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Sailing
I use speed ratings quite extensively for both flat and jumps and agree with rudeboy that they are only one factor amongst many that need to be considered.
I personally use Topspeed, but can also recommend the ratings on the ATR website produced by Lawrence Taylor. I did my own for a while but it is VERY time- consuming, although quite satisfying.
A good way to start your own ratings is to give each race a ‘form’ value depending on the official ratings ( or suitable alternative such as RPR – Racing Post Ratings) and from that work out what time you would expect a race to take to run.  The RP standard time relates to an official rating of 100 – the RPR equivalent is 110 – the  standard time is achievable by a mature horse carrying 9st on good ground and assuming the race is run at a decent pace.  All you have to do is make the adjustments for class, weight and distance to see how much faster/slower than standard horses have run. You then need to make an adjustment to allow for the effect of the going before calculating the final ratings.
If you want to give it a try, email me and I’ll give you more detailed instructions.
(Edited by Artemis at 8:23 am on May 14, 2007)
snowman,
You are a man after my own heart. I picked up this thread and you have said, almost verbatim, what I would have said to MrE.
MrE,
Listen closely to snowman: he has wisdom.
Jar,
Nick Mordin, writing in the Weekender this week has some interesting observations about coumputerised systems. Briefly, he states that many professionals (presumably including bookmakers) are using them and that they tend to come up with similar results. He goes on to say that this inevitably leads to more efficient markets and less value for people using such systems.
I think the main reason computerised (and manual) systems based on ratings do not work so well is because a lot of people, including layers and odds compilers, are using them. This causes the selections to be overbet and condemns their users to have to suffer poor value. Most of the providers of form-based ratings tend to pinpoint the same horses as being the best- in or well- handicapped. Also, the additional factors such as C, C/D, D, trainer%, jockey%, wins/runs%, etc. are also heavily taken into account in most systems, again causing some horses to be overbet.
There is no easy way, at least none that occurs to me, of getting round this problem. I think you need to get your own ‘handle’ on these factors and perhaps try different approaches. Also, I feel that the market also needs to be factored in – I understand that professional syndicates who bet on pari-mutuel systems always include the market (i.e. the collective opinion of all backers) in their computer models.
If anyone wants a good read on computerised betting systems, they might try Nick Mordin’s book titled ‘Winning Without Thinking’ – especially the appendices.
Also, Adrian massey has an excellent site where he produces his own computerised ratings but they are based on very limited data. Well worth a look.
