pocholin

Vadim is that your car? Do you know if the person properly broke in the brakes for the first 500 miles? That is the real question.

Here is a picture of my cross drill rotors on a 96 suburban (lots of weight), I've pulled trailers with up to 5000 lbs on them, driven it hard for the most, those rotors have been in my suburban for over 2 years, this is the second set of pads they see and they've never been turned yet, that is about 35,000 miles.
Like somebody said a picture is worth a thousand words, but you don't know the reasons why rotors look good or bad.
The first 500 to 800 miles are essential for the life of the rotors, some people think I got new rotors I can start braking like a F1 driver, not true in the beggining.

vadim

So, is it "instead" or "also"?
Now, do an experiment: heat an iron and then put it on a cold pot with a flat bottom turned upside down. Wait a few seconds and feel the pot. Watch it get hot from the iron. That's metal-to-metal heat transfer. That's how heat dissipates from the rotor - to the wheel attached to it. It is absolutely normal. If this doesn't happen, be alarmed, as your rotors are likely to get fried.

vadim

No, that's not my car, but it's a MB. I just keep this photo to scare others who believe that cross-drilled rotors are the next best thing after sliced bread. I've heard of things like this happen to them from more than one person.

JustinTRW

You're 100% right, please add the word "all" between "transferring" and "the", which was mistakenly omitted. Honest mistake. :p BTW, you're not saying the brakes are fully relying on the wheels are you? (to cool down)

Anyway, to the issue at hand, which was.........would the C32 brakes reach the threshold of lock-up faster than the stock C320 brakes (on the same vehicle)? Please, let's get this answered.

Boo2

I thought that was a picture of someone who had their rotors drilled from regular rotors.

vadim

No, of course not. They install vented rotors for a reason. I was just trying to make a point that heat dissipation through metal (rotors, hubs, wheels) is normal, so hot wheels is something that should be expected during spirited driving with lots of brake pedal use.
Put it this way: wheels/tires/weight/suspension being the same, the C32 brakes require less pressure in the brake lines to lock up the wheels. That should be obvious, just because the brake rotors in a C32 are bigger in diameter than those of C320. But breaks are *assisted*, that is, the car applies as much force as needed to do this for you. With the brake assist feature all you have to do is to hit the brake pedal quickly enough and hold it depressed, and the rest will be done for you. In this regard, it's arguable wether the "upgraded" brakes will result in a quicker action.

JustinTRW

Ok, I think we are still talking about different things

What am I saying is, I don't think that the regular setup will reach lockup instantaneously when maximum brake pressure is applied (with brake assist on). That is the real issue I think.

So, if the C32 brakes (both setups using assist) reach lock-up sooner, the C32 brakes will stop the car in a shorter distance. My whole argument rests on assuming the stock brakes will not reach the ABS threshold right away. If it does, then I'm wrong concerning a single 60-0 test. So...let's discuss.

vadim

See, that's the point. I think that would make a difference *if* the brakes were not power-assisted. Now, with computer-controlled power boost, it is no longer an issue. A difference in reaction time between C32 and C320 is likely within milliseconds.

FrankW

i thought that picture was from someone who had did the drill by themself. the picture was from a thread not that long ago. just look at the pattern of the holes. Brabus can't possibaly make that kind of mess.


another thing i want to add is that on my brother's car he had changed the original rotor to the brembo rotor and the braking feel is much better than the original. the brembo cross drilled rotor did help the car stop a little faster than the original rotor. tires are 235/45R17.

JustinTRW

How can power-assisted brakes increase actual stopping power? To my understanding, the only thing this system does is apply maximum brake power sooner. The C32 brakes would still have a higher maximum brake power.

The way I currently understand it: if you were to apply the same system to the accelerator, all it would do is eliminate the delay from zero gas to full gas. The more powerful engine would still win. What don't I understand about brake assist?

trench

Actually, the size of the F1 wheel was set years ago and has more to do with limiting the shape of the tire's contact patch rather than the brake rotor size. Also having to use higher profile tires gives higher slip angles which also means less grip. The end result is the same - lower speeds. What's interesting about the high profile F1 tires is that with their large sidewalls, combined with the car's unbelievably stiff suspension, half of the car's suspension "travel" is caused by sidewall deformation.

The carbon fiber braking systems currently provide more than enough stopping power at the current rotor diameter. If more stopping power were required for some reason, there is nothing in the rules that prevents the teams from running larger diameter inboard brakes (although this is an unfavorable trade-off from an aerodynamic and cooling point of view - even though the car would have better handling characteristics due to a reduction in unsprung weight). However, continuing improvements in the technology of the carbon/carbon brakes has mitigated the need for any drastic measures such as these.

Cheers, BT

vadim

First, please define "stopping power".

