3 piece cranks vs. 1 piece cranks?

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Jun 28, 2009
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I have a couple of nice Trek Mtn. bikes that all have 3 piece cranks that run buttery smooth and feel pretty lightweight (never actually weighed them to see). I also have several cruiser bikes (new and vintage) that use 1 piece cranks that run fairly well and are sturdy. Then I saw that Steve's Skull Skates bike has a nice 1 piece crank and it began to make me wonder what the advantages and disadvantages were for each. Should I look for a better 1 piece crank (is there such a thing, lighter, smoother?) or are 3 piece cranks better? BMX guys seem to prefer 1 piece whereas everyone else seems to like the 3 piece...

What are ya'll's thoughts on this? Advantages/disadvantages for both? :?
 
Nov 24, 2009
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My take on this:
One-piece cranks are generally heavier, easier to bend (there are some Cr-Mo and TUBULAR BMX versions that are pretty darned tough, though) but cheaper, require less maintenance, and definitely have more of an old-school vibe. Your pedal selection is definitely more limited on one-piece cranks (1/2" pedal) unless you want to use old-school cruiser-style pedals. If you're building a bike with a small, threaded bottom bracket, you'll be hard-pressed to find a one-piece crank that will pass through the shell, or a bottom bracket to mount it in there.

Three-piece cranks are generally lighter, stronger, and have the widest assortment of pedal types (9/16") and bottom bracket applications available to them. In the case you DO damage a crank arm, replacements are often available without purchasing a whole new crankset. They don't look nearly as old-school as a one-piece crank, unless you're using inferior cotter key cranks like on old Raleighs, which usually get loose and bend/damage more easily. Shims and varied crank spindle widths are available if you need to adapt a wide, multi-speed crankset to a narrower, single-speed frame. Three piece cranks are very strong AS LONG AS YOU KEEP THE ARMS TIGHT. Allowing them to loosen can quickly wear the surfaces where they mate to the spindle, allowing them to wobble and "click".
 
May 27, 2010
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Yep, your man above has got it bang on. What i don't get is what BMX era you live in? Check any BMX mag and i can guarantee you will not find a single 1-piece crank in there! The only bikes with 1-piece cranks are VERY cheap kid's bikes, VERY, VERY cheap adults bikes and anything belonging to some kind of bicycle collector. In the factories of Taiwan they will be getting those things at about 50p each! (The skull skates bike has been specced by a skate board company... say no more.)
I have finally given up with the 'American Bottom Bracket' for my custom builds as it now seems only Profile make decent cranks for them, and that weight and cost is just not really on any more. The real BMX world is going over to the 'mid bottom bracket'. 'European Bottom Bracket' all the way for me... what with the industry standard shell widths of 68-mm, 73-mm and now 80-mm and axle lengths starting from 108-mm and ending up with the specialist 140-mm what won't they fit? With the advent of external bearing cups you now have 1/4" bearings back in them giving a good life span with ceramic options available... why use a flexy piece of heavy steel rod on your rod (sic). Do you really believe manufactures such as Monark, Higgins and Shelby etc. would spec them on bikes nowadays?
No moaning about the cost please, the truly utilitarian shimano BB (UN52 or whatever code they have changed it too) should cost no more than £20 and Sturmy Archer now make a cool old skool track C/Set for £30.... good grief that's the same price as a pair of Brooks Grips!
 
Jun 28, 2009
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So which is easier to change chainrings on? I've changed them on a 1 piece but never on a 3 piece. And will a chainring for a 1 piece also work n a 3 piece?
 
Apr 20, 2009
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StepChld said:
So which is easier to change chainrings on? I've changed them on a 1 piece but never on a 3 piece. And will a chainring for a 1 piece also work n a 3 piece?
Depends on specific example. Usually the 3-pc doesn't need to be removed from the bike, as the rings are bolted to a central "spider" that is part of the arm. There are similar ring "spiders" that fit 1-pc as well, but they're not very common. Sometimes the "spider" on a 3-pc is one of the sprockets, which would require changing the entire crank arm. In other words, a 1-pc ring is generally not useful for 3-pc apps.
 
Nov 24, 2009
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deorman said:
StepChld said:
So which is easier to change chainrings on? I've changed them on a 1 piece but never on a 3 piece. And will a chainring for a 1 piece also work n a 3 piece?
Depends on specific example. Usually the 3-pc doesn't need to be removed from the bike, as the rings are bolted to a central "spider" that is part of the arm. There are similar ring "spiders" that fit 1-pc as well, but they're not very common. Sometimes the "spider" on a 3-pc is one of the sprockets, which would require changing the entire crank arm. In other words, a 1-pc ring is generally not useful for 3-pc apps.
Ahhh! But newer BMX 3pc. cranks, which use splined spindles, often use a chainwheel like a 1pc. crank. I think the diameter of the center hole is different, but most modern sprockets come with an adapter ring to make up the difference on the smaller diameter mating surfaces.
 
