front and rears tires different series? is this a problem?
 

I have continental extreme contact dw 305 35 19. for my rears I bought last year. Those seem to discontinued. As i'm looking the cont. extreme contact sports 255 35 19 for up front. They look very similar in tread pattern and specs. By not having the exact same series continentals will I see feel any issues? Also should I be getting 255 40 19 instead?? Thank you in advance

The important figure is the actual diameter of the tire.

Use this calculator here for quick reference:
https://tiresize.com/height-calculator/

As long as your front and rear are within, i think 3% of each other, you won't have issues.

As for different types of tires front and rear - unless one end is complete and utter garbage, i suspect you won't even notice the difference in daily driving

If you're doing any sort of harder driving, then, obviously you want to keep the same tire on all 4 corners

thank you for that info never knew that so my rear 305 30 19 is 26.2" in height. If i did 255 35 19 it would be 26". So that should work well. thanks again

I'm having the same problem. I bought wheels off of a forum member that have the EC DW on them, and they're practically brand new. Well, there's a big screw right on the corner of my front passenger side sidewall. Continental no longer carries the DW in 245/40/19. Obviously, I'll have to replace both fronts with something similar (I'm thinking the Extremecontact Sport).

I've never ran different tire models on the front and rear. Should I replace all 4? It just seems ridiculous to spend all this money to replace almost new tires.

I have the same set up. I have the DWs on the back 305. The extreme contact sport in the front 255. It runs so nice now. No need to buy all 4. The sports were the replacement for the dw. I’m very pleased with the handling and comfort of this set up!!