Can someone please help me understand brake upgrades..

One thing a larger diameter rotor will help is heat dissipation. Even if all things else are kept the same, a larger rotor will allow longer time between heat inputs for a given segment of rotor (i.e. longer time to radiate and convect away heat).

 

larger rotors and calipers provide a longer, stronger lever, to provide stronger stopping power.
I's all about leverage-and greater cooling.

Greg

 

Just for the record, at the same pad size larger diameter rotors have more swept area. For example a 10" rotor with 2" wide swept area = 112 sq in per revolution; a 12" rotor with 2" swept = 138 sq in. That is 23% more area.

The reason for CCM brakes is unsprung weight and less fade. It isn't because they are larger diameter.

 

What everyone needs to know about modern Ferrari Brakes:

1: Ferrari brakes are capable of applying enough clamping force on the rotors to lock up any of the tires you can fit to the hubs. You cannot use any more clamping force than this. ABS systems intervene in the lockup process to take over when more is too much. Modern Ferrari brakes can slow the cars from absolute top speed without fade half a dozen times (I'm talking 180->0 decelerations}. (Any real sports car will have brakes this capable)

2: Bigger rotors are for dealing with heat. First, a more massive rotor will heat up slower simply because it has more mass. Secondly, a more massive rotor is likely to have more surface area where heat may be transmitted to the air and cool faster. Second, the larger radius of clamping will make it easier to lock up the tire. The bigger pad will make it easier to lock up a tire. This results in a lighter touch being used to slow the vehicle. Some drivers like this lighter feel, but for the most part one can adjust the brake boost to perform the same task.

3: Another way, possibly the best way, to deal with heat is to apply more air. The challenge parts can be adapted to stock parts.

4: If you are not taking the car to the track you need do nothing. There is nothing one can do on the back roads to heat up the brakes like track work. After a stint in the midst of Texas summers we can roast hot dogs by holding them between the spokes of the wheels as the rotors cool even after the cool down lap.

5: If you are taking the car to the track and stick with street tires, the only thing you need to do is get fade resistant pads (like Ferrodo DS2500 or such). I have run 72 minute stints in my F355 in the midst of Texas summers at 103dF with DR2500 and fresh fluid lapping within 2 seconds of the track record (3000 pound 400 HP cars on street tires).

6: When you start using r-compounds or even slicks you get into the arena where you must choose braking performance or rotor life. {Hint: choose brake performance} The very first thing you should do is add more air cooling, if this does not solve the problem then go to bigger rotors with new calipers,....

7: Big rotors and big calipers for road cars is pure bling. If yo have the money and don't want it burning a hole in you pocket any longer, you should consider spending that money on driving lessons and track day long before you even think about spending the money on brakes.

 

+1 --> Mitch!! He's right on the money. For street use, even what we would call "spirited" driving, stock brakes are fine. Upgrade the pads if you think you need more "bite" in your brakes, use fresh fluid, bleed the brakes and consider stainless braided brake lines. Otherwise, bigger brakes buy you nothing in terms of street performance.

On the track, different story. But on the track, you are fighting heat buildup. Bigger calipers, pads and rotors create less heat and disapate heat better. But you may get more out of installing cooling ducts than going to bigger brakes right away, and more cost effectively.

Last, I agree re: driving lessons. Learning to use the brakes properly on the track is a big part of driving better and faster.

 

Part two is true but part one not so much. They do not create less heat they simply distribute the heat over a larger mass so the absolute temperature is lower. Same amount of energy is disipated.

 

Hi James,

Basically, brakes turn speed into heat.

Going further, larger diameter rotors offer more mass to heat more slowly, greater surface area to dissipate that heat and probably better/more efficient vanes to pump more heat out, (curved rather than radial vanes).

For sure, use better pads, (higher coefficient of friction & greater heat resistance).

Getting back to the speed is heat idea, as others have said, vent more air to get rid of the heat.

Use better, (more heat resistant) brake fluid & change it anually or more frequently if you track a lot and really get the brakes hot.

