So are you talking about 100 miles round trip or 100 miles one way? One thing I've kept in my mind is that biking 20 miles means that these tired legs and sore ass are going to have to haul me back another 20 miles to my origination point. For instance, when I said that 15 miles about did me in, it was about 7.5 miles out, and then 7.5 miles back in. If I had tried for 15 miles out that day, I would probably still be laying alongside the road in a ditch somewhere right now. Once my hip started hurting, no way I could have pedaled 20 miles back. At least not during the remaining daylight hours.
I guess my philosophy about riding a bike just might be different. I'm not riding to get anywhere, I'm riding to BE somewhere in the moment and SEE what is around me that you just can't get by being in a car. Any exercise that I get doing that is just gravy. One of the main reasons I chose mountain bikes is because chances are I'm going to be wanting to go places I might not be real inclined to take one of the cars into. In most cases we will be riding the bikes just to see what is around the next bend and probably won't have any real good idea of how far we have gone. Which means, I guess, that I could get myself into trouble by going further than I needed to before I am ready.
Speaking of which, at the bike shop that had what looked like an electronic odometer/speedometer for sale for $40. These things any good? I can see where it might be nice to know the distance gone, if for no other reason than perhaps to know how far I went without having any problems, and see if that is stretching out the more I ride.
I found I have a slow leak in my rear tire (losing about 10 psi in four days). so I need to take my bike back to the shop when I can. Coincidentally enough, that was the tire that the girl at the shop used to show us how to change a tube on the road. Of course, it would have helped, too, had she given us the correct tubes as spares. Regular Schrader valved tubes won't work in these wheel rims on our bikes. So I have to get that straightened out as well.
BTW, Connie and I took the bikes out yesterday to a local park with a pretty nice 2.4 mile paved trail. This is bordering the national forest here which has bazillions of miles of sandy and packed dirt roads. We went off onto one of these sand roads, and I have to admit that the soft sand is murder trying to go through. I didn't lose control of the bike, but it was a struggle. Connie had quite a struggle with it too and several times got off the bike to walk it through the softer spots. And man my legs are feeling it today! I found that it was best for me to be in a very low gear and just power through the sand. Of course, the legs took the brunt of that. To be honest, that was really no fun because you absolutely could not expend any concentration at all to look around at the scenery. That front wheel really wanted to go sideways without warning. I guess spots of soft sand here and there on a trail or road wouldn't be bad, but a steady diet of it for a long stretch would probably use me up. Going up hill is hard work, but coming down hill seems just downright treacherous.
The entire race is 100 miles.....you don't ride out 100 and back 100.....so your tired ass would be okay!