Explain Cassette Gearing

[featuretile]

I keep reading all these numbers about triple cassettes and compact doubles, and I don't really understand what they mean. Could someone explain this to me? My bike has a 12-25 cassette, and a 48x38x28 chain ring (triple). Is that adequate for serious hill climbing? Someone suggested that I needed a bigger rear cassette. I'd like to know if that is necessary. Thanks.

[Cataboo]

I keep reading all these numbers about triple cassettes and compact doubles, and I don't really understand what they mean. Could someone explain this to me? My bike has a 12-25 cassette, and a 48x38x28 chain ring (triple). Is that adequate for serious hill climbing? Someone suggested that I needed a bigger rear cassette. I'd like to know if that is necessary. Thanks.

The combination of the 28 chain ring with the 25 cassette in the back should really be able to get you up hills... However, that depends on you, your biking style & your legs. If you need more gears to get up hills, you can put a bigger cassette ont the back of your bike - a 12-28 or a 12-37 if you want to get a mountain bike rear cassette & derailleur on your bike.

The smaller the # of teeth on the front chain rings, makes it easier to go up hills. The larger the # of the teeth on the rear cassette makes it easier to go up hills. You have smaller chain rings up front already than most road bikes.

[Jiffer]

The smaller the # of teeth on the front chain rings, makes it easier to go up hills. The larger the # of the teeth on the rear cassette makes it easier to go up hills.

Pretty sure this was spose to say that the smaller number of teeth on the front chain makes it easier to go DOWN hills.

I have an 11-28 double. I LOVE being able to pedal faster on the downhills. When I got my bike, all the components came off dh's previous bike. It had an 11-25 cassette. I rode that bike for over a year before dh realized I had such a difficult climbing gear. And, of course I didn't know any better! He sent me and all our riding buddies an email saying that I was an insane climber for doing the climbs I had done with that big gear. I was a snail going up hills, had to work so hard, and was mentally depressed to be passed by the entire world on hills. Since he changed it to an 11-28, I am STILL one of the slower climbers, all the more reason to give me the better gearing! But what a difference it makes. That and making myself climb hills to get stronger. I just experienced great joy last weekend on the club ride when I passed three people on a difficult climb. I don't think I've ever passed anyone on that particular climb EVER. Definite ego boost.

[indysteel]

Pretty sure this was spose to say that the smaller number of teeth on the front chain makes it easier to go DOWN hills.

I have an 11-28 double. I LOVE being able to pedal faster on the downhills. When I got my bike, all the components came off dh's previous bike. It had an 11-25 cassette. I rode that bike for over a year before dh realized I had such a difficult climbing gear. And, of course I didn't know any better! He sent me and all our riding buddies an email saying that I was an insane climber for doing the climbs I had done with that big gear. I was a snail going up hills, had to work so hard, and was mentally depressed to be passed by the entire world on hills. Since he changed it to an 11-28, I am STILL one of the slower climbers, all the more reason to give me the better gearing! But what a difference it makes. That and making myself climb hills to get stronger. I just experienced great joy last weekend on the club ride when I passed three people on a difficult climb. I don't think I've ever passed anyone on that particular climb EVER. Definite ego boost.

Hmmmmm; I'm pretty sure the post you quoted is correct. A smaller front chain ring and/or a larger rear cog make climbing easier, especially when used together. The smaller the gear, the less resistance you need to pedal, and the easier it is to climb. Although I'd further add that to spin fast during a climb takes pretty good aerobic capacity. It's easier for some, but harder for others.

IMO, no particular gear makes going downhill easier. Gravity does a pretty good job that on its own. Rather, using bigger gears on a downhill allows you to pedal without "spinning out." As such, you can go downhill faster.

I would assume that even with a 25 cog as your biggest cog, you should have been able to pedal pretty easily while going downhill. I personally, don't pedal on steep descents. I'm already going as fast as I want to go. If I do pedal, it's merely to keep my legs moving after a steep climb. For that, I just keep it in a fairly easy gear and spin.

