I know it's too late for this to be useful to him, but the adhesive elastic bandage is probably overkill in his situation. It is more durable, water resistant, and won't come off unless you want it to, but he should probably change the dressing once or twice a day for the first few days, depending on how bad the abrasion is.
A simple gause roll is easier to apply and remove, more comfortable and breathable, not to mention a lot cheaper. However if he plans on biking in wet or very dirty conditions, the adhesive bandage would be a good idea either instead of or better yet on top of the gauze roll (If one roll is set aside for this purpose it will last a long time, and has no need to be sterile).
I would also suggest scrubbing or even irrigating the wound with iodine before the application of antibiotic ointment.