OEM BBK: Acura RL 4 piston brake calipers

factionr said:

@swanarg Looks Awesome! Were you able to fit your Avid 1 rims without any spacers?

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bendrich said:

I have yet to find anyone here on these forums installing Acura RL 4 piston calipers in the front. So, I figured I would make a post about my thought process in going with this option.

I tend to get wordy once I sit in front of a keyboard so here is the TL;DR. 4 piston Acura RL calipers fit on my FK7 Sport with the fastbrakes adapter kit and 12.8" 350Z Brembo rotors. I have confirmed fitment behind the two sets of wheels I have for the car; Evo8 Enkeis (17x8 +38) and Spoon CR93 (17x8.5 +45). They seem to work well so far. However, I have only subjected them to the pad bed in process and some grandpa driving around town. It cost me $375 in hardware.

Please excuse my squat form. Boris would be disappointed.

Now to get wordy.

I began researching brake upgrades for this car after running the full straightaway for the first time at Miller Motorsports Park. It's well known that the original brakes on these Civics really aren't up to the task of multiple laps on a road course, even with race pads and high temp fluid. After one season of HPDE my original calipers were going to need rebuilding or replacing. They were very discolored and the piston boot was reduced to atoms. While a proper performance BBK would almost surely offer the best braking performance, they are very spendy and I do not have any intentions of taking this car back to the track as my CRX project is nearing completion. So I was looking for something to split the difference between refreshing the stock setup and ballin' out on a BBK.

Naturally, the first prospect I considered were FK2/8 Brembos. However, they are still quite expensive and I couldn't find information about how I would actually make them work in regards to mounting the caliper and which rotor to use (re-drill CTR rotors?) I also wanted to retain the use of my 17 inch wheels. I believe Acura TL-S Brembos with appropriate rotors would work - like on Civic 8s and 9s etc - and fit under 17 inch wheels. However, these require some permanent modification to the knuckle and proved difficult to find in the local pick-n-pull yards due to only being on specific TL models. I have read some posts about the Hyundai Genesis Brembos with appropriate rotors fitting, but also requiring 18 inch wheels. Additionally, they are designed to be rear mounted but it doesn't seem like anyone cares about that. The leading and trailing pistons are the same diameter anyway. DC5R Brembos are also designed to be rear mounted AND have staggered piston diameters, which makes them a big no-no for forcing them to work backwards.

Then I came across the RL caliper. These are designed to be front mounted, although they also have equal sized leading and trailing pistons anyway. They are on ALL 2005-12 Acura RL models which makes them very easy to find at the junkyard. The brake master cylinder piston diameter on the FK7 is the same size as the RL, which is especially convenient considering the RL BMC won't bolt up to the FK7 booster. Fastbrakes.com makes an adapter kit, which comes with shiny new bolts and crush washers by the way, to make use of these calipers with 350Z Brembo front rotors. I did not have to trim or bend my dust cover making this an easily reversible modification. The best part is that I'll get to retain the use of my 17 inch wheels.

RL Calipers are HUGE and ridiculously light. They weigh 8 lbs per corner fully loaded. The brackets are super light but the bolts are pretty beefy so let's call it 9.5 lbs mounted to be generous. The brake rotor hub rings are virtually weightless. The 12.8 inch rotor is chunky and comes in at 20.5 lbs. If you're feeling ambitious, you could put together this setup with some fancy two-piece rotors and save some weight. Thanks to 27Won for posting SI brake part weights on his BBK page. This would save 4-5 lbs off the complete front setup, a little less I'd imagine compared to the FK7. The rotating weight is considerably further from the hub but this is the case with all BBKs.

I was able to pick up the pair of calipers from the local junkyard for $40. The adapter kit is $170 shipped. If you're crafty and have the tools, you could probably make this yourself. I ordered new pads, caliper hardware, and rotors from RockAuto for $165 shipped. $375 all in which saves ~$200 compared to the SlickFab Genesis Kit. In that price, I'm not including brake fluid or the SpeedBleeders I installed. I will also admit that the RL calipers aren't performance oriented like the Brembos.

There are some considerations when it comes to frankensteining your own BBK together. An off the shelf kit, such as 27Won, is designed specifically for the car and made to work with the original BMC and ABS module. The factory caliper piston has a surface area of 2561 mm^2. The RL calipers have a combined piston surface area of 5809 mm^2. This is over 100% more piston surface area. Even the 6 piston Wilwood kit doesn't have that much surface area. There are a couple schools of thought on how this goes. One is that you're increasing front bias with all the extra beef up front. The other is that you're increasing rear bias because there will be so much extra pedal travel to fill up the big calipers with fluid, the rear calipers will be very pressurized. My decision was pretty much just to cross my fingers and hope the ABS module would figure it all out for me.

My only hard braking so far has been to bed in the brake pads. I didn't notice anything funny regarding brake bias or pedal travel. I still haven't noticed ANY difference in pedal feel for normal city driving, which I would consider a good thing. The brake line does contact the rotor at full lock. But if you're driving around at full steering lock all the time, there is likely an issue somewhere between the steering wheel and the driver's seat.

I considered painting them, but ended up sticking with the raw metal. I told myself I would clean up the calipers, but I got too excited after test fitting them with the wheels and ended up completing the install. I think it looks pretty pretty cool.

Happy Civic driving everyone!

The car is still on stands in these pics so ignore the monster truck height. And the pic of the stock brakes for reference was taken on the opposite side of the car.

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Jakupdoesnt said:

Do you have the part number for the 350z rotors from Rock auto? Or a link for them?

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bendrich said:

JBR1107EVC

That’s for the coated ones I got for going through salty winters. But it should lead you in the right direction. Just make sure it’s for the Z with the factory brembos

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CWIIIFK7 said:

Great info in this thread. I actually picked up a set of 2008 RL calipers this morning. Cleaned them up, belt sanded the ACURA logos off, and prepped them for paint. My rotors and pads are on order along with the FB kit. Can't wait to put it all together. For those who have completed this project in this thread, how are things going with the upgrade? Any odd issues to speak of? Thanks in advance!

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swanarg said:

No issues what so ever. Great upgrade can’t complain. I did have an issue with loud ass EBC red stuff. Couldn’t get em to not scream on light breaking even after 1500 miles. Swapped em for r1 concepts oem+ which are quiet. Occasionally they briefly squeal on light braking but it’s infrequent and disappears with more pedal pressure. One touch of the pedal it’s there then gone. Maybe weeks at a time it won’t happen at all. Not an issue IMO

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CWIIIFK7 said:

Also can confirm the weight of these things loaded. Just under 9.5 lbs. I'm interested to see how much the drilled/slotted rotors weigh along with the FB kit components for a total weight minus the OEM rubber brake line. Unsure how much that piece weighs.

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Unity Performance said:

Nice and light! I've measured the Gen Coupe calipers as well as factory Si calipers as well:

Factory calipers -1lbs than displayed as stock pads were in at the time

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