Cassette for climbing

my bike currently has a compact crank and an Ultegra 11-30 cassette (DI2) . I will be riding both the triple bypass (Colorado) and some big climbs in the Italian / French Alps in the next 6 months (hopefully). Listening to coach Chad, I have really worked on my cadence and with a relatively low FTP (215), I find on steeper climbs my legs really bog down and i cant hold the cadence I like. Would a 32 make a significant difference?, it looks like i might also use a 11-34 with a spacer(?). Any thoughts appreciated.

Yes ,I would definitely put on the 32. You might need to change the derailleur to a long cage.
Assuming these are really long climbs, you dont want to run out of gears 1/2 way up ,and trash your legs. If you feel fine ,no worries, its there if you need it. 11 34 would be good. Ive got that on my bike, being a small skinny rider with an embarrassingly low FTP. But I`m a climber, and seem to fly past people with much greater FTPs, so I guess its all relative

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A 32 or a 34 would be wise, especially since you will also be at altitude…although as noted you may need to get a longer cage read derailleur.(and chain)

Another option is to change you front chainrings, depending on what you currently have. If you already have a 50 / 34T crank, then that won’t be an option.

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Compared to an 11-30, going up to a 32 would make a slight difference but a 34 would certainly Make a big difference on steeper grades. Hell I live in Michigan (Flat to rolling hills) where I rarely see anything over 8% and never for more than 30 seconds and have a 11-32 on my bike.

Also, depending on your current set up maybe consider swapping to a compact crankset for the trip.

Edit: seems like @Power13 best me to posting the exact same comment.

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I took an 11-32 to the Alps last summer and was glad I did. Because normally you’re also going to ride big miles and probably string together a couple of big climbs in a single day. Even if you don’t mean to, it’s easy to have to climb a couple of 1,000-2,000’ “short climbs” while on your way to or back from the big climbs of 3,000-6,000’.

I had an FTP of around 256 at the time and with a large percent of the time in 34/32 I averaged 203W and a 78 cadence up Alpe d’Huez in 1 h 10 min. My natural cadence is 90-93 RPM but I was forced to be 80 or below to make sure I kept the IF down low enough to get the other climbs and miles in for the day.

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What chainrings are you on?

I did the marmotte last year with a slightly higher ftp. You definitely need 32. I think 34 is too much also taking into account you have a few more months to train. Good luck!

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Imo you can never have a gear that’s too low when doing some serious climbing. Being able to keep spinning at a comfortable cadence limits fatigue and spares your knees. So go for the 34 if that’s possible.

Think of it this way, would you rather end the trip having never needed the 34, or wishing you had that extra gear left when 32 wasn’t enough?

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Good opportunity to use my favorite online gear calculator. It lets you compare two setups against each other.

So setting everything else constant, you can compare that at 60rpm with 30t cog, you’re going about 5.5mph (actual speeds don’t matter here, it’s the relative difference in cadence we’re after). And then, looking at the 34t cog setup, slide the cadence up until it reaches the same speed, 5.5mph, and you’ll see you’d be spinning about 68rpm.

So if going the same speed, you’d gain about 8rpm faster spin with the 34 vs 30 big cog.

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I have no idea about the hills you have mentioned. I have recently swapped to a 50/34 with an 11/34 cassette.

Love the combo and would never want anything less.

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compact

very cool!

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My gravel bike is for climbing, off-road, but climbing, 42/28 chainrings. 11-32 cassette. I’ve thought of going 36/24 rings and 9-32 cassette.

You should try some climbs and see. Going 30 to a 34 would help, like one more gear. A 32 would be meh. If you can’t swing/hack up lower gears. Get a GRX setup. I use SRAM and can put MTB stuff on, and hack up cranks with narrow q and mtb rings.

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holy cow…i thought i was at least of average intelligence…until i tried to understand this calculator

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Yeah, and I’d even consider SRAM’s 11-36 cassette. I did some climbing today and even if you can turn a 33:30, a lower gear will allow you to spin more quickly.

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A few thoughts:

  1. Yes, get a bigger cassette. Lots of options, especially if you add a wolftooth roadlink, longer cage and longer chain.
  1. Triple bypass is on Colorado mountain roads. These are not as steep as mountain roads in the Alps. Whatever you need for triple bypass, you’ll Need more for the Alps.

  2. Add some low cadence sweet spot/tempo intervals to your training. I find this helps a lot for climbing.

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I would like to add, that I dislike big jumps, for more flatter riding. That’s why I chose to drastically reduce my chainrings and use a tighter cassette that offered 1T jumps until the end gears. With smaller rings the jumps are not as big, in terms of gear inches, as well.

Edit: I live in a hilly area. My road bike is 50/34 11-32. Climbing a 1hr 12% hill is brutal. It depends on your W/kg but I’m only 3.2 if you were 4+W/kg it might not hurt as much. But take into account you’re going to do it day after day for a week or more.

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I’m with @Power13 on this one! Make sure you’ve got that 1:1 gear!

34 small chainring, 34 largest back cog.

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And you can use this website to calculate power output at that speed on a grade.

http://bikecalculator.com/

Eg at 5.5mph on a 10% grade (not uncommon in the Alps), a 70kg rider will be putting out 214W.

So it you plan on long rides in the Alps, it might be worth a 36 or 40 tooth big cog.

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This should plug into your crank. This will give you an extra gear, basically. A 4T ring drop is noticeable to 46/30. Add in the Shimano 11-34.

https://absoluteblack.cc/oval-road-chainrings-30-46-and-32-48-for-110-4bcd/