Replacing rotors
 

I just replaced the front pads and rotors on my 99 E430. Based on others comments I was concerned that the rotors would be siezed on; in fact both rotors were broken around the retaining screws and so with a small tap fell off. To be specific there was a conical crack running from the front face of the rotor just outside the recess for the head of the retaining bolt through the rotor to the back so that when you pulled the rotor off a washer like piece of rotor fell out.

Maybe the retaining bolts had been over torqued or maybe the old rotors were out of spec.

I realize this isn't a big deal (the wheel bolts do the work) but wondered if anyone else had seen the same?

Peter

Over-torquing the retaining screw would cause the bearings to wear quickly and possible spindle damage. This crack you mention would most likely be from pot holes in the road, over-torquing of the lug nuts, or a combination of the two. Be careful at tire centres: Some of these guys go overboard w/impact tools!

Sounds like a tire jocky at one of those chain stores got to them with an impact gun. The local Town Fair Tire is famous for this, I swear they set the gun's for 200+ foot pounds.:rolleyes:

toque spec for reatining screws
 

What is the torque spec for rotor retaining screws. Im unclear how over doing it could wear bearings. what gives:o

I believe the torque spec on that screw is only a few inch-pounds, and don't see how over-torquing that little guy could do anything to a rotor or bearing.

Not much, but it wasn't the retaining screw that cracked them. Just tighten it a bit with a 1/4 drive.

I have a 99 E430 as well and just replaced the front rotors and pads. Now I have a vibration in the steering wheel anytime I apply the brakes. Would appreciate any suggestions as what might be causing this. Thanks......Highwater

I would first check the rotors for runout. Remove the caliper, place something stationary up against the edge of the rotor, spin it and see if it is running true.

If I found one that was out of round I would try removing the rotor and cleaning the hub and back of the rotor. There may be some debris on the mating surface. If not, you simply have a bad rotor.

If I couldn't detect a rotor that was not spinning true, I would try cleaning both hubs. If the problem is still there... Replace the rotors again...

Good luck!

Thanks SPEACE. Is it possible to turn the rotors if they are not true?

Highwater

It is not recommended to turn MB rotors, but some do. I turned a pair that were nearly new, but had been "glazed" by some EBC Green Kevlar pads I tried. They lived out the rest of their service just fine!

If your rotors are new, why not return them as defective?

I hold high hopes that you will find some debris behind one of the rotors.

This is uncommon, but if a wheel bearing is very loose it can make the wheels shake when braking, but you would have had that going on before you replaced the rotors. When I have a front wheel off the ground I always try to rock it from top to bottom. If it rocks freely there is a problem; check the wheel bearing, and ball joint. If it rocks side to side there is slack in the tie rods.

I'm sure you will find the problem. There aren't many things that can cause this!

skhagen, brake disc retaining screws should be torqued to 7 ft/lbs ... if you're going by the book.

Yes, this screw would break before it could be tightened enough to do damage.

What is the wear pattern of the brake pads? If one pad was pushing more than the other, it could have created the forces necessary for this fracture pattern.

Does the fracture surface have shiny (micropolished) dark corrosion on the surface. If so, this is a good indication of metal fatigue versus bulk (single event) fracture.

Thanks for the response. Im thinking 280 was refering to the wheel bearing nut.
On my W210 I found that the bearing adjustment plays a major part in new brake systems. After my brake job I experienced vibration aswell and found that the bearings had been adjusted loosely or just needed attention, causing vibration. Before it didnt and after it did.
Logic dictates unlikely but the more I read the more I realise murphy's law exists. Pack and adjust the bearings(correctly) before you buy anything.

OOPS! By "screw" I meant to say the bearing retaining nut (obviously held in place by the screw) if too tight, could cause bearing wear.........................................