Cassettes?

kimmydct

OK, so I admit I'm a bit clueless when it comes to bike parts.  (I am my LBS' dream customer!)  Anyway, I've seen a lot of references to different cassettes based on a particular course elevation and I'm getting curious.  I'm doing Rev3 Maine and IMFL (both flat) so wondering what the ideal cassette is.  (Please don't ask what I have now... no idea)  I have whatever the 2008 Cannondale Synapse Fem Carbon came with!  Not sure if at my level (FTP of 160) I should even worry about it, but I am interested in working smarter for my first IM.

As a side note, is there a "Bikes for Dummies" book I should get my hands on? 

Paul Hough

@ Kim - it goes something like this.... the number of teeth your chain is in on the big ring divided by the number of teeth your chain is in on the rear cassette = the number of revolutions that your rear wheel MUST turn for each full turn of the pedals. So if you are in the 54/12 that's 4.5 turns = very hard unless you are going down a hill. But if you are in the 39/27 (small up front, largest on the rear), that's only 1.44 turns which is why it feels so much easier. If you had a compact crank for the last example, then you would be at 34/27 = 1.26 turns -- even easier. So your crank type and rear cassette determines the options you'll have for the course. Unless you are really strong, you don't need an 11 anything on the rear, even at Florida (I used a 12-21 there). But the hillier the course, the larger the last sprocket on the rear cassette should be because as Rich would say ..."mo gears is mo better!" Count the teeth of the smallest and largest sprockets on your rear cassette and you'll know what you have. The only problem with a greater range of gears on the rear is that you have fewer options in the middle to hit your sweet spot.

John Withrow

x2 on what Paul said. For IMFL, a 12-21 or a 12-23 would be ideal for you. But an 11-21 or 11-23 would also work even though you will likely never use the "11" on that course. A 11-23 cassette is much more popular and will be easier/cheaper to find. What exactly does 11-23 mean you ask...? Well, on a 10-speed cassette, that means there will be 10 different gears ranging from 11 teeth on the smallest to 23 teeth on the biggest and if you care, all the ones in between are: 11,12,13,14,15,16,17,19,21,23 (you see how it skips 18, 20, and 22? those will cause slight cadence gaps. these will be much bigger on say an 11-28 cassette which has: 11,12,13,14,15,17,19,21,24,28)

Now you have a homework project to do... I think that your bike actually has a 9-speed cassette on it. Most newer bikes come with a 10-speed cassette. So in addition to counting the number of teeth on the smallest and biggest gears on the rear cassette, also count the number of different gears on the rear cassette. Are their 9 or 10 different gears?

If you have a 10-speed cassette, you can buy a 11-23 Ultegra cassette on Amazon for $76 here: http://www.amazon.com/Shimano-CS-6700-Ultegra-Cassette-10-Speed/dp/B003933G06

If you have a 9-speed cassette (my guess), then you can actually buy a 12-21 (or any other size) for around ~$70 here: http://www.amazon.com/Shimano-CS-6500-Ultegra-Bicycle-Cassette/dp/B0006ZTEJC/ref=sr_1_1?s=sporting-goods&ie=UTF8&qid=1343067024&sr=1-1&keywords=shimano+ultegra+9+speed+cassette

William Jenks

You might want to check what your current one is before buying another. The default on many bikes is 12-25. Then you can gauge whether you're more interested in getting a "harder" gear (e.g., 11) or an easier gear (e.g., a 12-27). With your "level", it's definitely important. I would err on the side of having the easier (bigger number on the cassette) gears.


[break...and coming back...]

I did a quick web search and found this bike: http://www.bikepedia.com/quickbike/BikeSpecs.aspx?Year=2008&Brand=Cannondale&Model=Synapse+Feminine+6&Type=bike#.UA285I5sLHo

Assuming this is it, you have a 12-26 cassette and a triple crank with 50/39/30.

If it's correct, then you need to be careful, because you have a 9-speed cassette, whereas most of us have been assuming you have a 10-speed, which is the standard on more expensive Shimano gruppos (105, ultra, etc).

FWIW, I live in the rolling hills of midwest and use a 50/34 up front and 11-26 in the back. FTP of aboutt 245, and weight of about 150 lbs. For a flat course, I wouldn't need to switch it because I wouldn't be able to find/use anything "faster" (i.e., a 10). Switching to an 11-23 instead of the 11-26 would only narrow the gear gaps. i trade having some gear gaps for the ability to climb hills a little easier.

Make sense?

Cheers,
Wm