Supercompact 46-30 Chainset on Road Bike

[Ross K]

As an alternative option...

I've been running a 46-30 Shimano 105 for years by converting an old 5703 triple (50-39-30) involving removal of the outer and replacement of the middle with a TA 46t ring.

Unsurprisingly it works fine with the original 5703 triple mech matched to double 5700 shifters.

The advantage of this system is you can stick with cheap Hollowtech BBs and if you use a crank arm power meter they're relatively easy and cheap to buy.

[mattsccm]

Then go with a crank that uses the old TA Pro Vis 5 50.4 BCD chainrings. You can get outer rings from 40t to 52t and inners from 26t to 42t: https://specialites-ta.com/128-pro-5-vis. No shifting aids (pins or ramps) on the rings, though. However, if you're happy with a 46t outer, Velo-Orange make a compatible chainring in that size that has such shifting aids. The VO chainring bolts for 50.4 BCD cranks are also much superior to the TA bolts.
Cheers Nick. Thats on my list but too pricey. I like using older Stronglight 80 cranks. 86mm BCD and cvan be run as triples or doubles (or even singles).
Easier to find though are modern triples as suggested above. Got a few and plan to gring off the step where the outer ring goes and polish it up.
The gravel trend has brough a few super compacts out such as the FSA and the Sugino but they are pricey.

[Ianwhitwell]

My local bike shop first suggested a Middleburn R02 x-type crankset, but the 46 and 30 chainrings do not seem to be available at present.

You can fit a 94BCD spider to the RO2 crankset and use rings of those sizes. Here's an RO2 crankset on one of my bikes with that spider and TA 42/29 chainrings. Spa sell 94BCD TA chainrings in 29 or 30 inner and 42-50 outer. The RO2 isn't cheap, but it's very nicely made and very pretty.

IMG_20180822_163836.jpg

Thtas a very clean chain and rings. Impressed. Mine never looks like that

[Vaughan]

Happy Ending.

I thought I should wind up this thread now as, in the end, I decided I needed a new bike anyway and so took the opportunity to select the gears that suited me. I got a Ribble SLR with a Shimano 105 groupset. The nearest option to what I wanted was a compact double (50-34) with a wide ratio (11-34) 11 speed cassette. That gave me the 1-1 bottom gear that I wanted, but the small sprockets did not suit me. I would very rarely use a 50-11: and I cannot understand why anyone who needs a 1-1 would be able to usefully push a 50-11! Also, the spacings at the top end on the 105 are too wide (11-13-15-17 .... 30-34). And then I found out about the 105 compatible Miche 11 speed cassettes and bought a 12-34 which was perfect (12-13-14-15 .....27-30-34). However, although the cassettes have the same pitch and overall width, the freehub body on my hub was not long enough for the Miche. I than realised that three large sprockets on the 105 cassette are dished so the whole cassette sits a few mm inboard compared with the Miche. In the end, I married the inner three 105 sprockets (27-30-34 same as the Miche) with the outer eight Miche ones. I was concerned that this would not work as the Miche sprockets are thicker that the Shimano ones (1.8/1.9 versus 1.5/1.6 and the spacers are thinner to give the same pitch of 3.74 mm), but after some experimentation with the spacers, I was able to get all 11 gears to line up cleanly. And all the gear changes are working fine on a road test: and the bike is beautiful! It has been an interesting journey, and I would like to thank all the contributors.

[gxaustin]

I swapped out my 105 compact crankset for GRX 600 - 46/30. It was very easy and although the chainline is moved outward the Q factor remains the same.

[Vaughan]

Thanks gxaustin for the comment on using the GRX 600 - 46/30. That was the first option I looked at with my local bike shop, but they thought that I would need to change my STI shifter as well, as there would not be enough throw with my existing Campag 10 speed shifter to cope with the moved chainline. Was this an issue for you? Anyway I love the new bike!