>>1717212Mix of the bike being too large (too much reach) for you, and your fitness being too shitty to put enough power into the pedals to take the weight off your hands.
There's good reason everyone gets find to start on a 90s rigid mtb, and it doubles for us fatties; riding position more upright so we're not kneeing our own gunt, components will hold up longer, less reach built into the frame so our hands don't feel like we're holding a plank, and spinny gears to get up hills.
Ignore frame size charts based on height, they're for 130lb fuckbois. Picrel, I'm 6' but my 54cm road bike needed to have the stem chopped way down to get the fit. 18" 90s mtb frames fit me perfectly.
