One for the brains trust

Includes handbrake, cylinders, shoes, discs, rims and rubber.

Moderators: reidy, Blacky

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Jason
Posts: 123
Joined: Wed Apr 16, 2008 12:30 am
State: WA
Location: Margaret River

One for the brains trust

Post by Jason »

Hi All,

My FC runs a grey 132, with 1&1/16 inch brake slaves on the rear. My Ek & FB each run a grey 138 with 1 inch rear brake slaves. All have 1&3/16 on the front.

Wouldn't the bigger motor run bigger brake cylinders not smaller? Just one of those quirky moments where I'm ordering parts, drinking beer and thinking that there must be a logic to what I don't understand.

Cheers
Jason
Cheers

Jason

______________
Grey and proud!
ardiesse
Posts: 1074
Joined: Thu Jan 19, 2017 9:57 am
State: NSW
Location: Sydney

Re: One for the brains trust

Post by ardiesse »

Jason,

The standard FX-FC brakes are quite prone to rear wheel lockup (that's if you can stomp down hard enough on the brake pedal to cause it). I believe the prototype testing before the release of the FX was done with the equivalent of a five-passenger load in the car, and so the suspension and brakes were set up for this condition. Hence the advice to carry a bag of cement in the boot of your humpy. With just the driver in the car and an empty tank, the cars were quite tail-happy and the brakes were proportioned too much to the rear.

GM-H never did anything in a hurry. Eleven years later, when the FBs came out, they had 1" rear wheel cylinders, making them only slightly less prone to rear-wheel lockup under hard braking. But the FBs have 1-3/4" wide brakes, so you get about two decent stops from speed before the brakes fade away, instead of not-quite one with an FC.

A disc-braked HD must have been a wonder at the time . . .

Rob
Jason
Posts: 123
Joined: Wed Apr 16, 2008 12:30 am
State: WA
Location: Margaret River

Re: One for the brains trust

Post by Jason »

Hi Rob,

Thanks so much for that, makes perfect sense.

I always thought the cement was for the body roll but the braking theory makes more sense, my first car was a FJ holden ute. I don't know how many times old blokes would tell me to put a bag of cement in the back.
Cheers

Jason

______________
Grey and proud!
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