WRX brakes

[DangerViking]

I had an idea this weekend that may be completely retardulous or could be absolutely brilliant, depending on how it works out. Here's my question:

Since the bolt pattern on the WRX is the same as the AllTrac, provided I got wheels big enough to accept the larger rotors and all, what would be the problems involved in swapping over the rotors and calipers from a WRX?

As I see it the issues I'd need to deal with are these:
-Different brake lines (possibly?), but Marion was already investigating custom-making SS lines for the Trac anyway, so that's not a huge problem
-Mounting the caliper. This is probably going to be thr trickiest one, unless somehow it just works and only needs longer bolts, spacers, etc. Anyone have measurements for the bolt holes on a WRX caliper? Pictures would be cool too (off the car, of course)
-Offset. Not sure how much of a variable this is, though I seem to remember the WRX's offset was slightly higher than the AT's, how much of a problem would this cause?

Basically I just want to know if I'm completely retarded, or if this is remotely possible (at less than the cost of a big brake kit). Anyone ever done/looked into anything like this?

[moxie]

People regularly perform swaps like this.

It seems to me the braking systems on most cars are fundmentally similar, so it is def. possible.

The really big snags are disc offset and caliper location like you mentioned.


We would have to see where the rotors end up being, and if it is possible fab a bracket to put the caliper in the right location and still fit wheels and have room for suspension.

Erin, can we borrow an old caliper and rotor from you?
They are at Dynocomp right?

[Max Power]

You also have to worry about a bias problem. Big brake kits are designed to limit this problem (at least the good ones are). You could always go the adjustable proportioning valve route from Wilwood though.

[DangerViking]

Bias problem? what do you mean?

[Max Power]

Bias is the amount of hydraulic pressure that goes to each side of the car. There's a proportioning valve the splits the amount of force front to rear. This is determined in the design of the car and depends on things like weight distribution, weight transfer and I would assume tire traction. So, using the stock All-Trac hydraulic system, you might find yourself locking up one side of the car much earlier than the other (all cars tend to lock up something earlier, but you might find yourself locking one side up MUCH earlier).

[DangerViking]

good to know :) From what I've seen on the writeups for the big brake system, it uses the stock prop. valve, but I'll see if I can find any more info on it. Thanks!

[moxie]

That's a good point :)

Yay more stuff to worry about.


This is actually one reason I am leery of a lot of kits. I wonder if all the companies are doing all of the research to stop these kinds of problems.

I remember reading an article where some shoddy Civic BBK increased stopping distances by 10ft.

[wgnths]

i had to use the wilwood proportioning valve on my nova when i upgraded the brakes....took some dialing in to get them working right. and yes, my stock brakes should all be at dynocomp.

[Max Power]

I know Stoptech is pretty good about doing actual testing and piston resizing to make sure and avoid those problems. That's why Stoptech is cool... that and Marion can get them :)