when ever i change to new pads on a old rotor with out getting them resurfaced first i always get "brake shudder" , i say always get your rotors resurfaced or get new rotors when getting new pads

That's not the reason for your "shudder".

And resurfacing rotors costs more than buying new rotors...

I've never had any issues going back and forth between track pads and street pads on the same rotors (not resurfaced) with the 240Z, S2000, and RX-7. Mainly running Carbotech XP8 or XP10 pads, but also Cobalt XR2/XR4, Hawk HP+, Porterfield R4.

cost me ten bucks per rotor last time....

Sounds like you need to bed the pads.

nope , did that too

Sounds like your rotors are warped. Maybe just replace them lol

also you just admitted i was right with this post , thats the whole point of bedding pads , new pads new rotor, try to use new pads on an old rotor that has not been resufaced and you're going to get shudder when braking hard

Sometimes, but usually its a warped rotor. Eventually the new pad if its an aggressive compound like a metallic, will bed in pretty quickly. Most track guys that switch from street to track pads regularly dont bother with resurfacing rotors. They burn through rotors fast enough. Its just added time, expense and unnecessary trouble to go through when focusing on other parts of prep for the car. If your serious about tracking and still run the car on the street regularly, have a dedicated set of rotors for your street pads and a set for track, then swap everything.

Need to also consider the time to call / schedule time with machine shop, drive there, wait or drop-off, then picking re-surfaced rotor up. With the added time factored in, a new rotor shipped to my door is far cheaper.