Originally Posted by MRMIGS
Any choice of gear ratios that allows a whole number division ( or non prime numbers) between the # of teeth back and front will probably adversely affect the life of the chain. This is because through the power cycle the front sprocket will always be lugging on the same teeth in the rear sprocket.
Here's an example: Using the 16/48 configuration you mention, tooth #1 on the front sprocket will always be driving teeth #"s 1, 17 and 33 in the rear. Given the smaller # of teeth on the front sprocket the wear and tear on the rear will be magnified if at least one of the two sprockets does not have a "prime number" of teeth. Examples are 13 or 17 up front and 41, 43 and 47 in the back.
Thank you. I thought I was being smart just getting my fractions right.
As always, there is more information available and I'm learning as I go along. Your insight and knowledge are very welcome as this thread is meant to be educational and helpful! I guess the most popular 14/42 (1:3) isn't such a good idea. I was fairly limited by what sprockets were available for the DR650 for what I wanted to do and I also wanted multiple duty, so not everything could be optimal. At least I was able to get a steel rear sprocket instead of aluminum for better wear. I will probably be using the 16/48 (1:3) the least of all and its use will then probably be the gentlest, so hopefully my chain life will not be too bad. Everything is a compromise, in one fashion or another. This will be mine. Thanks!