Warped Brake Rotor and other Myths

[Duncan]

While wandering aimlessly around the internet while SAU was offline, I came across the following overview of brake problems. Very interesting reading.....

http://www.stoptech.com/whitepapers/warped...rotors_myth.htm

And for those interested in further info, they have a whole heap of other infor here: http://stoptech.com/technical/

[Duncan]

ANd here's another interesting one, comparison between 350z 4 spot brembos to the regular 350z brakes.....resulting in a difference of 5feet (less than 2 metres) in a stop from 160km/h...

5feet in 336feet is only 1.5% difference, and this was after repeated heavy stops.

http://www.zeckhausen.com/testing_brakes.htm

[Roy]

Car & Driver did a similar article last year, which happened to test one of the StopTechs brake kits against some more recognised names, showing similar results.

Test Car was a WRX (US Spec which only uses two piston sliding caliper, not as good as Nissan 4 spot)

So tested kits were, std car, std car with upgraded pads and fluid, Brembo F50 Kit, Brembo Lotus Kit, Stoptech it and Prodrive Kit (Alcon)

Stopping Distances 70mph - 0 , 3 Stop

Brembo F50;....................185 / 183 (Average / Best)

Brembo Lotus;..................200 / 196

Prodrive;...........................198 / 194

StopTech;..........................187 / 186

Stock;................................205 / 196

Stck with pads and fluid;...187 / 184

So you can see the one stop max of the upgraded pads and fluid is damn good when you consider the $$$ to % difference.

Stopping Distances 70mph - 0 , 25 Stop

Brembo F50;......................299 / 288 (Average / Best)

Brembo Lotus;...................305 / 294

Prodrive;............................308 / 295

StopTech;...........................297 / 290

Stock;.................................340/317

Stck with pads and fluid;....316/299

Not the world of difference you would be led to believe by the "you need 6pot caliper 334mm rotor crowd."

Specs of the kits:

Rotor Weight (pounds) Size in inches (diam / thk)

Brembo F50;.................15.8..........................13.1 / 1.3

Brembo Lotus;..............12.9..........................12.9 / 1.1

Prodrive;.......................16.5..........................13.0 / 1.1

StopTech;......................13.9.........................12.9 / 1.1

Stock;............................14.2.........................11.6 / 0.9

Caliper Weight Piston Size, (mm)

Brembo F50;..........8.6 pounds...........40 / 44, Leading / Trailing

Brembo Lotus;.......6.8.......................36 / 40

Prodrive;................9.1.......................34.9 / 41.3

StopTech;...............9.3......................36 / 40

Stock;....................10.8.....................43 / 43

...and COST!!!

Brembo F50;........................US$2,995

Brembo Lotus;.....................US$2,595

Prodrive;..............................US$1,999

StopTech;.............................US$1,695

Stock with pads & fluid;...... US$130

Scary numbers when you look at $$$ vs benefit, for our road cars, not race cars that race in competition. And remember thet US Spec cars dont get the same 4 pot calipers that WRX get in Aus.

So would expect better performance from OZ Spec WRX or Nissan 4pot calipers with pads and fluid.

[Duncan]

Great info Roy.

Yeah, I was surprised at how little difference upgraded brakes can make. These guys made the important point that the stock brakes on a car are perfectly able to stop the car at the limit of the tyre's grip...once. Which is of course all a road car needs to do.

The real benefit from big brakes comes from repeated stopping under tough conditions...but even then, the numbers above show its not as big a difference as you would expect for the price.....

Looks like the most important issues is getting great pads and fluids, and seeing if that is sufficient...

[benm]

Yup interesting reads....

I don't think i'd ever use Brembo's unless they came on my car already, simply not worth the price.

[B-Man]

Cool - I just saved about $1800 ! Thanks guys !

[Roy]

Id like to know the model of Brembo brakes the GTRs come with.

I think in the defence of the big $$$ brake setups, as Duncan said, a car can only stop as quickly as tyre grip will allow. So tyres are a great equalizer in this sort of comparo.

In addition to this test it would be good to see the WRX have some slicks thrown on it, and compared the stopping distances.

But in the case of a car using treaded road tyres, it questions the benefits of sexy Brembo/Alcon/Ap brakes.

