My best score was 489 for the Centurion South Downs 100 (23:12) which was quite a bit slower than my 100 mile PB of 22:40 for the Autumn 100 which had scored only 479 points. Even my slowest 100 - the North Downs Way 100 of 25:31 scored 487.
Find your score by going to the above link.
Being statistician and actuary, I naturally had to do a bit more digging into the index. It works a bit like age-grading for parkrun but instead of adjusting for age and gender, it adjusts for distance, elevation change and "hardness coefficient". This makes sense as the North and South Downs Way races are similar lengths to the A100 but a lot more climbing. A bit more digging and I back engineered the formula. I have expressed it as "Hardness score / Time in days to finish". The quotient is slight different for women but should have the same relativity. I had used the men's formula as there were more data points to calibrate it.
Nobody from the A100 2016 achieved the level for free entry with Mark Denby, Susie Chesher and Jess Gray achieving the automatic (but not free) entry level*. Interestingly Susie was closer to a free spot (750 vs 707) than Mark (850 vs 769) despite Mark winning.
*I think they would need 5 races at this level to qualify rather than just one
Now having back engineered the formula, this should be a way of comparing 100 mile races to determine which is the hardest as you only need 1 data point for the database for a race to determine the "hardness / distance / height change" factor. Please note this is not my opinion but merely a back engineering of the ITRA factor. I have picked races which are close to 100 miles to compare them.
Interestingly the A100 comes out as the lowest score / "least difficult". It is a relatively flat course but I am putting this down to the amazing support you get on a Centurion event with great aid stations and course marking so the controllable difficulties are mitigated. It should be a hard race as it is done in the British Autumn and certainly has the potential to be very challenging if the elements are unfavourable. However in recent years it has been dry and fast with mild conditions. The quotient can change from year to year depending on how well the runners perform or if the course changes slightly. I have grouped all editions together.
I have put together a table of the "quotients" for each race. This is the score you would get if you finish in exactly 24 hours. I have also included my ranking of 480, PB of 489 and Jim Walmsley's ranking of 916 (Ultra XL distance). In a separate post, I will put a table of times for each race to get automatic qualification but I am struggling with tables in this blog. http://76thmile.blogspot.co.uk/2017/02/additional-table-for-itra-rankings.html
This table is only for races which have UTMB points - the Barkley marathon and Sparathlon/Comrades (road) don't appear for example.
The "hardest" 100 miler in the list is the Ronda Dels Cims where a sub 24 would score you 1,045 points. A projection of Jim's ranking would imply a finish time of 27:22. Admittedly RDC is 170km (same as UTMB) but it is an absolute monster of a race. Other notable scores are Hardrock (888), Spine Challenger (905), UTMB (806), Hurt (740), MDS (720), Arc of Attrition (662), Lakeland (647), Leadville (609), WSER (574) and North Downs Way (515).
On this basis, my PB of 489 would just about scrape me a finish at Leadville just under the 30 hours cut-off but 44:24 compared with the 48 hour Hardrock cut off. However you know what people say about extrapolation...
Hopefully you have found this interesting and don't take it too seriously. Here is the full table in case you are interested.
And I guess Killian's 22:41 at Hardrock is slightly better than my 22:40 at the Autumn 100...