Brake boosters ….Single diaphragm vs.Dual diaphragm

[Panoz78]

Hi Everyone
long time lurker first time posting .
After being on this forum for some time I feel that I am confident on most brake issues/ problems.
Here in Australia we have a Gm Holden which is very similar to a Nova
They come with disc front / drum rear ,single diaphragm 11-12 inch booster
The sports models (GTS) and luxury model (Statesman) come with disc brakes front / rear with a smaller 10 inch double diaphragm booster

Can anybody give a reason why the disc brake rear uses the double diaphragm please ?

[79 Camaro]

Send a note to Tobin at KORE3.com and he can confirm but I believe the front and rear discs like more line pressure. If I recall my high school auto shop days rear drums are "self energizing" so they don't need so much line pressure.

[stab6902]

Yep, the 10" dual diaphragm booster has more surface area so it can provide more assist before it reaches runout (the point at which it stops multiplying the force of your foot).

Pedal feel also tends to improve as boosters get newer/more advanced/more expensive to produce. I'm guessing GM went to the dual 10" booster on the disc/disc cars for a combination of reasons - the rear discs could probably use the extra line pressure, the pedal feel of the booster is probably a little better, and they probably had more budget to work with on the more premium trims.

[Panoz78]

Thank you 79Camaro and Ryan for your replies and insights .

What you both have said makes sense now I know exactly what the difference is .
Here in Australia we are very limited to the modifications that we can do .
Our 70’s muscle cars here have all the parts and a lot of the time it’s better and easier to use factory parts..

I also emailed Tobin @Kore3 and he was a great help aswell ,giving me the 5 minutes of his was a great insight.

Thank you .