I´m dreaming, but only dreaming, of running under 2:50 in the famously PB-friendly Berlin Marathon in September, but I'll be pleased with each and every 30s under 3:00...
I believe there are several methods to predict your marathon time or to calculate your ideal pace: multiply your 10K time by (in my case) 4.63-4.70, divide your 10K pace by 0.88, or add 20-30s to your min/km pace, and there´s the nice calculator at:
http://www.runwestflorida.com/predict.htm - so there´s both variety and room to veer a bit on the optimistic side...
My goal, as said, is a 2:50 on a flat course in perfect running weather. I´ve done a 3:14 in 1999 and 3:02 in 2000 in similar conditions, so at least the simple arithmetic is on my side
In the same period my 10K times have dropped from just under 40 in 1999, 38 in 2000 to bubbling over 37 this year - which wouldn´t appear to be sufficient for me to achieve that 2:50 goal.
(I seem to have had _some_ natural speed - and since I could 'comfortably' run a mile at a certain pace, it has so far been a relatively simple exercise to build endurance to last 10K on a pace close to that pace - but I may now have approached the limit of that speed.)
Is the predictive rule really so strict? Does anyone have exprience of 'surpassing' their 10K time, of running a marathon in excess of what any prediction would´ve allowed? ´