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Square taper BB's

Old 08-10-19, 11:40 AM
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oldschoolbike
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Square taper BB's

I realize this may be a hypothetical or even rhetorical question, but here goes:

If square taper bottom brackets are so heavy, flexible, and crude compared to modern hollow axle systems, why does square taper still seem to dominate the track and single speed worlds? I would have thought track and single speed riders would most want the claimed improvements, especially in stiffness, but uptake seems minimal to zero compared to road and MTB riders.
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Old 08-10-19, 11:57 AM
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I think, at least for Shimano, the Octalink is the bottom bracket of choice for track.

The Campagnolo Record square taper bottom brackets were fairly light, with hollow spindles.

Keep in mind that many of the Walmart bikes are made to look like track bikes, but really aren't close.
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Old 08-10-19, 02:12 PM
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Newer does not always mean better. It might mean cheaper to make or faster to assemble, which saves the manufacturer money. Or it may cater to the "gotta have the latest" crowd,
There is something to be said for older technology which has stood the test of time. How many previous "modern" BB systems have gone extinct, while square taper soldiers on?
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Old 08-10-19, 03:20 PM
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Originally Posted by oldschoolbike View Post
why does square taper still seem to dominate the track and single speed worlds?
Because square taper is cheap?

High end track cranks do not use square taper:



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Old 08-10-19, 05:01 PM
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Originally Posted by oldschoolbike View Post
I realize this may be a hypothetical or even rhetorical question, but here goes:

If square taper bottom brackets are so heavy, flexible, and crude compared to modern hollow axle systems, why does square taper still seem to dominate the track and single speed worlds? I would have thought track and single speed riders would most want the claimed improvements, especially in stiffness, but uptake seems minimal to zero compared to road and MTB riders.
If by "track" you mean keirin, consider that it is the NASCAR of the competitive cycling world.
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Old 08-10-19, 05:07 PM
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They don't all use square taper.

But, where they do, it's a combination of cheapness, lack of track popularity limiting tech development, and the ability to tune q-factor.
Or, in the case of Japanese Keirin, it's because they have very strict fairness rules dictating that bicycles be built with very specific technologies. Those rules were established over half a century ago, and they've found little reason to change them, so the bikes are still made with the same sorts of old-school designs.

Small weight differences aren't very important in track because there aren't any climbs, and "stiffness" concerns with steel square taper spindles are silly marketing nonsense.
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Old 08-10-19, 07:05 PM
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Another reason to use square taper would be on a long tour, where replacements are much more likely to be readily available than the latest-and-greatest BB du jour.
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Old 08-10-19, 07:25 PM
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I like square taper simply because it's what I'm familiar with, availability of parts, and most importantly, it's what I know how to work on.
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Old 08-13-19, 06:36 PM
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Just say "no" to square taper. It's junk technology that eats crank arms, and possibly injures the rider.

If the crank arm becomes loose, which happens when the fixing bolt gets loose or falls out, the crank arm is ruined.

If the fixing bolt is over tightened, which happens a lot, the crank arm "walks" up the taper. The crank arm develops a crack from being overstressed, then it breaks off without warning—usually when the rider is standing on the pedals—sending the rider to the ground.

Just. Say. No.
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Old 08-13-19, 06:58 PM
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Originally Posted by terrymorse View Post
Just say "no" to square taper. It's junk technology that eats crank arms, and possibly injures the rider.

If the crank arm becomes loose, which happens when the fixing bolt gets loose or falls out, the crank arm is ruined.

If the fixing bolt is over tightened, which happens a lot, the crank arm "walks" up the taper. The crank arm develops a crack from being overstressed, then it breaks off without warning—usually when the rider is standing on the pedals—sending the rider to the ground.

Just. Say. No.
Spindle arms can come loose to. Hence all the photos out there of riders with Hollowtech2 arms stuck to riders feet and not the bike.

Post-sq-taper designs have had durability issues as well....HT2 arms coming apart, short-lived BB life due to poor sealing compared to sq-taper. etc.


Not at all saying spindle isn't better....but almost all the issues taper cranks have spindle cranks have had as well....exception being that 3-piece cranks can be adjusted for an out of spec BB shell--with 2-piece cranks the shell must be machined nearly perfectly. But, spindle cranks can be nearly a pound lighter while being much stiffer.

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Old 08-13-19, 07:11 PM
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Originally Posted by terrymorse View Post
Just say "no" to square taper. It's junk technology that eats crank arms, and possibly injures the rider.

If the crank arm becomes loose, which happens when the fixing bolt gets loose or falls out, the crank arm is ruined.

If the fixing bolt is over tightened, which happens a lot, the crank arm "walks" up the taper. The crank arm develops a crack from being overstressed, then it breaks off without warning—usually when the rider is standing on the pedals—sending the rider to the ground.

Just. Say. No.
Hunh.
Wonder why, over several decades & tens of thousands of miles, none of this has ever happened to me. Ever.
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Old 08-13-19, 07:16 PM
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Originally Posted by rccardr View Post
Hunh.
Wonder why, over several decades & tens of thousands of miles, none of this has ever happened to me. Ever.
Luck.
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Old 08-13-19, 07:22 PM
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Originally Posted by terrymorse View Post
Luck.
Mmmmmmmmm.....that's a lot of luck.
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Old 08-13-19, 07:30 PM
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Originally Posted by rccardr View Post
Mmmmmmmmm.....that's a lot of luck.
Some people live charmed lives. Others, not so much.

https://www.sheldonbrown.com/brandt/...ng-cranks.html
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Old 08-13-19, 07:38 PM
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Originally Posted by terrymorse View Post
If the fixing bolt is over tightened, which happens a lot, the crank arm "walks" up the taper. The crank arm develops a crack from being overstressed, then it breaks off without warning—usually when the rider is standing on the pedals—sending the rider to the ground.
The crank arm "walks up" the taper with every installation, even if it was torqued properly. This is a form of long-term wear for square-taper cranks. But, it typically takes a very large number of installations for a failure to occur, either from a bottom-out of the taper or a fatigue crack.

