Would like to hear about the advantages,or the disadvanges, of 18" versus 20" rear tires on a Blaster. The bike will be used by a 12 year old ( 5'4" 120 pound )to start the learning process of riding in competative competion. The Blaster, except for bolt ons, will be basically stock.

 

The 20 inch tire is going to offer more ground clearance than the 18". But may be more prone to roll because of the taller side wall. (assuming the same size rim)

I can't remember which tire comes stock..But a smaller tire will effectively change the gearing too.

you might loose some top end unless you compensate with gearing changes.

the only other thing I can think of at the moment is weight.

 

Heheh.. I like the saying you have their. I will have to tell that to all my buds that want to get a ride As for the tires, If top end and clearance are not a major factor, go with the smaller tires, It will make the bike handle a little nicer and will teach your grandson how to avoid getting caught up on rocks,ect. for when you/he upgrades the bike to something bigger. It will also help acceleration which is usually a major factor in racing.