Lower gears on a road bike

Question Detail: 

I am recovering from a recent heart attack and need to lower the gears on my Specialized Roubaix. Current drivetrain is Shimano 105 with compact double chainset. I’ve looked at the option of using a 10-speed 12–36 cassette with a 9-speed mountain bike mech. Would smaller rings be another possibility? Or a triple chainset?

From CTC supporter, John Plant


The first option (described in Cycle Magazine Aug/Sept 2011 Q&A) is the best one, as it’ll take off the most gear inches per pound spent and give you gears that are more convenient to use. But do not delay in buying the necessary ‘Shadow’ design of rear mech. This year Shimano are deleting the 9-speed option from the better quality MTB groupsets, and 10-speed MTB mechs don’t work with road shifters. There’s are still few 9-speed Shadow-type mechs (which you need for more than 34 teeth in back) but I’d not be so sure that Deore is good enough quality to work with 10-speed precision. The importers say they’re already out of M972 and M772 rear mechs – but some retailers still had stock at time of writing!

Smaller chainrings aren’t really an option. You can’t fit fewer than 34 teeth on those cranks. And apart from bolting an inner onto a Stronglight ST55 single chainwheel (contact Spa Cycles), nobody sells a more compact double – I’m thinking 46-26 would be nice – unless it’s an even smaller MTB double that’ll be too small to work with a road front mech. And an MTB front mech will neither fit your bike nor work with your shifters.

A triple is an expensive option. Apart from the chainset and bottom bracket, you’ll need new STI levers and two new mechs. That’s virtually a whole groupset, but it won’t knock off as many inches unless you also swap the inner ring for something smaller than 30. This is possible (down to 24 teeth) with most road triples, but not on Shimano’s latest models, where the inner is fixed directly to the middle.

Chris Juden, Senior Technical Officer

Article tags

Share this article

  • Patron: Her Majesty The Queen
  • President: Jon Snow
  • Chief Executive: Paul Tuohy
  • Cycling UK is a trading name of Cyclists’ Touring Club (CTC) a company limited by guarantee, registered in England no: 25185. Registered as a charity in England and Wales charity no: 1147607 and in Scotland charity no: SC042541. Registered office: Parklands, Railton Road, Guildford, Surrey GU2 9JX.

Copyright © CTC 2016

Terms and Conditions