Your model would be applicable to brakes if and only if tires would never lose traction. "Stopping power" is as good as the adhesion of the tires to the road. As soon as you reach the point when tires start skidding instead of rolling (known as wheel lock-up), any further increase of the force of friction between the pads and the rotors is pointless. Power assisted brakes help achieve this point sooner. [back to square 1]

Going back to the engine analogy: suppose you have two identical cars with two different engines: 1000hp and 1500hp. Which one will win on a wet road from 0 to 60?
Both are capable of spinning wheels at any speed in this race.

MB-BOB

trench, avlis isn't making this up. A couple years ago, one of the Rags (AutoWeek, I'm pretty sure) ran a preseason comparison of F1, Cart and IRL technology. The article covered the many good points that you have made. But it also stated that the current 12" (or was it 13") diameter wheel in F1 was set in place (among the other reasons) to naturally limit maximum brake rotor diameters. I thought it odd, thus memorable, because I'm not sure you can even buy a road car nowadays (in the US) with wheels of 13" or less dia. (not even a Mini Cooper). I had 4-lug, 13" wheels on my first Honda Accord, but that was 25 years ago!

trench

Actually it's kind of a moot point anyway. Since I posted the above I looked up the rule regarding brake size.

It states:

Article 11.3.2 All discs must have a maximum thickness of 28mm and a maximum outside diameter of 278mm.

Likely this is to prevent teams from doing what I described with regard to mounting larger inboard brakes (which I can't find a rule against - positioning, not the size). After I thought about it I figured it would be easier to simply impose a rule on brake diameter size rather than simply limit them by using smaller wheels.

Here are the wheel rules (since you were wondering about the size):

ARTICLE 12 : WHEELS AND TYRES
12.1 Location :
Wheels must be external to the bodywork in plan view, with the rear aerodynamic device removed.
12.2 Number of wheels :
The number of wheels is fixed at four.
12.3 Wheel material :
All wheels must be made from an homogeneous metallic material.
12.4 Wheel dimensions :
12.4.1 Complete wheel width must lie between 305 and 355mm when fitted to the front of the car and between
365 and 380mm when fitted to the rear.
12.4.2 Complete wheel diameter must not exceed 660mm when fitted with dry-weather tyres or 670mm when
fitted with wet-weather tyres.
12.4.3 Complete wheel width and diameter will be measured horizontally at axle height when fitted with new
tyres inflated to 1.4 bar.
12.4.4 Wheel bead diameter must lie between 328 and 332mm.

The wheel rules came about partly from tradition (from the sizes being employed at the time they were origially written - about 1978 or so) and partly from reasons to slow the car by the means I mentioned earlier.

Cheers, BT

MB-BOB

Thanks for looking it up, trench. That means that the maximum disc diameter is 278mm X .0394" = 10.95" and the maximum practical wheel diameter is 332mm X .0394" = <13.08".

And this measurement is what essentially limits the braking capacity of the tire at the contact patch. (Just to get back on topic)

TimmyC230boy

thats why on my Camaro I could stop shorter with the upgraded brakes I had because I had 275/45/17 rims. Those tires make a huge contact patch with the road thus allowing for more force to be applied to the brakes before the wheel would lock up.

JustinTRW

Stopping power, as it applies to ONLY the rotor and caliper system, is the ability for the caliper to slow the rotor to a stop. Look at this scientifically as possible. Let's say the only variable is the rotors/caliper system. Both are going to lock the wheels w/o ABS, that I know.

You still do not get my point after about 5 posts of trying. Wheel lock-up I understand. I'll break it down statement by statement. Stop reading when you don't agree, then respond.

ABS prevents you from reaching lock-up. Agree? Ok.

Once ABS is activated, any extra friction the caliper may be able to apply to the rotor via the pad is useless. Agree? Next...

Power assisted brakes cause ABS to activate sooner vs. a car with the same setup (brakes included). Agree? Next...

Now re-read what you wrote, "As soon as you reach the point when tires start skidding instead of rolling (known as wheel lock-up), any further increase of the force of friction between the pads and the rotors is pointless." I agree here.

Power-assist simply applies maximum pressure the calipers are capable of applying. Agree?

You stomp on the pedal at 60 mph. Brake assist causes the caliper to apply its maximum pressure. Agree?

The stock brakes do not cause ABS to engage immediately after this point, it takes measurable time (time * speed = distance). ABS WILL engage because the tires would skid at some point. Agree?

The C32 brakes on a C320 (despite probably being heavier) would cause the wheel to lock-up sooner, thus reducing the time for ABS to engage. Agree?

Both brakes are equal while ABS is engaged, assuming consistency, and no fade. Agree?

