jlippinbike

A1. There are probably three main differences between Saturday morning rides that last up to 50 miles and the longer rides that last 200k (125 miles) and 300k (187 miles). First difference is that a somewhat "trained" athlete can complete the Saturday morning rides on an empty stomach and not be required to eat at all and still finish the ride in the company of his buddies. A rider's glycogen stores will usually last until the 50 mile mark. Whereas any ride longer than 50 miles the rider has to figure out how to replenish depleted glycogen stores if the glycogen stores are going to be tapped for fuel. If you are fat adapted, then you can go further than 50 miles without fuel, but probably not all the way to 300k unless the ride is real low intensity and you are seriously fat adapted. Second difference is riding cadence. It doesn't make much difference for the Saturday morning rides whether you are a gear pusher or a spinner. But gear pushers that want to skimp on their training miles for a long event often have lots of problems trying to jump up to the long distances on event day. Riders who ride using a higher cadence tend to have little problem doing less miles in training for a long endurance event. The problem spinners tend to have jumping up to a long ride is not have their tail end (butt) broken in so it won't prematurely wear out before they reach the end of the 300k ride. And the third difference is kind of related to the second difference. Sore tail end. Riding 150k (93 mile) training if not done super regularly might not harden your rump up so the 300k ride will be a joy.

A2. Keeping your training rides to 150k for a 300k event is certainly doable. In fact, if you treat your 300k event as two 150k rides you plan to do back-to-back, then you should be telling yourself during your 300k event at the 150k mark that you just have another 150k to go and you know you can do that since you do it in training all the time. Of course, the real issue is how many of those 150k rides are you doing? Are you doing just one a week? Or are you doing three a week. Training volume matters when you are aiming for an endurance event. Three 150k rides in a week goes a long way compared to one 300k ride a week when training for a 300k event. Somehow you will want to train your tail end to put up with punishment. And ideally you will want yourself to be fat adapted. I personally have done fat 300k rides at an average pace of 14 mph without having eaten 12 hours prior to the start and not eating anything during the ride. That's fat adapted.