Those where 1.9 or something similar and they where almost 'slicks'. This is what i did:Д¬hanged my wheelset for one made of light narrow rims and the smallest 26' tires I could get at the moment. Many tourists use flat bars, preferring the more upright posture, and you can always add aero extensions if you feel you need them (mostly for the more varied hand positions). For shorter rides this is not so much an issue, but for, eg, touring you'd appreciate the longer wheelbase, more appropriate posture, and more stable steering of a true road bike.ДЄdded: One might consider replacing the flat MTB bar with drop bars, but that's complicated (new bar, stem, shifters, brake levers, etc), expensive, and unnecessary for simple recreational/commuting purposes. The main thing you'll be missing after all this is the geometry of a road bike. (Someone may make a commercial product to do this.)

If there is no lock-out on the bike you can use pieces of plastic drain pipe, cut open on one side, strapped to the cylinders. You will almost certainly need to change your chain length for this, and might run into a tooth capacity problem with your rear derailer, depending on how you do it. A larger front sprocket and/or smaller rear cluster. Next, try to increase your top end gear inches. You do not have to switch to 700C rims, though your choices with 26' rims will be somewhat limited. Yeah, so long as you're more looking at simple recreation/commuting and not expecting to set any speed/distanced records, you can do a fair job of conversion.ДЇirst get smoother, higher pressure tires, ideally a bit narrower than your current ones.

you'll need different shift levers probably.ДЄll in all it's probably going to be a lot cheaper to get a used road bike and refurbish it than to convert an entire mountain bike.

your brake levers would need to be swapped to short-pull models meant to be mounted on a drop bar.

Mountain bikes generally are geared much lower than road bikes.

You'd also need to replace your crankset.

Many mountain bike frames will fail on at least one of these counts.

you'd need to make sure that your frame and fork can accomodate 700c wheels and is drilled for caliper brakes.

If you want to take it all the way, you'll need to swap out the following: I've tried this before and the ride quality is a bit off compared to a road bike. You can set up a mountain bike with slick tires and drop bars if you want. Mountain bike frames are designed for a different posture and are often designed for a suspension fork, as well as generally being beefier. The geometry and construction of the frame is different. A mountain bike will never really be a road bike.

Shimano bike vs iron horse bike