Snoop Dougy Doug said:
330X28mm brembo discs, Brembo 4pots no more than 1k installed (even on the high side).
That's a pretty sweet deal. That being said, Im ALL for new comers and innovation in brick tuning. Personally, I was looking into 6pots just because I can
Nick, the car stops unbelieveably hard. Theres NO reason to upgrade the rears.
There is EVERY reason to upgrade the rear, rather than me spending ages typing at my error prone snails pace I'll copy / paste an article i wrote for the Supra MKIV twin turbo forum I am active on, and on which cars I spend a lot of time doing serious mods to.
Brake upgrades can set out to try to achieve several objectives.
The commonest are to increase resistance to fade and or increase
braking effort for a given pedal effort. IE, the pads are
pushed against the discs harder for a given pedal effort than
before the upgrade, or the brakes will stop the car from 100 MPH,
hard, for more times before fade sets in, than previously. The feel
from the pedal, that almost intangible quality, can also be addressed
and sometimes improved upon by brake size, or pad material changes, or
brake flexi hose upgrades to something less squashy than rubber.
It's easy to get carried away by the thought of brake upgrades.
The limitation in most cars as to how short a distance they can
stop in is tyre friction. Leaving aside pedal feedback, and fade,
it is almost certain that a Supra on stock Jap spec brakes will
stop in just as short a distance as one with an AP six pot kit on
it, a Brembo kit, Pauls KAD kit, or whatever. It may not feel to
the driver that it does, but usually such is the case if you just
nail the pedal as hard as you can. The fancy kits may *FEEL* to
stop the car faster, due to less pedal effort, and a better bite,
but in reality, if you hit the pedal as hard as you can with stock
Jap spec brakes, UK spec brakes, AP kit, KAD, whatever, the car
will stop in the same distance. Repeat this test 10 times and stock
Jap brakes may be on fire and long since faded, or the fluid boiled,
UK ones may be very hot and bothered, but the upgraded ones will
probably still be working within pad, disc and brake fluid temp
limits. Add in the intangible "feel" factor, and a desire to brake
as hard as possible, using as little skill as possible, but WITHOUT
relying on the ABS to take over, and for sure a well set up brake
upgrade may well allow more finesse.
Herein though lies the rub.
Upgrade only the fronts and the brake balance of the stock car may
well be compromised. Let's take stock brakes. You press smoothly on
the brake pedal with (say) 50 pounds force. The car stops fine. 70
pounds, the fronts are just beginning to lock (car makers ALWAYS aim
for the fronts to lock first, as rear wheel lock makes the car very
unstable and liable to swap ends). The rears are doing as much work
as the brake engineers deemed safe to prevent premature rear lock up.
The ABS cuts in, and maximum retardation has been reached. Now, take
a car with big front discs and calipers. Only 40 pounds pressure now
gives a smooth, lock free and powerful retardation. 50 pounds and the
new, more powerful, (for the same pedal pressure), fronts are locking.
The ABS cuts in. BUT, and this is the crux, those original rear
calipers and discs are still well below the caliper pressure where
they are able to achieve maximum retardation without fear of the
rears locking.
In other words the FRONT brakes are doing TOO MUCH work, albeit without
breaking into a sweat, and the rears are, to exaggerate a bit,
just along for the ride. The BEST scenario is to upgrade front AND
rear brakes, carefully ensuring the original balance of effort at any
given brake pedal pressure remains as designed, but that the more efficient
front AND rear brakes stay cooler for more hard stops, and that old
intangible "feel" from the brake pedal is improved, at lower rates of
driver effort on the pedal. The latter may or may not be good or
desirable, and can be engineered out by changing BOTH front and rear
caliper piston sizes, or pad areas. In a race car the balance would
be adjustable via 2 brake master cylinders, with a driver selectable
change in mechanical leverage effort between front and rear brake circuits,
one cylinder operating the front brake calipers, the other the rear. This
can also be achieved on road cars, but to do so is usually complex and
expensive, especially if ABS and brake circuit failure safeguards are to be
maintained. It is far easier to calculate the caliper and disc sizes, along with
pad area and compound to achieve this, as near as available off the
shelf equipment will allow.
Caveat. I said before makers engineer more effort on the front brakes to
encourage straight line stopping if the tyres are locked up . They err on
the excessive side, as, in the wet, the rear tyres can take a lot more
braking effort than in the dry, due to less weight transfer onto the front
tyres, as they will lock before as much weight is transferred when the grip
of the road surface is reduced. So adding yet more front brake effort worsens
this existing imbalance, especially in the wet. If it were not for the
ABS the front wheels would be locking up very early. On the Supra a
relatively sophisticated ABS allows some effort to be taken off JUST
the fronts, and an artificial and very inefficient balance is returned.
On cars with lesser (1 or 2 channel) ABS, or no ABS at all, a brake
upgrade on just one end of the car can be lethal.