If the C32 brakes cause ABS to engage sooner (because the tires would otherwise skid sooner), reduces stopping distance because..... time * speed = distance. Agree?


What's wrong with my logic? The way that I see your theory is correct is when both brakes are so incredibly powerful, that the time for ABS to engage is next to nothing for both. Like in your 1000hp vs. 1500hp analogy....both cars are so powerful anyway.

I agree that stickier tires help A LOT.

JustinTRW

You know what Vadim? Just re-read my post. Basically the discussion we are having comes down to the question I asked previously.

If brake-assist causes ABS engagement right away in both cases, no real difference in braking distance.

vadim

Exactly!

JustinTRW

LOL! I already knew that would be that case, but I don't know if that IS the case. Brake-assist on very weak brakes would not cause ABS intervention. That's why I skeptical of immediate ABS engagement.

vadim

Justin, why would the stock brakes on a C320 be weak??? This is a German car!!! They drive fast as hell, and sure have mastered the brakes on mass-market cars better than anyone else.

JustinTRW

Of course they are not weak. I've never slammed on the brakes of a non-abs car with brake-assist to find out how quickly the wheels lock.

pocholin

It is not your car, you don't even know for sure they are brabus, some people are saying that someone drilled them themselves. How can you say this is what happens to all crossdrilled rotors, if that is true on all cases how comes Porsche is still using them on most their cars, lambo, brembo, etc.
Like I already mentioned before the life and effectiveness you get from your crossdrilled or any kind of brake rotors is going to be determined by those first 500-800 miles.

Despite of what people argue here about the ABS and stopping distance on different rotors, my suburban brakes quicker than on stock rotors, and tires don't lock up as soon as they used to, Stillen guarantees 10% shorter distance by using their rotors and metalic pads, and belive me it worked.

vadim

I'm not saying that this happens to all cross-drilled rotors (where did you get this from?)

The fact is - it has happened to the one in the picture, and the rim looks 2-piece, expensive enough to expect an accordingly priced rotor underneath. That's enough of a material evidence for me. YMMV. Cheers.

steve s

wow! eight pages of posts...took a long time..lemme c if i remember everything.

c32 brakes look ssoooo much better than the ones mb slapped onto our c36. they r actually brembos made specifically for the c32...unlike the c36, mb just raided their parts bin for most of the stuff (read my c36 spec), where the front rotors are from the sl600 front rotors. they look normal, butt ugly. the c32 brakes have the "AMG" logo on it too...cool

f1 brakes are either on or off, no in between...if they had actually had low profile tires, the international racing body deemed it too fast and unsafe for drivers. another thing, traction is way important. f1 introduced groved tires, cart still has slicks....alex zanardi could not transfer his awesome late braking skills from cart to f1 because the f1 does not have as much traction (part of one of many reasons, bmw was new) and was more twitchy than cart. if u've driven a regular sedan, like an accord w/o abs, u can feel just when the brakes start locking up, and when it does...u can't do a thing but let go or hang on, no turning capability (race car drivers are supposed to be able to modulate the threshold expertly). tires are huge too...i know the accord chassis can do lots more, but the tires just howl like crazy, they're the long-lasting, quiet, all-season tires...if u had s-03 or even slicks, it would stick a lot better.

does a brembo kit really run u 3K for the new c-class? i had those 13" brembos on my volvo 850 wagon, for 2.2k...btw, the pads are expensive ($200 for a pair). i swapped out the old ones when the stock rotors were worn to minimal thickness at 40k. another thing u should get is stainless steel braided brakelines. change to higher spec brake fluids (and change it every 2 years). and get some really good pads. on my volvo 850 turbowagon, the rears hardly get any brake dust, all up front now. either way, if u have cash to burn, and would like the knowledge of knowing u've got great brakes, get either c32 or brembos.

have u driven the old ~95 integras?? it's got tiny-*** brakes. i borrowed my cousin's ricer (i laugh at him all the time, he's done some stupid stuff to his car) when i was in la. i missed a "hiding" entrance, and slammed the brakes (no cars behind). normally, i would've been able to stop with my volvo 850 turbowagon (13" brembos and 215-45-17 s-02). my cousin had stock brakes, but 215-40-17 s-02...that thing just would not stop...abs kicked in like crazy. don't tell me those wimpy *** brakes could stop that ricer the same as if he had 13" brembos. ok..ok, so if abs engages at same time, no diff. but 13" would still be stronger than those wimpy stock ones.

brakes, u want the stickiest pads, the most pad surface and the most leverage, which means farther away from the center so bigger brakes. u also get better heat dissipation with larger rotors. (volvo decreased the 2.4 inline-5 n/a to 2.3 inline-5 turbo so as to increase amount of metal to help dissipate the extra heat.)