Replacing brake discs..

[ss109]

I am going to replace *just* my brake discs with some vented Brembo discs that will work woth my existing caliper, etc. I understand I will have to get some diffrent pads, too. I was wondering if this is a job a do-it-yourselfer can manage or if I should seek professional help. If so, what would be an estimated price for installing 4 new discs?

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'92 300E
'74 Vette

[Aaron]

This is definitely an "easy DIY'er". You will need a 17mm deep impact socket to remove the lug bolts and a 5mm allen head socket to remove the screw which holds the rotor to the hub. In addition, a 19mm to remove the caliper bolts and a 13mm and a 15mm for opening up the caliper to R&R the pads will be needed. The 13mm to unscrew the bolt and the 15mm to apply counterhold with. As far as pads go, I would imagine a set of PBRs or Mintex pads would be the best choice for using cross drilled rotors. Although, unless you do alot of autocrossing or track events, this setup really isn't necessary. Oh, I almost forgot, a pair of larger channel locks to squeeze the piston back into the caliper will also be needed. Ate makes a nice piston reset tool that works in a jiffy if you're constantly changing pads, but the channel locks will be fine for normal use. To change the pads and rotors, you will need to proceed as follows:

Jack up the car and remove the tire. You will see a top and bottom bolt which holds the caliper closed. Put your 15mm on the "inner" part of the bolt to apply counterhold and completely remove the "outer" bottom bolt. Do the same for the top except don't remove the bolt, just loosen it. You can then swing the caliper up and remove the pads. Next, you will want to squeeze the piston back into the caliper with the channel locks (remember to place a rag over the brake fluid resirvoir to abosrb any lost fluid!). Next, let the caliper back down and remove both 19mm bolts that hold the caliper on. Set the caliper out of the way and take the 5mm allen bolt out and the rotor will come off. Don't be afraid to use a little persuasion if it's giving you a hard time. You won't hurt the bearings. Next, prepare your new rotor for installation by spraying brake cleaner on the disc surface and scraping off the protective coating with a razor blade. Install new rotor and reinstall the caliper with the 19mm bolts. Apply some anti-squeal paste to the backs of the pads and place them into the pad guides. Lower the caliper housing down and re-tighten both upper and lower 13mm bolts remembering to use that 15mm for counterhold. Proceed the same for both front wheels. The backs are easier to do as far as replacing the pads. Rather than a floating caliper, they use a fixed one and the pads are held in by a spring clip and two pins. Knock the pins out with a 4mm drift pin and remove the spring clip. Squeeze the pistons back into the caliper using the channel locks on the edge of the brake shoe ears that the pins go through. Remove the caliper mounting bolts and R&R rotor in the same manner as the fronts. The rears might be harder to remove due to pressure from the parking brake shoes. To loosen the tension, you'll have to back off the star wheel inside the hub with a large flat blade screwdriver. Once the new rotors are in place, reinstall caliper and install new pads and spring clip and pins. Pump the brakes up until the pedal gets firm and check the fluid level in the resirvoir. If you need any further assistance, please don't hesitate to drop me an e-mail on the side. Good luck!


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Rgds,
Aaron Greenberg
MB technician
Precision Motorcars, Cincinnati, Ohio
'67 250SE Cabriolet
'77 450SL
'80 300SD
'85 380SE
'89 420SEL
'93 300E 2.8
'74 Jensen Interceptor Mk.III
'81 DeLorean DMC12
'85 BMW 745i Turbo

[jeffsr]

If you replace the rotors, always replace the pads. The old ones are seated to the old rotor faces and can give you shudder, noise and the like. If you're savvy, it's not to hard to do. Have the right tools, be methodical, keep things clean. Don't know what the Brembo rotors go for. I guess you should have an idea about that by now. Also, don't know anything about your mech skills. Replacing rotors is not a difficult job, but it does require some knowledge of disc brake systems. If you have ABS, be careful with the sensors mounted behind the rotors. Good Luck...BTW what's wrong with the stock grippers? My 300's have more than enough stopping power with the stock MBZ brakes.

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Jeff L
1987 300e
1989 300e
1987 BMW 325

[This message has been edited by jeffsr (edited 04-10-2000).]

[phouse]

Whats the torque for the bolt that holds the rotor/disk on.? Will the procedures go for a 98 E430 Sport?

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Peter L. House
1998 Sport E430
Azure Blue

[jeffsr]

Very little torque required. This fastener does not carry any load when the wheel is in place. A educated guess would be around 5-10 ft. lbs., or just tighten 'til it's good and snug..

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Jeff L
1987 300e
1989 300e
1987 BMW 325

[brookspw]

Just replaced the warped rotors (and pads) on my 1991 190E. If you put the new rotors on, and tighten the allen screw it will spin like it has a LOT of runout. My guess is: the allens screw is just for minor alignment. What ACTUALLY holds / mates the rotor to the hub is the lug bolts.

When I put my rotors on and spun it (and saw that it "looked" warped) I just about had a heart attack. I don't know what the torque of the set screw is supposed to be but my guess is that it is not very tight at all. As a matter of fact, if it is too tight it wouldn't let the disc mate with the flange correctly.

By the way, on my just completed test drive it braked (?) like a dream, smooth as silk. I used Mintex pads and ATE rotors from PartsShop.

Somebody confirm my suspicions,

brookspw