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I own a Cannondale CAAD8 and absolutely love it. However it's not the greatest hill climber and I am considering on getting a bigger cassette to improve my ride experience on hills

The current bike specs are

Front Derailleur FD 7700

Rear Derailleur - RD 6500 SS ( Short Cage )

Front Chainrings - 2 Speed , 39-53T

Back Cassette - 9 Speed, 11-23T

I am happy to change the Rear Derailleur / Cassette / Chain - But I feel options of 9 speed are limited? Any recommendations on what parts can I upgrade ( without a major overhaul ) to improve the gear ratios?

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  • Very closely related bicycles.stackexchange.com/questions/75243/… Feb 1, 2023 at 19:53
  • @user2705196 good catch, although the OP is more limited because they have a short cage RD. And this is the old style, hard man short cage, which is probably rated to only a 28t max cog.
    – Weiwen Ng
    Feb 1, 2023 at 19:57
  • They also stated that they're happy to change the Rear Derailleur. So the question really becomes about what RD with what cassette. Feb 1, 2023 at 20:12

3 Answers 3

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There are a few options to improve your hill climbing experience by changing the gear ratio of your 2x9 drivetrain.

Your current rear derailleur limits you in terms of capacity (max sprocket 28t, capacity of 29t), your front chainrings are too large for your needs and rear cassette too narrow.

I would suggest doing the following: swap the rear derailleur to (at least) a medium cage one, swap the crankset to something more "compact" and the rear cassette to one with more range.

An example would be to use the Shimano RD-6500-GS in combination with the Shimano FC-R345 crankset 34-50 and the Shimano CS-HG400 cassette 11-32. That setup should work as you will stay within the capacity of the GS rear derailleur (50-34 + 32-11 = 37t).

In terms of gearing, your lowest gear will now have a 34/32 ratio (or 1.0625) vs your current lowest gear ratio of 39/23 (or 1.70). You can further review and compare gear ratios, top speed etc on this handy website.

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    A minor note: they most likely have an Octalink crankset, so they'd need a new BB.
    – Weiwen Ng
    Feb 1, 2023 at 23:39
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Options in 9-speed are somewhat bigger than in higher speed counts: you can use MTB/Trekking components as well (incompatibility between MTB and road start from 10-speed).

You will need to change the cassette and rear derailleur. The current (SS) is a short cage, and won't probably be able to handle a larger cassette and the increase in capacity that is required with a larger cassette.

If you want to stay within road components, the Sora RD-R3000 short cage could do the trick, the biggest supported cassettes are 11-32 (quite a nice improvement range). But Sora is 2 ranges lower than what you have now.

Trekking components offer a wider range: 11-36 cassette with a Deore RD-M592 or Alivio (M3100) rear derailleur — but the look might contrast with you typically find on road bikes. These are designed handle triple chainrings, so may be overkill in term of capacity, but are the only 9-speed that can handle 36T cassettes.

Be however aware that you'll have bigger intermediate steps when changing speeds. For those who prioritize being in the perfect gear for performance, it may be an issue.

Also, changing the chainrings is an option, but less effective: going for a 50/34 will only increase the climbing ratio by 14%, while changing the cassette and rear derailleur would be a 40% increase (Sora) or 56% increase (trekking) - even more if you do chainrings and cassette/RD. Of course you can do both too.

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  • I am quite sure it is 11-34, actually, for both Sora and Claris RDs (they are 9 and 8 speed, but work interchangeably quite well). They sell the bikes with 11-32 but 11-34 is allowed and 11-36 probably manageable. Feb 2, 2023 at 10:28
  • @VladimirFГероямслава good point, just had a look: 32T for short cages, 34T for medium cages (Shimano specs).
    – Rеnаud
    Feb 2, 2023 at 10:52
  • I see, then your statement was correct, I missed the short cage part. Feb 2, 2023 at 12:20
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You can change both the cassette and crankset without having to change your rear derailleur.

First, not being able to climb well with a 53-39 crankset and a 11-23 cassette is not a problem. That's what the top-level pros race on. You're not that strong - almost no one is. And even some pros don't use gears that big. Alberto Contador used to do hilly segments with a 50-34 crankset and an 11-32 cassette.

And unless you can spin out a 53-11 combination (meaning you have pro-level sprint capabilities...), a 53 is wasted. You don't sprint at 40 mph/60 kph, do you? And for any downhill where your spinning out a 50-11 combination, you'd do better tucking and getting as aero as you can.

Change your crankset to a 50/34 compact and your cassette to an 11-28. Your rear derailleur is rated for 27-tooth max cassette size, but this is Shimano. A 28-tooth cassette will work.

There are a lot of options for a 50-34 crankset. Assuming you have a Hollowtech II bottom bracket, you have a wide selection. And you can almost certainly use a 10-speed crankset such as a 105 FC-5750, or a new Tiagra R460. Or you can get a used 9-speed 50-34 crankset to match what's already on your bike.

A 39/23 combination results in about 44.7 gear-inches, while a 34/28 combination results in 32.0 gear inches.

It won't get you as low a gear as changing your rear derailleur would, but it might be enough. And if it is, you won't wind up with some of the really large gaps in gearing that an 11-32 or 11-36 9-speed cassette has. And if it's not enough, you can change out your RD and get a larger cassette later.

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  • Thanks for your thoughtful comments! Your point on not going for a 11-32 on a 9spd makes a lot of sense. I really like how well my crisp my current shifting feels > Your rear derailleur is rated for 27-tooth max cassette size, but this is Shimano. A 28-tooth cassette will work. According ton si.shimano.com/en/pdfs/si/53Z0D/SI-53Z0D-000-00-ENG.pdf , the Largest Sprocket says 28T. Am I missing something? Let's say we go with a 11-28T cassette and a 50-34T chainring , if I do the math right the Total Capacity would be = (50-34)+(28-11) = 33? The spec says the max is 29T?
    – p50runner
    Feb 4, 2023 at 2:36
  • I used bicycles.stackexchange.com/questions/7264/… to calculate the max capacity
    – p50runner
    Feb 4, 2023 at 2:41
  • @p50runner It's your RD-6500. The short-cage version is, by Shimano specs does indeed say 28. I'm the Shimano PDF I read when I wrote the answer might have been one for the GS version, which, despite having larger capacity is perversely only spec'd for a max 27-tooth cassette. As far as total capacity - I did my racing before 11-speed came out, and I used a 50-34 crankset with a RD-7800 SS, and occasionally used an 11-28 in moderately hilly races with lots of big-big cross-chaining and always used an 11-28 during off-season training, all with no problems. Feb 4, 2023 at 12:53
  • @p50runner I'd use an 11-28 cassette in races with moderate hills if the 50-28 combination was low enough for the climbs. That way I'd be able to stay on the big chainring the entire race, never having to shift the front. That meant all climbing was done with the chain big-big crosschained. And it worked without issue. You just have to make sure your chain length is right. Feb 4, 2023 at 12:56
  • Sweet! Thanks for the insight. So my new plan based on this is to get a SRAM 970 12-26 cassette and a 50-34T chainring. This means I am under the max tooth count. For max capacity I'll be (50-34)+(26-12) = 30T and the derailleur is rated for 29T so it will just be the cross two cross chain gears that potentially can cause issues. I'm hoping all I need in addition is a new chain. Am I missing anything else?
    – p50runner
    Feb 6, 2023 at 6:54

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