help!!!! drift tyre difference
 

hi,

ive noticed some drift tyres are like an egg shape across the tyre yet some are just flat which is what i class as a normal tyre,

this is what i mean by egg shaped:

http://www.ebay.co.uk/itm/4-PCS-HSP-.../121439907444?

and those above are known by the company as a number 1

and these below are what i call normal, known as number 3:

http://www.ebay.co.uk/itm/4-PCS-Whee.../111458950675?

does anyone know why they have different ride surfaces ( curved / flat ) and what are the advantages or disadvantages

thankyou for any explenation........