I have a 2 year old Trek 2300 with a 9 speed Shimano 105 group. What do I need to do to convert to a compact crankset - I have a crazy mountain ride coming up and I will need the extra spin...

Ritchey compacts will work with your existing bottom bracket, other models would generally require replacing the bottom bracket.

However, you might want to consider just going for a wider range cassette, such as my Century Special 13-30 or one of the Cyclotouriste 13-34s. (Your present rear derailer should work fine with the 30, but you would need a new rear derailer to go bigger. However, suitable derailers are dirt cheap, as little as $20.)

Sheldon "https://harriscyclery.com/9" Brown

Thanks - What is the biggest cassette that will work with a standard Shimano Dura-Ace rear derailleur (7800)? If I can fit a 30 on the back, I wouldn't need to convert my other bike (the trek 2300) to a compact for this ride. To fit the 13-34 cassette (do you have one in a 10 speed that would work with Dura Ace??) do I just need to get a long cage derailleur?

I get asked this a lot. Here's my boilerplate answer:

We do lots of custom cassettes in 9-, 8- and 7-speed. Most of these custom cassettes involve adding a larger rear sprocket for a lower gear.

Unfortunately, the design of Shimano's 10-speed cassettes features a recess in the spider mount for the larger sprockets, allowing the innermost sprocket to be closer to the spokes than the shoulder on the Freehub body.

This makes it impossible to substitute a different low-gear (largest) sprocket. As a result, we are unable to offer custom 10-speed cassettes, at least at this time.

The largest 10-speed sprocket currently available from Shimano is 27 teeth, and there is no way for us to install a larger one on a 10-speed system.

We have recently received IRD brand 10-speed cassettes in 11-32 and 11-34 sizes. They're expensive but they work well. See: https://harriscyclery.com/10

Here's another option: Most 10-speed setups will allow you to install a 9-speed cassette, and these are available in a much wider range of useful gears. The 10-speed shifters will index a 9-speed cassette if you use the "alternate cable routing" shown at: https://sheldonbrown.com/derailer-adj...html#alternate

9-speed cassette options are shown at https://harriscyclery.com/9.

Note, if you have a Dura-Ace 7800 hub, or a "10-speed" Ultegra 6800 wheel, those will _not_ accept a 9-speed cassette. Other Shimano-compatible hubs will work with 8-, 9- or 10-speed cassettes.

If you want to go for a sprocket bigger than 30 teeth, you will likely need to replace the rear derailer, but those are not expensive.

There is supposedly a Miche 10-speed cassette that goes to 29, we have these on order, but they seem to be vaporware at the moment.

All the best,

Sheldon

I can speak a little to using 9-speed (DA and Ultegra) rear derailleurs with big cogs. For a ride with long uphill sections (Virginia's Skyline Drive), I replaced my Ultegra 12-27 with a SRAM 12-32 cassette. Derailluer is a short cage DA 9 speed and I used the same chain. The derailleur was able to shift into the big cog from the small chainring (39x32). This gave me about 10rpm/mph, which worked out really well for the long uphill grades and is almost as low a gear as a road triple (30x27). I also used it for a hilly (~6,000 ft climbing) century.

You have to remember to AVOID cross-chaining, especially the big-big combination (52x32). While I could shift into big-big on the workstand, the derailleur was out of capacity and I risked damaging the drive train if it was under load. While I have not tried it, I suspect a long-cage (U9 triple) derailleur and a longer chain would work. I've read other posts on bikeforums (check the touring and roadie sections) where people have used MTB rear derailleurs that have no problem with an 11-32 or 11-34 cog set.