Wednesday, August 24, 2016

MC286 with SRAM 1x

SRAM has been pushing their 1x groups for road use lately, and has taken it a step further with the recent release of the SRAM Apex 1x group. One important aspect of the new group for anyone trying to build a cyclocross bike on a budget was the release of a new version of the PG-1130 cassette: a 11-42 cassette that is compatible with the 10-speed freehub standard that is found on older road wheels and is still in use on MTB wheels.

At the time I was buying the frames and parts for these bikes, I noted in my post about components that my choice to buy Mavic's budget-oriented Crossride MTB wheels forced me to use only 10 of the 11 cogs in the Shimano 105 cassette because MTB wheels are still using the 10-speed freehub standard. Building a cyclocross bike with the Crossride wheels and SRAM 1x at the time would have required using an XD cassette and buying the XD driver that is available for this particular Mavic hub (which retails for $100). The ability to use a wide range cassette that is compatible with the built-in freehub on stock MTB wheels reduces the cost of a SRAM 1x build significantly.

Since Heather likes the SRAM shifters on her road bike better than Shimano, this summer I decided to convert her cyclocross bike to SRAM 1x so I could use the Shimano 105 group on another bike. For the conversion, I used SRAM Rival brake levers and right shifter, Rival crankset with 42t chainring, Apex derailleur, and the aforementioned PG-1130 cassette.

The original setup consisted of a 50-34 crankset and 11-32 cassette. The new setup results in a lowest gear (42/42 for a 1:1 gear ratio) that is slightly lower than the original 34/32. The highest gear, a 42/11, is approximately equivalent to a 50/13, meaning that the new setup replicates the original setup minus the highest gear of 50/12 (since the 11 tooth cog was never installed). Having ridden my cyclocross bike for over a year, I don't believe I've ever used the 50/12, so I don't believe this is particularly important for the type of riding we do (or most riders do) on this kind of bike.

Gearing range is clearly not a problem, but the other possible caveat to a 1x conversion is gear spacing. I did some spreadsheet analysis of the gear ratios on the original 2x10 setup compared to the 1x11 setup and found that the difference is not that large. The 12-32 cassette has a maximum jump in gear ratios of nearly 16%, between the 19 and 22 tooth cogs. The 11-42 has a maximum jump of 18%, between the 13 and 15 tooth cogs. Perhaps more importantly, that larger jump is closer to the edge of the range in less used gears, where the largest jump was previously in the middle. The difference should not be particularly noticeable to most riders.

Based on our experience so far, I think the SRAM 1x groups are an excellent choice for cyclocross and gravel bikes. It's not surprising to see so many bikes coming out with this setup from the bike bike brands.