I do, however, pedal through rolling hills so that I use momentum to my advantage. That typically means shifting from the smaller gear I used to climb the hill to a bigger hill for the downhill and then back to a smaller gear for the next roller when gravity starts to slow me down. Depending on how steep the rollers are, that may require multiple shifts--front and back. For that reason, I think rollers can be rather exhausting mentally. The second day of the Horsey Hundred in Kentucky is like that and by the end of it, my brain is beat.

[Jiffer]

Hmmmmm; I'm pretty sure the post you quoted is correct.

I don't think my brain will ever make sense of all this!!! I'm apparently a cassette and chainring moron!! Thanks for the correction.

But yes, I was referring to going downhill "faster", which having a bigger downhill gear makes it "easier" to do ... because I do pedal as much as I can on descents. I have friends who can't keep up with me sometimes and, therefore, the group on the Saturday club ride when we do a big descent together after regrouping at the top of a climb. One of my friends sometimes loses the group and, therefore, can't finish the rest of the ride with them once it's flat again. A bigger gear would make it "easier" for her to keep up. She did actually change her cassette and does have a harder gear than her Ruby came with, but she still has to work hard at keeping up and if she's not strategically at the front of the pack when we descend, she may lose us.

Funny this post came up. Shortly after reading it, my dh told me he's thinking about switching something else on my bike to give me easier gears. (Not even going to pretend I remember which "thing" on which part of the bike he said he was going to change!) But yay for me if it helps my pathetic climbing!!!

[Cataboo]

Erm. A bigger chain ring in the front will make it "easier" to go downhill without having to spin too fast. Or a smaller cassette ring in the back.

A smaller chain ring in the front will make it easier to go up hill or a bigger cassette ring in the back.


the downhill thing I think depends much more on weight, wind resistence, etc... As a solid heavy little person, I tend to go down hills very fast whether or not I'm pedaling. tires & hubs'll affect it as well.

[OnTerryOh]

I keep reading all these numbers about triple cassettes and compact doubles, and I don't really understand what they mean. Could someone explain this to me? My bike has a 12-25 cassette, and a 48x38x28 chain ring (triple).

To answer your first question
The numbers are the number of teeth on each of your chainrings.

48 x 38 x 28 means that the largest chainring attached to your pedals has 48 teeth, the midsize ring has 38 teeth and the smallest has 28 teeth. A 12-25 cassette means you have a number of chainrings in your rear cassette, ranging from a smallest ring with 12 teeth to a largest with 25 teeth.

Gear ratios and uphill riding
When you pedal, the chainring attached to your pedals drives the chainring in your rear cassette, making your back wheel turn. The number of times you pedal in relation to how many times your back wheel turns is a gear ratio.

The lower the gear ratio, the easier it will be to pedal up the hill.
To calculate a gear ratio, divide the number of teeth on a front chainring by those on a rear. A good gear ratio for uphill riding uses the smallest chainring on the front and the largest on the rear. Think "small front, large back".

For example, the smallest chainring on your pedals has 28 teeth. The largest chainring in your rear cassette has 25 teeth. 28/25 = 1.12, which means that for one revolution of your pedal, your rear wheel will revolve 1.12 times.

This is the lowest gear ratio your bike has to offer, the easiest for riding uphill. You'd be pedaling a lot, but getting up the hill without much pressure on your knees and quadriceps in this gear.

A new cassette or new bike?
The more teeth the back gear has, the easier it is to ride uphill.

Let's suppose that you bought a new cassette with a largest chainwheel having 34 teeth. Using your bike's smallest front chainwheel of 28 teeth with this, the gear ratio would be 28/34, or .82.

For one revolution of your pedals, your back wheel would turn .82 of one revolution. You would be moving slowly but the climb would be much easier than on your present bike.

Is that adequate for serious hill climbing? Someone suggested that I needed a bigger rear cassette. I'd like to know if that is necessary. Thanks.

Yes, I think your present bike is adequate. In my opinion a bigger rear cassette isn't necessary.

Uphill riding and what bike you choose depends on your fitness, cycling experience, the grade of the hills and how much money you want to spend.

[Pedal Wench]

An easy way to remember when you're on the bike - the closer the chain is to your bike, the easier it is to pedal. Move the chain, on either the front or back, closer to the bike is easier - further away is harder to pedal.

