Big Brake Kit using Acura RL calipers

Finally got around to installing a big brake kit on my 93. Used 07 or later OEM Acura twin piston alloy calipers fitted to a custom set of rotors that "Titanium Dave" lined up for me. Dave also did a beautiful job of machining alluminum caliper brackets to accomodate the big rotors. Wheels are 5-Zigen 17's that barely clear the calipers. Total package saves about 3 Lbs. per side. Initial impression of the performance is good, the brakes are clearly more powerfull and it's easier to get into the ABS but they don't seem touchy. RL calipers are pretty cheap on EBAY. I used a red epoxy paint on the calipers and buffed off the Acura letters. I dunno.....something different I guess.
BTW, this is not the first application of this set-up, Morgan from Portland Acura did the same mod on his red 91.

Easier to get into ABS = more front bias than stock, which over powers the front tires -engaging ABS sooner than stock? (possibly)...

Looks a hell of a lot better though!

stuntman said:

Easier to get into ABS = more front bias than stock, which over powers the front tires -engaging ABS sooner than stock? (possibly)...

Looks a hell of a lot better though!

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I think you are right on the bias. Any idea on tweaking the front/rear bias?

I remember when this one guy mentioned doing it atleast a year ago, he got his ass chewed out by just about everyone here. Congrats on the success.

Hey Dave, how much for the rotors?

nsxpilot said:

I think you are right on the bias. Any idea on tweaking the front/rear bias?

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You can install a proportioning valve or use a less agressive pad up front/more agressive at the rear. The latter feels less mechanically sound though and I'm not sure I'd be comfortable with it.

What are the piston stats on the RL caliper?

Looks great! Any more pics of the entire car/wheels?

What pads do you run front and rear? Rear brakes stock?

Despite the commonly-held taboo that running different brake pads front-rear is bad, Their is nothing wrong with running different pads front and rear. Many race teams do this to balance the initial bite, coefficient of friction, bias, and characteristics of their car. Even despite having proportioning valves.



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KooLaid said:

I remember when this one guy mentioned doing it atleast a year ago, he got his ass chewed out by just about everyone here. Congrats on the success.

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Of course he got his ass chewed out, it's a detrimental and possibly dangerous modification. All that you're doing is replacing the front NSX caliper which is designed to apply a specific amount of torque to the rotor based on the weight of the car with a caliper that is designed for a completely different car. The dangerous part is that the RL is a front engine car so the brakes are designed using calculations based on the car's weight bias. The NSX doesn't have anywhere near the same weight on the front wheels as an RL. Fitting RL calipers has now dramatically shifted the brake bias to the front wheels.

Contrary to popular belief, a big brake system is designed with greater heat dissipation in mind to reduce or eliminate the risk of fade during race conditions. Properly engineered BBKs are designed to apply essentially the same torque to the rotors as the factory brake system. A BBK for a street car is merely a cosmetic modification as you'll never generate enough heat under normal driving conditions to actually warrant one.

Get those RL calipers off the car before you kill yourself.

I strongly suggest everyone read the StopTech White Papers before attempting to modify their braking systems.

Yes and no...

Playing devil's advocate:

A 4 piston caliper has 2X the amount of pistons (sizes unknown) of the stock NSX front calipers. 2X the pistons require 2X the volume of brake fluid, so while the rear pads clamp down on the rotor like they are designed, the front calipers don't have as much initial 'bite' due to the less pressure acted on the pads due to having 2X the pistons and volume needed to create the same pressure on the rotor. Thus a front BBK will move the bias slightly rearward

It's not ideal and you do most likely have too much front bias. You are aware of your braking abilities/limitations of yoru current setup if you are engaging ABS, but you're car is not going to blow up on you. Their are things that you can do that can better balance the car out.

**** This is not really any different from tracking your car with a Brembo, Stoptech, or any other manufacturer's "BBK" when leaving your stock rear brake system alone.


Dont' freak out, just find a good resource to work with to hammer out the details/develop (finding a better pad combination and or proportioning valve) to increase the performance and balance of yoru car back to or better than stock.

stuntman said:

**** This is not really any different from tracking your car with a Brembo, Stoptech, or any other manufacturer's "BBK" when leaving your stock rear brake system alone.

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That is incorrect. Re-read my post, next, go read the StopTech White Papers then report back.

A StopTech front caliper sold for the NSX is going to apply essentially the same torque on the rotor as the OEM caliper which is considerably less than the RL caliper. I'm assuming the Brembo is similarly designed but I have no clue as there is no way I'm putting anything mechanical that originates in Italy on my car.

stuntman said:

Their are things that you can do that can better balance the car out.

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There are 2 things he can do.
1) Re-install the NSX calipers.
2) Install an aftermarket caliper specifically designed the the NSX.

Your're right! Or his car will blow up



In all seriousness. If he's engaging ABS, then he is aware of the limitations/braking ability of his car. The activation of the ABS is showing the limitations of the front tire's grip and excessive bias towards the front. You can drive and or track a car like that without any issues. Depending on his pad choice at the moment, the deceleration rate of his car is either close to stock or could be a bit off, but i doub't it will double his braking distance.


Their is plenty of things he can do if you have the right though process and trial and error.

Thanks for the input.....seat of the pants assessment is always difficult but "feel wise", the stopping power seems at least as good as stock. Not grabby, very strong and progressive. ABS clearly kicks in earlier if you hammer the pedal, otherwise they feel pretty much stock in normal driving conditions. Won't give up on the mod, will look into options for tweaking the bias tho.

Hugh said:

That is incorrect. Re-read my post, next, go read the StopTech White Papers then report back.

