Well... since I live in Texas, and just an hour ago rolled in from a mountain bike race (at Warda), and have two kids under 5' tall, and they race mountain bikes and off-road duathlons (and win, I'm proud to say), and in the industry and with regular-sized people there is lots of misinformation about WSD and misconceptions as well, and since I have personal knowledge I think I can help:
Juliana, Racer-X, Scalpel, Giant NRS, Fuel, and some others are all nice bikes, but no, no, no, no and no.
First of all, the only one that will fit you is the Racer-X XXS. Secondly, you don't want, or need a full suspension for the races in Texas, or any of the Xterra courses.
What you need is this (taken at today's race ;-) :
A small-framed hardtail with;
26" wheels;
RockShox SID fork;
Kenda Karma tires (run tubeless);
lightweight wheels ;
hydraulic disc brakes;
Sram XO triggers or grip-shifters; and
Selle Italia SLR or Fizik Aliante or Gobi saddle
Why?
I can't remember EVER seeing a competitive, young, small, woman racing on anything other than a hardtail. You put out MUCH less power than a larger woman or even small man, so the extra weight (and complexity) of a full suspension bike will be much more an issue with you than with a more powerful rider. My daughter is 4'7" tall, and that's a 12" frame. There are a few bike companies that makes frames that small. When my brain is not as mushy (I really did JUST drive in from the race and I'm really tired) I'll recommend some frames and also shops in Austin.
24" wheels just don't roll over terrain as well as 26" wheels do, there are no high-performance 24" tires, you can't build a 24" wheel lighter than a 26" wheel because the available 24" rims are heavier than the 26" ones, and suspension forks for 24" wheels are heavy, have lots of stiction, and are almost non-adustable.
RockShox SID fork is the lightest, and the most adjustable fork for a lightweight person. My daughter weighs 70 pounds and it's fully functional with her weight (although I have some secrets I might share with you to make it work even better ;-) .
Kenda Karma's are, light, versatile and THE tire for the Texas courses, and truthfully if you also have a set of Kenda Nevegals you have virtually every course in the US taken care of. Tubeless (with Stan's fluid) because you can then run crazy-light air pressures and not have to worry about pinch-flatting or flatting, period.
Lightweight (as in light, not the brand "Lightweight") wheels, just because you don't need anything more. If you want the killer setup, go with the Stans custom-bulit wheels (www.notubes.com ) and he can build you a set of 1,300g (+/-) wheels for under $600. If you want light and bullet-proof, then Crossmax SL's like in the picture.
Hydraulic brakes are a godsend for small people with small hands because they take so much less effort and modulate so much better. Specificially I recommend Magura Marta SL's (the bike in the picture has prototype SL's but production ones have silver bodies), which weigh as much or less than the lightest V-brakes.
SRAM is da bomb, it's just plain better than XTR and the two shifter systems work better with smaller hands.
Since you're that small I assume you're petite and relatively-narrow hipped... accordingly WSD saddles are WAY too wide for you, and you can't get behind them for descents... the SLR is narrow, and the XP version has more padding and is perfect for mountain biking. IF you have a favorite road bike saddle, though, try and use that first. My daughter uses the regular SLR and Fizik Aliante on her bikes.
I probably have more information but I'm exhausted and my brain is mush, so I'm off to beddy-bye... I'll post more tomorrow and should be more articulate as well ;-)
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http://irondad06.blogspot.com/
http://irondad.blogspot.com/