Can I machine/turn my rotors?

[jbripps]

Hi all,

I'm new here, so hello. Anyhow, I'm going to be replacing my brake pads all around, and have recently heard that BMW rotors can't be machined? Is this true? If so, what's the best source for rotors? I have been advised to use a fine sandpaper to dull them.

I have a 1999 323i, which is the new body style.

thanks,

 

[Big Daddy]

They can be machined although BMW recommends against it. That is one reason that BMW keeps rotor prices down, so that you can replace them. I would not machine them, if they are warped, pitted or grooved I would replace them. Why do you need to "Dull" them? I would get a set of gas slotted ATE, Brembo, or similar rotors. Frozen Rotors are very good as well, I have a set on my roadster. My 318is is running ATE Gas Slotted!

 

[jonnyz16]

Don't go cheap on the brakes . Rotors might not be that much for your car .

 

[William330]

They can be machined although BMW recommends against it.

This is the first I am hearing of this.

Is BMW the only real-world (i.e., not Ferrari) manufacturer to have this approach?

What makes BMW rotors more special than the rotors of the other 10,000 car
models on the road?

My 330Ci rotors aren't even vented, they look pretty generic to me.

 

[Big Daddy]

Here are some links about turning rotors:

Frozen Rotors

Garage Boy

Kolamotorsport

I was told that BMW rotors are soft. Hope these help.

 

[AZRobert]

This is the first I am hearing of this.

Is BMW the only real-world (i.e., not Ferrari) manufacturer to have this approach?

What makes BMW rotors more special than the rotors of the other 10,000 car
models on the road?

Many european, and even some asian manufacturers do this. I think it's just to insure braking performance. Most home (shade-tree) mechanics will just "pad slap" their vehicle when the brakes begin to squeak (without even turning the rotors, because thay don't have the lathe). If you don't AT LEAST turn the rotors (not sand them) you cannot ensure a smooth,even braking surface for the new pads (new pads also need to be 'seated' also). Merely 'sanding' the surface does not "true" the rotors. By encouraging rotor replacement (by making them inexpensive) manufacturers are promoting continued brake performance for thier performance oriented vehicle.

[/QUOTE]My 330Ci rotors aren't even vented, they look pretty generic to me. [/QUOTE]

Your rotors (all 4) are vented. They may not be drilled, or sloted like some aftermarket alternatives. Vented means that both sides of the braking surfaces (of the rotors) are seperated by vanes that allows air to circulated to aid in the cooling of the rotors. In the older E30's (like mine), only the front discs are vented - the rear discs are solid.

 

[Kirby]

This is the first I am hearing of this.

Is BMW the only real-world (i.e., not Ferrari) manufacturer to have this approach?

What makes BMW rotors more special than the rotors of the other 10,000 car
models on the road?

My 330Ci rotors aren't even vented, they look pretty generic to me.

Volvo has the same recomendations as what has been discussed above. And like Big Daddy said, I was told that Volvo OEM rotors are soft so that you have to replace them, not turn them. It's not a rip off scheme to sell parts, they use soft rotors for better braking performance and they feel that replacing them is the right method of maintenance, just like you would replace pads, shocks, etc when they are worn out. It's just a different philosophy than most of the US manufacturers.

I was going through Volvo rotors every 20K miles. I chose to buy aftermarket Brembo rotors when I had 40K on the car. It now has 200K on the car, 160K on the Brembos, with very little wear.

 

[William330]

Thanks for the additional info.

I once paid almost $500 for a pair of Nissan 300ZX rotors.

How much are factory BMW E46 rotors?

I've seen them at bavauto.com for about $400 / pair for vented + drilled rotors.

 

[Zchild]

I paid $379.00 total for new Zimmerman Cross Drilled rotors front and rear, and Pagid Pads front and rear plus new sensors front and rear. I got all of the parts from ImportedCarParts.com. It took me about 4 hours of work to do the entire job. I did have to spray an acrylic resin remover on each rotor before installation to remove the acrylic coating. Good luck and Happy motoring.

 

[William330]

I paid $379.00 total for new Zimmerman Cross Drilled rotors front and rear, and Pagid Pads front and rear plus new sensors front and rear. I got all of the parts from ImportedCarParts.com. It took me about 4 hours of work to do the entire job. I did have to spray an acrylic resin remover on each rotor before installation to remove the acrylic coating. Good luck and Happy motoring.

That sounds kinda cheap, are these name-brand products?

Are the brake sensors supposed to be replaced with the discs?

It's good that you did it yourself.

 

[Zchild]

William330, I researched all of the parts prior to find the best recommended brake parts on the market. I discovered the Zimmerman Cross Drilled rotors where the best because they prevent brake freeze by allowing air to flow between rotors and pads so brakes do not lock during hard braking. I also discovered that the Pagid was the most recommended pad on the market. The next step was the most difficult and time consuming. Shopping for the best price for the best parts. The higher end parts shops i.e. Bavarian and Bimmertoys wanted much more for the same brands. I then began simple searches of the net and finally found shops like Importedparts.com and BMW Parts wholesale. My mechanic whom I work hand in hand with for difficult jobs instructed me to change the sensors with the pad and rotor change. He also said it was an easy enough job to do myself. Good Luck and Happy motoring.