Bottom brackets best to worst?

father_jack

What are the best, and worst types of bottom bracket?

I've only had square taper BB's so far, they seem easy to fit, last a long while, and pretty enclosed away from weather.

I've read a bit about press fit BB's and they seem to be pretty hated. Short lifespan, and soon suffer from crunching. Also require special tools. And the idea of bearings just pushing in held on by friction (and want to remove it easily, without damaging anything) doesn't seem that good idea.

I know of Octalink BB they seem similar to square tape BB in concept just the axle has splines which the chainset pushes onto.

UndercoverElephant

Depends, best and worst for what?

Longevity? The old-style internal bearing ones are great, because they can be sealed very well. Maintainence wise? Cotter-pins are a pain and they last so long they get well stuck. That and you're never quite sure which length to get. Also, power transfer isn't as good. ISIS are very similar, just splined instead of square.

The outboard bearings type, Octalink are very easy to use and maintain, but largely disposable in longevity. I replaced the one FSA on the Pinnacle after all of 500 miles, as it was getting stiff. You can get better ones, though, I replaced it with a Hope one which is still great after 15,000.

Press-fit allow the best power transfer. Great, solid BB shells, thicker spindles. But they do have the downside that they can creak. They're cheaper and lighter for the frame manufacturers too.

The Rookie

Well if your bike has a threaded BB shell you can';t use press fit however much you want to, so that renders your question non-sensical. Likewise if it's press fit it can't take threaded.

Octalink by the way is not external bearing its Internal like square taper but a spline pattern like ISIS or powerspline.

For a commuter with threaded BB I'd go with Square taper (better bearing size than the larger diameter axle splined variety) or external BB (not GXP though as the ball bearings are extracted from cottage cheese) for a 'sportier' commuter.

If the frame is press fit you have no choice but to use a BB that fits whatever 'standard' (a misnomer given the number there are) it uses.

A little light night reading
http://www.bikeradar.com/gear/article/c ... ets-36660/

Snakebite the 2nd

Blimey, "Cotter Pin", haven't heard that since the late 80's!!

I've only ever used square taper in my serious cycling, and have had no issues.
This normally entails replacing the whole BB in one go at very irregular intervals.

Eventually I'll move over to the splined shaft cranks, but only because it will come on a bike I have bought.

father_jack

The Rookie wrote:

Well if your bike has a threaded BB shell you can';t use press fit however much you want to, so that renders your question non-sensical. Likewise if it's press fit it can't take threaded.

Did I mention what bike/BB shells I have?

Nope.

:roll:

The Rookie

A mate bought a brand new cotter pin cranked bike last year!


Decent ST (Shimano UN53) seem to last forever, a bit heavy though.

father_jack

It's a shame as a new bike I'm considering (Boardman CX Team) is nice but the BB is crap press fit. So are the new road bikes and flat bar road bikes/fast hybrids. To stick with sqaure taper I'd need to look at lower range bikes, CX Comp instead of CX Team.

tgotb

My favourite (though they no longer seem to be available) would be square taper with loose bearings. Trivially easy to service, and it doesn't matter how much cr*p you get in them because it's so easy to dismantle and clean them. My least favourite would be anything with cotter pins. I'll never forget the sensation of riding along with one loose crank. Ugh!

Of the modern bearings, I've yet to discover anything for a 30mm spindle (BB30, PF30, BB386Evo etc) that has vaguely effective seals*. BSA/Hollowtech, whilst *slightly* heavier and less stiff, is pretty well sealed, and replacement bearings are cheap as chips so you can afford to keep a couple of spares. My favourite is BSA/Hollowtech with Rotor cranks, because they seem to have a better spline/clamp than Shimano.

Contrary to what many people think, your frame BB shells don't constrain you to a specific BB configuration. There are adaptors that allow you to use any BSA BB (square taper/ Hollowtech, GXP) in a BB30/PF30 shell, and systems that allow you to use a 30mm spindle in a BSA shell (I have a bike that uses B386Evo to achieve precisely this).

* All my CX bikes have 30mm spindles; I like the extra stiffness and reduced weight, but keeping the bearings in good condition is a pain in the behind.

MisterMuncher

Each system has pros and cons, but if BB, shell and install are all up to snuff they'll all do the job 100%.

Early advice for install of press-fit bearings wasn't great, and has led to a certain amount of FUD about them, but anecdotally at least, I've certainly found them no more troublesome than external or square taper once I'd figured out the initial foibles. The tool requirement isn't that steep, and tbh the other types also need a special tool or two.

The issue with square taper is that there's not many new square taper cranks above entry level, and it is heavier (unless you go very exotic with the BB itself) and noticeably less stiff.

Hollowtech-style external BB's are a nice, reliable system, but again they're only as good as the sum of the parts and the quality of the install.