Now, if track pads, better fluid, ducting, stainless lines and fresh fluid are not getting the job done - ie, you are getting soft pedal, (boiling fluid), or hard pedal with no significant retardation, (pad fade), THEN it is time to use a larger rotor to get better heat dissipation. Bigger pads or more pressure aren't gong to do squat,you got to get rid of the heat.

If i can back up a minute, if you track the car and find that the pads and or rotors are wearing out in a few track events, then you need bigger better brakes. It is my experience that using brakes at their highest practacal temperature is going to eat pads and or rotors.

For my 308, i skiped the brembo big brake kit, because of the F/R imballance, (in fact, my very first post was, how do you improve the rear 308 brakes). I surveyed every model specific thread and noticed complaints that the stock brakes weren't up to tracking, u to and including the F-40!!!

I happened on a set of F-50 rotors and calipers, 355x32 mm and 40-44 mm 4 pot calipers for $700, (ok, i sniped a guy for the deal , then sought Girodisc's help in finding used real calipers, including parking brake calipers, building hats and caliper mounting brackets. Martin helped me through the math and hardware and i have a front brake set up that is lighter than stock, (though, with probably more rotational inertia) and a slightly heavier rear set up. I could probably do a faster lap time if i reduced the mass of the rotor.

So, the result is that, on track days, i have linear, almost non wearing, killer brakes.

To back track a bit more, one of my main objectives in doing the "big brake upgrade" was to lighten up the pedal pressure a bit, Improve brake controll, via more "Leverage". We 308 guys do not have abs or Electronic brake distribution, so we need all the help we can get, even if we are down a 150 or so on HP.

I believe bigger diameter rotors leads directly to better leverage and hence controll at the limit of adhesion. Similarly, if you are really leaning on the pedal, possibly having things flex, reducing the effort and component diflection, (calipers, hoses, pads, brackets), you gotta be gaining in linear controll, by increasing the hydraulic leverage, (bigger pistons) and lowering the diflection.

Sorry for the rant,

One of the most critical issues with big brake upgrades is that most only address the front, where most of the braking takes place - BUT MINIMUM, consistent braking is not achieved if you are letting thebacks coast, doing little work. Cranking up the pad coefficinet of friction si not necessarily linearly related to the front, so there is a lot of fiddling to get it right.

You can fine tune the brakes with an adjustable proportioning valve and bypassing the stock prop valve. This would be an improvement for the Brembo big brake kit for the 308.

Going further, i don't know how the electronic wizidary needs "tuning with a better brake set up.

This Front/Rear brake proportioning issue is critical for a balanced, controllable, even wearing system. It is a job for some professional help. Martin at Girodisc was there 100%, and no, i unfortunately do not own stock in Girodisc

HTH,
chris









Can someone help me understand what makes great brakes? And what advantage is to be gained by an increase in rotor circumference?

Sorry if this question is relatively elementary but it is a topic that I have always wondered about...[/QUOTE]
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Chris is right on the money regarding the utility of a proportioning valve in obtaining optimal performance. Street use doesn't require a proportioning valve - as was said above, Ferraris have lots of stopping power and reasonable static bias front/rear as-is. For track work a dynamic proportioning valve (cockpit adjustable) is essential. And, be aware, the optimal front/rear bias changes depending on a variety of factors that can change during the course of the day - in rain the optimal bias will change because of less weight transfer to the front during wet braking than dry for example.

One or two points which haven't been mentioned yet:

1. Larger pads and rotors do a better job of transferring the heat into the rotor because there's a larger "contact patch" through which the heat passes from the pad face into the rotor. So, larger rotors are helpful not just because they are a larger heat sink.

2. Greater swept area (again, larger pads and rotors) allows for more controlled modulation of the braking force. In other words, it's easier to modulate the pressure more precisely so as to achieve maximum braking force just short of locking up the rotors. It's not about being able to apply more pressure, rather how precisely it can be applied.