How the heck do I get this thing off? Sekine crankset
 

Hello,

I am going to take this bottom bracket apart. Trouble I'm not really sure how to get in there... I've done this a handful of times before but this particular Sekine (former) 10-speed has a bit of a different set-up than what I am used to. Typically I would just remove the center cap, unscrew the nut with a ratchet, then use a crank-puller... but this one looks weird. I have attached a picture. Can anyone help me?

those are cottered cranks.

obsolete, don't bother servicing that bottom bracket, just replace it and crankset with modern ones
removal is likely going to be destructive to the cotter pins anyway

I've removed them using a 4" machinist "C" clamp. (finer threads than a "wood workers clamp)
Apply penetrating oil frequently for a day or 2.
Back off the nut 2-3 threads.
Use a small socket or similar for a receiver on the "nub" end. (I've used a 10mm rear axle spacer)
Apply C clamp with fixed end on the nut.

Yes they are obsolete but then so is square taper and that doesn't stop people from having an unhealthy love affair with them:rolleyes:

Look here, jammysosa, for instructions on how to remove the crank. And, yes, you should replace it with something easier to work on.

That's an odd statement. Perhaps you meant "old tech". Much like 8 speed STI (which contrary to popular belief, is not obsolete either).

Unless you meant something other than this definition of obsolete: no longer produced or used.

Obsolete has more meanings than no longer produced. It can also mean a part that is not longer current or a part that has been displaced by newer technology. Let's face it, square taper was the next generation after cottered cranksets. As it replaced cottered cranks, it has been replaced by other technologies.

And just as the cottered crank had its difficulties that the square taper solved, newer technologies solve problems that the square taper have. If a square taper crank becomes loose, it is a ruined square taper crank. You can also over tighten a square taper and crack it. That doesn't happen with ISIS which replaced square taper or with external bottom bracket cranks which replaced ISIS. A loose arm on either of those doesn't necessarily ruin the crank and both are a bit easier to tighten in the field than a square taper.

I'm with cyccomute on this one. Cottered cranks are still functional if you have the knowledge to work on them and the nostalgia to want to. They are now the province of the C&V types.

Otherwise they are many generations out of date and there are several lighter, easier to work on and easier to find parts for designs now available. Square taper cranks and bottom brackets are far more available and certainly lighter than any cottered crank and even newer designs like Octalink/ISIS (already out of date) and external bearing cranks have overcome the minor disadvantages of square taper.

How the heck do I get this thing off? Sekine crankset
 

Thanks! I'd like this to cost 0 dollars since the main goal here is to learn. I'm going to try and be careful in breaking it all down - cleaning, greasing, and then putting it all back together. I'm pretty new to this stuff with a tiny budget and all I have to work on is old Sekine and Raleigh 10/12 speeds which were given to me or picked up from kijiji for next to nothing.

Depending on their age and origin, the Raleighs may be even more difficult since many Raleighs used proprietary bottom bracket threading until at least the late '70's.

You will probably need a new pin for both sides. Driving them out usually buggers the threads. The pin should cost around $5 like this one. Finding them in a shop could be difficult because the technology is so old and out of date.

How the heck do I get this thing off? Sekine crankset
 

Thanks again! Immediately glad I joined.

If it doesn't need servicing leave it alone. There's a good chance you may need new parts if you take apart a cottered crank.

I agree. A bottom bracket overhaul is not something done that often (in fact with cartridge BB's so popular it's even more rare) so if it's working smoothly don't bother. Overhaul a hub, which is far easier and done far more often.

Replaced where? Certainly not on the majority of bikes. Department stores sell far more bikes than enthusiast bike shops and those bikes are likely all square taper.

ISIS and Octalink rely on a tight fit between the splines and arm, much like the tapered fit on a square taper crank (though because it's tapered, it is more tolerant of size variation, at the expense of crank position variation). I guarantee if you ran an ISIS or Octalink arm with a loose crank bolt, you'd ruin it in short order. ISIS and Octalink both require 8mm hex bits to tighten and need 30+ ft. lbs. of torque on those fasteners so they aren't all that easily tightened in the field (no more so than square taper). Integrated spindle cranks have an advantage in that the arms can be R&R'd with a multitool but again, leave those mounting bolts loose, and you'll quickly damage the arm.

I don't really feel like getting into a debate about the merits of each system. I know they each have their advantages and disadvantages. None of my commonly used bikes have square taper cranks either. But, to say square taper is obsolete is ignoring a huge portion of the bike industry and downplaying all the disadvantages of the new tech that has replaced it.

At my shop, we actually have a cotter pin press. It is probably 60 years old, and still works fine.....

I've got one in my toolbox. Really glad its no longer in use. Fitting new cotter pins right is a time consuming fiddly job.

