Few years ago, I got a men's Infinity Boss Three hybrid bicycle from Costco. It comes with 700c tires. I would like to replace them with mountain bike wheels, inner tubes and tires for more comfortable ride quality on paved bike trails.
My question is that what size of wheels, inner tubes and tires will fit on them? I don't plan to replace the drivetrain and brake components.
I realize the 700c tire's diameter is 27.56". Looks like I can just get a pair of 27.5" mountain bike tires?
Sorry - no. Presuming your bike matches the photos found on-line, your bike looks like this:
Found at https://costcofan.com/costco-infinity-boss-three-hybrid-bike/
This bike has rim brakes, and they will only ever suit one size of rim. You cannot change away from 700c wheels safely unless your bike has disk brakes, or if you can somehow re-work the rim brakes to function for you.
It will be more cost-effective to buy an additional bike that matches your requirements rather than try to adapt this entry-level bike to be something its not. You would probably spend more on new wheels than this bike cost new.
Assuming the photo in Criggie’s answer is accurate:
These bicycles usually come with ~35mm tyre width. Depending on the fork, frame and brake clearance it should be possible to mount tyres with up to around 45mm width, especially when used without mudguards.
Upgrading to ~45mm tyres should improve comfort noticeably, assuming you lower the tyre pressure to make use of the additional tyre volume.
For tyre compatibility in general what matters is the bead seat diameter of the rims. It’s the same 622mm BSD for 700c, 28" and 29" MTB tyres. However for 27.5" tyres the BSD is 584mm, so you won’t be able to mount them on those rims. Changing to rims with a smaller diameter would be difficult or even impossible on this bike.
If you can find 29" MTB tyres with sufficiently narrow width (the ~45mm I mentioned above) you should be able to use them. But you’ll probably want a trekking/city bike tyre like the Schwalbe Marathon.
