Ok so I’ve been wanting to buy my first bike for a while now but I’m not sure what size bike will fit me the best. I’m planning on getting the Vitus Nucleus 27 VR mountain bike (gray 2021). I am about 5’11” with 32” legs. The medium for this bike goes from 5’7”- 5’11” and 30”- 32” legs. The large goes from 5’11”- 6’3” and legs of 32”- 34”. Which size do you think will fit me the best and should I be looking at other body dimensions to find the best fitting bike for me?

Welcome to BF.
First bike?, you need to ride both sizes and decide.

For me the distance from saddle to handlebars is most important. That determines your upper body position. Find what’s comfortable to ride today, if you stay with the sport, your position on the bike is likely to change.

I've little to no experience on riding mountain bikes but will think that like road bikes, once you get in the range of suggested sizes by the manufacturer, you are okay with either. The smaller bike might feel a little sportier and the larger bike more like a four door sedan going down the road.

Depending on your fitness level and previous riding experiences your position on a bike might change quite a bit. As well your preferences might change in how you want to fit. So just pick a bike, preferably by riding each as long as you can convince them to let you. Then make certain you aren't spending your whole wad on this one bike so if after a thousand miles you find you chose poorly that you have some cash to do something else. Hopefully it's only a stem, saddle, or handlebar change which aren't too much money.

Are you really going to ride this as a mountain bike? Off paved roads? If not, then you might be misunderstanding why they put the word mountain with bike.

One way to determine bike size is to use an online calculator: https://www.competitivecyclist.com/S...ulatorBike.jsp
Be sure to choose mountain bike if that's what you want.

I don't know why they list legs, it has nothing to do with how a bike fits. but if you're curious about leg length, measure your "cycling inseam" which is the height from the ground to your pelvis. this is usually at least two inches longer than your pants size. inseam is a measurement of pants, PBH (pubic bone height) is sometimes used to ensure that a bike has a safe amount of standover clearance.

for the size of the bike while your'e riding it (do you plan to ride the bike, or just stand over it?), you're between a medium and a large. for most mountain bikes, I'd say you should be on a large. in general, sizing up will give you a more stable bike, and sizing down will give you a more nimble bike. however, I am looking at the geometry share for one model of that bike and it says that the upper end for a medium is a 5'10" rider. at 5'11", the medium is probably going to be cramped. at 5'9", I would chose a medium and expect that someone taller would need an unconventionally long seatpost and stem to make it fit, which would likely compromise handling on trails.

I think this would apply to any human being attempting to operate a bicycle.


You should feel like you can easily weigh the front or rear axle of the bike at any given moment as necessary. If you feel like you're always leaning a bit too forward as you ride, most likely you would benefit from a shorter top tube as well as a taller stack (or may simply get away with changing to a shorter stem)

You should also consider reach according to how balance you feel out of the saddle, with your weight in the cranks. This is mostly important for ensuring a smooth ride over obstacles.