OK, first off, here's the ride in question:

http://www.mapmyride.com/routes/view/54870942
It starts off with a little bit of rolling terrain, a short medium gradient climb, and some more rolling. Then, through the center of town (Roswell, GA), across Highway 9, and down towards Big Creek, then up Grimes Bridge Road, then a plummet down to the Chattahoochee River. I follow the river for a few miles, then climb up Eves Road, cross Holcomb Bridge Road, up past Centennial High School, up to Old Alabama Road. That's the highest point on the ride, about 280 feet above the river.

The early part of Old Alabama is mostly flattish, with some rolling hills mixed in. As it goes along, it starts to roll more. After it crosses Holcomb Bridge Road, part of it is a dive back down to the river, where I run out of gears. Then it's a few flat miles along the river, then a climb up away from it, and a return home. According to MapMyRun, total climb is 675 feet.

Last week, I did a triathlon in NW Georgia. The ride part is described by the race director as being hilly. The course profile is here: http://gamultisports.com/tugalootria...n_profiles.pdf , and here's the MapMyRide equivalent: http://www.mapmyride.com/routes/view/134728791
MapMyRide gives this ride a 610 ft total climb, somewhat less than my loop, which is five miles shorter. I would rate the two rides as being equally strenuous. My fellow triathletes all considered this course to be hilly. Now triathletes aren't known to be all that much in the way of being mountain goats, probably because of that odd running thing we do post-ride, but this particular group I was hanging with have been training for an ironman distance race for the last 10 months, and will be doing one in seven weeks, so I'd say they're all extremely fit. I feel confident that most of the world's riders would agree that this ride is hilly. Not mountainous, but certainly hilly.

I should probably throw in these mitigating factors: I'm fairly slow. I did a sprint tri on a nearly flat course in middle Georgia in August, averaged 18.3 mph on a wet course, could have gone a bit faster in the dry. On the other hand, this ride is in a busy suburban area, and there are probably close to 20 traffic lights on the route. I cross two state highways twice each, and probably lose a total of six minutes, more or less, to traffic lights and congestion. Since I'm not real fast, the 8 minutes is around a 9% improvement, not as significant as it would be to a faster rider.

Now, back to that question, is it bike or is it rider? I'm going to say the bike enabled the rider. Let's say I tried to do this ride on a fixie. I'd never make it up the climbs, and would have to get off and walk. Come to think of it, I'd have to be on the brakes on many of the descents as well, there's no way I could spin fast enough. Trying to do this ride on a fixie would add at least an hour to my time. I'd be fine on the section along the river and a few other places, but other than that, I'd be way slow. If I switched to a bike with gears, would that be bike or rider?

I do believe the biggest difference is the number of gears and the range they cover. On my steelie, I have to get up out of the seat and crank to get up the hills. On the carbon bike, I can stay seated and maintain a cadence. Once at the top of the hill, on the steelie, I've usually gone anaerobic and need to recover, while on the new bike, as soon as the hill flattens out, I'm grabbing another gear.

I do think the indexed shifting helps a little, too, though not nearly as much as gear availabilty. If it were super important, nearly all tri bikes would have indexed shifting, while at the current time, most don't. I suspect that will change in the next few years. Also, the bike being five pounds lighter does indeed help when going up, which is probably 40 percent of the ride, time wise.

Because of the reduced effort on the earlier climbs, I'm fresher at the end of the ride and can make that second climb up from the river with a lot more gusto. I have done a lot more running this summer than I ever have before, but it's been at the detriment of riding, which is even more reason that I think most of the improvement comes from the bike.

As I become more comfortable with the gears on the new bike, I'm confident more minutes will come off. Also, tri season is over and I'll have more time to ride, so who knows what I'll be able to get that time down to this fall.