A StopTech front caliper sold for the NSX is going to apply essentially the same torque on the rotor as the OEM caliper which is considerably less than the RL caliper. I'm assuming the Brembo is similarly designed but I have no clue as there is no way I'm putting anything mechanical that originates in Italy on my car.



There are 2 things he can do.
1) Re-install the NSX calipers.
2) Install an aftermarket caliper specifically designed the the NSX.

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I don't think there's anything aftermarket DESIGNED specifically for the NSXs (they are fabricated for the NSXs). They're all made in the same process by trial and error.
The only brakes system specifically "designed" for the NSX is the stock brakes system.

Hugh said:

Get those RL calipers off the car before you kill yourself.

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Please note Hugh's avatar, this is what happens when you drive with these calipers!

Thanks for the graphic visualization!!!

KooLaid said:

I remember when this one guy mentioned doing it atleast a year ago, he got his ass chewed out by just about everyone here. Congrats on the success.

Hey Dave, how much for the rotors?

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Hugh makes a good point, this set is designed as a cosmetic upgrade, nsxpilot wanted a set of calipers that would fill up his wheels and look more aggressive. These will have higher ability to dissipate heat, from larger rotors and the mass of the aluminum calipers, but these alone will not stop the car quicker. They change the brake bias which makes the car transfer more weight to the front tires under hard braking, giving a sensation of car stopping quicker.


I have a full set of brackets and hats on the shelf, rotors on order.
Cost:
Set brackets, hats, fasteners, rotors, $1300
Hats, fasteners, rotors, $750
2 used calipers, $200(I have one set)

nsxpilot said:

I think you are right on the bias. Any idea on tweaking the front/rear bias?

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I agree with Stuntman, let's try a set of Hawk HP Plus on the rear. They have good initial bite and should help with the balance. I have a set in stock, will send you an e-mail.

An other option would be to put a proportioning valve in the front lines to reduce pressure in the front calipers.

The best option is still the bigger caliper for the rear end, that set of Brembo Lotus calipers I have sitting on the shelf with larger rotors...

Ponyboy said:

You can install a proportioning valve or use a less agressive pad up front/more agressive at the rear. The latter feels less mechanically sound though and I'm not sure I'd be comfortable with it.

What are the piston stats on the RL caliper?

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RL calipers have (4) 39 mm pistons, wish these were differential sized piston, would give flatter pad wear and reduce shudder.

titaniumdave said:

An other option would be to put a proportioning valve in the front lines to reduce pressure in the front calipers.

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This is not an option. The nsx abs is hooked up diagonally. RF and LR tied together as are LF and RR. You would need two valves not one. I have not heard of this working properly.

different pads front/rear, larger rotors and offset bracket for the rear or different calipers for the rear are your choices.

If the bias is off your breaking efficiency is reduced. Stopping distance has increased. The rear tires are doing less work.

Pads may fix most of the issue.

For what it's worth.

By simply using offset brackets, larger rotors and retaining the stock calipers on the front will effect the bias.

The swept area has increased.

Later,
Don

nsxnut said:

For what it's worth.

By simply using offset brackets, larger rotors and retaining the stock calipers on the front will effect the bias.

The swept area has increased.

Later,
Don

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Bias will change with rotor size, especially if only one end of the car is changed.

What has changed is the effective lever, larger diameter rotor with the same caliper means the clamping force is applied at a greater distance from the rotational axis, netting increased potential braking torque.

Swept area for the rotor has increased which increases heat dissipation capacity, this does not effect the brake bias because the pad area has not changed.

titaniumdave, do the calipers from the TL-s work as well , I have a set of almost new ones just sitting around , if they measure the same , maybe someone can use them?

titaniumdave said:

Bias will change with rotor size, especially if only one end of the car is changed.

What has changed is the effective lever, larger diameter rotor with the same caliper means the clamping force is applied at a greater distance from the rotational axis, netting increased potential braking torque.

Swept area for the rotor has increased which increases heat dissipation capacity, this does not effect the brake bias because the pad area has not changed.

Click to expand...

SWEPT AREA
Definition: Total friction area contacted by the pads during one revolution of the rotor.

We are saying the same thing.

One of the first upgrades I did to my nsx was larger front calipers and rotors.
Also put on larger rear rotors and offset brackets. My bias was off but wasn't to bad.
On the street it appeared that this setup worked better.
On the track it was obvious this setup was not the ideal.

I have since changed out all 4 corners and have a much better system.

If I was to do it all over again I would get the Comptech Indy break setup.
I believe this is possibly the best setup for the track.

Later,
Don

I've tracked a few NSXs with stock rear brakes (with agressive pads) and an off-the-shelf Brembo "Lotus" GT caliper (40/36) but this is a universal caliper and was used with their larger 2-pc rotor available for the NSX. I would hardly say this kit was 'designed' for the NSX.

Tracking a car with R-compounds at the limit of the car, this Brembo front caliper and more aggressive rear pad was FAR better than stock in terms of braking ability, shorter stopping distances, prevention of brake fade.

I would highly recommend this application for people who drive their cars on the street and want a better looking front brake package, as well as people who track their cars.

I'm sure their are many other kits out there that would have a similar result (possibly the RL calipers as well). Point being, their are things he can do to make the brakes work, be as good if not better than stock.


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titaniumdave said:

Please note Hugh's avatar, this is what happens when you drive with these calipers!

Thanks for the graphic visualization!!!

Click to expand...

Hey now! I drive with these calipers.....

angus said:

titaniumdave, do the calipers from the TL-s work as well , I have a set of almost new ones just sitting around , if they measure the same , maybe someone can use them?

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Don't know the dimensions of TL-s, just worked with this one caliper from the Acura line. Most sets I build are with Brembo calipers.