Any advantanges with Zimmerman cross-drilled brake rotors in lieu of standard rotors, when employed solely for street use? Shorter stopping distances? Any disadvantages, other than higher cost?

This topic has both pro and con postings through-out this site. Use the search feature in the upper right-hand corner of the page with the words: cross drilled

I like them and see their benefits, others do not.

Here is a recent thread: Cross drilled or not?

Keep us posted,

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

Cross drilling was originally done as an attempt to release a gas that was generated by a very specific pad material under racing conditions.

I personally believe that it caught on strictly because of its cosmetic effects.

To help understand whether it is useful or not, stop and think about the physics involved with brakes. Brakes simply convert the kinetic energy of motion and mass into HEAT. The brake components recieve this energy in a short amount of time, then dissipate the energy by transferring that heat into the air as they cool. This means that the brake components, mostly the rotors or drums are a CONTAINER of that energy.

As the MASS of that container increases, there is more volume for containing that energy. Drilling holes in the rotor DECREASES the volume of mass that can be used to deal with the energy (heat.) This means that it is not as effective as a brake component. I'm quite sure that the engineers TOTALLY understood this when they cross drilled those first rotors, but the advantage of dissipating the gas emitted from the pad material outweighed the disadvantage of the loss of mass due to the drilling.

As with ANY engineering problem, there are multiple factors that must be considered and often compromised.

If you like the looks of these rotors and it is that important to you, I say go for it. If you are simply replacing rotors for functional purposes, you are wasting your money. I don't doubt that they work okay, but you are paying more money for a smaller HEAT CONTAINER.

Good luck,

Just to add an engineering complication to this, it is also true that re-radiation of that heat to the air must happen, or the brakes will fail. This radiation of heat will be proportional to the total surface area of the rotor, and that can be increased (or decreased) with drilled holes. Lots of little holes will do this best, but location to avoid any heat transfer restriction is also important. I think the bottom line would be how well the rotor is engineered, and not simply whether they are cross-drilled or not.

the problem with them was that tiny spiderweb cracks developed at the holes and eventually compromised the rotor's integrity as it spread. i don't know if this is no longer an issue since cross drilled rotors are still available.

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joE
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"
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I've had poor results with cross-drilled rotors.
Perhaps it's the roadsalt and gravel in my climate.

My theory is that the abrasive road grime collects in the holes and gets trapped in the works instead of being swept away.
This trapped debris digs deep gouges in the rotor face and pads.
The chamfered holes may even encourage this to some extent. Many of the holes were completely clogged with debris. These ran about 1.5 years/22k miles to get this bad.

Looking at the pic, note that only the outer 1/4 inch or so of diameter (where there are no holes) is still in contact with the pads. The swept area that has holes has worn away so badly that there is no contact between pad and rotor.
The pads would otherwise have been about half-worn.

These are Brembo rotors with carbon-fibre pads on a modern Jeep. I'm currently running slotted rotors on both my Jeep and my MB for comparison.

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1986 300E 5-Speed 240k mi.

Don't confuse radiation with convection. Drilling holes will not increase radiation effect. Heat loss by radiation will only happen if the surface "sees" a cold surface for most of the 180° hemisphere, not another hot surface. (Heat Transfer 301 class)

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95 E320 Cabriolet, 159K

"Heat Transfer 301" ?

Actually, any surface above 0 K will radiate energy. Proximity to a cold surface is irrelevant. However, what I was referring to is convection - using 'radiate' as in the action of a vehicle's 'radiator'.

Steve

...dunno which particular model M-B you drive, but I never knew Zimmerman made cross-drilled rotors for M-B...

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1995 black pearl/black Mercedes-Benz E420 :

FastLane now offers them...

You are lucky...for my E420, I can't find Zimmerman cross-drilled...only the standard Zimmerman rotors listed...

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1995 black pearl/black Mercedes-Benz E420 :

Due to the fact that the cross drilled holes are perpindicular to the motion of the braking surface, there is negligible air flow through these holes. The fins on the other hand supply SIGNIFICANT air flow.

Yes it is true that the area is a key factor in an ideal situation, but since there is no air flow past the area in the inside surface of these holes, the effect is negligible.

Again I will say if you want to justify using these rotors because they look cool, then be honest with yourself and admit that you are buying them for their cosmetic effect. If you think you are functionally improving your brakes, again be honest with yourself and save your money.

Have a great day,