Brake problem! need advice!
 

MY X5 is a 2004 4.4. At 7k miles my rotors warped so i brought it in and they changed only the rotors not pads. The brakes didnt grab as good as new but not that bad so i didnt go back to the stealer. Now at 13K they warped again. I went back and they changed only the rotors again. not pads. I got in and the brakes barely grabbed. It got better over the next few hundred miles. But no where near the way it grabbed new. then im on the highway today and a 530i was messing with me so we both punched it. We got into traffic so i hit the brakes and they started getting loud like a rubbing sound and started to fade immediately i had only half the stopping power as usual. Then when i got home i looked at the rotors and there was a bright blue ring around the rotor. so it must of got hot as hell. What the hell is going on here. Does anyone know and can help me. These things fade so easily know. i hate it.

YOU ABSOLUTELY NEVER CHANGE THE BRAKE ROTORS WITHOUT CHANGING THE PADS!!! (pad cost is minimal; dealer is being petty). It is the worn pads which are damaging the new rotors, and they will continue to do so until they are R&R. Get the to another dealer, as the one your using doesn't know his A$$ from that hole in the ground!

Thats what i thought. and i told them that and they said no we only change pads if they are worn out they will not damage rotors. no how do i get them to do that with out going to another dealer. Anyone else evar have this happen to them.

Your dealer is "denying the obvious". If a disk has to be replaced it’s because its surface is damaged. Since the pads interface INTIMATELY with the disk any damage to the disk WILL damage the pads. Replacing the disk then allows the damaged, unevenly worn pads to damage the new disk. Your ineffectual braking subsequent to disk replacement was due to the unevenly worn pads not making full contact with the new disk and damaging the new disk as they wore the disk to match their damaged surface.

If the dealer simply doesn't get it, you NEED to find another dealer because this brake problem is just symptomatic of MANY other matters they won't get!

Contact BMW N/A and explain the situation to them. No way your rotors should be warping in that short amount of time unless your doing some serious auto-xing with your 4.4. There is something else that may be wrong but then again, the dealers should have changed the pads also.

honestly i dont know what the heck is going on with this X5. Its just had so many problems since new. Has anyone else ever had warped rotors at 7k then again at 13k. Now i dont even know if the second time was because of the original problem or if it was from replacing the rotor and not the pads.

only if they were machined rather than replaced.

no there were definatley replaced

The are three main reasons I get here on problems with warped brake discs!

1)Cold water reaching a very hot disc!Breaking very hard in the rain or washing the car when the discs are hot.

2)Incorrect disk installation!Sometimes mechanics take discs off and just put the new ones straight on,when they should clean/polish the wheel hub surface before putting new disc in!THIS OBVIOUSLY DOESNT APPLY IN YOUR FIRST CASE since the discs were new!

3)warped wheel hubs!We get a lot of problems on HONDAS !In this case its not the discs that are warped!

During the years, I havent got many cases here of pads damaging the discs!

The problem with old pads with new rotors is that the old pads have formed to the irregularities of the old rotor surface. Now the irregularities of the old pads don't line up with the relatively flat surface of the new rotors. So now you only have a portion of the pad material contacting the rotors. You described this as having half the braking power.

Depending on how irregular the old pad surfaces are you may be able to remedy this by going through the proper pad bedding procedure several times. Hopefully the pads will reform to the new surface enough to get proper braking.

It's a good idea to go through the bedding procedure with new rotors, even if you didn't notice any problems. The bedding procedure transfers pad material to the rotors for proper braking. So when you change out the rotors you should do it again.

G/L

There isn't much mention here of the pads being properly bedded in, both when the vehicle was new, and when the rotors were replaced. Rayxi mentioned it, and I agree with those comments, but I think it should be emphasized.

The sense of having less braking power is likely most related to the lack of bedding in, and is not related to the surface area of the pad that is in contact with the rotor. Braking torque is a function of clamping force and rotor diameter, not of brake pad contact area. Clamping force is a calculation based on the hydraulic system specifications. This all assumes that the pads have been bedded in, and that the brake rotor surface has had some pad material transferred to it.

The variable I left out of the previous example is pad coefficient of friction. It varies greatly with pad selection, and can vary with temperature. But, given that there is no mention of changing to a different pad composition, I would look to the bedding in step.

The 'warping' may have to do with the brakes being 'ridden hard and put away wet' to use an old horse analogy. The driving habits being described may include use that crosses over into abuse for the composition of the standard OEM pads, and the vehicle may have been parked with the brakes very hot; that would result in pad material adhering to the rotor as the pads remain in contact with the hot rotor. This results in a problem that is often referred to as rotors being warped. This can also be related to water hitting the hot disks, as Powers1 mentioned, causing uneven cooling and resulting transfer of pad material.

DinanM3, the X5 is much heavier than your M cars. Have you considered whether the brakes may be being overheated and that this may be part of the problem? It seems to me that the rotors aren't the problem, as they were replaced and the same problem re-occurred. That makes the rotors sound like a symptom, not a cause.

I also don't agree that you always must change pads when rotors are changed. Often, yes, But if the pads are near new, and are worn evenly, but are glazed, deglazing them can be sufficient. (glazing is usually heat related) Then, they need to be bedded in.

Hope this helps.

Dinan, does your dealer properly torque the lug bolts when they perform the service? Aside from all the other issues with old pads/new rotors mentioned above, this is one of the most common issues with alloy wheel/rotor combinations. I always retorque the lugs after the delaer has my car- whether its the X or anything else. Typical technicians will attach the lugs with an impact and some use a "wobble stick" The only correct way to attach the wheels is with a click or beam type torque wrench.

I generally have no problems with rotor warpage and haven't for a long time. I have had some "sensitive rotor vehicles" most notably a 1995 and 2000 Jeep grand cherokee ltd. and was able to get 80000+ miles from a set of rotors without the dreaded brake pulsation. I actually got into an argument at a delaership (Pontiac) with the service manager about this issue and he stated that they don't have time to hand torque wheels. I then asked him if they use wobble sticks for their rods, mains and head gaskets. He said no- they use a torque wrench- why? because its more accurate. I left and never went back. I have also seen techs guess by how the impact sounds whether they have the torque correct.