1.85 or 2.1 inch wide tire?

[Dismay]

What are each tires benfits and disadvantages?

[reflux]

dude, here's the short version of my response. size 2.1 offers the best (imo) combination of traction and low rolling resistance for xc riding. when you get into narrower tire sizes (ie 1.85) you start limiting the tire to certain conditions (mainly just climbing, fireroad, etc). tell us what conditions you will be using the tire in and we'll give you more feedback

[oldfart]

Small tires are lighter and will be faster climbing and accelerating. They will sink in mud a bit more which can be good. You get the tire to the firm stuff underneath unless its really deep in which case you're stuck. More clearance too if the mud is sticking. But the small tires lack volume so you need to run them harder so you don't bottom out and pinch flat or dent the rim. Traction on loose dry surfaces is not as good or on big cobbly trails where you need volume to bridge between cobbles rather than go between. This is assuming similar tread patterns.

[crazybastard]

thiner tires are faster sprinters but the fat ones will not roll as much in loose gravel and other things like that

[Big_Papa1080]

2.1" is better. gives u more traction.

[The Toninator]

dismay i ran 1.9s (sworks team control pros) for a while then switched to 2.1's (pan racer fire xc pros)
i will not go back for local conditions:
2.1's are way better in the sand.
Cornering and traction in all conditions is better
Might be a little more rolling resistance but they are actually lighter than the smaller tires so i think the size -v- weight negates each other.