Square Taper v Octalink

[Blue Hills]

I know this topic has threaded through one or two threads primarily on other subjects in the past, but I'm particularly interested in this.

Views/reasoned opinions, preferably from experience, of the relative merits of square taper and Octalink bottom brackets.

The bottom bracket will be used on a tourer using mountain bike type bits and gearing, so I'm not interested in the availability of road chainsets. The bike will be 8 or 9 speed so I also don't care about 10 speed and above etc.

My own experiences are from one bike with square taper, a Cannondale fast city bike with Octalink and a Dahon with I think ISIS, which I take to be a development of the Octalink principle.

The square taper bike lasted something between 10 and 15 years before I needed to change the bottom bracket. Well actually, a bike shop changed it as I'd been daft enough to not periodically extract it and grease the threads every year and couldn't get it out - now all sorted on that front. I think the original square taper had been some generic thing fitted by Ridgeback but it clearly did its job. The bike shop put a UN26 in (I understand the UN55 is better - can anyone also tell me why this might be?) and that is also going fine after a few years.

The Octalink in the Cannondale seemed to perform OK. Had to change it once but can't complain.

The ISIS in the Dahon was a piece of *** and had to be replaced after very little use. But always possible that that was not because of a probem with ISIS as such but down to Dahon's often dodgy parts sourcing - the old one turned out to be from some unrecognisable chinese company.

I rather thought that Octalink was on the way out but Shimano's relatively recent 9 speed Alivio uses Octalink.

Also, if you were travelling i some far flung places and needed a spare, which would be easier to get hold of?

Since Octalink is a relatively (I stress relatively) new idea and failed to dominate/take hold of/transform the components market I'm inclined to think square taper would win on this. But I thought I had better ask.

 

[Drago]

Octa was very good. The problem was with lower end versions. The larger diameter axle means smaller besrings, and on the cheaper ones those bearings werent the best quality and being smaller had to work harder and failed quickly. To be fair cheapo square taper didn't fare well with cheap cranks that would quickly go all sloppy an the axle.

The better quality ones with tougher bearings are superb - a bigger, stiffer, yet lighter axle with a greater contact area which makes for a stiffer and more reliable interface. Best of all the bearings are kept inboard and away from the crud.

 

[Yellow Saddle]

Octalink is rubbish. ISIS is rubbish. I'll explain.

Octalink is the spawn of Satan because it was conceived from an evil premise - lighter is better. Weight weenies complained about the weight of square tape BBs and wanted something lighter. So the engineers in Osaka got together, drank far too much saki and developed what seemed obvious - a BB with a hollow axle. Hollow is lighter and believe it or not, stronger. However, hollow is bigger and therefore the bearings had to be smaller because all bike frames had standard BB shells and the legacy was too big to try and change with one introduction of a new BB. So, the engineers compromised on the bearing size and today those BBs don't last as long as their square taper cousins. Further, the attachment mechanism had to change so they make it splines. The first Octalink BBs were designed for road bikes where people don't do bunny hops and stuff and the splines were short and sufficient. However, the MTB market quickly developed around the same time and Octalilnk failed dismally on MTBs because of people standing on their pedals and jumping and landing violently. Octalink tore out of the crank. No problem. The engineers at Osaka got together again, drank some more saki and created Octalink II - this version has longer splines. It worked. However, they really screwed it up (there was some meths in the saki) and make the entry both press-fit and blind. This means that the BB entered the crank under pressure (not loosely in other words) but that the splines in the crank were recessed and thus invisible as soon as the axle is inserted. This means the mechanic had to get the insertion exactly right. If he was slightly off with the splines, he would happily crank up the bolt and not even know that the splines inside are mismatched and cutting themselves new grooves in your expensive crank. Error number two,

Then, the Americans got jealous of the lighter stuff the Japanese were producing but failed (stubbornly refused, I think), to license Octalilnk. They then merrily created another standard, bypassed the patent by putting nine instead of 8 (Octa) splines on there and voila, yet another standard was born. For 100 years we had square taper and in just one decade we had three new standards - Octa 1, 2 and Isis. Isn't that progress?

Meanwhile, bearings and splines failed left, right and centre. The engineers in Osaka bought some more saki and set about their evil work. After heavy drinking, they came up with Hollowtech. Now, within a decade we had another standard. Again, lighter. However, they forgot that the crank spindle, under torque, flexes a little bit on the left crank (the right crank feeds directly into the chainring) and happily ignored the fact that the bearings, in spite of now being outboard of the BB shell and thus technically bigger (but that's another story), won't cope with the flex in the left. Now we had BBs that failed continually on the lest side. More progress.

Next episode: The stupid doings and screwings of the consumer by the drunk engineers in Osaka by means of press-fit BBs.

 

[Blue Hills]

Octa was very good. The problem was with lower end versions. The larger diameter axle means smaller besrings, and on the cheaper ones those bearings werent the best quality and being smaller had to work harder and failed quickly. To be fair cheapo square taper didn't fare well with cheap cranks that would quickly go all sloppy an the axle.

The better quality ones with tougher bearings are superb - a bigger, stiffer, yet lighter axle with a greater contact area which makes for a stiffer and more reliable interface. Best of all the bearings are kept inboard and away from the crud.

Thanks for your reply Drago.

