bigger tires?

They should fit your stock rims. The tire size you listed is for am 8 inch rim and that is what a Blaster has in the rear.
 
The last number in the tire size is the rim size. In this case 8" which is the size of a stock blasty rim. The width (2nd #) usually dont matter for the rim size, unless its some custom tire. Height (1st #) has no effect on the rim size.
 
I think he is refering to the width on a stock width wheel. Just my guess. And yes they will fit.