2011 XF S/C 25,200 miles here.
Just had the rear brake pads replaced, front's still at 50%. Also next day changed all 4 tires as I knew they were pretty much worn out, and Jag service also mentioned.
Tires I did later at my local tires place - Jaguar did not 'push it on me' .

Yes, I like to drive hard from time to time, but would you consider this within 'normal' range for this car?

As I also like to down shift and slow down with the paddles, I thought the pads would last a little longer.
Of course, the 2011 models includes free maintenance, but just curious what to expect for my next one......

 

My '12 is in for Annual Maintenance and other things mentioned in the "Interior Noise" thread..But the tech told me that these XF's will wear-out the rear pads faster than the front..the braking sequence is designed that way to start applying brakes to the rears first to prevent nose dives on braking...makes sense to me..

Could you tell me what kind of tires you HAD on and what you went with as replacements? Thanks

 

Totally normal for this car.

 

Nonsense actually. The car doesn't react to which end brakes first or hardest. Nose dive is a function of weight transfer which is affected by suspension geometry relative to CG and spring rates. In theory a car can be designed to nose up under braking, just as it can be designed to roll into a bend, nobody would because it would be tough to drive but zero dive, squat and roll have been built before now. In fact the latest McLaren MP 4 uses hydraulic pressure to control roll squat and dive allowing just enough to make it feasible for mere mortals to drive. Ayrton Senna's Williams which he drive and then died after crashing had active suspension which pretty much eliminated all these seat of the pants forces and perhaps even the great Senna wasn't quite able to do without those signals. Dive is a function purely of the moment generated by the CG being above the pitch center due to deceleration forces exerted from below the CG. If instead you used an air brake on the roof the car would nose up, whether the air brake were on the hood, roof or trunk lid. It's out on the trunk lid precisely to help counter nose dive under braking from the heels but it doesn't matter which end if the car is braking the wheels the forces are the same. Ditto roll but laterally around the roll axis below the CG. That's why sportscars and race cars try to get that CG so low.

Squat is resulted in the same manner but with the forces reversed.

Counter intuitive but nevertheless correct. The tech you talked to didn't know squat or dive or perhaps even roll ....

 

OEM were Dunlop. I went with Hankook, per recommendation of my long time tire guy, who does all kind of high end cars. I never heard of them before, but many with high end cars are starting to convert over as the word is getting out. I saw there a 911 S getting Hankooks.
$250 rear tire, $180 front. (each).
Hopefully, these will last to the end of my lease (another ~24,000 mi.)

 

Thanks for the info Yida..Hankook in my experience, wear good and are quiet...they'll treat you right.

Juglar..You are so full of hot air, that I'm surprised the Perma-frost in North Canada hasn't melted yet..

Just read these topics..I don't have the time or care to quote them all to prove how full of NONSENSE you are...Please..stop trying to impress everyone with your vast lack of knowledge.

https://www.google.com/search?q=rear...ient=firefox-a

 

Um, none of those links take you to a suspension engineer. (Actually, this one sort of does: http://www.google.com/patents/US4398741 )

Moving brake bias to the rear can only reduce nosedive by reducing total brake force. Unless the suspension can use the additional traction at the rear moving brake bias rearwards reduces total braking force and, of course, nose dive.

I'd be interested to know what you think the forces at work could be to cause nose dive to change depending upon which wheels are braked without first changing total brake force. Draw yourself a little vector diagram marking the CG and the pitch axis plus the directions and size of all the forces and you'll see that I am correct.

Also, just because you don't understand this doesn't make you right and me wrong, it does help prove I am right about this being counterintuitive.

Finally, better to remain silent and be thought a fool than speak up and leave no one in doubt.

 

 

First off to the OP, I can not comment on the brakes, but I think that getting 25,000miles isn't great, but I guess it depends fully on your driving style... As for the tires, that is perfectly normal for performance summer tires, I would actually tend to think you actually got some good mileage out of them... normally 15K to 20K for performance summer tires... As for the Hankooks if you went with their UHP summer tires, V-12 or better, then you will be very happy with them... I have had nothing but great success with Hankooks, and surely that's what I'll be going with when my stock Dunlops wear out.



Now as for this...


Jagular, you're ability to argue any point with or with out a cause is at the very least inspiring...