That said i would still kill to have six pot Endless brakes hiding behind my rims

[Duncan]

Well, the way I understand it...brakes stop cars by turning movement into heat. And when they get too hot the less heat they can absorb the less you stop. Obviously "too hot" varies depending on the pad material.

So, basically, you don;t need bigger brakes unless your current ones are overheating (fading). Mine do

But what you don't get, according to the info above, is significantly shorter stopping times....you just get less fade.

[Roy]

Yeh conservation of energy, cannot be created only transferred blah,blah,blah.

Kinetic energy in rotating wheel is slowed by way of friction, which turns into heat, noise etc.

The tyres friction coeffecient means that once a certain force is exceeded (equates to braking force), the tyre's face will slip relative to the road surface. Now there are two forms of friction coeffecients, static and kinetic, static being higher then kinetic.

When the tyre isnt locked up that equates to static friction, no relative slip between the two faces, when the tyre locks up you are relying on the kinetic friction coeffecient (remember this is the lower friction coefficient) so that expalains why locked up brakes means longer stopping distancesas there is less friction.

So when the tractive effort of the tyre is exceeded, the sudden change in friction levels courtesy of a shift in friction coeffecients results in the brakes locking.

If you are able to increase the level of friction between the road and tyre by way of increasing either the perpindicular load on the tyre (vehicle weight), or by way of friction coeffecient (tyre compound and contact patch) then you can further reduce stopping distances.

It is here that bigger brakes can shine, with larger pad areas aiding firction levels, better temp control, and using stiffer calipers and coming with braided lines offer more pedal. If the performacnce ceiling of the tyres is not limiting the total stopping ability of the car, or actual caliper/disc.

But yeh, ability to transfer energy into heat and then dissipate that heat, Duncan when you run road tyres on your car, as opposed to D01Js, do you see the same level of fade?

Ramble, ramble, ramble....

[Duncan]

Good rambling, although I suspect we're talking to ourselves lol

Actually, I don't get much fade at all with the stock brakes, and I do push a bit....

I get less fade with the cheater tyres on, but thats because it can carry better midcorner speed, so I'm not on the brakes as much in the first place.

I don't think my car is a great example, for a skyline it has low straight line speed (stock power output) and high corner speed (cheater tyres).

[benm]

C'mon Duncan...... i'm still waiting for you to put about $3k into it so you can show John what a set of r33 tail lights look like into turn 1 at EC.

[Roy]

I recall you mentioning the corner speed, less braking point. I keep neglecting to consider that. I suppose it averages out as the increase corner/exit speed means you arive at the next corner quicker, but again you are not needing to slow as much.

On my GTSt (similar to yours, compared to others a bit vague on the straight ahead) i rarely ever got fade with the std braking setup, it was only on the quiet Wakefield open days where i found myslef strolin' around for 20-25 laps as there isnt really any time restriction on sessions.

Funny it was one of these days where i ruined my rotors by running out of pads. On 20min session with the occasional slow corner or two because of slower cars the brakes seemed to hold up fine.

If you are serious about braking performance, another thing that may stop you from needing to go to expensive brakes is using a decent quality wheel, ie no 18" full face chrome rim. Good quality rims, especially those with a slant to lightweight and performance typically offer improved cooling around the rotors. You happen to run Volks dont you Duncan, perhaps another factor.

With cold air intakes being all the go, you can get ducts from places like Revolution Racegear for brake cooling, only you have to be careful where you guide the flow to as not to cause hotspots on the rotor, but still a cheap and effective brake mod for the weekend racer.

[Guest RedLineGTR]

Thanks for all the info was a very interesting read and a learnt alot

[red900ss]

As was mentioned the ability of the brakes to repeatedly slow the car after multiple applications is the main benefit of upgrading a braking system. I bet the stockies felt pretty cr@p after 25 applications, and with 40' to go you'd still be going fast enough for some serious damage.

Wheels also play a major part in helping the brakes cool by heat soak through the contact face of the disc and the inside of the rim. Think of the surface area of a rim compared to a brake disc and where it's positioned wrt the slipstream.

The other benefit is reducing unsprung weight with an aftermarket system. So not only do you get a braking improvement, but handling will be better too.