MisterMuncher

Father Jack wrote:

It's a shame as a new bike I'm considering (Boardman CX Team) is nice but the BB is crap press fit. So are the new road bikes and flat bar road bikes/fast hybrids. To stick with sqaure taper I'd need to look at lower range bikes, CX Comp instead of CX Team.

The Boardman CX notoriously had a batch go out with badly/wrongly installed BB30 bearings, which definitely didn't help the reputation of that system. There's nothing at all inherently wrong with press-fit bearings if they're done right.

timothyw

I can't see anything fundamentally wrong with the PF30 standard that the boardman uses, so long as you're happy with a chainset with 30mm axle - they work the same way as pf86 which I've not had any real problems with.

If you decide you want to use a 24mm axle shimano chainset then the converter bottom brackets are eye-wateringly expensive, so that's one issue.

BSA screw fit bottom brackets are the most widely compatible, but they are more flexible under power than the press fit standards, and by their nature will give you a somewhat heavier bike. Whether these effects are actually noticeable probably depends on the end user.

BB30 on the other hand I would avoid like the plague, bearings sitting directly in the frame sounds like a terrible idea to me.

rhodrich

I'm stuck in the dark ages, as all my bikes are either square taper or cottered. Most of the square taper ones are loose ball too.

What's the advantage in having a 'stiffer' bottom bracket? Surely you've got to be a beast to be able to bend any size axle? I've certainly never felt any disadvantage in having a supposedly bendy square taper BB. After all, if it really was an issue, how come most track bikes still use square taper? Even if the axle wasn't stiff, it would act as a spring, and just give you back the energy in a different part of the pedal stroke. There's nowhere else for the energy to go....

For commuting purposes, square taper is king. If you don't get 10,000 miles out of a sub £20 Shimano cartridge BB, even when used in all weathers, you've either gone for a cycle underwater, or you've been extremely unlucky. Spa Cycles do a decent range of high quality square taper chainsets here: http://www.spacycles.co.uk/products.php?plid=m2b0s109p0

fat_tail

Hollowtech external BB are fine if you avoid the Tiagra ones. I have used Dura Ace 9000 and now running 105. Got over 9000 kms on the Dura Ace compared to 2000 on Tiagra. They are around £20 compared to £10 for tiagra, Tiagra seem to be made of cheese.

craker

Is there a tool needed to fit newer Ultegra Hollowtech BBs? They're smaller in diameter than they used to be and come with a plastic ring which fits overs the shell to turn it by hand. The instructions have absolutely no mention of an installation technique (torque, tools) merely a strongly worded recommendation to use Shimano lubricants.

Of the two I've got on the go at the moment, the newer one has started creaking (that's a hand tightened one per my question above), the older one feels a bit stiff despite low mileage, good weather riding (best bike). My experience with external BBs on the whole is a bit rubbish, but I've just replaced the square taper BB on my year old Langster as it had started clicking. Less than impressed with that, though it could have been an installation issue.

tgotb

Rhodrich wrote:

What's the advantage in having a 'stiffer' bottom bracket? Surely you've got to be a beast to be able to bend any size axle?

I feel the difference (weight and stiffness) on my CX bikes, where I frequently lift the bike over obstacles, and often find myself doing a couple of pedal strokes at ridiculously low RPM / high torque. Mind you, I am towards the stronger/heavier end of the spectrum, and it could be that it's all in the mind (which still counts when you're racing). On the TT bike, which I don't beast around, a 24mm axle seems to be fine.

Rhodrich wrote:

I've certainly never felt any disadvantage in having a supposedly bendy square taper BB. After all, if it really was an issue, how come most track bikes still use square taper?

I always thought that was related to the narrower Q factor, and the fact that the chainring has to line up with a single sprocket on a narrower rear hub. With a Hollowtech-type BB you're constrained to a specific Q factor, whereas square taper gives you the flexibility to move the chainrings and cranks in or out by changing the BB for one with a different width. For the same reason my Brompton and tandem both have square taper, and I'd guess it's probably standard on anything with hub gears. The ultimate in high-end track bikes is probably the UK Sport bikes; anyone know what they have?

Rhodrich wrote:

Even if the axle wasn't stiff, it would act as a spring, and just give you back the energy in a different part of the pedal stroke. There's nowhere else for the energy to go....

Not really; in practice you don't get all the energy back in a useful way, and some will always be lost as heat (for geeks, the second law of thermodynamics).

ugo.santalucia

TGOTB wrote:

Not really; in practice you don't get all the energy back in a useful way, and some will always be lost as heat (for geeks, the second law of thermodynamics).

First?

The second deals with free energy as a balance of enthalpy and entropy

fat_tail

craker wrote:

Is there a tool needed to fit newer Ultegra Hollowtech BBs? They're smaller in diameter than they used to be and come with a plastic ring which fits overs the shell to turn it by hand. The instructions have absolutely no mention of an installation technique (torque, tools) merely a strongly worded recommendation to use Shimano lubricants.

there is an adapter you can get. I had one included in the Dura Ace bb I bought. Didn't get one with the Ultegra 6800 one I bought recently

tgotb

ugo.santalucia wrote:

TGOTB wrote:

Not really; in practice you don't get all the energy back in a useful way, and some will always be lost as heat (for geeks, the second law of thermodynamics).

