Bottom brackets best to worst?

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Father Jack
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Bottom brackets best to worst?

Postby Father Jack » Tue May 10, 2016 18:47 pm

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.
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UndercoverElephant
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Re: Bottom brackets best to worst?

Postby UndercoverElephant » Wed May 11, 2016 06:26 am

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.

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The Rookie
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Re: Bottom brackets best to worst?

Postby The Rookie » Wed May 11, 2016 07:17 am

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.

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Snakebite the 2nd
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Re: Bottom brackets best to worst?

Postby Snakebite the 2nd » Wed May 11, 2016 07:21 am

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.

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Father Jack
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Re: Bottom brackets best to worst?

Postby Father Jack » Wed May 11, 2016 08:13 am

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:
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The Rookie
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Re: Bottom brackets best to worst?

Postby The Rookie » Wed May 11, 2016 08:15 am

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

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

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Father Jack
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Re: Bottom brackets best to worst?

Postby Father Jack » Wed May 11, 2016 08:50 am

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.
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TGOTB
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Re: Bottom brackets best to worst?

Postby TGOTB » Wed May 11, 2016 08:50 am

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.
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MisterMuncher
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Re: Bottom brackets best to worst?

Postby MisterMuncher » Wed May 11, 2016 08:58 am

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.

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Re: Bottom brackets best to worst?

Postby MisterMuncher » Wed May 11, 2016 09:15 am

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
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Re: Bottom brackets best to worst?

Postby TimothyW » Wed May 11, 2016 09:17 am

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
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Re: Bottom brackets best to worst?

Postby Rhodrich » Wed May 11, 2016 09:23 am

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
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fat_tail
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Re: Bottom brackets best to worst?

Postby fat_tail » Wed May 11, 2016 09:31 am

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.
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craker
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Re: Bottom brackets best to worst?

Postby craker » Wed May 11, 2016 09:39 am

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
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Re: Bottom brackets best to worst?

Postby TGOTB » Wed May 11, 2016 09:44 am

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).
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ugo.santalucia
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Re: Bottom brackets best to worst?

Postby ugo.santalucia » Wed May 11, 2016 09:48 am

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
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Re: Bottom brackets best to worst?

Postby fat_tail » Wed May 11, 2016 09:58 am

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
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TGOTB
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Re: Bottom brackets best to worst?

Postby TGOTB » Wed May 11, 2016 10:01 am

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!
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TimothyW
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Re: Bottom brackets best to worst?

Postby TimothyW » Wed May 11, 2016 10:02 am

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.
Last edited by TimothyW on Wed May 11, 2016 10:22 am, edited 1 time in total.

TGOTB
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Re: Bottom brackets best to worst?

Postby TGOTB » Wed May 11, 2016 10:21 am

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...
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