Optimal Intensity training ratios I have used my googlefu now but I don't come up with any good research articles.

I read that a lot of elite riders train mostly on low intensity, is this the case and why?
To increase fet oxidtion, and endurance muscle fibers and decrease the risk of injury? 

This article says that it is not good (in isolation) in higher levels:
http://en.wikipedia.org/wiki/Long_slow_distance

I also read something about 85/15 rule of race pace (85% of youre training should be lower then race speed and 15 % of the time at faster speed).
Long slow distance is great for building up a strong aerobic base (circulatory and respiratory systems), if you have the time. However, unless you choose good rides it can be boring and few people would consider doing it on an indoor trainer.

For those who don't have that time, there's a century training plan in Chris Carmichael's Time-Crunched Cyclist and most people would consider a century long-distance.

However, if you're not so concerned about getting a great time, then the amazingly-simple way to train for longer rides is to go out and ride, each time slightly increasing the distance. A bit more detail on long-distance riding is given on YACF.