My 2010 XF Premium is truly a gem, it is stinkin fast when you want it to be and all fun all the time, even back and forth to work is a joy (what happens when I get there is another story).

Shortly after I got the car, the front brakes have "squeeked" intermittently, this became more and more pronounced as the miles piled up. Kept telling the dealership that this was unacceptable, but they kept insisting that there was nothing wrong with the brakes (in spec, etc).

Then after my winter tires were dismounted and my summers were put on (yes I did rush the season somewhat) the car developed a vibration, back to the dealer for another spin balance and was told everything was "ok". The vibration continued, they x'ed the tires and put the fronts on the rear. The vibration continued although to a lesser degree.

Back to the dealer, now the two front wheels have a slight "dent", they say it must have been a pothole, possible but who knows? I think I would have remembered hitting a pothole and they even said they were "surprised" the tires did not bubble if I hit a pot hole hard enough to "dent" the two front wheels.

They need to "straighten" 3 of the 4 wheels on the car, cost to me $450 plus the rebalancing. OK that is now done, the dealership then replaced the front rotors (slight pulsating) and pads, at no cost. I am happy to report the car is squeek free and vibration free. I still think the dealership did not tell me everything about those wheels.

Sorry for the long story. My service advisor and his boss made every effort to keep me informed. But they do need to improve their "loaner" fleet from Enterprise, terrible.

 

The wheels are as soft as butter. I've had mine (front wheels) returned to round twice. I avoid potholes but obviously as the dealer has agreed the wheels are not strong enough.

The issue is with the size of the brakes.Reality is that Jaguar could have designed smaller, more efficient brakes if they could have been bothered. Porsche manage to brake much faster cars repeatedly on track days with discs that only require 18" or 19" wheels not 20" wheels. Let's hope they've hired some brake engineers to fix the problem for the next Gen XF.

 

The wheel size is cosmetic, except for the XF R. 18 inch wheels fit the standard XF brakes and even some 17 inchers.

Porsche 911 brake well mainly because they hang the engine off the back of the car and fit very grippy tires. As you are aware, the tires actually stop the car, the brakes are there to dissipate the heat. Also, if you put hard springs and stiff shock absorbers onto a car it will brake shorter, generally speaking due to improved weight transfer effects (i.e. all four wheels can do more of the braking if the nose doesn't dive).

Size of the brake disc has very little to do with braking effectiveness or F1 cars would be in deep trouble with their tiny wheels.

 

Which means the Jaguar needs much better tires to improve braking and reduce the brake discs to fit smaller lighter wheels. It's lazy engineering where they are currently.

 

I think he was refering to the noise and not how effective the brakes are. You can have brakes that stop on a dime, but can still make noise. I do think the weight of the caliper, the whole set up in general is affecting the "noise" generated while braking.

 

Consistent brake squeal or squeak is not acceptable with street brakes. Dealers try to tell you this is normal and it is not. However, it is usually not a manufacturing issue.

Brake squeak or squeal usually results from vibrations at the edges of the pads due to the edges of the pads sticking and slipping in a harmonic way, amplified by the rotors. The most usual reason for this is insufficiently hard braking for long periods, which may be periodically needed to ensure the brake pads are wearing properly. Occasionally dust or debris can cause a squeal or squeak but that is occasional and will last only until the dust or debris is ejected from the brake. This sort of noise also will not be progressive nor permanent.

Your symptoms suggest that you may be braking too lightly for long periods as in stop and go driving in heavy traffic. The cure for this is to find an empty stretch of road and re-bed the brake pads by accelerating and braking very hard for about 5-10 sessions each session should be interrupted by short periods of cruising to allow the brakes to stay cool. Get the brakes too hot and you get another problem. It is best not to stop between sessions to avoid pad deposition issues ("marking" of the disc) which will produce "warped" disc symptoms. You are trying to wear a bit off the pads in a short time to try and re-contour the edges of the pads and clean up any uneven pad deposition on the rotors which may be exciting the vibration which causes the squeal. Don't apply the park brake until the brakes have cooled off, about ten minutes of cruising if you get the brakes properly hot during the bedding in.

If your brakes still squeak after they have been properly cleaned up then they need to be repaired. Either the pads are worn in incorrectly (your problem) or the pads may have been installed without adequate anti squeal lubrication or shims (whichever Jaguar uses) which would be a manufacturing issue and therefore a warranty item. The dealer is not likely going to accept a warranty claim on brakes without as bit of a fight as they are not covered: wear item.

 

I've heard there has been some success reducing brake squeak on the XF's by replacing the anti-rattle tension spring on the front calipers with parts meant for the single piston supercharged 4.2L caliper. Supercharged part # is C2C37534.

Cheers,

 

Jagular

Thanks for your insights. Yes the car is driven daily in traffic. I did try the approach you are referring to, get the brakes hot. Since they replaced the pads and rotors under warranty, the brake feel is better and I have tried to give the brakes a workout.

I have always been told that the first 100 miles is critical and to use them normally, if not somewhat hard to properly seat them.

I am grateful to the dealer for doing the work under warranty. Again, your insights are appreciated.

 

The top model already uses Pirelli or Continental's top tire line. The reported stopping distances for the XF (and other Jaguar models) indicate that the brakes are among the best performing brakes of any cars in comparable class.

Size of the rotors by itself is not particularly relevant.

Brakes only need to be as powerful as the grippiest tire expected to be installed.

Rotor size, pad material, caliper piston size, number of pistons and relative size front to rear are all interrelated variables. there is no one combination that is "better" than another.

For street brakes large rotors help by being able to maintain a relatively cool temperature under widely varying conditions. The smaller the rotor the hotter the temperature it will operate at when used hard. Larger rotors increase the range of cool running important for street brakes to perform as well on the first application as the fifth.

Otherwise, large wheels and large brakes are just marketing.