What Cassette is best for Climbing 4000-5000M Elevations?

Hi everyone. Im a 60kg super skinny cyclist with an FTP of 193W. I have a 2013 Super Six with 10 Speed (105 5700). Current setup has 50-34 Chain rings and 12-27 Cassette. I mostly ride on flats but visit some hills for 500-600M climbing once every two weeks. I will hopefully participate in an event soon with a total 4000-5000M climbing. I wanted to ask what cassette ratio would be best specifically for the event as it has alot of climbing . Thank you

The amount of climbing actually doesn’t have that much of an impact on your gear choice, but rather the grade. The grade, combined with your Power/weight will determine your climbing speed and that will determine your gear ratio needed.
With a ride this long, you will likely want to go far below your FTP.
The way I approach Chainring/ cassette choice, is Iook for the the parts where I suspect going the slowest. Usually the longest and steepest climb.

Then I plug my weight, my bikes weight (don’t think weight weenie here, you have water, spares, a pump, food, maybe lights etc on your bike and are likely not naked either), the power I want to go at, the type of bike I am riding, and the grade into this Tool:

http://bikecalculator.com/

It will give you a speed. Say 11kph at 8% at 180W.

With that information in hand.
I go into this tool:

There you can put your tire diameter, your chainrings and your cadence.
You can now play around with different cassettes and see what works.
It is always advisable to have a spare gear, and not be forced to ride at 70 cadence, in your smallest gear, at threshold for prolonged periods of time.
If you have to choose between cassettes, choose the one with the lower gear (so the bigger sprockets). Never have I ever heard anyone arrive at the finish line of an epic mountain FONDO and say „damn, I didn’t find a big enough gear, should have gone for a faster cassette“

I am not terribly unfit and not too heavy either and I am choosing a 1:1 lowest gear or lower for epic Alpine days.

Hope that helps.

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This. ^^^

4000+ meters of climbing implies there’ll be some steep grades. And a long day out.

If I was doing an event like that I’d want at least an 11-32 cassette. Maybe more. As reference, I’m low-mid 3s W/kg.

You can expand the capacity of your current derailleur by making the chain longer and using the wolf tooth road link.

This will allow you to run an 11-32 cassette. And you could probably also go to 11-34, or even higher depending on your derailleur.

With this approach, I’ve gone as high as 11-40 with a medium cage ultegra derailleur, 50-34 cranks.

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Unless you are extremely particular about cadence and jumps between cogs, you will appreciate having a 32 on the back (at your weight and assuming some fitness, a 34 would be overkill unless the hills are particularly brutal).

My 11-32 works for Colorado roads, which tend to be less than 10%. If I was riding grades in the 10-15% range, which I understand are common in the alps, I might go all the way to my 11-40.

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Any cassette will do on an e-bike.

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Your preferred climbing cadence is so important here, which in turn is a function of your crank arm length. Short cranks → more spinning.

I know people advocate spinning up climbs, like Chris Froome. Personally, it sends my heart rate nuts and I don’t enjoy it. I’d climb comfortably at an average 70rpm for an hour. I average typically 82rpm on my flat rides.

There is loads of analysis out there about crank arm length…its a can of worms. Obviously, if you increase your crank arm length, you can decrease your cassette size, and retain the same mechanical advantage.

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For a day like that, 11-34 will likely be more fun than an 11-32.
1:1 gear is still deep into 4W/kg at 80 cadence at double digit grades.

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Think it depends on your climbing power and how cadence sensitive you are.

For ages I rode the Alps with an 11-28 and didn’t think twice about it, but my preferred cadence is around 95-100 and I’ve started gearing down to try and get closer to that. Been running 11-30 for last couple of years and did the Marmotte on that, was fine but if new DA allows 11-32 then I’m tempted. That will mean I can climb at sweet spot (or maybe even just below) and be much nearer my happy place cadence.

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Which as I said, would justify the 34 :slight_smile:

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You can slap a 9 speed deore Rd on there and run an 11-40

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We are all different but I did the Marmotte (@ circa 65kg) with a 30/50 compact and a 12-29 campagnolo cassette.

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Thanks alot everyone. This was my first post in this forum and Im amazed by how helpful and informative advice I received. Honestly I have never looked at my cadence when climbing.
I will observe this in the next rides and figure out what would suit me. The wolf tooth chain link advice is also really helpful.
Thanks again everyone.

As above depends on how steep and how long the steepest hills are. Do you know what grades you can expect to be climbing?

13%

How do you feel when climbing with your current setup? Do you often land in your lowest gear? Do you feel like you’d want lower gears? Can you ride at a low cadence for a long time? Think how you’ll feel when you get to those hills really tired, or how riding up and down them all day will feel.

You can try to work it out from the calculators, but I think experience is also good - see how you feel now, and then imagine to be really tired!

Yes, I just did a 2 hr ride today with 488M elevation gain and with around 4-7 grade climbs . I observed my cadence and gears. I feel comfortable in spinning the bike at 80 plus rpm rather than grinding.
My current setup of 12-27 was enough for today but I was easily stepping into z4 on climbs. I would prefer to have more gears and be on the safer side but I cant say of how I would feel when spinning on lower gears for all day. I try to keep the lowest gear for the end of the climb and wasnt using it for most of the time.
More climbing and observation will make it easier for me to decide what would suit me best.

Given your FTP and weight (3.2 W/kg) and preference for 80 rpm cadence, I would go as low as 11-40 for an epic alpine day. 11-34 at the very least. Anything less will just be harder work to manage your power at a sensible cadence. Compact chainrings of course too ie 50/34. You can’t afford to drift into z4 on 5000 m climbing days!

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I’d go with as big as you can. I’d guess you have a short cage derailleur with your 11-27. So you may not be able to go to 11-40, even with a road link. But 11-36 could work.

If you are comfortable doing the work yourself, buy a few cassettes, a new chain, road-link and play around to see what works. Send back the cassettes you don’t need.

You just have to confirm big-big doesn’t rip the chain/derailleur off, and in small-small, you still have some chain tension left.

Yep.

9sp MTB rear derailleur is compatible with 10 speed road (except Tiagra 4700), and you get a long cage with lots of capacity. 11-40 works for this one, and it has the wrap capacity for road cranks. You can then use any other cassette you want, without changing anything, if you set the derailleur up for max wrap instead of the shortest chain.

https://www.amazon.com/Shimano-9-Speed-Mountain-Bicycle-Derailleur/dp/B0064QND30

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