Re: GTV6 inboard brakes - why?

[James Montebello <jamesm@domain.elided>]

With inboard brakes, all of the (quite heavy) brake hardware is sprung,
so you have much lower inertia at the wheel when dealing with suspension
forces, which substantially contributes to good roadholding over less
than perfect surfaces.  All of the Alfetta-based cars had inboard rear
brakes, from the Alfetta sedan and coupe to the Milano/75.

The chief disadvantage of inboard brakes on the Alfetta is cooling,
and, in the case of the 116, lots of brake heat being poured into the
transaxle.  The cooling can be helped some by ducting.  Not much can
be done to keep brake heat out of the transaxle short of significant
reengineering.  Not having the rotors mounted to the hub does keep
brake heat away from the wheel bearings.

The Lotus 72 F1 car had inboard brakes at the front, and chimney-like
cooling ducts to keep them cool.  This added some overall weight to the
package, since it needed half-shafts just to transmit the braking force
to the hub, but it was a net win in unsprung weight.  Unfortunately, one
of those shafts broke and caused the accident that killed Jochen Rindt.
F1 rules may now prohibit inboard brakes, I'm not sure.  Certainly no F1
car uses them today.  That may be for packaging reasons (clean airflow
around the transaxle is probably more important), it may be that with
the advent of carbon brakes, the savings in unsprung weight isn't
worthwhile anymore.

james montebello


On Thu, 19 Sep 2002, Zak McGregor wrote:

> Hi all
>
> I was just wondering about the GTV6 and why inborad discs were chosen -
> anyone have any insight into that? I would have thought from a technical
> point of view that the closer the discs are to the wheels, the more
> efficient they would be.
>
> Thanks
>
> Ciao
>
> Zak
>
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