Many of the roads on Koh Tao are not very good and so if you think that you may have problems with some of the roads to the more remote beaches it's best to park up your bike and walk down to the beach. 

 

 

Another tip when renting a bike to look for a place where the bikes don't appear to be brand new, as this is usually a sign that the bike shop replaces any parts that get scratched immediately to make it easier for them to charge of any new minor scratches.