neutrinocounter

I want to convert a double chainring to a triple.

Will I create chainline issues?

This is on a recently acquired Nishiki mixte. Any advice appreciated.

curbtender

You will need a bottom bracket compatible with your new. crankset and a front derailleur.

neutrinocounter

Thanks for the reply.

If you don't mind, what is the critical compatibility I should look for in a matching bottom bracket?

3alarmer 

...there will be a recommended spindle length for your new, triple crankset. This should be the ideal length, that will mount your crank far enough outboard so the inner chain rings clear the chain stay, but not so far out as to throw off the chain line to an unworkable degree. If you're using an older triple, there might be some spindle end taper differences that you need to consider.

neutrinocounter

I appreciate the reply.

I'm looking at cranksets on ebay, and the recommended spindle length is nowhere to be found. Is this something I can measure? Also, "spindle end taper differences" sounds scary.

Is this doable by a non-mechanic? I may need to find something else to do with my time and money .

Bike Gremlin

Simply put: for this to be done, one should measure the rear chainline, then find the appropriate bb spindle length (for square taper, or set the spacers correctly for Hollowtech BBs) to get the cranks to that chainline.
It can be a bit of a trial and error. Shimano states the optimal Shimano BB spindle length for their square taper cranks. Usually on the package. Stating which chainline (in mm) is achieved with that spindle length.
If using non Shimano cranks, or non-Shimano BB, it boils down to trying shorter/longer until a match is made. I prefer Shimano, because they are standard and still easily available, so once I figure out which length is needed, I can use that for the replacement.
How to measure rear and front chainline.

dedhed

Let us know what cranksets you're considering. Many times the spindle length information is available on line if you know where to look.

https://www.sheldonbrown.com/bbsize.html

https://velobase.com/ViewComponent.a...4b128&Enum=115

https://bike.shimano.com/en-US/produ...C-T3010-8.html

JohnDThompson 

I'd go directly to the crank manufacturer's web site to find spindle taper and length specifics. You'll need a few specialized tools to remove the crack arms and the current bottom bracket. If you're lucky, the same tools will serve to install the new parts, but it's possible they might need different tools.

curbtender

Times are a little off...I'd usually say you should take a class. Bike shops and co-op's have them. You learn about your bike and get access to tools. Pretty sure they are in limbo right now. Park tool has a good series of videos. https://www.parktool.com/blog/repair-help
Where are you located?

John Valuk

You didn't ask about rear derailleur, but..

...some "road triple" setups use a longer-cage rear derailleur, compared to their "double" counterparts.

Some riders report that they get along fine after converting from double to triple up front without changing the RD, just by taking appropriate care not to "cross chain".

HillRider

This is just my take but I think ebay is for people who know exactly what they need. To buy something without knowing how to use it is asking to waste money.

neutrinocounter

Bike Gremlin Awesome reply. Thanks.

neutrinocounter

dedhed Thanks for the great info and links.

neutrinocounter

What I learned is that I don't know enough to take on a double to triple conversion without a lot more thought and knowledge. For now, I'm going to leave the crankset alone.

Awesome replies from everyone and most helpful.

Geepig

Another option is to buy an almost trashed bike similar to your own, and then experiment. I bought one last week for about 15 dollars, delivery included - everything but the frame is a bit bent, but not enough that I cannot swop bits over/around.

bikemeister

Dang, alot of good info in this thread! You guys are great!

79pmooney

My advise? Buy the crankset you want. Try it. Observe the chainline. Need different? Buy another bottom bracket or spindle of the same model only of the appropriate length to adjust the chainline.

Or buy a Shimano bottom bracket. If length is wrong, exchange it for a better length.

Or buy that Shimano, then order a Phil Wood bottom bracket based on the Shimano but of the offset and length you want. (The Phils make it easy to fine tune the offset.) Yes, Phil bottom brackets are expensive. I buy them because 1) they will build any length/offset you want and 2) I want the absolute minimum Q-factor to spare my knees. They are also bulletproof, so smooth and last forever.

Retro Grouch 

The analogue approach.

Since you're talking about a mixte frame, I assume you are also talking about a square taper bottom bracket. That simplifies things because there are a lot of them around.

Take the widest square taper bottom bracket that you have on hand and bolt up your chosen crankset. Most likely your crankset will be too far out. Now you can either estimate how far you can move your crankset in before one of your chainrings rubs the frame or you can hold a straight edge along your middle chainring and see how far you need to move it in for the straight edge bisects your cassette.

neutrinocounter

I've decided to take the easy way out and do nothing for now.

This bike is a used and recently bought Nishiki that has what appears to be a new bottom bracket with some kind of clean greenish stuff showing around the edges. Also, the crankset has a place for a 3rd chainring on the inside where a granny gear might go. I thought it would be easy to just bolt on a new chainring and make sure the shifter works.

It's been a good learning experience and I thank all contributors to this thread.