Girling caliper question

[John Fitzpatrick]

These aluminum Girling AR calipers, circa 1965-70, are different, front vs.rear. The one has a steel horse shoe shaped plate fastened to the lower face, as seen in the photo. Can someone tell me what its purpose was and why it wasn't used on both front and rear calipers?
Thanks,
John

 

[Jac Mac]

I wonder ( guess) whether it might be to try & minimise caliper flex at the front which presumably would have higher line pressures.

 

[Dave P]

Great answer Jack!

Calipers flex under pressure. If those are the calipers you are going to use I would recommend purchasing a translucent crack detection kit from a company like Pegasus racing supply. Make sure it is the translucent test kit. (Don't ask me why I know there are two kinds) Calipers have a cycle life and tend to get softer after going through many heat cycles. Part of my job was to build the pressure testing machine used to rebuild AP racing brake calipers here in the US.

 

[John Fitzpatrick]

Thank you both, gentlemen. Limiting flexing makes more sense than what I had been thinking about which was shielding of some sort. Still, I wonder why it wouldn't have been put of the rears as well. I thought that flexing would have the same effect as pad wear, but then, it would have increased some with temp. I'll take a close look and see if they might have been a field modification, but it looks pretty factory-ish. And correcting flex with a reinforcement would have been less costly than re-engineering the castings. Hmm... Jac, you have to be onto something with the line pressure differential, or front and rear both would have had the reinforcement, even with a 50-50 balance.

 

[Dave P]

John :

On most racing applications the front master cylinder is smaller bore diameter that the rear. This causes the rear line pressure to actually be lower than the front. In most applications the front supplies the most braking force. To much rear brake is really a bad feeling on corner entry as the front and rear want to change places. In a mid engine car there may be some differences.I have mainly dealt with front engined cars.