Training & Nutrition - Late ride hill implosion

Need some advice. I just finished my second century of the season, this one had over 7,000 feet of climbing. I've done this ride every year for the past 5 or 6, so I know it well. Anyway, I started out great, climbed really for the first half or so, but toward the end I just hit a wall---no power in the legs whatsoever for climbs (thankfully 3/4 of the climbing was done). I know this is due to fatigue, not enough long rides coming up to it due to travel, etc.

However, this problem has persisted for a couple years now---I climb really well at first, can keep up a great pace without working all that hard, and then suddenly, nothing left. I do about 5 centuries a year, and most are mountainous. I train for hills more than anything else, doing lots of climbing repeats, muscle tension intervals, etc. I keep a cadence of 70-80 when riding mountains (except when impossible due to steepness).

That is all background information for my real question, which is this: Anyone have any suggestions on how to extend my leg power longer into a long, mountainous ride? I ride with guys pretty much exclusively, and while I keep up with most of them (or even drop some :D ), at the end of long rides they still have power on the hills and I don't. The one thing I haven't done much of is weights (like leg presses, extensions and squats). Might those help? Any other ideas? It kind of annoys me to be passed on hills by people that I dropped hard earlier in a ride!

Possible reasons (others will add more I'm sure):
1. Bonking - are you eating enough?
2. Pacing - maybe you're going too hard during the early miles
3. Cadence - a higher cadence would help conserve your legs for later in the ride

Good points!

I am trying to eat well and consistently while riding, and drinking Gatorade/Heed etc. I always find it hard to eat enough while riding because it makes me a little ill, but I'm forcing myself to do it anyway.

I could back off on the early climbs, but the pace I'm going feels good, i.e. I don't feel like I'm really pushing it. So I'd kind of hate to slow down!

Cadence-wise, I'm very comfortable in the 70s-80s, but when I get higher I inevitably go slower and feel more tired. But maybe working on that would be helpful...

Everything Serpico7 said:

70-80 is low cadence. You should try to practice a higher cadence, it can pay off later. If your pushing a low cadence, your just wearing out your legs while your lungs are not working enough. A higher cadence is a way to share the load.

Eat. 300 calories per hour, starting before the ride starts, not 2 hours into it. I know its hard to do, but its a must.

Pacing, also hard to do, but a must on long rides.

I don't have anything earth-shaking to add.

I think you are mostly riding at too low of a cadence and putting too much force into the pedals. That means that you aren't taxing your cardio system very much, but your legs have limited endurance and you're burning them out.

On the food side, you should find it easy to get 250-350 cal/hour. Ditch the gatorade, as it's not a good endurance beverage (too sweet and not enough carbs). Find something else to eat along with your hydration drink (I like bagels & newtons).

You might also want to try pedalling exercises if you aren't doing them now. Both one-legged pedalling and high-cadence drills can improve muscle recruitment and help your legs last longer.