Wow. I would have a few questions but there are a few things I can share. First of all Volkswagen, BMW, and General Motors are the three least customer-friendly manufacturers in the world, mainly due to their business practices that squeeze money from their customers after the sale. For example, BMW will not release paint codes to any independent body shop. If they want to match an existing paint color, they have to buy the paint from BMW and it's very expensive. That does nothing to benefit the owner. BMW also will not release their repair information to any popular aftermarket services such as AllData and Mitchell-On-Demand. They want all repairs to go back to the dealer which is extremely selfish. GM has similar practices and they are losing a lot of repeat customers because of that.
No brake rotors should cost $700.00. A new rotor for a Dodge Viper costs less than 50 bucks. BMW must be awfully proud of their parts to charge that much. Something to consider the next time you're car shopping, and you might mention that to the salesman next time you're there.
As for insisting you buy new rotors during a brake job, a couple more things come to mind. One is labor cost. Since most new rotors cost less than 20 bucks, at least for small cars, it is more cost effective to replace them rather than to machine the old ones. When you consider that the cutting bits on the brake lathe get dull and must be replaced quite often, and the mechanic has to set everything up and do the machining, those are costs that can be easily offset by just popping new rotors on the car, ... But not for $700.00!
Next, there is a gray area when measuring the thickness of the rotors that can lead to some confusion. As I mentioned earlier but didn't explain real well, there are two measurements that are published by all manufacturers. They are "machine to" and "discard". Most commonly the machine to spec. Is.030" thicker than the discard spec. I'll use a common rotor I'm familiar with on my Caravan. It can be legally machined down to.830". Going thinner than that will almost always not cause a problem, however, if the other guy runs a red light and you hit him, a good lawyer's investigator is going to examine your car very closely and he WILL find that under-size rotor. (They really love to find any modification to ride height, wheels and tires, and anything that affects braking and handling). That guy's lawyer is going to convince a jury that you are partly at fault for the crash because even though his client admits to running the red light, you were less able to avoid the crash due to the compromised braking system. Every mechanic has heard the horror stories about one of them sitting in a courtroom trying to explain why they cut that rotor beyond the published legal limit. THAT'S what every mechanic and every shop owner has in the back of their mind when they work on your car. Even if your rotors are legal when the car leaves the shop, they have no way of knowing what happens later. I have my own brake lathe and I could cut my own rotors undersize, then if I'm in a crash, I could still blame it on the shop that did my brake work a year ago. If they sold me new rotors, there's no way I could blame them. They have proof they followed procedures and the car was legal when it left their shop. With used rotors, all they have is the mechanic's documentation on the repair order stating the finished thickness, and that can be fudged.
Now, that might be stretching it a bit, but every shop has had someone sitting in a courtroom at some point for similar things. Getting back to my example, the mechanic can only cut that rotor to no less than.830", but the discard spec. Is.800". That means the rotor can be allowed to wear another.030" after it is put back on the car. That will never happen from normal braking as long as the pads aren't allowed to wear down so far that they start grinding metal-on-metal. At the next brake job the rotor will be too thin to machine and it will have to be replaced.
Another point of confusion is "lateral runout". Most people understand "thickness variation". That's shown on the left side of my sad drawing. We measure at four to six places around the rotor and compare the readings. The measurements between the red arrows, the green arrows, and a few other places must be the same. When they are not, we will feel the brake pedal pulsate up and down when we apply the brakes. No used brake rotor is perfect and that is one of the reasons we always machine them as part of a conscientious brake job, (as long as they're thick enough). Unless there was a complaint of a really bad pedal pulsation, we don't bother to measure for this because it is usually so insignificant and it will be corrected by the machining process.
What's harder to understand is that lateral runout. In my drawing on the right, the mounting surface, (shown by the orange bracket), is obviously warped. It is common for the thickness variation to be acceptable but this warpage will cause the rotor to wobble. During braking, it will tug back and forth on the brake caliper and on the steering linkage so you'll feel it in the steering wheel, but not necessarily on the brake pedal. This is relatively time-consuming to measure on the car because many rotors flop around once the wheel is removed that was holding it tightly in place. The setup to measure lateral runout shows the same thing that will become apparent when the rotor is mounted on the brake lathe. All rotors have some lateral runout, it's just very little when you can't feel it, but when we start to cut it on the lathe, metal is going to be removed from the areas shown in blue first. Once those high spots are removed from each side, THEN we can measure it accurately for thickness. At that point it will be trued up but by the time the wobble is machined out, it may be beyond the "machine to" spec. We can't know that until we get there.
