Racing Brake Package

[Subaru_Nation555]

Just got the newest edition of Subie Sport in the mail a couple of days ago. Noticed an add for a brake upgrade for Subies by a company called Racing Brake. Its a 4-piston caliper kit with Hawk Pads. Its lighter then the Genuine Subaru 4-pots and fits under 16" WRX wheels. Caught my interest so I visited their website. Turns out they have been testing on a 1994 Legacy Turbo. Just thought I'd post this. Anyone else heard about or used this product?

http://azpinstalls.com/racingbrake/4pot/

[vrg3]

Looks like repainted Wilwood calipers and a mounting bracket. Cool.

[Legacy777]

Looks like repainted Wilwood calipers and a mounting bracket. Cool.

ditto

Still a little pricey though IMO.

Opposing piston calipers are nice, and they do add to the overall feel of the braking system, but for a pretty much street driven car....even agressively.....you really don't need them.

I'm more then happy with my setup....granted it's pretty much 100% frankensteined....but no opposing calipers. We'll see how it holds up on the track. I'm hoping to go up to one of the track days in the next couple months.

[vrg3]

Oh, I didn't even look at the prices. Those are kind of expensive. I wonder if they would be willing to just sell the brackets by themselves. Then you could buy used Wilwood calipers relatively cheaply.

Floating calipers do have some advantages over opposing-piston calipers... They're a little easier in terms of maintenance, and they tend to do better when the rest of the braking system isn't quite perfect.

[evolutionmovement]

For the price I'd go for WRX brakes - about the same pad surface area. The rotors are the same size, so no extra heat sinking advantage. You'd need some serious rubber (for our cars) to use better brakes than a WRX set up with good pads. I can lock my 205 Kumhos if I want (and that's in the dry). WRX brakes have good feel too. ABS may be a little different, but it can't change the coefficient of friction between the tire and road. And if you're going with more serious rubber, you'd likely be running 17" wheels and might as well go for an even bigger brake upgrade for little more.

Steve

[BAC5.2]

Vikash - Wilwood calipers don't have dust seals, until the Dynapro calipers, which cost even more than the RB 4-pots. The RB 4-pots look really promising. A few of us locals have been discussing them, and they look like a MUCH better alternative to Subaru 4-pots.

Steve - The advantage to the Subaru 4-pots is the fact that they have ROUGHLY the same pad surface area, but total piston area is slightly larger than the stock WRX brakes. This lends well to rearward bias, and we all know Subaru's are notorious for forward bias. They also add a LOT of feel to the setup with better modulation. You gotta drive both, to notice the difference, you can't really imagine it.

On the street, you don't really notice, but when you start getting REALLY into the brakes, you can get a lot of rear end float.

[evolutionmovement]

I like the rear end float as it helps pirouette the car like a ballerina. My point is that there's little advatage without the tires to exploit it and wide enough tires would require 17s, ignoring clearance issues.

Steve

[Legacy777]

Steve - The advantage to the Subaru 4-pots is the fact that they have ROUGHLY the same pad surface area, but total piston area is slightly larger than the stock WRX brakes. This lends well to rearward bias, and we all know Subaru's are notorious for forward bias. They also add a LOT of feel to the setup with better modulation. You gotta drive both, to notice the difference, you can't really imagine it.

The pad area on the subaru 4-pots is slightly less then the WRX. The piston area is actually smaller then the WRX. Not sure if you meant to put smaller, since you said they tend to shift bias rearward.

[scottzg]

out of curiosity, why does everyone say the brake bias is too far forward?

I'd sure rather it be too forward than too back...

[vrg3]

Wouldn't you rather it be about equal to weight distribution on hard deceleration?

[Legacy777]

If you look at the car as a whole, and how it brakes, let's call that how the chassis brakes. There is an optimum front/rear brake distribution to get the maximum braking for that chassis. It can vary depending on weight distribution of the car, cargo, traction conditions, etc.

There are a lot of different variables that designers have to look at. They will typically give the car more front brake bias because it's typically "safer" then too much rear bias, due to the rear end locking up and coming around.

IMO, they tend to give too much front bias, which decreases the overall chassis braking, but increases their margin of safety under almost all braking conditions so the rear end doesn't lock up first.

The people that want to move bias rearward want to do so to improve the chassis braking, and reduce nose dive. You'll always have a marked amount of nose dive with the macpherson type suspension, regardless of shifting bias around.

[Legacy777]

Wouldn't you rather it be about equal to weight distribution on hard deceleration?

This is a little tricky to answer. Your f/r brake torque/distribution ultimately plays a roll in the weight distribution of the vehicle under hard braking. So if you were to change brake bias, your weight distribution would change under hard braking. However, there's probably some point where weight distribution change will minimize/cease due to bias change depending on your suspension setup.

I don't claim to know exactly how to calculate the best bias setup, but I do know, there is a lot that goes into it.

I've got a braking dynamics book at home. I can take a look and see what they say on the subject.

[vrg3]

Yeah, you're right, Josh, they are interrelated. I just remember how people used to "tune" their adjustable prop valves by going out to a parking lot and braking hard with a buddy watching, adjusting the valve until the fronts and rears locked up at the same time. That ought to be the knee of the curve, right?

[Legacy777]

What exactly do you mean by "knee of the curve"

I know if I were going to adjust a prop valve like that. I'd take it to that point where all four lock up, and then reduce pressure to the rears just a tad to take in account for the fact that braking during a corner, you have different weight shifts, and the inner rear wheel could have less traction in that circumstance then when braking in a straight line.

[vrg3]

It was a figure of speech meaning the optimal distribution.

I think I'd do the same as you -- get all four to lock up together and then back it off a little for safety.

[scottzg]

Why would you trade controllability for ultimate braking distance on a street car???

Heck, why would you on a track car? A higher threshold is pretty useless if you can't aproach and exceed it safely.

seems like if you wanted to tip the bias back, it sure wouldn't be much.

[BAC5.2]

How do you figure you are giving up controllability?

[scottzg]

Brake in a turn and the car goes sideways.


Example:

Just like the car that pushes its way through corners all day long, a car which is heavily front biased will be slow and frustrating, but relatively easy and benign to drive. On the other hand, like the oversteer monster that people are afraid to even drive around the paddock, a car which is severely rear biased will be a scary, twitchy ride resulting in a bad case of the white-knuckle syndrome. Envision an imaginary co-pilot yanking up on the park brake handle in the middle of every corner, and you begin to get the idea. While a rush to drive at speed, it will be horribly slow on the stopwatch.

[BAC5.2]

I think that'd be with excessive rear bias.

Excessive front bias, in my experience, throws the rear around too.

Simple fix, if going to fast, don't brake in a turn. Lift throttle, counter steer, accelerate. Much more controlled.

[skid542]

^^^ Exactly. I know I'd like my car to have a more even distribution (come summer I'm getting some wagon calipers) just because when I brake before a turn I can feel the back end getting loose. This got worse when I removed my AC system. Makes you have to plan your line and your entry speeds more because if I hit my brakes in the middle of a turn I'm pushing hard, garuenteed (experience) that my back end will swing out. On occasion this can be fun if I come around a corner and see that I have a clear road and can then hit the brakes to throw it out but the best way is still - lift throttle, counter steer, accelerate out of it.

[evolutionmovement]

If on the edge in a corner I always turn out slightly when applying brakes (for whatever reason I may have to) to prevent lock up and reduce change in chassis balance as much as possible. Sometimes you can't take the best line to allow for this safety margin, but that's one of the differences between track and street driving. Maybe because I have a wagon, but I'm very happy with the brake balance.

Steve