Excessive torque will move the starting point for that installation cycle slightly farther up the taper, which means that the crank will suffer more of that permanent wear than it should have. In today's cartridge-BB world of very infrequent re-installations, this almost never becomes a problem in the first place.
To cause a problematic amount of added walk-up on a single installation from overtorque, you'd have to go really nuts. Like "bust out a huge cheater bar for no reason" nuts. The kind of behavior that will wreck any kind of crank interface.

(What is a big problem for taper interface wear is when someone misinterprets the walk-up as loosening of the fixing bolt, and repeatedly re-tightens the bolt after every few rides. Each time this is done, it restarts the walk-up cycle and puts a re-installation worth of wear on the interface.)
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Old 08-14-19, 07:26 AM
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Terry, I think you're being a little dramatic.

To the OP, it's a little heavier and required multiple sizes to be made. The nee outboard ones are lighter and streamline the manufacturing process.

Square taper bearings almost always last longer.

Broken cranks or flex has nothing to do with it. Maybe marketing.
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Old 08-14-19, 08:16 AM
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Originally Posted by terrymorse View Post
Just say "no" to square taper. It's junk technology that eats crank arms, and possibly injures the rider.

If the crank arm becomes loose, which happens when the fixing bolt gets loose or falls out, the crank arm is ruined.



Just. Say. No.
...no.
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Old 08-14-19, 08:55 AM
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Originally Posted by HTupolev View Post
In today's cartridge-BB world of very infrequent re-installations, this almost never becomes a problem in the first place.
That's what I'm hoping for with all of my old bikes. After installing cartridge BBs, the cranks just stay on, year after year.
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Old 08-14-19, 10:42 AM
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Originally Posted by terrymorse View Post
Just say "no" to square taper. It's junk technology that eats crank arms, and possibly injures the rider.

If the crank arm becomes loose, which happens when the fixing bolt gets loose or falls out, the crank arm is ruined.

If the fixing bolt is over tightened, which happens a lot, the crank arm "walks" up the taper. The crank arm develops a crack from being overstressed, then it breaks off without warning—usually when the rider is standing on the pedals—sending the rider to the ground.

Just. Say. No.
I,m sorry, but you don't have a clue. If a sq. taper crank is torqued properly it will not walk up the taper until it cracks un less someone keeps retorquing the bolt.
The reason for the newer BBs is strictly marketing to people who need the "new and improved model". Otherwise there wouldn't be so many.
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Old 08-14-19, 11:26 AM
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Originally Posted by davidad View Post
I,m sorry, but you don't have a clue. If a sq. taper crank is torqued properly it will not walk up the taper until it cracks un less someone keeps retorquing the bolt.
The reason for the newer BBs is strictly marketing to people who need the "new and improved model". Otherwise there wouldn't be so many.
Terry isn't drawing attention to the fact, but he knew the guy who wrote that stuff.
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There's no such thing as too far.. just lack of time
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Old 08-14-19, 05:23 PM
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The greats of pro cycling used square taper without issues. I have had square taper on every bike since the beginning of time, and have had zero issues. I know some seriously powerful riders that use square taper without issues. I even use, God forbid, Shimano UN52 square taper BB with Campagnolo Nuovo Record crank, and have had zero issues. Been using it for 20 years this way.

Marketing BS for sure.
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Old 08-14-19, 05:30 PM
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Originally Posted by davidad View Post
I,m sorry, but you don't have a clue. If a sq. taper crank is torqued properly it will not walk up the taper until it cracks un less someone keeps retorquing the bolt.
Please note that I stated "if the fixing bolt is over tightened". I stand by my statement. Even a crank arm assembled with the specified fixing bolt torque will walk up the taper, as evidenced by the looseness of the fixing bolt after some use. The bolt becomes loose because the arm has moved up the taper during use. If the cyclist is lucky, that will not be enough to initiate a fatigue crack.

As you state, re-tightening the fixing bolt will continue the crank arm's journey up the taper, increasing the possibility of a fracture.

And believe it or not, I do "have a clue". Would you like to compare CVs?

Originally Posted by davidad View Post
The reason for the newer BBs is strictly marketing to people who need the "new and improved model". Otherwise there wouldn't be so many.
Two words: proprietary & patents.
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Old 08-14-19, 06:12 PM
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...it's a wonder more people haven't been killed by square taper BB's.
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Old 08-14-19, 06:24 PM
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Originally Posted by ThermionicScott View Post
Terry isn't drawing attention to the fact, but he knew the guy who wrote that stuff.
I suspect you're thinking of this guy. I knew him when he had hair (yes, I'm old).
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Old 08-14-19, 07:46 PM
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I guess I'm a bit old skool on this one. 3 RAAMs, and a bunch of time at the Major Taylor in Indy, and countless hours in the saddle for commutes and daily cycling and no failures in my square taper bottom brackets. I volunteer at a local bike project and I see a lot of over tightened crank arms but none that have ever failed. Maybe wee need to re-think putting aluminium crank arms on steel spindles. For my 200 pound body though they work quite nicely. Smiles, MH

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