Mountain Biking - Differences in Stem Angle for MTB?

I have a Ritchey 4-Bolt on the bike right now and I believe its a 6 degree angle but i was wondering if there were any pros and cons for getting a straight stem with no angle? Please shed some light. And also when i see the different sizes in MM (90MM, 100MM, 110MM, etc.) What is that size referring too?

The length of the stem, as in the tubing that the bar attaches to, if that makes sense.

Only thing the angle will effect is the height of the bar. If you have a 6 deg up angle, a zero degree will put the bars a bit lower - I dunno, 1/2 an inch maybe? It'll make the effective length of the stem slightly longer too.

If the angle is too much and the bars are too high, while climbing steep stuff it will be tough to keep the front end down.

If the angle is too little and the bars are too low, steep drop offs will feel all that much steeper.

The angle and length of the stem changes the bar position which will definitely effect handling in the more pronounced trail situations.

Choose wisely.

Thanks soreyes. Nice to see a quick and easy explanation. How does stem length influce handling? Longer = Faster?

Thanks soreyes. Nice to see a quick and easy explanation. How does stem length influce handling? Longer = Faster?

Im pretty sure the Shorter the Stem the faster the steering and visa versa

Im pretty sure the Shorter the Stem the faster the steering and visa versa

I would concur. Also, a longer stem will have you stretched out further possibly making it a little harder to get back when descending. Over the past decade it seems like there may be a trend towards shorter and stouter stems. This might be to support steeper riding that would be encountered with northshore style gravity contraptions and dropoffs.