacturers continue to fit press fit bottom brackets to mountain bikes? It's a stupid idea and no one wants them.

ilovedirt

RockmonkeySC wrote:

Why the hell do manufacturers continue to fit press fit bottom brackets to mountain bikes? It's a stupid idea and no one wants them.

A better question is why do they continue to fit press fit bottom brackets to non-carbon bikes?
Or better yet, who decided it was a good idea in the first place, and why?

rockmonkeysc

I had one in my Anthem and it lasted as well as a normal one but was a real pain in the arse to change while offering no advantage.

benpinnick

^ This. While there's no reason to expect a shorter life from a PF BB there's also no good reason to spec them. Someone in a marketing department will tell you its because it allows a wider profile for the BB housing and therefore stiffer, but they will conveniently forget to mention that it is unnecessary as standard BB housings are plenty stiff enough in MTB land, and also that they are heavier (in a carbon frame layup) as MTBs are generally built with impact resistance in mind as much as stiffness, and so you'll just end up with the same thickness of carbon on a bigger tube, which means any potential weight saving is lost again. Seems to me like a road bike idea that should have stayed on the dark side.

schmako

In your experience what is the best crank/bb combo for maximum milage in wet/muddy conditions?

cooldad

A good old fashioned cartridge BB and whatever cranks match.

The Rookie

UN55 all the way.....The old LX square taper cranks were unbreakable and looked good.

cooldad

Until the nd side loosened and trashed the taper.

But yes, with a bit of regular checking.

Herdwick

from all the parts on a mtb worth exploring, why you choose to make a topic on BBs?!
It's a pair of bearings that an axle runs through, should be simple and durable and easy access for maintenance, if not, then easy replaceable.
How long a BB bearing lasts it depends on the quality of the bearing, how well it's sealed and proper maintenance, not how the BB cup it's secured on the frame.

cooldad wrote:

A good old fashioned cartridge BB and whatever cranks match.

Well it could be that simple but marketing gurus choosed otherwise.....

rockmonkeysc

Herdwick wrote:

easy access for maintenance, if not, then easy replaceable.

Bottom bracket berings aren't servicable and if they're press fit then replacement isn't so easy.
The press fit shell will wear with repeated removal and refitting and loose the interferance fit which leaves you with a scrap frame.

Herdwick

RockmonkeySC wrote:

Bottom bracket berings aren't servicable

Well they could be, a circlip holds them in the bb cup so it's easy to make them removable and fit new ones,
but external bb is easy to remove and fit a new one, so almost as good as buying a pair off the shelf replacable bearings. Although just buying a pair of bearings would cost less, pretty much as sealead bearing headsets, once you get the cups you replace the bearings when worn out not the whole headset.

RockmonkeySC wrote:

if they're press fit then replacement isn't so easy.
The press fit shell will wear with repeated removal and refitting and loose the interferance fit which leaves you with a scrap frame.

my point exactly, plain stupid and who uses them should be shot :evil:

BR_Gregor

Have now opened the thread on which James will be replying. It's here (or just head into the BikeRadar office sub-forum): viewtopic.php?f=40033&t=13019725

If you have a question please ask and he'll give you his best shot!