A bike cassette is the component of your bike that attaches to the freehub on your rear wheel. It is easily recognized as a large cluster of straight splines that your bike chain loops over that controls the torque being pushed when you are pedaling. The entire cassette is then attached by a threaded lockring. The major perk to this being that when these sprockets wear down or you wish to change your gear ratios, you only need to change the cassette. On modern bikes you will have either 9, 10 or 11 sprockets.
In a perfect world all Triathlon and Cycling races will take place on a perfectly flat course. We all know this isn’t the case however and this is where your cassette can make a huge difference in your performance. Cassettes are one of two components on your bike that directly impact the quantity of gears and ratios your bike has, the other being your chainset. This means that you can directly affect the ease of your ride by ensuring that your cassette has a higher volume of teeth.
So when you are cycling uphill, you are able to shift to the larger sprockets generally 28t or 32t. The greater the number of teeth the sprocket has the easier the gear is. The reasoning for this is due to the torque required to turn the back pedal, the higher the gear the less torque is required.
The opposite is true for when you are cycling on a flat course or a downhill. You would then want to shift into the lowest gear, the smallest sprocket with the least number of teeth. This will increase that torque on the pedal and thus allow you to cover more ground for less revolutions of the wheel.
These principles are essential to learn if you are a beginner in triathlon. They can mean the difference between completing the cycling portion of the race or not!
Choosing the right cassette for your bike is going to come down to learning your cadence and basing your needs on the race. Cassettes for a triathlon are generally going to be best if you are posed with a race that has a lot of altitude climbs to it. This way you can shift into a high 28t or 32t for the way uphill, but shift into a very low gear like a 9 on the way downhill. I suggest that you ensure that your triathlon bike is fitted with a cassette that has a wide range of teeth. This spread will give you the most room to increase and decrease torque as needed so you can stay within your ideal cadence range during the cycling portion of the event.
So now that we have got the basics of bike cassettes out of the way let’s get into specific types of cassettes and what they are good for. As you start looking around at cassettes you will quickly notice you are barraged by number combinations like 11 32 and 11 25. So let’s demystify these real fast before we dive in as it is very simple. The number is referring the amount of teeth on each sprocket. So an 11 32 for instance, has 11 teeth on the smallest gear and 32 teeth on the largest gear. The speed of the cassette refers to how many sprockets there are in total! It is that simple!
So as an example you could have an 11-32 9 speed cassette. This cassette would then have a variation of teeth on each sprocket such as this: 11-12-14-16-18-21-24-28-32. Each number on the sprocket corresponds to the quantity of teeth on that gear!
As you change from road bikes to mountain bikes or triathlon bikes the gap between gears narrows. The main reasoning for this is most cyclists prefer to have a short gap in gear change. Most standard road bike cassettes will have an 11 or 12 on the smallest sprocket and generally a 25 or 28 on the largest sprocket out of the store. If you bike has a 25 sprocket you can comfortably upgrade to a 28 which will provide you a nice jump in performance when it comes to elevation climbs. However you are looking to upgrade beyond a 28 you need to check the derailleur on your bike. Larger sprockets tend to require a long cage rear derailleur or they will not fit.
The general rule however is if you struggle with hill climbs then the larger the sprocket the better. So if you know your race is going uphill you should invest in a 28 or a 32 cassette.
As we move into Triathlon’s and Time Trial Cycling though the rules change for cassettes. The general rule here is the narrower the gap in gears the better. This provides for a smooth transition between gears and you are able to maintain a steady power and cadence while staying in an aero position. Here are some of the gearing sizes for the top 10 finishers in Kona:
1. Lionel Sanders, 11-25 cassette
2. David McNamee, 11-25 cassette
3. Sebastian Kienle, 11-26 cassette
4. James Cunnama, 11-25 cassette
5. Terenzo Bozzone, 11-25 cassette
I think you are seeing the trend here. I would have included the 1st place finisher Patrick Lange however his gearing size is a mystery. If I had to guess though, it would be 11-25. There is only one finisher in the top 15 whom had a higher gearing size and that is Thiago Vinhal with an 11-28.
You have three companies basically competing in the drivetrain and cassette market. You would like to think they all work with each other and are cross compatible but that is not the case. We have made you this cheat sheet however to help you when searching for a new cassette to ensure it fits with your drivetrain:
SRAM – Works with SRAM and Shimano cassettes
Shimano – Works with SRAM and Shimano cassettes
Campagnolo – Only works with campangolo cassettes and drivetrains!
Whether your old cassette broke or you have need to improve your cycling performance we have you covered. Here is a round up of the best bike cassettes you can get in 2018!
The SRAM PG-1070 is a great 10 speed cassette that comes with a lot of bang for the buck! First off it comes in every sprocket gauge you can think of from 11-23T through 12-36T. It has full sized cog teeth to ensure better grip on your chain. And a smooth shifting to reduce noise and friction during hill climbs, or just if you frequently change gears.
This is a nice lightweight 11 speed cassette from Shimano. The R8000 Cassette comes in a variety of gear options including: 11-25 through 11-34T and 12-25, it also come in 14/28 which is handy for other cyclists outside triathlon. It also contains tech from Shimano's Dura Ace line of cassettes and is compatible with SRAM and Shimano drivetrains.
The SRAM eTAP XG-1190 is a top class cassette for triathlon's! It is lightweight, has smooth transition and comes in the core cog sizes you would want for a triathlon, 11/25 through 11/32. It is made from high grade steel and is durable as well as quiet! An added bonus to this cassette that you won't find many places is a manufacturer 2 year warranty!
The flagship product from Shimano, as far as cassette's go. The Shimano Dura-Ace 9100 comes with the Dura Ace technology providing faster and smoother shifting. It has a tool free joining link that provides quick installation and is constructed with 5 titanium sprockets! This means lightweight optimal performance from your cassette.
Lastly we have the Shimano CS-5700. This is a great early replacement cassette from your stock bike cassette that came with a entry level road bike. It features drilled out cogs to reduce weight, has nickel plating to increase durability and includes locking. It does only come in two cog sizes 11 25 and 11 28 but that covers all the bases for triathlon unless you have a lot of hills. It is also very affordable if you need an upgrade from your basic cassette!
When choosing a new cassette for your triathlon bike it is important that you get one that has the right cog profile for the cycling you frequently do. If you are going to be doing an upcoming race that involves hills make sure your cassette has the gears you will need to succeed.
In terms of the best cassettes for triathlon cycling there is no better than the Shimano Dura-Ace 9100 Cassette!
This cassette is truly the cream of the crop when it comes to performance, cog profiles, weight, durability and shifting! Which is everything we could ask for in a cassette and more!
Hey there, my name is James and I am the creator and editor of this site. I have been doing Triathlons for a while now and am competing in 70.3 Ironman's as well come this year. I created this site to help those new to the sport and to share my journey with other athletes.