Changing to a more agressive rear cassette. Do you need new shifters too?



Can I interrupt this excellent thread to ask a similar question?

I have an 11-23 9 speed cassette with a 39x53 chain ring (Shimano Ultegra). I'm training for a mountain climbing weekend and want to get some nice big cogs at the back - 12-27 I'm thinking. Do any of you experts know whether I'll need more chain or other adjustments to the bike? If so I'll take it into a shop, if not I will buy the cassette on the internet and do it myself.
 
milker said:
Can I interrupt this excellent thread to ask a similar question?

I have an 11-23 9 speed cassette with a 39x53 chain ring (Shimano Ultegra). I'm training for a mountain climbing weekend and want to get some nice big cogs at the back - 12-27 I'm thinking. Do any of you experts know whether I'll need more chain or other adjustments to the bike? If so I'll take it into a shop, if not I will buy the cassette on the internet and do it myself.
Because of the different ways chains can be sized, all you will get is a guess...Why don't you buy the cassette. Install. Check big/big length. If you need a longer chain buy it.
 
Doctor Morbius said:
I agree with this 100%. Riders should train at the cadence that feels the most comfortable for them within a certain range. It is at that cadence that they will be able to produce the most sustainable power on the bike. Sprints are the exception but that is not sustainable power.

I don't know what cadence Magnus Backstedt uses but I have serious doubts that he's a 115 RPM kind of guy! :D
All this aside, the point is that if you can only manage 30 mph, swapping from a 12-23 to a 11-23 will only give you another 9% (or so) before you max out, a little under 33 mph.
So, either check for a faulty speedo (maybe you're not peaking at 30), or start working on increasing the cadence.
 
milker said:
Can I interrupt this excellent thread to ask a similar question?

I have an 11-23 9 speed cassette with a 39x53 chain ring (Shimano Ultegra). I'm training for a mountain climbing weekend and want to get some nice big cogs at the back - 12-27 I'm thinking. Do any of you experts know whether I'll need more chain or other adjustments to the bike? If so I'll take it into a shop, if not I will buy the cassette on the internet and do it myself.

To some extent you can compensate for a mismatched setup by keeping close track of which gear you are running. Just make sure you switch gear at the front before you've worked your way across all the rear sprockets and you should be fine. It takes a siezeable mismatch to make the bike unrideable.

Do note that chain and cassette wear together, and shifting might suffer when you mix brand new with with worn in stuff.