Good rotors?

[jerods87e30]

First time actually replacing rotors for my 325es, what's a good front rotor you guys would recommend? Can't afford perf. rotors at the moment, don't really need them either. Is anything from "Advanced Auto Parts" or "AutoZone" really gonna cut it? thx

-J

[StereoInstaller1]

I have no clue what is local to you, but OE is Brembo, arguably the best quality rotor in the world.

Lots of online stores have them somewhere around $40/ea. You can likely get someone to order them for about $50/ea locally.

Slotted/drilled/cryo rotors are not needed unless you are seriously modded in the motor department...and are mostly rice anyway.

Luke

[whiltebeitel]

Slotteld/drilled/cryo are pointless. Pads are key for stopping power, since modern pads don't build up gas, which those rotors evacuate. If the stock rotors aren't doing it, See Massive Lee.

I don't think it matters what rotor you get from the local parts store, it will most likely be fine. A friend blew one of my calipers at an autocross, and I went to O'Reilly's and I got thier $40 rebuilt caliper. I've used these brakes at many autocrosses and a track day since I replaced them. No worries.

[MR 325]

Go with OE Brembo rotors, they're good quality.

[Jean]

Go with OE Brembo rotors, they're good quality.

x2

[PaintPro21]

Balo makes excellent rotors as well, and they've been known to handle track abuse vs many other oe rotors. fyi most of these companies including brembo are getting their rotors made in random countries like china and the philipines, so it's not like the country of origin really matters anymore.

[Stu]

Brembo OE replacement rotors have been cracking and warping quicker than Advance Autoparts rotors for me on track--with both Hawk and Carbotech pads and in similar weather conditions. For normal daily driving, get whatever is cheapest. Cryo rotors are a good option for longevity with an aggressive compound like a Hawk Blue or HT-10.

[10/10ths]

Brembos have worked the best for me, and they are cheap. Even if you were willing to pay extra for slotted/cross-drilled rotors, you still would be better off with stock.

[euroshark]

I'm going with Brembos for my 750il brake conversion on my 6er, I don't see the point in using anything else!

[Massive Lee]

First time actually replacing rotors for my 325es, what's a good front rotor you guys would recommend? Can't afford perf. rotors at the moment, don't really need them either. Is anything from "Advanced Auto Parts" or "AutoZone" really gonna cut it? thx

-J

Brembo, Zimmermann or ATE are appropriate.
Keep away from EuroRotor that are brand X products cast... in Asia.

Also keep away from drilled rotors if you drive your car hard. Even ATE's Powerslots aren't really needed.

[e30lyf]

Brembo, Zimmermann or ATE are appropriate.
Keep away from EuroRotor that are brand X products cast... in Asia.

Also keep away from drilled rotors if you drive your car hard. Even ATE's Powerslots aren't really needed.

+80

[gearheadE30]

I've got zimmerman x-drilleds from the previous owner. I wersonally think they look cool, but they aren't worth the price and there was no noticeable performance increase, even on the track.

[moatilliatta]

Some good info i found

Darrick Dong; Director of Motorsports at Performance Friction: "Anyone that tells you that drilling makes the disc run cooler is smoking crack."

Power Slot: "At one time the conventional wisdom in racing circles was to cross-drill brake rotors to aid cooling and eliminate the gas emitted by brake pads. However, today’s elite teams in open wheel, Indy and Trans Am racing are moving away from crack prone, cross-drilled brake rotors in favor of rotors modified with a fatigue resistant slotting process."

Stop Tech: "StopTech provides rotors slotted, drilled or plain. For most performance applications slotted is the preferred choice. Slotting helps wipe away debris from between the pad and rotor as well as increasing the "bite" characteristics of the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage. Many customers prefer the look of a drilled rotor and for street and occasional light duty track use they will work fine. For more severe applications, we recommend slotted rotors." (Note that even though Stop Tech sells both drilled and slotted rotors they do not recommend drilled rotors for severe applications.)

Wilwood: "Q: Why are some rotors drilled or slotted?
A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity."

From Waren Gilliand: (Warren Gilliland is a well-known brake engineer in the racing industry and has more than 32 years experience in custom designing brake systems ...he became the main source for improving the brake systems on a variety of different race vehicles from midgets to Nascar Winston Cup cars.) "If you cross drill one of these vented rotors, you are creating a stress riser that will encourage the rotor to crack right through the hole. Many of the rotors available in the aftermarket are nothing more than inexpensive offshore manufactured stock replacement rotors, cross drilled to appeal to the performance market. They are not performance rotors and will have a corresponding high failure rate"

From Baer: "What are the benefits to Crossdrilling, Slotting, and Zinc-Washing my rotors?
In years past, crossdrilling and/or Slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads...However, with today’s race pad technology, ‘outgassing’ is no longer much of a concern...Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’s offerings."

Grassroots Motorsports: "Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)

AP Racing: "Grooves improve 'cleaning' of the pad surfaces and result in a more consistent brake performance. Grooved discs have a longer life than cross-drilled discs."

also from AP: "Cross drilled...can compromise disc life. Radiused drilled...mainly used for aesthetic reasons on road applications."

...I'll keep looking for more. Note that these quotes are from people who are in the racing business, not the poser business.

[Massive Lee]

Thanks Moatilliatta for the good quotes.

Hopefully, people will understand that what makes your car looks "cool", also makes your rotors run too "hot", to the point of causing cracks.

[87-325ic]

good info!