People have many ideas about what the perfect bike should be. It might be an old school steel frame with a rigid fork or a single pivot full suspension. Others will go all out on weight saving and ride exotic components. For some, brand A is the pinnacle of the technology, while others argue that brand B deserves that title…
I have ridden many bikes over many years and I came to the conclusion that everybody is right! The most important thing is to believe that the bike you ride is best one suited for you. So if you think that red framed bikes are faster than green ones, then buy a red one. You will ride your bike more often if it appeals to you.
For 100 mile racing, I will strongly suggest that you consider a full suspension bike. Most of those events will take anywhere between 7 and 12 hours to complete. Comfort on the bike will greatly affect your performance for the last 2 to 3 hours. Full suspension bikes absorb more roughness in the terrain so your body doesn’t have to.
Over 100 miles there is a quite a variety in terrain. It’s sometimes smooth and other times really rocky and technical. Your equipment needs to hold up in all conditions. I found that carbon wheels are perfect, even though they are expensive. They are not only light, but are also very stiff. One year I rode extremely light alloy wheels and after each 100 mile race they needed to be trued. The following season, I rode carbon wheels and after the entire series the wheels were still in perfect condition.
Don’t be obsessed by the weight of your bike. I used to select each component by comparing its mass. I did not have any mechanical failures but after talking to a World Champion, he convinced me that weight was not the most important factor in delivering a good performance. That especially applies for tires.
My bike of choice: the S-Works Epic 29 from Specialized. I mean it was good enough for the Olympic Gold medalist… so no need to wonder if it is an efficient bike. The brains in the fork and rear shock are locking up the suspensions for you when riding on smooth terrain. On rough ground, the brains open the shocks are the bike feels incredibly smooth.