Inboard disk brakes?

[Kardax]

I think the reason they're not more popular is due to cost, complexity, and space concerns.

Cost - Any non-driving wheels will need another CV joint and bearing to hold the brake. Cooling ducts will probably be necessary, impacting the design of the whole vehicle.
Complexity - The above parts aren't free.
Space concerns - Two of the brakes are going to take space away from the engine compartment, which is usually cramped already.

The result does lower unsprung weight (improving grip), but also raises overall weight (reducing acceleration) and may hurt aerodynamics for the cooling ducts (reducing acceleration, top speed, and efficiency).

Everyone loves low unsprung weight but one has to ask if all the consequences of this particular technique are worth it.

-Ryan / Kardax

[TEG]

Yeah - I had mentioned the joints & half shafts and space issues in other postings before.

So, yes, for non-driven wheels it adds extra weight, cost and complexity.

*But* for driven wheels where you already need a half-shaft and something inboard (e.g.: motor or differential) then why not put the discs inboard as well?

The Alfetta GT where I first encountered inboard brakes had inboard discs on the driven rear wheels only. The front wheels used in-wheel discs so there were no half shafts in front.

[AGR]

Ceramic discs is the HOT set up, similar to carbon fibre. There isn't a single F1 car that uses inboard brakes, and if there is a car that is very sensative to weight, its an F1 car. They all have outboard mounted ceramic discs.