I traded in my C50 for the C109RT after 4 years of riding it.
First off, the C109Rt rides great; big differance in power and brake performance, especially with my wife riding with me. The C50 had to work on hills and the brakes required a lot of fore-thought. On the C109RT, I don't even feel a differance with a passanger. Tons of acceleration, I'm more comfortable, and best of all, the wife is comfortable so she rides with me more often.
Two things of note though:
1. The first turn out of the dealer, I kept trying to lean; man, that fat back tire just din't want to do it. After a couple of blocks I didn't even notice it.
2. If you get one, it doesn't like gravel AT ALL. Watch the linked brakes, if you get too much on the rear brake pedal alone, the fronts are activated and you'll go down. And when you go over, you won't be able to stop it unless you have solid footing due to the weight. Nice and gentle and that back tire will stabilize you quite well.
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