Re: Inboard brakes

[Will Owen <nashwill912@domain.elided>]

CM Smith wrote:

> Indeed, unsprung weight is the reason...
>
> The E type Jag is another inboard disc brake design that works well, now
> they really did have beefy half shafts as they served as upper rear
> suspension links! Colin Chapman would've loved 'em.

Chapman very much might have, as he used a similar layout on both formula and sports-racing cars. He also used the half-shafts as
links in his so-called Chapman Strut rear suspensions. Using axle shafts as links has its good points, not least of which is that it
eliminates those often-troublesome sliding splines. You do have to build'em awfully beefy, though.

Another important attribute of inboard brakes is that they uncouple rotational braking forces from the suspension. In other words, the
rotating force from the brakes is transmitted directly into the chassis instead of being carried there by the suspension arms, which
leaves only the fore-and-aft braking loads to be resolved through the suspension. Mounting the final drive on the chassis offers the
similar advantage of resolving all of that rotation right there instead of making the suspension deal with it.

What's so cool about that? Well, when I peel off of Orange Grove to get onto the 110, there's a nasty lip of scootched-up asphalt
right at the top of the ramp, pretty much at my usual apex. If I'm pushing it a bit as I usually do, the Milano's wheels do a little
skip sideways, just enough to give me another five degrees of rotation, and then we're right back into the forward-thrust business. In
a live-axle car, even one as well-designed as the Berlina, that same hop is both more ponderous and more lively, with a fair amount of
twisting, thumping and bouncing going on back there, all at a good deal less forward speed. Both unsprung weight and rotational forces
are at work here.

Inboard front brakes? The front-engine Mercedes GP cars of the '50s had'em. I believe at least some of the Alfasuds did, too, as does
of course my Citroen...

Will Owen
Pasadena, CA
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