I have an SV8, its great no doubt, but a couple of times when I drove it to the limits (I MEAN TO THE LIMITS), the brakes start to squeak. I sent it to the dealer, and they gave the worst answer a dealer could give "Its Normal". Well, they are still squeaking after 30 minutes of hard driving, and that should not be "Normal". Has anyone experienced this, or know anything about it.
thanks

 

just go in and make them replace the pads..

 

How many miles did you put on the brakes before you "took it to the limits"?

Brake squeal results from harmonic amplification of the pad sticking to the disc and then releasing from the disc thousands of times per second. Most common cause of this for street brakes is failure to bed the brake pads in before using them hard.

Brake pads are usually installed with a little lubricant on the steel backing plate to allow the pad to vibrate independently of the caliper which can reduce the tendency to squeal.

However, if you wear the pads suddenly to a sharp edge they will squeal.

Try making a series of hard stops from 60 mph (100 km/hr) allowing the brakes to cool a bit between stops and don't actually stop just slow to 10 mph and then accelerate away again. This will help clean up the rotors and maybe reduce the sharp edge on the pads which is the cause of the noise.

Brake pads deposit pad material onto the faces of the rotors which increases the coefficient of friction between the iron or steel disc and the pads. Using the brakes very hard before this deposition has been completed evenly can cause squealing for a long time.

Although brake squeal is common and normal it isn't acceptable on a modern car. However, most brake squeal is caused by driver error, not defective pads.

 

Jagular, Thanks, this is the first answer I heard that makes complete sense. You are correct, I did not give the brakes any time "bed" as you put it. I will try and do the stops from 60 mph. If the noise continues, which I can't stand, do I have to change just the brakes or the disk as well.

 

Jagular, I went ahead and changed the front brakes that were making the sound, how long would you say the break in period for the new brakes should be. thanks

 

My personal rule of thumb is 1,000 km (600 miles) to bed in new brakes, a new clutch or new tires. Certainly, 1,500 km which is the engine break in would be sufficient.

Ironically, heavy traffic is a good place to bed in brakes as long as you also do several very firm stops (well "almost stops" works better as it is not good to stop the pads on one spot on the disc when they are very hot)from highway speeds at some point.

The key is to allow the pads to deposit some of their material onto the discs and to allow the pads to conform to the tiny irregularities between the machined surfaces of the new pads and the rotors. Modern OEM quality rotors are actually honed with a cross hatch these days to speed up this important process.

Brakes improve in performance rapidly in the first few hundred kilometers of driving as the pad material gets embedded into the rotor surface.

Clutch facings need the same care to work properly and last long. As the ZF 6 spd in the Jaguar makes extensive use of its lockup clutch it is wise to break that in also before driving hard.

Tires need the relatively smooth mold surface to be scrubbed off the tread surface before they give full designed traction.

Jaguar also has a specific run in period for the rear axle (differential). You are supposed to drive gently for even longer than the engine break in to allow the differential time to "bed in". The XF is the first car I've owned that specifies a break in period for the differential.