There's two ways to approach this. Some mechanics just keep on taking more and more passes until the high spots are gone and the friction surfaces have the proper finish, then they measure it and find out it's too thin and has to be replaced. An unscrupulous mechanic could just keep on cutting and cutting much more than necessary to make it undersize so you have to buy a new rotor. More experienced mechanics will measure the thickness after every one or two passes, and if they reach the machine to spec. They stop right there so you can see that it wasn't cutting all the way around so it's not true yet but can't be machined any further.
By the time lateral runout is taken care of and we find out the rotor needs to be replaced, we've spent a lot of time on the car that was basically wasted. That's just one of the many things that get factored in when the shops calculate what they have to charge for their hourly labor rate. If they can keep those costs down and follow procedures that make the mechanics more efficient and more productive, they can charge less per hour, and that makes their shop more attractive to customers than the competitor down the road. BMW, and especially GM haven't learned that yet. GM, like one fellow I worked for once, try to squeeze as much from a customer the first time because "they aren't coming back a second time". That's how they remain profitable even though sales of their new cars is way down.
Okay, enough of my ranting. One more thing to keep in mind is that service advisers usually never were mechanics and they don't know much more about cars than their customers know. Their job is translate what the mechanic has found into words the customer can understand, and very often things get mixed up unintentionally. Sometimes they have to purposely dumb down or simplify some explanations in hopes the customer will understand what they're trying to say. Along with that they have guidelines and policies they have to follow which resulted from past experiences. The dealership owner may have told them to push really hard to get customers to buy new rotors for any of the reasons I explained, to save you money in the long run, to save them the cost of machining, to prevent fraud on their mechanics part, to reduce the chance of lawsuits or complaints, or even just to sell you more stuff. You should always have the right to refuse a recommended part or service but not just because of the additional cost. You should only do that when you are an informed customer, you understand why they're recommending that part or service, and they can explain and document why that is needed. Some people refuse everything that is recommended because "they know better". Some people just think they're stupid when it comes to cars so they go along with whatever is presented to them. There has to be a middle ground.
One final comment about maintenance plans. At the very nice family-owned dealership I used to work for, I overheard way too often "what you need isn't covered". Usually that was with the "extended warranty" companies that were in no way affiliated with any car manufacturer. Some were real good about paying for covered repairs but many required so much documentation and they had other hoops to jump through. They were looking for any reason to avoid paying a claim. After all, every claim they paid meant that much less profit. A very big percentage of the cost of the policy, often as high as 80 percent, goes back to the person who sold you the contract as a commission. That doesn't leave much to fund the actual repairs. One common strategy my service advisers suggested was to cancel the policy and get a pro-rated refund and put that money toward the repair when the company refused to pay for it. Another common strategy is to make you pay for the repairs, the you submit the claim to get reimbursed. Dealerships often wait months to receive the payment. Angry customers on the phone get a lot faster results.
There's another solution to your concern if the mechanic had a valid reason to feel you needed new rotors. Lie! When a part would solve a customer's complaint on a vehicle in warranty, but the manufacturer says that part isn't bad enough to warrant replacement, we had to lie and document it as having more wear than it really did. The bottom line is that was the part needed to solve a problem. We were solving that problem on the manufacturer's product and they want satisfied owners for good word-of-mouth advertising. It's under warranty so the manufacturer should pay for the repairs. Plus, the manufacturer was supplying the parts which cost them a whole lot less than if we had to buy them locally. Everyone wins, but we had to fib because we disagreed on what was considered bad enough to replace. I suspect your mechanic would have found a way to say the rotors were bad enough to replace if they really needed to be.
Tuesday, May 22nd, 2012 AT 12:54 AM
