what is the difference between the A4 and the S4 brake set up?
if thr is a difference, i asume that the S4 brakes are better, can you put them on a '98 1.8T quattro?
i would like to upgrade my brakes, but keep the OEM look.

 

You would need to swap the leg and hub as they will not bolt up to the A4 set-up.

 

The S4 rotors are larger. They are slightly better but nothing to brag about. Not sure if they'll even fit but you'll need the S4 caliper bracket and maybe the caliper. The A8 rotors can also be fitted with some modification. The best bet to upgrage your brakes is to just get better pads and better tires, unless your going to the track the larger S4 setup isn't worth it.

 

search please... they won't fit on the B5, but they'll fit on the B6. Just get TT caliper brackets and A8 rotors and call it a day.

 

i was planning to change the brake lines, rotors, and sport pads on the A4 set up, but i was wonder if i could swap the A4 set-up for the S4 and still get cross-drilled rotors for the S4.
What about the brake lines, can i use the A4's lines?

 

Get braided stainless steel lines, the Audi TT caliper brackets and some aftermarket crossdrilled A8 rotors. The S4 setup isn't gonna work. Keep in mind if you haven't done so already you'll need larger diameter wheels for everything to fit.

 

Does it matter what TT or what year the TT is?
i am thinking on getting some 18's, i hope thr big enough for the A8 rotors?

 

18's will most likely clear and i think any tt will work but not 100% sure

 

i guess the safest bet would be using an '98 5sp quattro TT?
Because i have a '98 A4 1.8T 5spd Quattro.

 

Check out some of the brake kits at ECStuning.com.

they have some complete setups that look pretty nice.