Zimmermann Cross Drilled Rotors - United Bimmer Community

**elsabor67** · 10-23-2007, 07:07 AM

Just got off the phone with the guys at Turner M.S. and they can't get me the TMS cross drilled rotors I ordered and offered me the Zimmermannn front and rear set for the same price.

Does anyone have any experience or had this brand before and how were they on your car?

**GreenTourer** · 10-23-2007, 07:53 AM

Elsabor, what are these Zimmermann Cross Drilled Rotors? Educate me on this if you please

**m3flyer** · 10-23-2007, 11:27 AM

Quote:

Originally Posted by elsabor67

Just got off the phone with the guys at Turner M.S. and they can't get me the TMS cross drilled rotors I ordered and offered me the Zimmermannn front and rear set for the same price.

Does anyone have any experience or had this brand before and how were they on your car?

...are superb rotors for the money. Made in Germany by German craftsmen.

IMHO they are better than the TMS cross-drilled rotors which are just OE BMW rotors that have been sent out for machining.

By the way, I have Zimmerman cross-drilled rotors on both my rides. They rock !!!

Quality control on the Zimmermans is judged vis-a-vis German TUV guidelines and AFAIK they have been approved by TUV.

**mzbmw325i** · 10-23-2007, 11:32 AM

i don't want to deviate from the thread but has any one tried the brembo oem front rotors, they are cheap on the tire rack and i am thinking of getting them for my E30.

nick_318is · 10-23-2007, 12:15 PM

^I have they are great I love that the BMW blanks are so cheap. I'm happy to hear such a report on the Zimmermans, I might have to order them the next time I change the brakes.

**Numark318i** · 10-23-2007, 03:24 PM

Quote:

Originally Posted by mzbmw325i

i don't want to deviate from the thread but has any one tried the brembo oem front rotors, they are cheap on the tire rack and i am thinking of getting them for my E30.

ye ai got the brembos also. they are great.

and yea maybe ill look at zimmermans for my next set of breaks.

**elsabor67** · 10-23-2007, 03:39 PM

Quote:

Originally Posted by GreenTourer

Elsabor, what are these Zimmermann Cross Drilled Rotors? Educate me on this if you please

No problem GT. The way I understand (and correct me guys if i'm wrong) is that the holes on the rotor are supposed to work as a fan to maintain the rotor cool under braking so they won't over heat and then your brakes fail. this is what they look like...

I wasn't aware that the TMS rotors were OE BMW rotors. Thanks for the info M3F.

I thought about the Brembo's MZ, but a Soldier that works with me has them on a Honda Accord (Bigger ADing Ding Level) but he was having alot of problems with them.

**Numark318i** · 10-23-2007, 03:41 PM

something i was told was that slotted rotors are better then drilled since the rotors tend to crack between the drilled holes under severe stress. (ie a track day) but otherwise theres no difference.

keep that in mind i guess?

**GreenTourer** · 10-23-2007, 04:01 PM

Ah, I see...........I think what you call rotors in the U.S. is we call vented and drilled discs in the UK, thus my confusion. Never heard them called that before.

**MTurboPower3** · 10-23-2007, 05:19 PM

Why would you try to get tms rotors? I would get original BMW rotors. I don't know anyone who has Zimmerman rotors but good luck.

**m3flyer** · 10-23-2007, 05:23 PM

Quote:

Originally Posted by elsabor67

No problem GT. The way I understand (and correct me guys if i'm wrong) is that the holes on the rotor are supposed to work as a fan to maintain the rotor cool under braking so they won't over heat and then your brakes fail. this is what they look like...

I wasn't aware that the TMS rotors were OE BMW rotors. Thanks for the info M3F.

I thought about the Brembo's MZ, but a Soldier that works with me has them on a Honda Accord (Bigger ADing Ding Level) but he was having alot of problems with them.

...the holes vent gas from the rotor surface which tends to cause extra heat, warping, and cracking on a sealed surface rotor.

Same thing with slotted... they vent the gas.

**charterali** · 10-23-2007, 06:51 PM

Zimmermann are better then OEM. I have them in my W124 300E. They work very well.

**xsperf** · 10-23-2007, 07:18 PM

i had zimmerman on my older bmw, and i have brembos on this one, they are both great. and about the cracking, thtas if the holes are DRILLED, usually they are drilled if its like a 'made in Taiwan' deal where they are a knockoff, replica, but the real deal is not actually drilled, the holes are molded

**m3flyer** · 10-23-2007, 07:18 PM

Quote:

Originally Posted by charterali

Zimmermann are better then OEM. I have them in my W124 300E. They work very well.

**215BIMMER535** · 10-23-2007, 09:19 PM

i have zimmerman cross-drilled on my e36. have had them for about 2 years, they are great! only shame is theyre hard to see through my snowflakes...not enough gap in the spokes. oh well they have served me well and i do a good amount of hard braking both on the highway and country roads.

**m3flyer** · 10-24-2007, 12:37 AM

Quote:

Originally Posted by GreenTourer

Ah, I see...........I think what you call rotors in the U.S. is we call vented and drilled discs in the UK, thus my confusion. Never heard them called that before.

...vented points to the area in between the inside disc surface (where the inner pads touch) of the rotor and the outside (where the outer pads touch) surface.

If you stand a rotor on end and look at it as if it were a "blade", the vented area is the space in between the inner and outer surfaces.

Non-drilled rotors can be vented (space in between surfaces with vanes to guide the air through) or non-vented (solid). Either of these then can be cross-drilled or slotted.

That is all...

**m3flyer** · 10-24-2007, 12:58 AM

Quote:

Originally Posted by xsperf

i had zimmerman on my older bmw, and i have brembos on this one, they are both great. and about the cracking, thtas if the holes are DRILLED, usually they are drilled if its like a 'made in Taiwan' deal where they are a knockoff, replica, but the real deal is not actually drilled, the holes are molded

...that is not exactly the way it is.

Cross-drilled rotors are machined, drilled, and the holes are double chamfered (beveled edges to reduce wear on pads). The inner (lower) bevel will act as a wear indicator and once reached you should change out the rotors.

Rotors are cast & machined and only a very few rotors are made with "holes-in" (some Porsche and other exotic car rotors). They still must be drilled out and chamfered because the "hole-in" casting is really just a dimpled casting and each "hole" (dimple) does not go totally through the rotor.

There is no easy cost effective way to make holes totally through a casting other that drilling them out because of the vented area between the inside and outside and the vanes within. To attempt do so would most certainly be hugely labor intensive and cost prohibitive.

**Dudesky** · 10-24-2007, 05:50 AM

Quote:

Originally Posted by m3flyer

...vented points to the area in between the inside disc surface (where the inner pads touch) of the rotor and the outside (where the outer pads touch) surface.

If you stand a rotor on end and look at it as if it were a "blade", the vented area is the space in between the inner and outer surfaces.

Non-drilled rotors can be vented (space in between surfaces with vanes to guide the air through) or non-vented (solid). Either of these then can be cross-drilled or slotted.

That is all...

Correct. Contrary to popular belief, the holes or slots on the surface are not for cooling the rotors. They are for dissipating the boundary layer of gases that build up between the pad and rotor, hence maximizing braking power.