SI = Speed Index, which takes into consideration of track conditions etc. a higher number means a faster horse. but lets face it - the margins are slim.
wire to wire does mean leading the whole race, however just up” usually means they were leading at the last second so thats a bit of a conflict unless 2 horses were “neck to neck” the whole race and she only got ahead last second.

as for racing potental of a yearling - you must also consider how good the father was, and the training, as well as the confirmation of the foal. More horses are UNsuccessful on the track than are successful… and MOST horses who race - do not have long carriers. Many break down or are destroyed early on.

I believe that the average speed index of each track is 100, and so a horse that ran a race with a SI of .85, means it ran the track slower than the avergae speed of a good run on that track. And a horse with an SI of 105 means that it ran just faster than the average speed. The SI is calcuated by the track distance divided by the time the horse ran, I think. And I think each track’s SI can differ based on the length of the track, or the length of each race. So, a horse running a 1/2 mile wouldn’t have the same track time average as a horse running 1 mile, but the SI would calculate out to still be the same.

So, if the track average for a mile course was just say 1 minute, to keep numbers simple, a horse that ran the race in 55 seconds would have an SI of .105. And a horse that ran the race in 65 seconds would have an SI of .95, or 75 seconds would be an SI of.85

As far as the “wire to wire, just up” quote, my interpretation of that would mean that the horse in question ran head to head with the immediate competitor until the finish line, but fell back at the bitter end and probably ended up second or third.

And as far as this yearling with a dam with the SI of .105 being a racing competitor, that’s just not enough information to go on. You really need to know the dosage on both parents to make that kind of determination. If the mare’s SI was .105 after only ever running 1 race, that doesn’t mean she’s a good race horse, and it doesn’t mean her foal will be a good race horse. If her SI was still 105 after running 20 races, then she’s something to take a look at, and weighing in the sire’s dosage, you’d be able to have a better idea on if that yearling will show some speed and stamina on the track.

I’m sure there are plenty of horses out there running though whose parents haven’t proven themselves or don’t have good dosages. So, it doesn’t necessarily mean you can’t train that yearling to race. Just like everything, racing is a crap-shoot, and sometimes the long-shots pull out the surprising victories.

OK….just to add….. I looked at the 2 horses you listed. I didn’t bother to look up their parent’s racing info - but that is something you can do easily. Just solely going by what the ads say as is….
The chestnut colt mentions NOTHING at all about his actual racing history - so me, not knowing anything about the QH racing circuit wouldn’t know if those 5 champions in his pedigree are anything to write home about on the race track. Although, he is paid up for a $100k race in 2008, so someone must have thought he’d be a good race horse - I’d look into his lineage and get the dosage on his parents and grandparent if you can.

The grey colt, with the dam SI of .105 - isn’t his dam… if you read the ad, it says the horse with the SI of.105 is his maternal granddam. So, it’s his mother’s mother that had that SI. There’s no mention of the quality of the race horse either of his parents were, and maternal granddams are just too far back for me, without knowing the direct parent’s dosages.

You need to know number-research before you look into either of these babies, unless you just want to take the plunge - which isn’t to say they won’t end up winners. I love greys, but for you in your needs, I’d look at that chestnut a bit closer - see why someone thought he’s worth it enough to register him for a large purse before he’s even broke.

I work in the racing industry in South Africa. It is hugely popular here, more so than the US. Speed index and merit rating are the same ting. If the yearling’s mom had a merit rating of 105, she would have been a very good race horse. Merit ratings are determined based on a horse’s performance and the average here is in the mid 70’s-80’s. Horses can gain points or lose them and this helps determine what kind of fields they should be running in. Merit ratings work the same way over any distance. A horse with a higher merit rating is a better horse on the whole than one with a lower rating but that doesn’t make it faster. A sprinter is much faster over a short distance than a stayer and vice versa, horses are rated within their distance company. It has NOTHING to do with track conditions. That is a PI or pentrometer index which measures the softness and condition of the track. The yearling you are talking about would probably be a good buy, depending on his sire. He might not have very good lines on that side. Despite what some people say, the best predictor of a horse’s potential is its parents. A good pedigree is not a guarantee for success but it does make the odds better. In any case, unless you have alot of money sitting around, don’t go out looking for racing prospects because training and other expenses are huge and you can’t train the horse yourself without being a licensed trainer with the jockey club. As for wire to wire, it means the horse ran from the front to win, (here we say hands and heels). Just up means the horse just got up to win at the end, usually by a short head. Hope this helps. Also, most race horses do NOT break down or get put down after racing. At least not in this country. Most go on to be fabulous riding horses for jr. and adult riders.