Originally Posted by djbowen1
I currently have a 12-25 which i am fine with and will be buying a new cassette soon, thee are so many options in sizes. Is there any rhyme or reason to choosing a size? 11-21 souns nice for speed and 12-26 good for climbing? i havea triple setup now. I am replacing the old one due to the fact that it's a well worn tiagra cassette now.
A useful tool for comparing various chainring/cassette cog ratios and combinations is a spreadsheet that I've used before. It has two gear ratio tables that allow up to 5 different chainring sizes to be entered and up to nine cassette cogs, for each table. There's an entry area for whatever cadence you would like to use and an entry for wheel circumference. Once you make your entries, it calculates gear ratios and the speed in mphs. for each chainring cog combination.
Measuring wheel circumference isn't complicated. Most people I've talked with use the chalk mark on the floor and simply roll the wheel once and make another chalk mark. A method considered more accurate (but will yield lower speeds and distances on your computer), is the dynamic version of the chalk mark. That is, the marks are made the same as before but with the rider mounted on the bike
If anyonne is interested I'd be happy to emnail the Excel file.
letmeknow:
dacook@fedex.com