You are correct in mentioning momentum shift, but where specifically does the momentum shift take place??? You keep bringing up suspension setups and putting air brakes on the roof to get uplift vs diving nose... Why even are we discussing this... simplify things to make your point... Take two identical cars with the exact same setup no changes in weight distribution, shocks/ springs/ suspension, and have one simply brake the front wheels only, and one brake the rear wheels only... What do you think will happen???

Lets simplify it even further, why think car, the momentum theory should apply to any moving mass, So lets look at a bike (bicycle), I'm not talking about today's fancy bikes with suspension on front an rear wheels, and disk brakes, but a simply fixed front wheel and fixed rear wheel bike. Lets say you create enough momentum, you will have to peddle very fast to get up to speed, and you have two scenarios...

1) On one hand you will apply the rear brakes only. What do you think will happen if you were traveling at 25km/hr (~16mph) and you slam on the rear brake, you squeeze down on the brake handle, and you will slow down to a certain point, but at some point the friction between the brake and the tire exceeds that between the tire and the road, and you skid your rear wheel... nothing else happens, you will generally slow down as a result of this friction that you induced...

2) On the other hand you will apply the front brakes only. What do you think will happen if you were traveling at 25km/hr (~16mph) and you slam on the front brake, you squeeze down on the brake handle, and you would probably go right over your handle bars...

Why such a difference when nothing else has changes other than switch which brake you apply? Well, you have changed the location of where your momentum shifts, a pivot point if you will. if the pivot point happens to be at the rear wheel vs the front wheel the way the mass/ momentum shifts will be different from one scenario to another...

You happen to mention that what you were attempting to explain was very counter-intuitive? Why do you think something that primarily can be broken down to simple physics, becomes counter intuitive? I think its very intuitive. And I agree with DPK and the service/ tech representative that mentioned this to him.

To the OP I apologize for going off on a tangent, to Jagular, its ok to make a mistake, I after have made many, and once I admit it, I can learn from them...

 

There are a number of factors that can be used to reduce dive when braking. These include brake bias and suspension geometry. It may even be that the rear brakes are designed to apply just slghtly before the front brakes as a stability feature. Cyclists and motorcylists would be familiar with this effect.

In my opinion another factor has to be considered when confronted with the common trait of Jaguars wearing the rear pads more heavily as compared to many cars.

The traction control system uses the rear brakes to reduce wheelspin. If a driver has a heavy foot, the brakes will be applied on one or both brakes in the rear. The pads will naturally wear more since they are used more. The front brakes are rarely applied without the rears also being applied, but with brake based traction control, the rears can often be applied without the fronts coming into play.

 

It's a public forum where discussion is encouraged. Insulting or demeaning remarks directed at other members are specifically barred in the rules.

 

You are correct. Sorry about that. Although my post was deliberately ambiguous it was intended as a reply to DPK's suggestion that I might be contributing significantly to climate change, although to reach the permafrost from my city would be an impressive achievement. I should have considered it to be a compliment.

Now if someone will explain how a four wheel hydraulic brake system actuated by the driver's foot can apply the rear brakes first and then the fronts we all may be wiser.

This phenomenon of brake induced suspension dive is interesting and indeed counterintuitive. A suspension could be designed with sufficient anti dive to actually squat under braking.

Momentum is not the same as a moment, although they are related ideas. Moment is a force acting over a distance. When the wheels are braked the tires exert a force opposite to the direction of the car's movement, but at the ground surface which is below the CG of the car. A moment results tending to continue the forward motion of the CG (in theory, of course there is no such thing as a CG, its an idea that simplifies analysis). The CG is at some height above the ground whereas the braking force is active only at the road surface. This produces a rotation resisted by the springs (and dampers transitionally) acting on the lever arms of the suspension. The front springs compress and the rear springs extend leading to dive. It is in fact this dive which requires smaller brakes to be fitted to the rear of the car. Note that the same effect results whether the front axle is braked, the rear axle is braked or both axles are braked and brake bias is not relevant to this phenomenon. The fore and aft location of the CG does make a difference because of leverage effects, a Porsche 911 for example will tend to dive less than an Audi.

