I've done some research on building a 50-39 crank.

I figured that I could use a compact crank and change the small ring from 34 to a 39. This does not seem to be possible because a 39t 110mm BCD ring does not exist?

So, that leaves me with replacing the 130mm 53t BCD outer ring with a 130mm 50t BCD outer ring? I see that FSA makes such a ring, but it would look kind of strange/ugly on a Dura-Ace 7800 crankset (my first choice). An Ultegra 6700 would be my second choice, but the outer chainring on that crank is $$$ and pretty much proprietary at this point.

Any tips would be appreciated.

Thanks in advance,
Bob

This looks promising.

https://www.google.com/products/catal...d=0CCkQ8wIwAw#

Bob

Surly makes one that is for 110BCD 39t but I don't think it is thin enough for a 10speed.
https://www.universalcycles.com/shopp...&category=2628

Looks like FSA makes a 38t with 110BCD spacing. That'd be close enough with a compact crank.

https://www.amazon.com/FSA-Road-110mm.../dp/B001C4S41U

I could use that an my existing FC-R700 crank (which has been a great crank). It says "use with 52t outer ring". Any reason it wouldn't work with a 50t ?

Bob

Ok, a little bit of research and deal hunting got me what I want. I got the Dura-Ace 7800 crank (smokin deal) for $115 and the 50t outer ring for $90.

The other option I found was that FSA makes a Gossamer 50-39 that someone on eBay is selling.

Bob

Watch your front derailleur. If it was designed for 52/39 or 53/39 chainrings, the inner cage may hit a 39T ring if you set it low enough for proper clearance over a 50T You may have to leave it a bit too high for optimum shifting.

Got it. Will do.

Thanks,
Bob