I am a few weeks away from a race that has 5km of climbing with 9% grade mixed surface climb thrown in between paved flat fast race surfaces. My current setup is a 53/39T w/ 11-28 cassette so, as expected I run out of gears quick on that climb. Would changing my cassette to 11-32 or 11-34 be enough with the chainrings I have on currently? Any recommendations greatly appreciated. FWIW I’m 62kg w/ ftp 210w so 3.38w/kg.
Ideally, you’d change your rings. If you can’t, go with 11-34 if your derailleur will fit it.
You can use the following websites to calculate speed for a given power, and cadence for a given speed and gearing.
At 190 watts (about 0.9 IF for you) on a 9% road climb, you’ll be riding at about 9.5 mph.
With 39 (ring) - 34 (cassette) gearing at 9.5kph, you’ll be riding at a cadence of about 65 rpm. Can you ride at that cadence for 30-35 mins (about how long the climb will take on a road surface)?
Note: if the climb is gravel, you’ll be riding even slower - speed and cadence. Meaning you almost have to change your rings (or add an 11-40 cassette or similar by getting a bigger derailleur).
Thanks for the reply & suggestions. I’ve been trying to find a compact chainrings but that seems impossible. I have a 130 bcd so only thing I’m finding in stock or options are 110bcd.
(I am in no ways an expert)
I have both my bikes running Rotor axle/chainring/cranks, so used a 46/30 (with 11-34 at the back) on the marmotte (175k with 5k ascent), and never really wished I had bigger, as would start running out of revs (going downhill only - sadly) at about 65 kmh. This still gets you at low cadence, but more manageable.
If I were to do it again, I’d go even smaller (ratio) rather than bigger. Possibly combining a 2x and classified powershift set up. But my road bike is 2x, and the classified system is on my gravel bike, which is otherwise set up as 1x.
98% sure compact chainrings don’t exist for 130. You may be able to find a 52/38 setup, but it ain’t gonna help you much.
Your other option is to add a Wolf Link adapter to your current setup, which will greatly increase your RD capacity, giving you the option of a. 36 or even a 40t rear cog.