Agree with gooshew... but also, the wheels could be off. Think of it this way, when someone puts weight on wheels it smashes them... puts pressure on the bearings AND on the core of the wheel. That is what spacers are for to help with the weight on the wheel. If you have changed the bearings AND the spacers, then the wheels may be off. Try this, with the wheels off of the board, hold the wheel in the middle such that it can spin when you hold it. Look at the wheel from both angles as it spins... is is spinning smoothly, or is it wobbly? Change out the bearings and try again... Also, within one pack of bearings there may be some that are good and some that are bad, try one wheel with several different bearings. Getting just the right gear for your board and getting it working right may take a little bit of time, .. but it is worth it! :)
First I've taught of are that your wheels are made from silicon try urethane wheels they are harder but better,silicon wheels are more for a surface that's more rigid,not so smooth.And the second thing I've taught of are that your bearings are not good,you should go to a skateshop and ask for any model of bearings,preferable abec 5 or abec 7(abec is some sort of rating at the bearings from how much i understood),I highly recommend to ask for Shake Junt , Bones Reds or FKD bearings they are pretty good bearings.Sorry for my bad English and I hope this answer was good,have a great day !
Try loosening the nuts for the wheels/bearings. It may be too tight, thus causing friction and slowing your board much faster. If you spin the wheel by hand and they stock within a couple seconds, loosen them.
Also, I don't know what bearings you got, but some super cheap bearings come already with the shields (sides) smashed in which doesn't allow for a good spin.
Unless your friend has huge wheels (longboard wheels) and you have tiny wheels, I don't think it would be your wheels. In fact, I know it wouldn't be.
So if loosening doesn't work, take out the bearings and look if the sides seem bent or smashed in.
Try tightening your bearings.
WD40 my friend.
