Thursday, August 2, 2012

Rear disc backing plates

The rear suspension of a Classic Revival Cobra chassis uses VE Commodore suspension, except for the upper control arm which is custom made. The suspension knuckle, arms and brakes are all standard (I am using aftermarket toe-links, but more on that in a future post). In my case I will be installing brakes significantly larger than stock, partly because I will do some track days and partly because I like big brakes :)

The big brakes however mean that the large rear discs will foul on the OE disc backing plates. While the backing plates on most front brake systems simply serve as stone-guards, on many rear braking systems (VE included) the backing plates also serve to hold the handbrake assembly together so the plates cannot be simply discarded. I would have liked to discard the immensely complicated (you will see in a future post) VE handbrake assembly altgoether and use a seperate small hydraulic handbrake-caliper as you see on many race cars, because it is clean, simple, and saves weight, but the approving engineer frowned on the idea of a non-OE handbrake, so the VE system will remain.

To clear the large discs I am planning on using, the backing plates need to be trimmed down. This is a simple 5 minute job with an angle grinder and cutting wheel, and then cleaned up on the bench grinder.

The original plate, purchased new from Holden.
This is the right-hand side part number GM-92195997. The left-hand is GM-92195996.

Excess removed, easy done by clamping the plate to the table and using a cutting wheel

Cleaned up on the bench grinder
The mounting holes etc you can see are for the handbrake mechanism

There was of course the option of using a HSV backing plate, as VE HSV uses a much larger disc than Holden VE's, however I will be using a different caliper to the HSV such that even the HSV plate would have required modification.

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