I have a mtb that I use to commute. It still has the stock tires it came with. I am looking at getting some slicks to improve the commute. Couple of questions... How important is PSI? All of the 26x1.5 slick's that I find only go to around 60psi. Is that ok, or should I be looking or something that can be pumped up a little more? Any suggestions on a good, fast (but fairly cheap) road tire?

FYI, my rim is 559x20

Thanks in advance.

My Specialized Armadillos are rated to 100 psi. $30 each. I run them up to 80, plenty hard at that pressure. You should be able find slicks up into the 75 - 100 psi range.

When I was still using my MTB as a commuter, I put on Kenda Kwest slicks purchased at my LBS for $15 each. They were nice tires. Think the max psi was 60.

I can get 60 psi with my knobbies. Is it worth it to upgrade?

Yes, knobbie just plain suck on the road. You'll easily get another 1-2 mph. I'm running IRC Metro 1.5" on one of my rides. They'll go to 100 psi. Think they're still ~$15 at Nashbar.

Slicks save you 15-20% effort over knobbies. Less weight to get rolling, less rolling resistance because you are not putting energy into flexing the knobs on contact, and greatly reduced wind resistance (The tread on the top of your tire is going twice as fast as you are... if you can hear it, it's slowing you down!)

Knobbies on the road do not corner well and your stopping distance is increased.

See the attached link:https://www.sheldonbrown.com/tyres.html#squirm

I used Specialized Fatboys which are totally slick but gripped well wet or dry. They are cheap, fast and you can get them at most shops that carry Specialized bikes, which makes them easy to find. https://www.specialized.com/SBCEqProd...62tqrfn.j27007

Second the Spec. Fat Boys.
They feel a bit scary in the wet to start with but it's all in the mind, they grip really well. They're also hard wearing. I've put about 500 miles on my current set and it hasn't even worn the molding line off yet.

I just bought a set of cheap Cheng-Shin 26x2.125 slicks, 12.99 each at the LBS. I had 26x1.5's on. These ride much nicer and I can't really tell a drag difference. I highly recommend something similar. The difference between slicks and knobbies for road riding is night and day. You wouldn't take totally slick tires mountain biking would you? No. Then why would you take knobbies on the road as a primary tire?

I put slicks on my son's MTB and he keeps up with me on my road bike. He said it made a ton of difference.

Think about it this way, your tires are the only contact you have with the earth when riding your bike (unless you are like me and fall off a lot). So you want a tire best suited for the surface you are riding on. If it is loose, like dirt, the knobby tires are ideal, if the surface is hard like concrete or asphalt, you'll like slicks with high psi much better. I think the surface you're riding on should determine what tire you choose, not the style of bike.

When I ride my mountain bike on the road, I use the 100psi Kenda Kwests--they have performed admirably.

Yeah, I should have been more clear. I ride exclusively on pavement/asphalt. That is why I am trying to switch out my knobbies.

You will be very happy with the results you get from the slicks...not only more speed from your moutain bike, but better handling. The knobbies tend to crawl in tight curves on pavement--the slicks just hold tight.