First of all, you sound like me... I've only ever done 2 centuries, the last being this weekend just gone; and I commute about 16 miles to work, but not every day. I'm not a cycle racer and I'm overweight by about 30 lbs.
Yesterday, I did 105 miles in 7h40m hours by the clock (5:40am-1:20pm), consisting of 7 hours in the saddle and 40 minutes stopped. I stopped for 20 minutes to eat a sandwich and buy more drink; and I got cramp an hour later and had to stretch for about 10 minutes. (The other ten minutes were junctions and the like where my cycle computer stopped).
Any longer stopped and I think I'd have got stiff. It's common for people riding centuries in groups to not stop, and serious people doing double centuries stop once after 100 miles to eat, and that's it.
It's very hard to figure out what a decent average speed would be. The Tour de France tracks at about 25mph average (which is a 4-hour century). So we have an upper limit. I personally track at about 15mph average on a 'hilly' route, where hilly is a century with about 5,500 feet of ascent, or about 20mph on a flat road. At 15mph, a century is about 6.5 hours; and at 20 it's 5 hours.
Where I live in the UK (near London), I am a tiny bit faster than most of the other riders I see on the roads; I tend to very gently overtake a few and rarely get overtaken. But it's a tiny fraction, so I think I've typical for the UK. That said, when I ride with others, the motivation makes me about 2mph faster.
If you're uncertain about timing for a century, don't race the clock first time. (My first one was 9 hours, with 4,500 ft total ascent). Just be prepared to limp home of your legs get stiff; or I usually make my last 20-30 miles tracking near a railway that I can jump onto. And my wife picked me up once. The biggest thing that's gotten me before, especially in winter, is stopping to fix a puncture and then being too stiff to reasonably continue.
Yesterday, I did 105 miles in 7h40m hours by the clock (5:40am-1:20pm), consisting of 7 hours in the saddle and 40 minutes stopped. I stopped for 20 minutes to eat a sandwich and buy more drink; and I got cramp an hour later and had to stretch for about 10 minutes. (The other ten minutes were junctions and the like where my cycle computer stopped).
Any longer stopped and I think I'd have got stiff. It's common for people riding centuries in groups to not stop, and serious people doing double centuries stop once after 100 miles to eat, and that's it.
It's very hard to figure out what a decent average speed would be. The Tour de France tracks at about 25mph average (which is a 4-hour century). So we have an upper limit. I personally track at about 15mph average on a 'hilly' route, where hilly is a century with about 5,500 feet of ascent, or about 20mph on a flat road. At 15mph, a century is about 6.5 hours; and at 20 it's 5 hours.
Where I live in the UK (near London), I am a tiny bit faster than most of the other riders I see on the roads; I tend to very gently overtake a few and rarely get overtaken. But it's a tiny fraction, so I think I've typical for the UK. That said, when I ride with others, the motivation makes me about 2mph faster.
If you're uncertain about timing for a century, don't race the clock first time. (My first one was 9 hours, with 4,500 ft total ascent). Just be prepared to limp home of your legs get stiff; or I usually make my last 20-30 miles tracking near a railway that I can jump onto. And my wife picked me up once. The biggest thing that's gotten me before, especially in winter, is stopping to fix a puncture and then being too stiff to reasonably continue.