Cassettes explained please

[Sky King]

I am so lucky to have a DH who is a bike mechanic. I am not helpless but changing a cassette isn't on the top of my list. I told him about this thread and after his smart alec remark "isn't a cassette something you put music on in the 80's" he reminded me of the blog post he did about gearing so am sharing to you.

[laura*]

he reminded me of the blog post he did about gearing so am sharing to you.

In that blog post he says: "A gear inch is not a real unit of measure". Actually it is! It's the size of the equivalent front wheel of a penny farthing.

[SFLiz]

This thread is old but it's on topic for me as I'm swapping out my cassette from a 12-30 to a 11-28 because I'm upgrading my wheel set. I'm wondering if I'll feel the difference on my climbs. I am going to change the cassette because my bike (2013 Ruby Comp) came with an otherwise Ultegra group set except for the cassette (Specialized snuck in a Tiagra) and the front derailleur is a 105. Bastards. Anyhow, I went ahead and got an Ultegra cassette because I figured since I'm changing out my wheels, it's be easier and inexpensive to install a new cassette without having to remove the 12-30 off my DT Swiss wheels. Those could be my training set and I could leave the 12-30 cassette on them. Even though I won't need a chain whip this time, I might still get one for my bike tool box. I'm going to be doing this myself. There are some good you tube videos that explain quite clearly how to install a chainring. Seems straightforward. I'll be doing this as soon as I get my parts/tools tomorrow, including my bike stand to help with cleaning/lubing from now on.

Anyone think I'll perceive much change from 12-30 to 11-28? I do a fair share of climbing here in SF area. Thanks.

[indysteel]

How much of a difference you'll notice will depend on how often you currently use your 30 cog. If you don't use it much, then you likely won't notice it at all. If you use it a lot or some, then you might, but the gear difference between a 28 and a 30 is pretty small. However, if you already feel like you are running out of gears on your 12-30 setup, then the 11-28 is arguably not your best choice.

If you want to know the exact difference between the 30 and the 28 cogs, use Sheldon Brown's gear calculator.

[ridebikeme]

+1 on giving everyone more time to respond. The other thing that I would mention is that if you don't get answers as quickly as you'd like, perhaps you should check with your nearest bike shop.

Another thing that I would mention here is that unless your bike or current chain/cassette is fairly new, you may have to change your chain as well. Your chain and cassette mate together, and replacing one without other may cause serious problems.

I agree with others, that perhaps a bit more information about you, your riding habits, terrain would be helpful. Hopefully all of the responses have guided you in the right direction.

[indysteel]

+1 on giving everyone more time to respond. The other thing that I would mention is that if you don't get answers as quickly as you'd like, perhaps you should check with your nearest bike shop.

The OP in this thread (and the thread started some time ago) is the one that made a snarky comment about people not timely responding, not SFLiz.

[ridebikeme]

Indysteel, thanks for the clarification although I wasn't gearing this response to SFliz.

[goldfinch]

This thread is old but it's on topic for me as I'm swapping out my cassette from a 12-30 to a 11-28 because I'm upgrading my wheel set. I'm wondering if I'll feel the difference on my climbs. I am going to change the cassette because my bike (2013 Ruby Comp) came with an otherwise Ultegra group set except for the cassette (Specialized snuck in a Tiagra) and the front derailleur is a 105. Bastards. Anyhow, I went ahead and got an Ultegra cassette because I figured since I'm changing out my wheels, it's be easier and inexpensive to install a new cassette without having to remove the 12-30 off my DT Swiss wheels. Those could be my training set and I could leave the 12-30 cassette on them. Even though I won't need a chain whip this time, I might still get one for my bike tool box. I'm going to be doing this myself. There are some good you tube videos that explain quite clearly how to install a chainring. Seems straightforward. I'll be doing this as soon as I get my parts/tools tomorrow, including my bike stand to help with cleaning/lubing from now on.

Anyone think I'll perceive much change from 12-30 to 11-28? I do a fair share of climbing here in SF area. Thanks.

I am considering doing the opposite. When I was in "bike school" I asked about putting the 12-30 cassette on my bike and if my short cage 105 derailleur could handle it. The teacher said that generally you can go up two teeth from what you derailleur specs say. He also said that the two additional teeth are enough to feel a difference as I now run out of gears on plenty of hills.

But I haven't tried it yet so I don't know if his advice is accurate.

[SFLiz]

I guess I can always just easily swap out the single 28 tooth cog on the new cassette and replace it back with another 30-tooth cog if I find that I need more on my climbs.

I'll have a better idea by end of weekend after a hilly ride.

[OakLeaf]

There's definitely a difference between my 25 and my 27. I first put on the 27 the year I did Columbus Fall Challenge, and I really think I would've been suffering on that ride without it.

The difference would be somewhat smaller between 28 and 30, but I'd think you'd still notice it on the steepest hills where you'd be using your lowest gear.


I'm not sure you'd really want to swap out the single cog. Whatever your jump is now (whether 24 to 28 or 25 to 28), adding two teeth to it would make it an ENORMOUS jump, which not only would be hard on your legs, but your RD as well. I can't imagine smooth shifting over a difference of 5 or 6 teeth, especially downshifting when you're really going to be wanting to preserve momentum. Since you'll have the cassette off anyway, you'll have to have bought both cassettes, and you'll have to adjust the B-screw, what is the advantage to swapping only the cog vs. the whole cassette?

[indysteel]

It appears that there is a 12-30 Ultegra cassette. If you're at all concerned, why not just stick with the same gearing you're currently running?

[SFLiz]

I'm not sure you'd really want to swap out the single cog. Whatever your jump is now (whether 24 to 28 or 25 to 28), adding two teeth to it would make it an ENORMOUS jump, which not only would be hard on your legs, but your RD as well. I can't imagine smooth shifting over a difference of 5 or 6 teeth, especially downshifting when you're really going to be wanting to preserve momentum. Since you'll have the cassette off anyway, you'll have to have bought both cassettes, and you'll have to adjust the B-screw, what is the advantage to swapping only the cog vs. the whole cassette?

Yup, you're absolutely right OakLeak - excellent point; thanks. I'm learning. It'll be too big of a jump from 24 to 30.

New cassette: 11,12,13,14,15,17,19,21,24,28
Old cassette: 12,13,14,15,17,19,21,24,27,30

Again, the members of this forum make up a wealth of knowledge. Thanks, OakLeaf and Indysteel. I'm going to see how this cassette feels; will let you know how it goes.

[SFLiz]

The difference would be somewhat smaller between 28 and 30, but I'd think you'd still notice it on the steepest hills where you'd be using your lowest gear.

Well, you two wise ones, you were right. Parts got delivered earlier than I expected yesterday so I swapped it out and was able to sneak a ride in before dark last night. I took to the steepest local climb I know of near me. Oy - I noticed the change, Ladies. I've taken one of the climbs before. It's a 19% grade. I used it to do four hill repeats while trying out bikes from the LBS. All trials I stayed seated. This time around I had to get up on the pedals. Then I tried a hill I haven't tried before. It's easily over 20% grade but since I didn't look down at my Garmin to check the grade I can't say what it is, and I didn't come through on Strava. I didn't finish it because I felt like I was going to fall backwards while I started the climb. I should have leaned forward but this was my first time off this hill. With my feet clipped in, I started feeling like my front wheel was lifting so I snapped off before I cracked my head and/or my Rubes.

Verdict - I felt the difference. Thanks to you both for your advice. That 11 tooth gear is great and it's not worth the loss of climbing confidence!