CPP rotors

I was just wondering if anybody else has had problems with CPP's rotors being untrue? I put everything on and spun my wheel and the rotor hits the brake pads in one spot. Took them to a shop and they said that they were 7 thousandths high in one spot.

No, but if you give 'em a call, I'm sure they'll send you a replacement.

Typical tolerance for rotor run out is about 0.006 inch. You say you have 0.007inch. That is more than I would like to see. I doubt it will be noticeable or cause a problem while you are driving. Is the rotor zinc plated? Zinc can contribute to more run out, but will go away as the zinc is a surface treatment the quickly wears away at the braking surface. If you call CPP we can get it replaced if you like. I’m guessing that it was turned when it was measured and it is not a problem now.

Was this measured on the spindle, or on a brake lathe? On a spindle with the correct wheel bearings is the only way to get a true measurement. If it was on a brake lathe, you may have measured some of the run out of the lathe itself. These are small measurements, about 2 hairs wide. It can be difficult to be accurate at these small values.

Danny Nix
CPP

When I bought my conversion kit from CPP my rotors were .012 out. I didn't even put them on. I had them trued. No problems after that. By the way, not bashing but CPP was indifferent about the problem.

Yes they are zinc plated. I didn't realize that 0.007 was the thickness of 2 human hairs, the right rotor had 0.001 run out. the problem is not the rotors its probably the hub. I talked to Jeff earlier today and he gave me some things to look at. Thanks for the help Danny.

Well I think I found the problem. There is a gap between the rotor and the hub. So what do I do now? send the hub back? Get the hub machined? Or get the opening of the rotor machined bigger? Probably wouldn't be a good idea to use a washer would it?
http://i225.photobucket.com/albums/dd228/carb00/DSC00968.jpg
http://i225.photobucket.com/albums/dd228/carb00/DSC00969.jpg

Well I think I found the problem. There is a gap between the rotor and the hub. So what do I do now? send the hub back? Get the hub machined? Or get the opening of the rotor machined bigger? Probably wouldn't be a good idea to use a washer would it?
http://i225.photobucket.com/albums/dd228/carb00/DSC00968.jpg
http://i225.photobucket.com/albums/dd228/carb00/DSC00969.jpg

The other side of the rotor has a chamfer that allows the rotor to fit flat onto the hub. Install the rotor the correct way.

I recomend driving the car before you get too excited about a small amount of run out. I honestly believe that you will not have any problems. The brakes are designed to work with the rotor moving a small amount. Most rear axles have a large amount of end play yet the brakes work just fine.

My daily driver, a 1986 Porsche, has aluminum hubs. The factoy maitence manuals say to set the cold wheel bearing clearnce at 0.004 inches. Thats not preloaded, but set with a small amount of clearnce. The brake rotor can be moved in and out a little bit. Yet with all this clearnce the car has the second best brakes I have ever driven, the best was my 1970 Porsche.

The point I am trying to get across here, is to drive the car. If your brake pedal is pulsing up and down while you apply them then you have enough run out to be felt. If this pulses enough that the tires lock when you are on the brakes hard then it is a problem. If you get a pulsing pedal, the next step would be to dertimine why, It could be the rear axle. C-clip axles are known to cause a lot of problems with rear disc brakes. That is why we use a floating caliper with the built in parking brake. This type caliper works much better on loose c-clips than a fixed caliper, or one with out a parking brake.

If you want to talk this over, or need som assistance on getting this working right, please call us.

714 522 2000
Danny Nix
CPP

I know that the rotor is on wrong and i'm not worried about the runout on the rotors. But when i put the rotor on and my tires and torque everything down in a criss cross pattern to 70 ft lbs the rotor wobbles like 1/8 of an inch.

Personally. I think you have gone above and beyond your responsibility checking this out, and it is time to return them and get some GOOD ones. Something is not right. You are alot more patient than I would have been. Good Luck.

Since the car can not be driven yet, I would like to try a couple of things.

Do both sides of the car do the same thing, by the same amount?

If you use an ink pen to make a mark on the rotor and the hub where the run out is at its highest point, and then reinstall the rotor on the hub with it rotated close to ½ turn different do either of the marks stay at the highest point of run out? Does the run out remain the same?

I use the round end of a drill bit as a feeler gauge to measure the clearance between the caliper and the rotor in order to measure the gap. What is the largest and smallest gap you measured? This difference in the gap is the run out.

Does the rotor make contact with the caliper bracket?

If you switch the rotors from the left to the right, do you get the same measurements? Do the measurements follow the rotor, or the hub?

Due to the manufacturing processes used, there is a small tolerance allowed in each of the components. It is possible for these tolerances to stack up. But hey should not exceed 0.040” radialy and 0.007” laterally.

I do not believe that there is a going to be problem in the way the brakes perform. If we send out more parts it is highly likely they will be exactly the same as the parts you have now, and we will not have accomplished anything.

If the car is driven, and there is an imbalance, pulsing pedal, or any other problem we will definitely take care of it.

I would like to here from anyone who has driven their car with the CPP 13 inch brake kit especially if they have had any problems with the way the 13 inch kit performs. CPP is unaware of any problems with the performance of our brakes. There will always be some small amount of run out due to manufacturing tolerances, but these tolerances have no noticeable effect on brake performance.

Danny Nix
CPP

7 thousands run out on a rotor is minimal.
very minimal!

I hard stop and heat can move it that much!

7 thousands I do not see as any problem.