Originally Posted by
Tim_Iowa
Yes, you would be OK with any 700c tires (622 is the actual rim diameter in mm, btw).
The smaller tires will lower the bike a little (40mm = 2mm lower than stock). This becomes a big deal if you lower it so much the pedal scrapes. On your hybrid, you can probably lower it a cm before you get into trouble. Thus, 32mm may be a sane minimum. It depends on how high the cranks are (aka bottom bracket height). Most hybrids have medium to high bottom brackets.
If you go from 700x42 to 700x19 you're only talking about lowing the ride by 23mm. If that's enough to cause the pedal to scrape something is badly wrong!
I wouldn't go from 700x42 to 700x25 without checking the rim will be OK. You don't want tyres working loose because they are too narrow for the rim. If you're not making big changes you should be OK.
The larger tires will raise the bike a little, by the same reasoning. The limit for large tires is the clearance of the frame. If you put a 2 inch / 50mm mountain bike tire on your rims, it may rub against the frame on the sides, on the top, or hit the brakes. Look at your current tires and measure how much clearance you have wherever the bike frame/brakes come closest. That should give you a rough idea how much bigger you can fit.
In this range, a few mm won't make too much difference in the ride.
Good point on going up sizes and the frame clearance.