SmokeyGatto

This is a great solution. I manage to cook my rear wheel bearings once every two years. Not a hard job but it is a pita.

I hate the thought of getting a bbk and shifting bias to the front. I was going to order the rx7's from Japan, but once i found out it shift more bias to the fronts I ditched that idea.. What the oem s2000 piston size? Iirc it was a 43mm. If so the larger pad will give the extra torque

spdracerut

FYI, the StopTech front BBK maintains near stock bias. They do it by sizing the pistons properly.

Anyway, the Sakebomb rear BBK solution looks really good.

Sakebomb, do you guys have a calculation on how much your kit will shift the brake bias? Or rather, maybe how much it changes the brake torque at the rear vs. the stock system for the same pedal displacement.

//steve\\

As far as replacement rotor rings go if you had a set that was toast you could likely easily have them sent out and replicated at least to the same size. Quality/vaned or not might be another question but it could be done. I like the kit a lot but it's pricey.

SakeBomb Garage

We did the calculations. It does give the rear more bias, which in the S2000 should increase overall braking force. Manufacturers err on the side of safety (more front bias) in order to reduce the number of conditions that could cause rear brake locking before the front. Locking rears before fronts can cause lots of problems for inexperienced drivers, however ABS and EBD in 2006+ cars pretty much solves this problem. For performance use, increasing rear brake torque is usually highly beneficial, allowing the car to make better use of the rear half of the brake system.

Numbers-wise: we measured the S2000 to be 40mm and the RX-8 piston to be 43mm, so just based on piston size you get about 15% increased clamping force as compared to the stock S2000 rear. Then you also get a 10% torque increase from the increased rotor diameter. Your front brake setup/pads will determine how much weight you can transfer and your suspension/spring rates will determine how much the car will dive and rear will lift, which might affect how much contact you have in the rear tires.

In any case, rear has about 20-25% more effective "braking force." Depending on your setup, tune with pads accordingly.

It is worth noting, this kit wasn't really designed for stock front brakes, but it will work fine with lower coefficient of friction pads. The kit was meant to be paired with our 325x32mm front AP brake kit or other similar BBK setups.

SmokeyGatto

<3 as soon as I get some spare cash and time that oil cooler and f+r bbk will be on order.

DavidNJ

Question: If BBK kits are designed to maintain OEM front/rear brake force ratios, wouldn't a lowered car require more rear bias because of less weight transfer? If so, what adjustments are typically made?

Most calipers have a limited variety of pads, and the pads typically operate in specific heat ranges. Using pad coefficient's of friction is at best a crude adjustment of brake bias.

Many racing cars and all of the racing cars I'm familiar with, either have a balance bar which adjusts the ratio of movement between front and rear master cylinders or an adjustable proportioning valve. A little misnamed, the proportioning valve reduces rear brake pressure past some cut-over pressure. I've never used one.

Some cars have electronic brake force distribution which uses the ABS sensors to distribute brake pressure. Honda announced their system in 1997 and I think the S2000 has it. If so, does it compensate for the different mechanical force distribution here or possibly with some front BBK kits or is that beyond its adjustment range?

SakeBomb Garage

You are right, certain things do change the amount of rear bias needed. Most OEM setups underbrake with the rear for safety. The RX-8 rear caliper has a pretty wide variety of pads available. For example, Carbotechs range from .47 in their AX6 to .65 in their XP12 pad (38% variation) and there are much more pads than this to choose from.

And yes you are correct. Race cars all have cockpit mounted proportioning valve or balance bars since they need to adjust brake proportioning based on that day's conditions/tire temps/weather/etc.

There are many factors in play here of course but many BBKs, aside from the Stoptech which is designed to stay somewhat close to stock bias, shift bias forward potentially decreasing overall available stopping ability (though they all increase heat capacity or heat dissipation capabilities). In 2000-2005 the S2k has ABS but not EBD. If bias is shifted too far forward in an ABS only system, the fronts will lock early and ABS will start pulsing. Thus the car will be missing the braking force available from the rear and will take longer to stop. Go too far in the other direction and you will get the tail trying to come around on you under hard braking. In 2006+ S2k there is ABS and EBD so if I'm not mistaken, this problem is mostly mitigated. Someone who knows EBD better might want to chime in but I'd assume it's still somewhat better to have it close to right statically than to just say ok computer figure it out.

Long story short, more rear braking force is always welcome. If you had a proportioning valve, for a given condition, you'd basically want to increase rear brake bias until the lock before the fronts, and then dial back slightly. Without a proportioning system, all you can do is get close for whichever condition you expect the most.

DavidNJ

Three questions:

1) Do the he AP front calipers just take the ubiquitous Superlite pads?

2) The rears are non-floating rotors?

3) Are the rear rotors standard AP parts (they seem to have the AP hooked slot)?

SakeBomb Garage

1) Do the he AP front calipers just take the ubiquitous Superlite pads?

Definitely. 20mm of pad goodness

2) The rears are non-floating rotors?

Yes they are non floating. We found it wasn't necessary with the rears since there are no longer heat management issues.

3) Are the rear rotors standard AP parts (they seem to have the AP hooked slot)?

The fronts are AP Racing rings. The rear is a custom rotor due to the required size... no one makes this disc size off the shelf. The slots are our own design, but compliment the AP J-Hook quite nicely and have a similar high-initial bite design =)

SakeBomb Garage

Brackets are in =)