I highly doubt it's 12k feet in 112 miles. More like 12k ft in 60-70 miles with 40-50 miles of down hill. Downhill stats sugar coat the overall stats. Full ride stats are nice but real life is that's pretty dang hard. You will realize this when you have 9000ft of vertical and only gone 50 miles
If your're serious, I'd break down the training three ways.
1)
Obvious is to ride your butt off on anything vertical. Each ride should have 1-4k ft of climbing, yes even those 20 milers. You can't train for a hilly century without hitting hills. Get used to them, get your cadence/rhythm figured out. Hit the trainer now if you haven't done it yet. Ride your bike for a long time once a week. Leave at 7am come home at 2-3pm, doesn't matter how many miles you put in, put in the TIME.
2)
These endurance rides are more of race of nutrition vs pedaling squares. Everyone is different but one thing is that if you mess this part up, it can be a
VERY LONG bad day. Get used to eating on your rides, eating while pedaling. Drinking 1 bottle per hour. Food should go in your mouth every 30mins, eating a gu or (100cals) ever 30-40 mins, eating something heavier (200-300cals) every 60min. Most people can digest 300-500cals per hr, anything more will sit in your stomach, any less will lead to bonking. Often the mistake is not to eat enough in the 1st 2-3 hours, but that is the critical time, it fuels the 2nd half of the ride. And sets it up for failure or success. If there are sag stations, stop at every one and grab one of everything, put half in your mouth and half in your pockets. If you're doing your own rides, plan which stores you will stop at and carry enough food in your pockets til you get there. For me, its every 2-3hr riding time to get full bottle from somewhere, either a school or 711.
3)
This might be the hardest but makes
#1 and
#2 easier. Dropping the weight. 5 months time, I'd aim to drop at least 10lbs a month til you flat line somewhere around month 3, then find a way to switch it up and get past the plateau. Running/jogging worked for me. Endurance cycling is hard to do without carbs, it's the stored fuel that we need + I'm filipino so I can never really cut out rice, but can limit them. Treat it the same way. Eat crap load of green rabbit food as I call it, heavy proteins like tuna or chicken for muscle recovery and do you best to cut out sodas and juices. I didn't say this part is easy, pedaling a bike is easy
People get all caught up is diets and losing weight, but the end game is power to weight ratio. When you plateau and you will. In my perspective you can split off in two ways. One is do everything you can to jump the hurdle and lose weight again aka cut more cals again which affect energy levels and on bike performance OR accept your body weight and push to get stronger/faster at that Body weight. pushing that weight will make you both stronger and faster and eating the same will keep the body fueled and primed. When you push through the plateau you will not only come out lighter but faster as well.
I bring up faster cuz in the big picture the ride time will be allot less then can be. There is a big difference in doing that ride in 9hrs moving time versus 12+ hours moving time. Iduno about you but sitting on the saddle 2-3 hrs longer to do the same mileage doesn't appeal to me very well.
If you're still reading this at this point.........YES it's worth it. Yes the training suck but will be awesome too, remember to look sideways on your rides and enjoy what you see. Yes the rabbit food will suck, but add more low fat dressing to make it better. Yes the food and beer after the event will be bliss. Take as many pics as you can during training and of the event, so you can look back and say "FUC Yah!! I did that and it was awesome"
Read my threads on the Rapha Gentleman's race I did last month for some motivation if you'd like
http://www.bikeforums.net/showthread...ighlight=rapha
http://www.bikeforums.net/showthread...ighlight=rapha