karlkras

Hi,
I'm pondering the purchase of a c. 1986 Miyata touring bike which, the good news, has been kept in very good original condition, and the possible bad news, has been kept in very good original condition.
It was originally spec'd with a biospace crank with a 3x6 gearing system. Personally I would want to do away with the biospace chain rings. Is this a simple matter of replacing the chain rings on the existing crank, or would I need to replace the entire crank? Also, how easy is it to still find chains that are compatible with 6 cog systems? The cost on this is only reasonable if I don't have to replace the entire drive train.

thanks!

idoxlr8

"Personally I would want to do away with the biospace chain rings" Why? Are you qualified to make that statement? There are still a few of us out here that ride Biopace CR. All my bikes have Biopace. Chains are easy to find. nashbar, wal-mart.

When buying a used bike, go for fit, not price. I would offer this guy ~ $80 to $125 for his bike. You'll have to repack all the bearings, replace cables and probably tires and tubes if you want a dependable ride. I know just pulled my Miyata out of storage, and had to do all of the above.

Chuckie J.

I believe he is very qualified to say that he wants to get rid of his chainrings. Exceptionally qualified!

well biked

Determine the Bolt Circle Diameter(s) of the crankset, you can just replace chainrings. Since it's a touring bike with a triple, the cranks are probably 110/74 BCD, or it could be 130/74 BCD. An "8 speed" chain will work just fine on your six speed bike.

Here's how to determine BCD, from Sheldon's site:

https://www.sheldonbrown.com/gloss_bo-z.html#bcd

karlkras

Great, and that's your preference, mine is otherwise.

I don't understand you... first you tell me to only buy upon fit, not price, and then you recommend how much I should pay for this bike. But thanks for the advice,

cs1

Sounds like a fun project. You'll find that new chainrings will cost about the same as a crank. IMO, look for a Sugino XD600 triple. They go for $80 - $100 new on ebay. You may need a new BB. Any 7/8 sp chain will work. No problem with the 6 sp freewheel and newer crank. Good luck and have fun.

Tim

HillRider

Nashbar has house brand replacement chainrings in a variety of bolt circle diameters at attractive prices but their web site shows most sizes are out of stock right now. If you buy "name brand" chainrings you will, as cs1 mentioned, find they cost as much or more than a new crank.

Nashbar has a couple of house brand cranks complete for $90 -$100 and is closing out Shimano 105 and Ultegra 9-speed cranks for $50 - $60. The Shimano cranks will require a new (Octalink) bottom bracket but the Nashbar cranks use the older square taper design.

well biked

Btw, I've bought quite a few of the Nashbar chainrings, they're actually made by Stronglight. They even come in a Stronglight package, and have "Stronglight" etched onto the chainrings. But yeah, the big challenge is catching them in stock-

DMF 

Biopace rings have a ready market on eBay. If you take them off, please recycle them. They aren't making any more.

well biked

And speaking of ebay, once you determine what size BCD you need, you can probably find some lightly used, or even brand new chainrings there for cheap-