Should I upgrade tires from 26X2.1 to 26X1.75 or am I wasting money?
I have a modest bike (considering $$$ bikes some of you have) hybrid hardtail GT Timberline (I think 06 model).
Right now it has stock 26X2.1 GT Guardian (Aqua...something) tires. I was wondering if getting something like Forté Gotham Road or Michelin Country Rock would do me any good.
I mostly ride city streets (lots of potholes) and asphalt bike trails with an occasional romp on gravel paths with good amount of roots popping out. I try to do about 30-50 miles every 3-4 days.
If the stock tires are knobbies, then it is definitely worth changing tires to a slicker tread for road/path use. the width is personal preference, I run 1.5" and I am going to try 2.0 since speed isn't as big an issue for me right now... So I want to see if the wider is more comfortable.
I will stick with relatively slick tread, as I don't ride the bike off road.
Reducing the width of your tires will not, in and of itself, necessarily make you/your bike faster (unless you habitually ride at speeds on the road at which wheel aerodynamics become a significant factor). There's always trade-offs! Biggest single change would/will be getting rid of anything remotely resembling mtb 'knobbies' -- i.e. any significant externally-applied 'tread' -- and running a plain or 'grooved' slick. Otherwise, and generally, by changing (i.e. putting on higher quality) tires you could:
1. Lower rolling resistance (less effort for a given speed over the road);
2. Lower rotating mass (= quicker acceleration), and
3. Increase 'comfort'.
For example, if you replaced your existing (stock?) tires with, say, Schwalbe Marathon Supremes in a 2" width, i.e. pretty much the same 'size' as you have now, you'd almost certainly notice all of the above. The Schwalbes are very expensive, and an extreme example, but you get the idea.
On a 26" wheel, don't forget that by changing to, e.g., a 1.3 or 1.5" slick you have to run at higher pressures (for the same rolling resistance and puncture resistance as the same tire in, say, a 1.75 or 2" width); this will inevitably reduce 'comfort', but increase acceleration slightly. It would also effectively reduce your gearing, because overall wheel diameter becomes pretty small. It's all a matter of trade-offs!
In my own experience, I've found that really high quality 1.6 or 1.75" slicks work for me; YMMV
Schwalbe tires tend to be on the pricier side; there's a good reason for that -- they are very well made and very effective in their intended applications, at least in my experience. Another option would be Panaracer, either the Pasela or the T-Serv. I've used Panaracer Paselas (the folding bead version), in both a 26x1.5 and 26x1.75 -- either version is very light (for this kind of tire) and very effective for just the kind of riding you describe, as well as being pretty resistant to punctures. Bonus: they are somewhat less expensive than many other similiar tires.
I swapped out my MTB tires on my Gary Fisher hardtail for Specialized Nimbus tires (26 x 1.5"). The tubes ran $8 for both, and $32 each for the tires at my LBS. I'm sure you can find a better deal online, but even at that price it was totally worth it. I've jumped curbs, ran through a patch of goatheads, over glass, etc. and been very surprised to rarely get a flat. I went from pedaling at about 14mph on my MTB tires to 17mph with the road tires. It was a great upgrade, and a very noticable change.