Need to replace front rotors. How difficult is this? 1999 M3

It's a very easy DIY. Full set of instructions, diagrams and torque values are on Ron Stygar's website: http://www.unofficialbmw.com/e36/brakes/e36_lets_brake_it.html. Only special tools really needed are a good torque wrench and a set of metric hex bits. If its your first time and you proceed slowly, it might take you an hour to do one rotor after lifting the corner. The other side will go much faster and you can probably get it down close to 1/2 hour.

Probably the hardest part is removing the rotor retaining screw. Due to it's operating environment, if it has not been disturbed (removed) in a while, it tends to get rusted in. Use plenty of penetrating oil (WD-40 or similar) and an impact driver to knock it loose. Be careful about getting oil on working surface of the rotor.

Everything else is a piece of cake. Make sure you use molycoat or another high temp lube on the caliper guide pins. It's important to make sure these are well lubricated to ensure even pad & rotor wear.

Yep, a rubber mallet can come in handy if your rims or rotors are wedded to the hub. I paint a thin layer of anti-seize compound paste on the hub to prevent this from happening in the future. Again, just make sure to keep any and all lubricants off of the rotor surfaces and the lug nut bolts/holes!

Several notes:

1. WD-40 is not a penetrating oil - it won't help with a rusted rotor set screw.

2. Caliper guide pins need to be installed dry as per the TIS. They should be clean, though, so just make sure to wipe them off well. Also note that the torque spec for these is very low.

3. If the rotors are rusted on, a rubber mallet will likely not be enough. Get a 3lb. sledgehammer. It'll be loud but you will be happy you have one. :)

4. Torque spec for the rotor set screw is also very low.

5. The suggestions to use anti-seize are excellent - between the new rotor and the hub and a little bit on the rotor set screw will make your life much easier the next time you replace them.

Dave

My caliper brackets bolts were on so tight/seized I had to use a MAPP torch to get them loose. I covered everything in wet towels, and torched away. The bolts came right out.

My caliper brackets bolts were on so tight/seized I had to use a MAPP torch to get them loose. I covered everything in wet towels, and torched away. The bolts came right out.

If you are talking about the bolts that fasten the brake caliper housing to the steering knuckle, then the torque is indeed high on these- something like 110nm. However, just to be clear to the OP who seemed to be new to this, it is not necessary to remove these bolts or the caliper housings in order to do a rotor or pad change. Only the guide bolts and the brake carrier need to come off.

If you are talking about the bolts that fasten the brake caliper housing to the steering knuckle, then the torque is indeed high on these- something like 110nm. However, just to be clear to the OP who seemed to be new to this, it is not necessary to remove these bolts or the caliper housings in order to do a rotor or pad change. Only the guide bolts and the brake carrier need to come off.

Really? The rotor seemed to catch on the caliper bracket (bracket to the steering knuckle) since there was very little clearance. I just removed it so the rotor could easily be put on and off.

The Bentley never mentioned to do this either, so clearly I'm retarded.

Really? The rotor seemed to catch on the caliper bracket (bracket to the steering knuckle) since there was very little clearance. I just removed it so the rotor could easily be put on and off.

The Bentley never mentioned to do this either, so clearly I'm retarded.

I guess your experience is different than mine, but I have only worked on non-M E36s. I suppose it is possible that the M3 brakes being larger, have less clearance for removing the rotor than the non-Ms. FWIW, I did dismount my Z3 brakes once completely when I painted them and I agree that it was a PIA. I have not touched the brakes on my new M Roadster yet, but I do plan to put in dustless pads sometime this summer, probably Axxis.

I had no problems changing pads or rotors with my 98 M3 or 00 M Roadster by just removing the caliper guide pins and pulling the calipers radially off the rotor.