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bmx bikes used 1-pc cranks auntill around the late 80's, thats what i consider to still be in the "pioneer" stage of the sport, the sport was still new enough to were companies were still experimenting with parts (companies that did amazing things for bmx were Hoffman bikes and FBM,. haro and mongoose got bmx started but quality wasnt a priority for them)
3-Pcs got popular for strength, 1-pcs bend and break and are sometimes a pain to tighten.
also something thats cool about 3-pcs is you dont have to thread the whole crank body through the bottom like you do with 1-pc therefore the bottom bracket size can get smaller so bmx bikes are more efficient and get lighter while maintaining (and in many cases gaining) strength.
if your kid wants to seriously get more into bmx the first upgrade they will want to make if they dont already have it are 3-pc cranks.

why i think cruisers usually have 1-pcs is stress on cruisers isnt usually an issue because you are sitting, also 1-pc cranks flow nicely and dont draw attention to the gear part of the bike.
 
Apr 20, 2009
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Here's my "old guy" opinion.1 pc cranks work fine for normal sized people doing riding that doesn't include big drops or a lot of hopping. 3 pc are definitely preferred for "serious" competitive work, HOWEVER, old cotter cranks suck, and some crankarm/ring sets that are designed for use on super light road bikes are easily bent or stripped if used for other purposes.
 
Jun 28, 2009
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Wow! That's a lot of great info to digest, thank you folks!
Part of the reason I'm asking is that for my current project I'm building a cruiser/off-road bike mix. I was going to go w/ a three piece crank eventually but then I saw Steve's Skull Skate's bike (which is just to cool!) and it made me begin to question if perhaps I was throwing the 1 piece crank away to quickly. I think I'll go ahead and replace the 1 piece, that the bike came with, and put on a 3 piece crank. Reasoning on this is 1) I ain't a lightweight guy :oops: and I need something strong and 2) I would like to change the chainwheel out easily for the varied conditions in my area's trails. Theoretically I would like to be able ride my bike on an off-road track on Saturday w/ a small chainwheel and then replace it w/ a larger one for a cruise w/ the family on Sunday. You might ask, "Why don't you just use gears?" ...I guess, just to be different and experiment around w/ the different size chainwheels 8)

Any suggestions on a bottom bracket, an adapter set and crank arms that won't break the bank?
 
Oct 15, 2007
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It seems like the 1 piece cranks are more likely to bend than the 3 piece cranks, at least from my experience. However, it's so much easier putting grease on bearings in a 1 piece crank as opposed to fooling around with the bottom bracket on a 3 piece crank which seems like more work to me.
 
Jul 7, 2010
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I prefer a three piece crank on my highbred cruisers because they operate soooo smoothly and make my ride more enjoyable(and look pretty cool too!). They take more time to setup initially but its time well spent. They also offer more options for chainrings. I like one piece cranks when I wish to preserve the period correct appearance of an older bike and I have found that if I take the time to set them up well they are very smooth also. Just my preferences.Enjoy
 
Oct 31, 2015
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If you're bending a one pc. crank, than you really need to get out and ride more instead of working on them and sippin beers. :wink1:
I don't really work on 'high' end bikes....(it's a cash flow thing, I.E. none)...so most bikes I do work on have one piece
I like 'em...to me..they look more like a bicycle crank 'should ' look...
Currently found an older...Murray Monterey mens frame that I'm working into a Klunker. ( I love the Monterey frame...highly overlooked, perhaps) in neighbors trashbin...great patina...and..an easy to work on,nice shiny (after some rubbing with steel wool), chain ring and crank arms....why change 'em.
errrmmm....
of course, and as we know from the forums here,:21: in about a month I'll probably be raving about 3pc. cranks after working on a few of em.
best,
Franco

 
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New bottom bracket systems used with three piece cranks with sealed bearing require no maintenance or adjustment. Tubular crank arms are light and can be purchased for a fairly cheap price now days. BMX style chain rings are an easy swap. Remove the bottom bracket axle bolt and remove the crank arm. Remove chain ring bolt and swap chain rings. Reassemble. Why would anyone want to play with open bearings and one piece cranks anymore unless you are doing a restoration.
 
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Oct 31, 2015
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yep. lotsof good points there.
I suppose it's probably because that's all I've found and been working on...sorta new to this....but catching on quick
I do indeed have it in mind to find a 3 pc. crank bike and use it to 'learn' on.....
I'll be catching up..
:)
Thanks for your input
Franco
 

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