Not only do they jump up and down, they also jump side to side. Its a joke. Schwalbe does have a warranty but I don't know how long it lasts. The tires only have like 50 miles on them and have been in storage for awhile. I bought bontragers awhile back and they are nice and true. But that was a different bike. After restoring the schwinn, I got the schwalbes back out and realized how bad they were comparing them to all the other tires I have. I wonder if they would give me 2 new tires. But if the new ones are the same, why bother. Maybe schwalbe sucks. I do know how to mount tires. Thanks for the replies. Keep them coming!