First?

The second deals with free energy as a balance of enthalpy and entropy

Ah, I appear to have been out-geeked :-)

Quick revision on Wikipedia suggests it's not actually any of the generally recognised laws of thermodynamics, though it is nevertheless true that it requires energy to bend things back and forth, and that energy is converted to heat. The second law limits what you can usefully do with that heat.

Apologies for the diversion - back to bottom brackets!

timothyw

Plenty of higher end track stuff isn't square taper - Sram omnium uses external cups, and Dura-ace track uses octalink which is a bigger and hence stiffer standard. Campag Record pista is still square taper however.

Sugino 75DD seems another popular one at the high end, and that's external cups too.

tgotb

One thing I didn't know until recently is that there are actually three different extractor threads for square taper cranks; turns out that my tandem has *both* of the non-standard threads :roll:

I couldn't even find a LBS that knew about the different threads, let alone one that had the tools...

davis

UndercoverElephant wrote:

Cotter-pins are a pain and they last so long they get well stuck.

I think I've been reading too much American engineering-type stuff. In US English-ish "cotter pins" are what we call "split pins", I think...

What are cotter pins, in UK parlance?

tgotb

davis wrote:

UndercoverElephant wrote:

Cotter-pins are a pain and they last so long they get well stuck.

I think I've been reading too much American engineering-type stuff. In US English-ish "cotter pins" are what we call "split pins", I think...

What are cotter pins, in UK parlance?

You're right, turns out it means something different in US English. Here you go:
https://en.wikipedia.org/wiki/Cotter_(pin)

Edit: One of the key features of cotter pins on bicycles is that they are designed to avoid overstressing the rest of the bicycle by deforming when you apply too much force to the pedal. The thread is normally made from a particularly soft material to prevent cyclists overtightening the nut, in order to disable this feature.

Sleeper Service

Not had a problem with the Tiagra Hollowtech BB I bought to replace the laughable FSA MegaExo unit. Early days, mind.

Nellyspania

Best ever has to be a good old Shimano UN55 type square taper; lasts for ages and ages, then when it finally gives out, 15 quid for a new one and about 5 minutes to change.

MisterMuncher

That. I couldn't say which is best, but MegaExo is definitely the worst.

tgotb

For anyone who has never worked with cotter pins, Sheldon gives a good flavour of what it's like:
http://www.sheldonbrown.com/tooltips/cotters.html

davis

TGOTB wrote:

davis wrote:

UndercoverElephant wrote:

Cotter-pins are a pain and they last so long they get well stuck.

I think I've been reading too much American engineering-type stuff. In US English-ish "cotter pins" are what we call "split pins", I think...

What are cotter pins, in UK parlance?

You're right, turns out it means something different in US English. Here you go:
https://en.wikipedia.org/wiki/Cotter_(pin)

Edit: One of the key features of cotter pins on bicycles is that they are designed to avoid overstressing the rest of the bicycle by deforming when you apply too much force to the pedal. The thread is normally made from a particularly soft material to prevent cyclists overtightening the nut, in order to disable this feature.

Right.... so you tighten the nut, and it pulls the wedge inwards, right?

dyrlac

Tim Moore's Gironimo (about his retracing of the 1914 Giro route on a vintage bike) also gives some flavour of the joys of cotter pins (in addition to being a genuinely good read).

Octalink/Square Taper for me, mostly because I have the mechanical aptitude to deal with these without needing to worry too much about buggering them up.

tgotb

davis wrote:

Right.... so you tighten the nut, and it pulls the wedge inwards, right?

Nope, that's the classic beginner's error. Tighten the nut, and you'll just strip the threads without ever getting the wedge tight enough. You need to bang it in from the other side with a hammer (having greased all relevant surfaces); the nut's just to stop it falling out again. You then need to bang it in some more (and retighten the nut) after you've ridden a bit.

Fitted properly, I should imagine they're fine. Fitted by a schoolboy TGOTB, you'll be lucky to get 50 miles out of them before the left-hand crank goes wobbly; I used to carry several spares.

ugo.santalucia

I have always been critical of external BBs, but I am enjoying a honeymoon with HT2 at the moment. Maybe it's because I barely touch the plastic bearing preload nut, while in the past I used to do it up by hand relatively tight. They are also so easy to install and so cheap these days that any alternative seems laborious and a bit of a drag.

Press fit systems are performance oriented and problematic, so I am not inclined to go that route any time soon.

TheStone

I've been HT2 for many years (other than a wasted few months with the FSA MegaExo).

Found the Shimano ones didn't last long, but cheap and easy to replace.

Put a Chris King one on the good bike in 2010 and haven't had any problems since (around 18,000km)