ive had back problems for the past 3 years. i spun up a tire swing and tried to jump through while it was spinning. i ended up hitting a tree. and recently i broke some vertebrae in my back, so yeah...
when i sleep on my sofa i have back pains for that whole day
its only when i sleep on my sofa though :S
but neway, i rode 17,5 high, and im 5ft 11
and i never got back pains. but im now riding 20 high so its all good