My CAAD8 is comfortable to me for distances - I rode 55 miles yesterday. I think the CAAD8 is a more relaxed geometry than some CAAD frames, so that might make a difference to some.
To some folks here 50 miles is a warmup - but I'm working on general fitness and it's a very good workout.
I've been doing 50+ miles per ride twice a week for a while. I'm planning to ride the CAAD8 in a full century in October.
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Dale, NL4T