besides the mph rating, will a V rated be a harder compound than the Z rated ?
i ask because im looking to ditch my mugens for some GSR rims, and they only make the tire i want in 15'' V rated

 

I dont know, but I went 150 mph on Yok S306's. Those pieces of crap cant be anything more than V rated, so if you're worried about speed you should be fine.

 

i think you can find out by just looking at the tread rating. if its lower then its softer. I had Nitto 450 V rated and the compound was harder then the Z rated Khumos i had on 15s. 195/50/15.

 

yeah, the speed rating (v vs z, vs anything else) doesn't have a direct connection with the tires compound. you have to look at the threadwear rating for that.

 

the biggest difference between Z and V has nothing to do with the rubber used, tread wear or traction rating, the carcass of a z tire has much more reinforcement and will keep its shape and remain strong under hard acceleration and high speed.
Z rated are very bad for drag race use if you have a radial, better find and H tire with decent traction rating and let some of the air out