What stem length should I get?
 

Ok I'm 5'8", 31" inseam. I ride a 55cm frame and the stem I have now is 90mm long. I feel fine on this set up, no back or neck pain from the position. The stem I have now is a typical road style stem as far as angle goes. The Jaguar has a pretty steep drop, a 58 degree angle I believe. I plan on running a NITTO B201AA Riser bar and it has 50mm rise. I suppose it should compensate for the drop some. Now, will I need to get a different length stem or is 90mm sufficient?

90mm for riser bars might feel a bit cramped if your drop bars give you a comfortable position.

I hope you have your brake levers worked out, since you can't use aero levers on riser bars.

You might find this bike stem calculator handy in getting an idea what different stems will do to rise and reach on a bike. This might answer your questions.

http://www.brightspoke.com/t/bike-stem-calculator.html

Yeah I think I'm gonna go with 100.