kgharris

There's a somewhat obscure product known as a tripleizer, which is effectively a smaller chainring for a double crankset that also includes a 74 BCD mount for a smaller chainring. I have an old 130 BCD shimano 105 double crankset that I would love to add a 34t chainring to. Do you think it would work for me to use one of those 130 and 110 BCD compatible chainrings from orgin8 and then use some spacers and chainring bolts to connect a 110 BCD 34t chainring?

BF says I'm new so I can't post a link yet. You should be able to google these terms and see what I mean: origin8 single speed chainring

My concerns are the strength and poor shifting performance on a single speed chainring. I'll be using it with an 8 speed setup with downtube shifters, fwiw.

Thanks and let me know if I'm crazy!

JohnDThompson 

It's possible as long as there are no clearance issue between the crank spider and mounting hardware. Some triplizers avoid this issue by putting the 74mm bolt circle between the spider arms.

dsbrantjr

I would not expect great shifting performance but certainly useable in a "bail-out" situation. Should be manageable with your downtube shifters, friction shifting overcomes a lot of issues..

HillRider

The most recent (and probably last) Shimano 10-speed road triple cranks used a "triplizer" middle chainring. The gearing was 50/39 (Tiagra) or 52/39 (Ultegra) with 130 mm BCDs and the 39T chainring drilled with a 92mm BCD for a 30T granny chainring. It worked but, unlike earlier triples with a 74mm granny BCD, the 30T granny was the smallest that fit.

2_i 

My remarks are as follows. (a) The last time I looked, the triplizers seemed to be out of stock across the board, no matter what brand. This may be tied to the general shortage of parts. (b) There is no principal reason for the shifting to be deteriorated, but the triplizer introduces more flex than in the standard crank, and the flex transcribes onto a slightly reduced efficiency. (c) The rings wear out, albeit slowly. At some point, the triplizer will wear out and will need to be replaced. The one of your choice might not be available anymore. I.e., if the solution works for you, get a backup one.

delbiker1 

As stated above, friction shifting is very forgiving of set up, along with easy maintenance. Some times you just have to try an idea to see if it works. Many things in the bike world that are stated to be non-compatible can be, and are, set up in a way that works. I have a few in-home, customized cassettes that do not shift well with indexed shifting, but they are fine with friction mode. I think the same would be true at the front dr.

To the OP, or anyone, I have a 4400 Tiagra triple with rings, available for cost of shipping, set fee box $16. The crank is 130 bcd and 170mm arms. IIRC, it is 52, 39, 30, well used but still fully operational. I can post a couple pictures if any interest.

kgharris

Thanks so much for the generous offer and apologies for the slow response. Your suggestion of a used crankset nudged me to check out local craigslist and I was able to find a solid exage triple crankset with steel biopace chainrings that I was excited to check out. It's been working great, but I think I will eventually try out the experimental 44t to 34t triplizer. I'll post the outcome... might be years away!