[tctrek]

All of these posts are very helpful! I had resorted to a letter game to help me remember about what gearing would make it easier to climb hills: "B"igger in "B"ack - that's why I'm changing out the back from a 12/27 to a 13/30 this week.

[Thorn]

An easy way to remember when you're on the bike - the closer the chain is to your bike, the easier it is to pedal. Move the chain, on either the front or back, closer to the bike is easier - further away is harder to pedal.

What a wonderfully, simple way to look at it...the further away from the bike, the harder the more work. Simple. Elegant. Thank you.

When I read these posts, the engineer in me knows that I can never explain it to someone. Words like gear-inch, gear ratios, etc, want to roll of the finger tips. But, PW, you have the perfect layperson's explanation.

[Pedal Wench]

What a wonderfully, simple way to look at it...the further away from the bike, the harder the more work. Simple. Elegant. Thank you.

When I read these posts, the engineer in me knows that I can never explain it to someone. Words like gear-inch, gear ratios, etc, want to roll of the finger tips. But, PW, you have the perfect layperson's explanation.

Nope - but I'm an engineer too - so I'm just speaking your language!

[laura*]

I keep reading all these numbers about triple cassettes and compact doubles, and I don't really understand what they mean. Could someone explain this to me? My bike has a 12-25 cassette, and a 48x38x28 chain ring (triple). Is that adequate for serious hill climbing? Someone suggested that I needed a bigger rear cassette. I'd like to know if that is necessary. Thanks.

What do you consider a serious hill? See this thread for a variety of opinions:

http://forums.teamestrogen.com/showthread.php?t=31034

You can simplify all the tooth counts into just two ratios: Your lowest gear of 25:28 and your highest gear of 48:12. Divide them to get a single number like OnTerryOh explained. Whatever change makes the low gear result smaller will make it easier to get up hills. Whatever change makes the high gear result bigger will increase your top speed.

All the intermediate gears simply give you more options. They also let you pace another rider while pedaling at your preferred cadence.

A long time ago when I moved to [your old neighborhood], it only took one ride on my road bike to realize that I needed an MTB's lower gearing to get up the hills. This is despite riding almost entirely on pavement. That MTB probably had a 12-28 cassette and the same chain rings as your bike. It's low gear (probably 28:28) still wasn't quite low enough, but I suffered without complaint.

In 1994, my next MTB had a low gear of 24:28. That was a nice improvement, but I wanted still lower. I asked a bike shop for lower gearing but they said nothing lower was available. I now know there were such parts available! I would have paid them a king's ransom but I guess they didn't want the business.

I recently modified the '94 MTB. I now have a wonderfully low gear of 22:34. The price is that my top gear is now only 44:13, and my gear ratios are far apart (because that bike uses a 7 speed cassette). This means that "roadies" can fly past me, and I may have trouble pacing another rider.


So - do you need a bigger cassette? When you ride up hills, do you find yourself in the lowest gear and wishing you had an easier gear? If so, get a bigger cassette. Ignore what the experts say you should have. If the gearing isn't low enough, you'll be less motivated to go riding. And with less riding, you'll lose fitness which will make the gears feel even tougher.

Considering the general area where you live, consider changing to perhaps a 12-27 cassette. There is little reason not to - just the cost and the slightly wider spaced gears. The reason the bike came with a 12-25 is that in some places (like say San Jose) the lower gearing is just not needed.

EDIT: I looked up the specs for your Specialized Vita Sport: Sugino triple crankset 28/38/48. Shimano Nexave FD and long cage Sora RD. Shimano Sora 8 speed 12-25 cassette. KMC chain. Your rear derailleur is speced for a maximum cassette gear of 27. And with your crankset, it has 17 teeth of capacity left for the cassette range.

This makes it somewhat hard to install a bigger cassette because there are few 8 speed choices without going to an MTB cassette (which would require you to also change the rear derailleur). Shimano has a 13-26 cassette but that's hardly a change. You might gamble and push the RD's 27 tooth limit to fit a 11-28 cassette but you might not like the ratio jumps.