Originally Posted by
mrfreezesdefy3
I have no problem on flats ,it's just going down hills and back up ,my current bike weighs 20 lbs and I'm going to weigh my old bike but I can tell it's heavier than the current bike I just bought
Probably a combination of not being used to the disc's on the way down and the bounce on the way up? Logging some miles will get you used to the new brakes and concentrating on a smooth pedaling technique on the way up may improve things.