Fair enough. Follow the suggestions for removing the cotters and crank arms, then repack the bottom bracket in the same manner as any other non-cartridge bottom bracket. While you'd like to have the cost "0 dollars" it would still be prudent to at least replace the balls, which would only set you back a couple bucks. Inspect the races on the spindle for pitting; if present, replace the spindle. Cottered spindles can be hard to source sometimes, so you may find yourself digging through used parts bins at your LBS or bike co-op. If worst come to worst, you may replace the entire unit and crank arms with something more modern. The cotters themselves may also be damaged. If the bike has been ridden with loose cotters, the faces become damaged and must be replaced:

http://www.os2.dhs.org/~john/worn-cotter.jpg

Sometimes the threaded shaft is damaged when driving the pin out, particularly if you don't use a proper cotter press for the job. Again, replacement is in order. Fortunately, cotters are inexpensive and ought only set you back a couple bucks for the pair.

Bon chance!

Cottered cranks, cotterless square taper, ISIS and, now, external bottom bracket cranks have always been used on "enthusiast" level bikes. The vast majority of cranks on department store bikes have been and continue to be Austabula single piece cranks. Just about every bike I see at the coop I work at that came from a department store has one on it.

ISIS style cranks depend on more than just a tight fit between the crank and the spindle. They have 10 mating surfaces as opposed to the 4 that a square taper has. The fact that the spindle isn't tapered means that the cranks can't squirm up the shaft and loosen as easily as a square taper. Nor can you overtighten them and crack the crank arm because the arm will bottom out before that happens. Yes, you could damage one if it were very loose but it would have to be very loose and you'd notice it long before you'd damage the mating surfaces. A square taper only needs to be a little loose for the crank arm to oval out. By the time you notice the arm moving on the spindle, it's too late.

As for integrated spindle cranks, it would be very difficult to damage an arm due to it being loose. Looking at just the Shimano crank, you might cause superficial damage to the shallow splines on the arm but the arm is clamped in place by pinch bolts. The splines don't serve any function other than alignment. Without them, the clamping mechanism would still work.

I forgot about Ashtabula cranks. They might outsell square taper there but it could be closer than you think. While one piece cranks are very prevalent on cruisers and BMX bikes, all those department store MTBs and (probably most of) the road bikes have square taper cranks.

I'm seeing all square taper here: http://www.target.com/c/road-bikes-s...c=1118559|null

and here: http://www.target.com/c/mountain-bik...c=1118559|null


No, you can't overtighten and crack an arm, though that's hardly the most common issue with square taper cranks. But that is one advantage as is the loss of the taper. They still need tight bolts to last and once you ruin the nice tight press (ISIS) or slip (Octalink, Hollowtech II) fit, you'll probably run into the same issues as a damaged square taper arm. Ask FSA how well their botched spline interface worked out on their early integrated spindle cranks (tons of complaints of loose crank arms back then).

Square taper still has a bearing advantage in either size or protection from the elements depending on which system you compare to.

No, it wouldn't work without those splines. Those splines transmit torque and the pinch bolts keep the splines tightly engaged. Bikes use a number of simple clamped fits but none of those interfaces see the torque that the crank arms see (handlebars are up there but even with a larger diameter interface they still can slip). With enough clamp bolts and spindle engagement and a switch to steel it could work but then the cranks wouldn't look so pretty and weigh so little.

Time consuming? Cotter pins are best installed and removed with a hammer. They're the fastest of any cranks to remove, except maybe two piece cranks with self extractors. Always plan to replace Cotter pins on reinstallation of the cranks.

- joel

Cotters are best removed and replaced with a cotter press. They are correctly called cotters in the USA.

I've always done this to remove cotters:
-unscrew the bolt
-spray a little PB "Blaster" on the pin
-tap the pin with a small hammer, at different angles, loosens it up
-after a few minutes, use a punch/drift with smaller diameter than the pin (reduces the chance of buggering the threads)
-if that doesn't work, re-apply the PB, tap it harder, whale away on the punch harder

YMMV, no guaranties that this will work. If it doesn't, you can always cut the spindle(s) off and replace with another crank spindle.

The only way you will end up with anywhere near zero dollar cost is if the cotters can be reused and there is no pitting or uneven wear on the spindle or cups, or if you put things back together the same even though they are worn. So you would gain essentially nothing in reliability, and as I noted previously, not a lot in practical experience - so you will have much more than zero time cost.

Yes, and if you use a cotter press, chances are you won't need to replace the cotters each time you service the bottom bracket.

I'm not suggesting that you should spend $50 on a press to fix your bike. It would be foolish to spend that much to service one bike, although I did. I just wanted to point out that a hammer is not the best method. You can try the hammer method (Sheldon Brown has good instructions) or you can find a shop that has a press and will do the job for a reasonable price. It's a quick and easy job with the right tools. Older shops will have a press. My local shop does.