Again, I’ve been doing more research into this discussion.
The design calcs I’ve found appear to focus on brake pad and disc surface area rather the diameter of the disc (or rotor). The diameter does figure in the calcs but only as a means to finding the surface area.
I’ve also found this article;
Testing Brakes with StopTech
In the first instance I think it needs to be recognised that it appears to have been written by a purveyor of said big brake kits and the opinions expressed are likely to be biased as a consequence.
What’s written about greater rearward bias improving stopping distance until it becomes too much and the car becomes unstable under braking appears to be accepted by the industry as a whole and it’s also a key consideration in the brake design calcs I’ve have found and seems to have resulted in EBD being developed. Obviously, the Nissan is rwd and will benefit more from a rearward bias than an fwd chassis but I believe the principal is still sound.
In giving the stopping distances a cursory glance, one conclusion is inevitable, bigger discs = shorter stopping distances. But, under closer scrutiny it’s not quite so clear.
The “performance model” uses sliding callipers and IMO can be discounted immediately for the purposes of this discussion.
I would presume that the “track model” with the OE brembo 4 pots was also fitted with OE pads. I think it can be taken as read, that the upgrade kits where also equipped with upgraded pads with a higher coefficient of friction.
With this in mind it’s worth looking at the figures again;
324mm OE brembos
Best 60mph – 0 114.32 feet
Best 80mph – 0 204.89 feet
Best 100mph – 0 325.35 feet (the larger 332’s achieved a best of 325.63)
Taking the 335mm option as a best case argument (car was also fitted with toyo proxes)
Best 60mph – 0 112.52 feet
Best 80mph – 0 204.42 feet (the smaller 332’s achieved 203.92ft)
Best 100mph – 0 323.51 feet
On the basis of this data I would conclude that there is no discernible difference between the brakes. A 2 foot difference could easily be dismissed as being down to track or tyre temperature, brake fluid temp, or a driver variable and can’t be described as an improvement, particularly given the variations the 332’s showed.
There is a greater, yet still insignificant, difference between the average stopping distances but after 20 hard stops, this difference could be attributable to brake fade and is evidenced by the brake temperatures.
This brings me back to my original points of thermal capacity and tyre grip being the limiting factors. The only significant difference the data clearly shows is the increased thermal capacity of the bigger brakes, but even this is flawed as the differing piston sizes appear to have moved the brake bias rearward and there is a corresponding increase in rear brake temperatures.
The calcs I found also described a direct relationship between clamping force of the brakes, pad surface area and piston sizes. I’ve not investigated anything beyond this as I don’t know, offhand, what the relative piston sizes of the 305’s and 330’s are.