11 or 12" rear rotors?
 

Hi,
Doing an RS FastTrack chassis with an LSA/Magnum combo on a 66 Chevelle. I'm guessing weight will around the 3500 mark

As for brake bias would 14" front with 12" rotors be too much/little for this combo? My question is about the rears. 11" or 12" or do you suggest bigger?

12" will fill the open wheel area better.

The Baer 13" front and 12" rear brakes on my LSA '66 Chevelle are a good match. The prop valve on my Baer Remaster m/c is set to mid range to balance front/rear braklng. IMHO the 11" rear would be too small unless you're running small diameter wheels and can't fit 12" rotors.

12” rear rotors all the way.
For the proper appearance
Just use smaller calipers and a proportioning valve.
My two cents

I think the proportioning valve only controls when the rear wheels lock relative to the fronts, not actual braking bias.

Wut?

How could you control wheel lock without controlling bias with a passive mechanical system?


Here is what it looks like on a graph. https://wilhelmraceworks.com/blog/br...rtioning-valve

https://wilhelmraceworks.com/images/...wilwood_pv.jpg

Well, as explained to me way back when by my auto shop teacher, don't shoot me if I'm wrong,...
the proportioning valve is there to slow the locking of the rear wheels, to make sure the front locks first. After the initial slowing of the locking [ by means of the spring loaded internal portion ] the valve does not perform any more function.
This is incorrect?

You’re accurately describing the function of a different part. It’s a common terminology issue. On cars with front discs and rear drums a “metering” or “hold off” valve was used to delay the engagement of the front brakes until the rear drums could build pressure. It was shaped like a barrel on old GM stuff. You’ll not need this when going to 4 wheel discs. But you will still need a proportioning valve.