325xi brake problem and recommendation

[holabr]

I have a 2001 325xi. After it sits for a while (12 hrs or so), the first time I apply the brakes I get a grinding noise. After that they seem ok although I don't think they are as responsive as they once were. I'm assuming that if the pads were worn down, the dask light would come on. Any ideas on what to check and how to fix it?

Also, I am considering changes the pads and rotors to an after market setup that would give better performance, less brake dust, and less squeal. Does anyone have a recommendation? Are cross drilled and/or slotted a good way to go? Anyone know anything about Zimmermann?

Thanks for the help.

 

[Zchild]

Hey Holabr, I do my own brakes on my bimmer. I've tried the cross drilled and if you're going for the look then they're nice however, the slotted are the better value and are proven to brake especially if you track you car. The cross drilled are no better value than the OEM product. I recently switched to a dust-less pad and have had no problems with response or wear. I'm told that the cross drilled have a tendency to hold heat and warp under high usage. Just my two and a half cents... Happy Motoring.
[driving2]

 

[rjp325i]

Slotted is preferred by most BMWs. Cross drilled rotors have a tendency to develop heat cracks surrounding the holes as well as acting like a cheese grater on your pads especially if you track the car. The cross drilled do look nice tho. When I had my E30 prior to my current E46 I used slotted rotors with much satisfaction as they also helped shed water in the wet. When the time comes to change out my brakes (when its out of warranty & free maintenance) I will opt for slotted rotors. Hope this helps you in your decision making.
Good luck in your choice.

 

[zman]

Since brakes is one of the vital part of car safty, do you have to check with your insurance if it is Ok to change car's brakes other than what the manufacture suggested?

I like to know the answer of insurance companies because it may void your insurance coverage. [read]

 

[Zchild]

Hey Zman, I got this information from the TireRack folks concerning brakes and they're replacement... I've always done my own brakes whenever time permits and have never called my insurance company to ask about brakes or any other parts for that matter. I suppose if my bimmer crashed and it could be determined that my brakes were faulty I would be held accountable, however if it was proven that I was at fault then I would be held responible whatever the cause or safety state of my vehicle. I was just rear-ended by a lady in Toyota Camry, the womans insurance company didn't care about her brakes, they cut me a check for my damages and fixed her vehicle.

BRAKES ARE A SAFETY CRITICAL PART OF A MOTOR VEHICLE

Brake components should be installed by a competent mechanic in a professional manner. Any incorrect installation of brake components can cause a major safety problem or an accident. If you are not a competent and qualified mechanic you should not attempt to install these products, but should take the vehicle to a vehicle dealer or competent automotive mechanic for their installation. In some cases, servicing or replacing brake hardware at the time of pad or rotor installation may also be required.

Disc brake pads and rotors are wear items and as such, should be inspected regularly and replaced as necessary.

Street and Highway Use

Brake pads should typically be replaced when approximately 1/8" to 3/16" of friction material remains on the steel backing plate.

Brake rotors should be replaced before their thickness has reached the prescribed "Worn Rotor Minimum Thickness" limit (expressed in millimeters) engraved on the edge of the brake disc.

Plain brake rotors may be turned on a brake lathe to remove scoring and to true the disc surfaces until this minimum thickness has been reached. Drilled and slotted rotors may not be able to be turned and should be replaced if they become scored.

[driving2]

 

[Kirby]

I use EBC Green Stuff pads on my 325i for autocross. A side benefit is lower dust compared to stock pads.

Here is what I consider to be an excellet tech article about brake mods.

http://www.scirocco.org/faq/brakes/pulpfriction/pfpage1.html

Specifically regarding slotted vs. drilled rotors. But remember, for typical street use, slotted rotors don't gain you much of anything except faster pad wear.

===========================================================

Those Poor Rotors
Let's look to some common rotor "modification" and "performance" upgrades that you may have been exposed to. We'll try to separate the marketing from the engineering: Bigger rotors will make your friends think you are cool, bigger rotors look sexy, but bigger rotors do not stop the car. What a bigger rotor will do is lower the overall operating temperature of the brakes--which is a GREAT idea IF your temperatures are causing problems with other parts of the braking system.

Take, for example, a Formula 500 racer, a small 800-pound, single-seat formula car. While the brakes are certainly much smaller than those found on a 3000-pound GT1 Camaro, that does not necessarily mean that they need to be made larger. In fact, installing a GT1 brake package onto our formula car would probably do more harm than good. That's a lot of steel hanging on the wheel that needs to accelerate each time the gas pedal is pushed. So the motto of this story is bigger is better until your temperatures are under control. After that point, you are doing more harm than good, unless you really like the look. (And hey, some of us do.)

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." These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of friction. The holes were implemented to give the gasses somewhere to go. It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads.

For this reason, the holes have carried over more as a design feature than a performance feature. 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.

The one glaring exception here is in the rare situation where the rotors are so oversized that they need to be drilled like Swiss cheese. (Look at any performance motorcycle or lighter formula car, for an example.) While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remember that nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operating temperatures and longer brake pad life, at the expense of higher weight. It's all about tradeoffs.

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?)

 

[zman]

My intention here is not to criticize your competent level, Zchild. I too have always done my own brake on my old cars.

I said what I said because of my friend's experience. He has all the knowledge about his car and how to replace its parts. He is a competent mechanic and always works on his car in a professional manner. He made some changes on his car (M3) and he was proud it. He always brags about it until one day he had an accident. A lady ran into his car while he was sitting still on the stop sign. It was clearly the lady fault. He brought it to his insurance for estimate and go through the regular process. While the lady insurance at the end paid for the damages, his insurance canceled his policy because he altered his cars parts with high performance parts himself. Had that accident been his fault, his insurance would not cover any damages.

I guess the lesson learned for me from my friend’s experience is to never replace those car vital parts with other than manufacture suggested parts IF you want to do it yourself. IF you do want to replace them with different parts, make sure they are performed by licensed mechanics and keep the receipt as proof. Even then, you probably would have a hard time to proof to the insurance company that the installed parts are as good as or better than what manufacture suggested parts.

 

[Section_8]

Brembo aftermarket 'OEM' Rotors, Hawk HPS pads all around, fluid for flush ->$300 All purchased online, much less expensive than going to a stealership. If you want to stay strictly OEM, you can still save money on getting the parts yourself, check out www.pelicanparts.com and other OEM BMW parts resources.

Aftermarket parts are fine with insurance as long as they are DOT approved. Yes - you can upgrade your brakes and be fine not only with your warranty, but insurance. What that means is: Don't go buy 'drilled' rotors from Joe Bob who got OEM ones, drilled them himself, then sells them on Ebay for a quick buck.


Theres the quick and dirty for ya.

 

[Kirby]

... Had that accident been his fault, his insurance would not cover any damages.

Only if his insurance contract explicitly specified that he cannot work on his car and/or install high performance parts.

Otherwise, this would be a great reason for suing an insurance company.