First things first... Thank you for the kind words in the previous post. It is great that you and hopefully some of the others are having a better understanding of the game.
Speed , stalk, close:
Here is the more complex answer: You identify the PURE speed first. That is horses that can only run one way.
Then, identify horses that would enjoy being the speed but have shown you that they can lay off a few( 1-3) lengths. With these horses, make sure that before accepting that each horse can actually do this , they have proven it to you. By that I mean they have had a non perfect trip and been able to accomplish it. Any horse with some ability can lay third to a duel outside and no horse ever close to it's outside eye and run well. Although getting a great right eye clear / left alone trip is not the fault of the horse it is certainly NOT of equal merit to the horse that sat off while in between horses with it's right eye covered up by the outside horse down the backside, then was able to move when asked to get clear of the outside pressure and secure a nice trip from that point on. One horse inherits a great trip and the other horse EARNS the nice trip from the 3/8s pole home. That is a night and day difference. Now, the horse that gets a great trip might be able to also accomplish dealing with a tougher trip, and there is no way to know this if they have not had to previously. More won't than will , so scrutinize the trip if possible.
Next is mid pack runners. These horses seem to always find themselves right in the middle of the field. In 10 horse fields , they would usually be 5-6 . There should only be few of these , even in the Derby. Problem with these horses is in the Derby, they will be probably laying 6th-12th depending on how much speed is in the race. If they do not have the ability to fire whenever the jockey needs them and the pedigree to have the stamina required, they will fail. Some of these horses might give you a hint from previous races but some will not and for those types, a good amount of guess work will be required.
Next is typical closers. They consistently close for each race from near the rear. Most of these types are horses that have learned at an early age to relax. These are typically horses( not always) that have been pointed towards the Derby for the last 6-8 months at least. The most viable of these are horses that have been able to show some ability to either be closer or move sooner depending on how the race shapes up.
Last is the deep closers. They get to the rear of the pack no matter how many are in the race and no matter how slow or fast the fractions are. Simply put, they like to come from last.
So the answer is 5 categories if you are working on a race like the Derby(18-20 horses).
If not such a cluttered group and for most races , 4 categories. Eliminate the mid pack group and move them forward or back depending on what they have showed. This is simply because it is damn near impossible to figure out which 10-12 stalkers will be where. By using a 5th category, it helps split that large group for hopefully more clarity. At least it has for me.
Again, for 99% of the races, use 4 categories.
Do not think that the deep closer category must have a horse in it. Some years it just does not. It takes time to develop running habits and styles and some years by Derby time, no horse has developed that style yet. Usually by Classic time or certainly when the horse turns 4, that style will usually have started to develop if it is going to. Remember, that style is not always developed by choice . Sometimes it is developed by a horse being weak behind ( a slight muscle soreness or weak hind end muscles, maybe a confirmation flaw, but a muscle tightness or a lack of muscle, that needs to get moving and get in to motion to loosen up. One of many reasons that you might see certain horses warming up more than others. Jogging will help the shoulders where jogging and then galloping quite a bit, will help the hind end. When horses have a stiffness in one area they will sometimes over compensate , thus creating a new stiffness or soreness somewhere else, but now I am rambling.
Anyway, with these categories, you should be able to identify where most horses will plan to be if things go right. And because in the Derby, things might not go right, you need to have identified those that have created there own good fortune during not so perfect circumstances if you can.
Also , remember that the Derby gets very strung out , so the lengths off the pace will most times be many more for all the horses than what they were accustomed too. That's O.K. though because they all have to deal with it at the same time. This goes back to earning a trip instead of inheriting one. Chances are, in the Derby, it will need to be earned.
The other problem with the Derby is that if most of the horses have run 5-6 times, many have not found there true comfort spot yet. Sure, the speed has, and the deep closers have but for many it is a work in progress. That is what makes it so great and of course, very profitable if you can figure it out.
Again, just for the Derby type events, I try to eliminate somewhat by category instead of bunching 20 together and picking a few. If I can find a solid few horses that have overcome tougher trips, or finished faster through doing math within fractions than others, or something like that, I think it goes a long way.
When looking at the PPs how many lengths determines each category? :
I never went by lengths other than just off the lead. Pace of each race as well as surface , speed of various tracks, where and when the timer starts at each track( Pimlico 6F virtually no run up, Monmouth 6F a big run up, for instance), etc. can skew that too much. I went by a general overview of each PP taking speed , surface, and what I just mentioned in to account. Start with each horses most recent win or best effort and work around that. Also, following the Derby trail will allow you to know from closely monitoring the races along the way that, for instance, the Florida Derby had a ton of speed, while the Wood had solo speed and the pace setter walked the dog so laying 3rd with a first quarter in 24 1/5 is not near the same as laying 3rd in the Fountain of Youth in 22 4/5. It might seem like that would take forever, but it really takes about a minute per horse to categorize as long as you understand and have followed the races leading up to it.
With the Derby being such a unique race, so much work can go into one race and then some faint hearted horse gets a perfect trip and it seems like it is all for naught. That's how it will be some years, but I will tell you this. You do this for the months leading up to the Derby and you will be so much better off than if you don't. Why? Because you will have force fed yourself the breaking down of a bunch of races and began to understand how to do it. In the long run( 8 months from now) you will be able to look at some typical everyday races and start to be able to see things that you never saw before. At that point, having a firm grasp on how 2 or 3 races on a card will probably play out will allow you to skip or bet drastically less on the others. Because ordinary races during any given card consist of horses that have run many more times and at the same track or distance much more often than the Derby horses had, the entire challenge of breaking down a race can only become easier than the most complex race each year in which we try to figure everything out with horses that have never run at the distance that we are trying too decipher. All this will make you a smarter handicapper, better at money management, and most of all , you will have developed an understanding of what is actually taking place on the track instead of just following the pack around the track hoping your numbers come in and not knowing why they did or did not. Don't get me wrong, some people just want to bet a few bucks and if they win, great. If not, oh well. That is fine, but if you really want to understand the game, doing what you are doing is a huge step in the right direction.
Great question. Keep me posted.