concept7

I have a ml 430 and was thinking about upgrading the brakes.
were can one find the cross drilled rotors?
or would one recommend the other type, slotted?

steve s

u could try any of the tuners... kleemann, renntech, etc... or u could try any of the internet shops, like tirerack, stillen... or someone like evosport (find ben).

Lynn

Cross drilled rotors are more prone to cracking than slotted rotors. Rotors that have the holes cast into them rather than actually drilled are far less likely to crack.

pocholin

I like crossed drilled rotor, and they also can cool faster than slotted. Don't worry about cracking them it is mostly a myth, cracking is going to depend on the quality of the materials and the proper brake in for the first 500 miles.

steve s

just make sure u properly set ur pads and rotors during the 500 miles...


and...OMG!! pocholin...u post *****!! 12k posts...that's just sick

Luke@tirerack

Slotted or drilled ????
slotted rotors maintain approx. 96% of the friction surface
drilled rotors maintain approx. 85-93% of the friction surface
drilled and slotted only maintain 80-91% of the friction surface

For many years most racing rotors were drilled. There were two reasons - the holes gave the "fireband" boundary layer of gasses and particulate matter someplace to go and the edges of the holes gave the pad a better "bite".

Unfortunately the drilled holes also reduced the thermal capacity of the discs and served as very effective "stress raisers" significantly decreasing disc life. Improvements in friction materials have pretty much made the drilled rotor a thing of the past in racing. Most racing rotors currently feature a series of tangential slots or channels that serve the same purpose without the attendant disadvantages.

the process of drilling rotors and slotting rotors was done for 1 reason and 1 reason only it is to disipate the gases that build up between the pad and the rotor which occurs under extreme heat ( when braking very aggressively like on a road course) and it has absolutely nothing to do with heat disipation. the only way to transfer more heat away is by using a larger heat sink which means use of a larger rotor whether in diameter or thickness. Since the caliper will only allow for a certain rotor thickness that solution is not very applicable because, if you are changing tha caliper opening width you might as well get a larger rotor diameter at that time

1) The brakes don't stop the vehicle - the tires do. The brakes slow the rotation of the wheels and tires. This means that braking distance measured on a single stop from a highway legal speed or higher is almost totally dependent upon the stopping ability of the tires in use - which, in the case of aftermarket advertising, may or may not be the ones originally fitted to the car by the OE manufacturer.

2) The brakes function by converting the kinetic energy of the car into thermal energy during deceleration - producing heat, lots of heat - which must then be transferred into the surroundings and into the air stream.

The amount of heat produced in context with a brake system needs to be considered with reference to time meaning rate of work done or power. Looking at only one side of a front brake assembly, the rate of work done by stopping a 3500-pound car traveling at 100 Mph in eight seconds is 30,600 calories/sec or 437,100 BTU/hr or is equivalent to 128 kW or 172 Hp. The disc dissipates approximately 80% of this energy. The ratio of heat transfer among the three mechanisms is dependent on the operating temperature of the system. The primary difference being the increasing contribution of radiation as the temperature of the disc rises. The contribution of the conductive mechanism is also dependent on the mass of the disc and the attachment designs, with disc used for racecars being typically lower in mass and fixed by mechanism that are restrictive to conduction. At 1000oF the ratios on a racing 2-piece annular disc design are 10% conductive, 45% convective, 45% radiation. Similarly on a high performance street one-piece design, the ratios are 25% conductive, 25% convective, 50% radiation.

3) Repeated hard stops require both effective heat transfer and adequate thermal storage capacity within the disc. The more disc surface area per unit mass and the greater and more efficient the mass flow of air over and through the disc, the faster the heat will be dissipated and the more efficient the entire system will be. At the same time, the brake discs must have enough thermal storage capacity to prevent distortion and/or cracking from thermal stress until the heat can be dissipated. This is not particularly important in a single stop but it is crucial in the case of repeated stops from high speed - whether racing, touring or towing.

4) Control and balance are at least as important as ultimate stopping power. The objective of the braking system is to utilize the tractive capacity of all of the tires to the maximum practical extent without locking a tire. In order to achieve this, the braking force between the front and rear tires must be nearly optimally proportioned even with ABS equipped vehicles. At the same time, the required pedal pressure, pedal travel and pedal firmness must allow efficient modulation by the driver.

5) Braking performance is about more than just brakes. In order for even the best braking systems to function effectively, tires, suspension and driving techniques must be optimized.

E55AMG99

Absolutely!

Most people don't understand the tire/suspension/braking relationship. I still can't figure out why more manufacturers aren't using slotted instead of cross drilled. Even though cracking is a minor problem on the street, slotted perform better.

pocholin

Thank you

mmgrad

another great contribution! thats an excellent explanation of the benefits & differences between slotted & x-drilled rotors.

Thanks!

concept7

WOW that was fantastic! I really loved reading that explaination. thanks alot!

Are you in the Racing industry or work for NASA?

mleskovar

Well done, even I can understand it!

steve s

here is something that came up a while ago...even tho it's more about big brake kits... (too bad the graphs with the stopping distances don't show up on the internet)...

http://www.caranddriver.com/article....rticle_id=2852