Newer three peice cranks in an old cruser
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Truvativ makes an adapter to put a sealed cartridge and three piece crank set in an old style one piece crank bottom bracket. It installs quite easily. My question, for those who have done this- what is the right width cartridge to keep the chainline straight? I bought a kit with the Truativ adapter, and a 127x68mm cartridge, but the 127mm was too wide; it pushed the front sprocket out too far. I'm looking at putting a very cool Electra three piece crank on my Dyno Roadster- Again- does anyone know the correct width cartridge?
JWM
JWM
Its not that simple. Your best bet is to put a known length axle in, look at how far off it is and get an axle that much shorter/longer.
The simple way to check is to put the bike together, stand behind the bike and look down the chain. You can see it go left or right and estimate how much it's off.
BTW, axles do have an overall length but that length is added up from the 3 sections, left, center and right. 3 piece axles come in a thousand different combinations of those 3 lengths. Frames with wider bb shells (72mm) typically need a wider center section axle. 68mm wide frames use axles withe bearings set closer together. Just knowing the overall length doesn't tell us how much sticks out the right side.
Old style triples often used the longest axles, one that is longer on the right side only. For a while crank manufacturers redesigned the triple cranks to use rather short axles, perhaps to reduce flex while pedaling hard. Now they are all over the place. Each brand and model of crank can take a different axle length.
The simple way to check is to put the bike together, stand behind the bike and look down the chain. You can see it go left or right and estimate how much it's off.
BTW, axles do have an overall length but that length is added up from the 3 sections, left, center and right. 3 piece axles come in a thousand different combinations of those 3 lengths. Frames with wider bb shells (72mm) typically need a wider center section axle. 68mm wide frames use axles withe bearings set closer together. Just knowing the overall length doesn't tell us how much sticks out the right side.
Old style triples often used the longest axles, one that is longer on the right side only. For a while crank manufacturers redesigned the triple cranks to use rather short axles, perhaps to reduce flex while pedaling hard. Now they are all over the place. Each brand and model of crank can take a different axle length.
BTW, those bb adapters work well or can be a royal pita depending on how your frame is constructed. Some manufactures keep the bb shell wide open so no problem. Others build the frames with the chain stays, seat tube and down tube protruding into the shell and those are usually in the way of adapters. Some adapters need to fit deeper in to the frame as they are deeper and more square ended on the inner end than the 1-piece crank bearing cups.
On a Dyno, I changed out the cranks with another one piece, it wasn't wide enough, so the above info is correct, each bike must be measured for a conversion. The clearance of the crank arms to the chain stays is the biggest concern
I have quite a few BMX three piece cranksets in my old cruisers, Redlines, Eastern and Haro cranksets with 19mm spindles, you don't need any kind of adaptor if you use this style crankset, they come with washers to adjust your chain line. Older American bikes are all American bottom bracket, advantage of a sealed three piece crankset over the janky ole one piece is that you can ride your bike fast and hard and won't have to worry about loose ball bearings coming loose or apart in the bottom bracket cups, three piece setups are bullet proof, plus they just look super trick.
Thanks for the feedback. This, and your post above give me some great info. True about the adapter- I put one in an old Schwinn frame. It went in OK, but I can see where there could easily be problems. Too, once in, it's nearly impossible to remove without damaging the aluminum. I may look into the BMX set up that Carbon posted as well. And, yeah- for our purposes the performance components are there for looks and cool factor. Who's going to go racing on a Dyno Roadster?
JWM
This is some fantastic information ! thanks a bunch guys as for the advantage I can do a lot more with it with looks and sprocket size . I have a few frames I want to retro so that's where i'm heading .
On some old bikes using the BMX style BBs I've had issues with getting the spacing right, it seems not all the old BB shells were tightly standardized on width and the spacer stack wasn't right. Using the Tru-vativ style adapter, it helps to used a track BB for a cruiser otherwise using a normal shimano, SRAM etc BB the drive side is offset deeply for a multi ring crank throwing off the chainline for a single. There are also the sealed YST units that I used on a Klunker build recently since everything was kinda funky size and alignment wise, these have collars that allow you to slide the spindle exactly where you need it. Even though it's 127mm it's not offset to begin with so it'll be closer to your chainline if not right on.
http://www.ebay.com/itm/New-YST-BMX...153?pt=US_Bottom_Brackets&hash=item565b9556a1
http://www.ebay.com/itm/New-YST-BMX...153?pt=US_Bottom_Brackets&hash=item565b9556a1
There are soooo many ss alloy cranks out there... I'd try the American-to-BSC converter, and once you pick a crank, you can get the right BB for your bike's chainline--which will be determined by the rear hub/sprocket..
With a 127mm spindle like you get on the YSTs,you're either going to have your chainline off or you're going to have the NDS crankarm way outboard, which will put you and your cranks off-center. I guess I could live with that, but why would I, when the right parts are available?
I'd feel crazy if I didn't mention that OPCs are awesome, and BMX cranks are awesome, too, and you need not goof around with kludges to run either of those.
JaxRhapsody
Rhapsodic Laviathan
Well, they break, have limited pedal options, and to me, they suck. I've broken two of the mtb cranks I had on my beach cruiser ahem boardwalk racer. never broke a 3piece. speed and performance come first on all my bikes.