What do you consider to be the lower end Octalink units?
Anything by Shimano?
Which do you consider to be the better superb ones?

I can't help thinking though, that despite initial appearances, your post speaks in favour of square taper.

Note that I am interested in using the BBs on a tourer.

The advantages you list for Octalink:

Lighter - of no interest to me and no reason why it should be on something that isn't racing, and very definitely won't be racing up hill.

Stiffer axle - not aware that my Shimano Square taper chainsets are wobbling./flexing in any way under the strain of my mighty thighs.

Reliable interface - I grease my square taper to ease fit, tighten with a commonly availble tool and for a while after fitting periodically check/tighten some more. Doesn't cause over tightening as I only yesterday removed the cranks and they came off with ease with the same commonly available tool.

But you do acknowledge/confirm that the bearings ARE smaller.

As for the bearings being inside, that surely applies equally to square taper?

 

[Fab Foodie]

Square Taper, cheap, simple, available, works.

 

[KneesUp]

As chance would have it I was looking into this only last night as I was thinking I really ought to put a BB in my road frame at some point.

My conclusion was:

Octalink - lighter, stiffer, wears out sooner, might be harder to get parts as new versions come out (and might be harder if you're in other countries I guess)
Square taper - heavier, not as stiff but stiff enough, available all over the world.

 

[Yellow Saddle]

Stiff enough is stiff enough. I don't understand all this phaffing about about stiffness.

 

[Drago]

Square Taper, cheap, simple, available, works.

works...ish. there still comes a price/quality point below which the technical deficiencies of square taper come to the fore. We've all seen cheap bikes, old and new, where cheap materials mean the crank socket opens up and allows the tapered end to slop around. This is square tapers equivalent to Octas bearing Achilles heel.

There's no perfect solution out there, just different deficiencies.

 

[KneesUp]

Stiff enough is stiff enough. I don't understand all this phaffing about about stiffness.

I overheard @Fnaar saying that to Miss Goodbody at the church fete on Saturday. As you know she likes a long ride, which must explain why he was telling her she needed to lubricate more I would imagine.

 

[Yellow Saddle]

works...ish. there still comes a price/quality point below which the technical deficiencies of square taper come to the fore. We've all seen cheap bikes, old and new, where cheap materials mean the crank socket opens up and allows the tapered end to slop around. This is square tapers equivalent to Octas bearing Achilles heel.

There's no perfect solution out there, just different deficiencies.

I disagree. No aluminium, including the cheapest aluminium (CP for Commercially Pure), which is not alloyed to make it stronger, is weak enough to never break out or enlarge the square taper. Crank sockets don't open up because of the materials used but because the crank bolt is not torqued onto the taper with the required torque. This then causes it to come loose and the resultant slop (lash) in the interface damages the square. This is the only circumstance under which such damage can happen, provided the tapers are matched.

Interestingly enough, once torqued properly, they tighten themselves even more by creeping up the taper until the bolt is loose enough to fall out. That's the purpose of the so-called dust cap - to prevent the bolt from dropping out and getting lost.

 

[I like Skol]

works...ish. there still comes a price/quality point below which the technical deficiencies of square taper come to the fore. We've all seen cheap bikes, old and new, where cheap materials mean the crank socket opens up and allows the tapered end to slop around. This is square tapers equivalent to Octas bearing Achilles heel.

There's no perfect solution out there, just different deficiencies.

I think you may be mistaking poor installation and maintenance for poor quality.
IMO the reason you see more of the cheaper bikes with loose and deformed taper cranks is that the cheaper bikes are not sold from bike shops so are never given the proper pre-delivery inspection that would check the crank bolts are sufficiently tightened and are also used by owners that are much less bike-aware so will never know to check if the bolts are kept tight.
The same owners will also not realise that when the crank has come loose once it is to late and the damage is done. They may retighten the crank to rectify the fault then condemn the square taper design as flawed when it then keeps coming loose no matter how tight they force the crank bolt.

Not a lot wrong with Taper cranks even the cheap ones IME.

 

[Yellow Saddle]

Are any of these deficient square tapers made by Shimano Drago?

Or are you just talking about real generic junk units possibly fitted to some BSOs?

Thanks for your replies - hope my responses don't read as aggressive - I am just trying to clarify these issues for an expedition tourer I may be speccing.

Shimano makes no junk and there are no deficient square tapers, only ignorant retailers, mechanics and owners.

 

[Blue Hills]

Thanks for quoting that post of mine in yours above yellow saddle - I think I managed to mistakenly delete it with some misguided tinkering.

Over to Drago, or indeed anyone else.

Some interesting responses.

 

[Drago]

Shimmy do make some gear barely, if at all, fit for purpose. Their cheapo cranks are either pig iron that would give Geoff Capes a hernia, or alloy so cheap the crank makes an Aero bar feel heavy. Their basic components are rife with cheap and inadequate materials.

Of course, the boys above have a point. El Cheapo specials are liable to have been assembled by someone like User wearing boxing gloves after 6 bottles of cider, which does nothing to enhance longevity.

 

[Fab Foodie]

Interestingly enough, once torqued properly, they tighten themselves even more by creeping up the taper until the bolt is loose enough to fall out. That's the purpose of the so-called dust cap - to prevent the bolt from dropping out and getting lost.

No self respecting roadie would have the dustcaps in anyhow to save .5 of a gram ....