Why is it harder to pedal after installing new rear mountain bike tire and tube?

On my 7 speed mountain bike, the rear tire and tube was punctured, so I replaced both with the same exact brand (Bell w/ kevlar) and same specs (26x1.95). Since then, I don't feel like I'm going as fast as before at my usual gears. It's a bit harder to pedal even at first gear, but still manageable,... show more On my 7 speed mountain bike, the rear tire and tube was punctured, so I replaced both with the same exact brand (Bell w/ kevlar) and same specs (26x1.95). Since then, I don't feel like I'm going as fast as before at my usual gears. It's a bit harder to pedal even at first gear, but still manageable, just a slightly slower ride. My two guesses are the rear wheel not being in true, tube may be tangled inside, spoke problem, bolts and/or lever holding the wheel may be too tight? or something with the brakes which are spent too. I spin the rear wheel after the install and the tire is a tiny bit uneven, but the rim looks OK. yet I'll find something to test the rim from truth. Thanks
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