try a heavy duty stem 4 down hilling there usualy short or try some new bars with more raise

a higher stem wont really help, a shorter one will, since when you are going downhill and you throw your body back, having a shorter stem means you wont have to reach as far. i have a Bontrager Select on my bike and i love it. i think its an 80mm, 10degree upsweep. it very comfortable and super, and only costs $25. i’ve been using if for 2 years and no problems at all. i dont do much downhill, but i use it on my XC race bike.

if you do alot of downhill, you may want to look into getting a dual crown fork with the integrated stem. they keep your front end up higher for more control and the built-in-stem angle is optimal for controlling a bike going on the steeps. if you have about $700 or $800 to burn, check ebay for a Marzocchi 888, rock shox boxxer, manitou stance kingpin (lower end, but still reliable), or maverack DUC32 (inverted fork, very light and very cool).

if you have a lower budget, then just getting a shorter stem will help. here are several short length stems i found on JensonUSA.com from $21-$80:

It depends on your current setup. There is no ‘magic’ number.

If you feel your grips are too low, you could try to either get a higher stem, shorter stem, or a high rise handlebars, it all depends on your current setup.

go to your local bike shop and “get fitted” to ensure all angles and riding style are compatible
it is worth the time and money

That’s an impossible question to answer in a web forum. You need to have someone look at your position on the bike and then recommend what stem reach and angle are best for your riding style, physiology, and application. Go to a good shop and tell them what you’re looking for. If you buy the stem there they might even put it on for free.