26 X 1.75 front and 26 X 2.0 rear tyre?
Yeap- no reason not to. I do the same on my mountain bike, I prefer the width of the wider rear to enable stability/grip whilst the front is just wide enough to steer in the direction. Most inner tubes will work over quite a range of tyre sizes &amp; the same for rims. Make sure you check the specification of both if you are concerned.