Brake bias is completely different but is made necessary by dive. By fitting a brake proportioning system, ball and ramp for example or as is now done wheel speed sensor induced brake line pressure modulation using the ABS computer, the reduced capacity of the rear brakes to exert braking force (CAUSED by the diving of the suspension) is countered by either limiting rear line pressure to a maximum by shutting off the rear brake circuit mechanically or by using the ABS to limit lockup to both rear wheels simultaneously (3 channel) or individually (4 channel).

Race cars utilize a brake bias adjuster controlled by the driver. When brakes are cold or tires are cold brake bias is moved rearwards BECAUSE the lesser total braking force causes less dive so the rear brakes can be asked to work harder. As the brakes and tires warm up the bias is moved forwards to exploit the additional weight transfer effects as total braking forces rise. This too is counter intuitive, using less rear brake when more grip is available from the tires. You have to remember that tire grip goes up with loading. This is why aerodynamic downforce works. Brake bias has to be adjusted continually for changing downforce balance effects, on race cars.

Under no circumstances are the rear brakes actuated first nor can they be actuated to exert more braking force than the fronts. Even if they could suspension dive would be the same.

Feel free to feel differently about this, you'll have lots of company.

 

Oh yes, one more thing to ensure this all relates to the topic of the thread. The reason the initial poster asked his or her question is precisely because Jaguar does such a good job of balancing brake bias so that the rear pads wear out as fast or faster than the fronts. This is so unusual as to be remarkable and many Jaguar owners have suspected that their brakes are deficient in some way because of this. Most other manufacturers fail to utilize their rear brake capabilities sufficiently or fit oversized rear brakes for unknown reasons. Jaguar fits small rear brakes and works them harder. Excellent and very consistent braking performance in street use is the result. The rear brakes are sufficiently well designed on these Jaguars that Jaguar can fit three different sizes of front brakes without changing the rear brakes at all, now that's engineering.

 

Jagular,

This is not unusual at all. I experienced faster wear of rear pads on all my previous Infinitis:1991 Q45, 2003 M45, 2007 G35x.

Regards.

 

There you go then. I have no experience with those brands. In fact, I am more used to fwd which tend to load the front brakes more due to static weight distribution.

There's no question in my mind that well designed braking systems for a well balanced car will wear out rear brakes just as quickly as fronts.

My XF was looking like going through two sets of rears for every set of fronts, which is the reverse of my fwd cars.

 

The ABS system can selectively brake any wheel that is desired, in any order, hence the ABS controlled traction and stability system that exists on the car.

 

Yes it can but not as directed by the driver's foot. Until the computer can know when to brake then all four brakes are applied simultaneously only by the driver and then the hydraulic line pressure is identical in all four lines until the ABS/stability software bleeds off any excessive pressure to prevent lock up. There is no mechanism for applying the rear brakes ahead of the front brakes. The dealership is just making that up.

The traction/stability control only applies braking to one wheel at a time except for awd models when one front and on rear brake can be simultaneously actuated. The idea that the traction or stability control can wear the rear brakes more quickly than the font brakes is a sound one.

No current manufacturer uses the ABS system to actuate the brakes to brake the car, radar cruise control excepted and I am not sure whether that uses the ABS or some aspect of the servo. Emergency brake assist also amplified the driver's input but again I am unsure whether the extra line pressure comes from the ABS system or the servo.

 

To answer the OP's questions, my XFR needed rear pads at around 18-19k miles. I think the reason the rears go first on these cars has to do with the algorithm of the DSC, which modulates the brakes (usually the rears) to help reduce loss of control in turns or exiting turns when applying power. The faster/harder you drive in turns, the faster the disproportionate wear on the rear brakes. Because Dynamic Mode/Track mode reduces the intervention of the DSC, you can probably get better wear out of your brakes using that mode (I often do, but not to get better brake wear), though less intervention could mean a higher risk of loss of control in an emergency situation.

I recently needed tires, too. They weren't pushed by Jag, but suggested during the brakes visit. The OEM Dunlops had a reasonable amount of tread left, but I decided to go ahead with the swap.

I replaced them with Michelin Pilot Super Sports in OEM sizes, which I ordered from TireRack and had them drop-shipped to the dealer for installation (which they were more than happy to do for me).

These are top rated tires according to TireRack's and others' testing. I have several friends who use them or switched to them, and all swear they are magical. I can see why. They grip better than the Dunlops and yet also ride better and run quieter. Tires make a huge difference in a car's handling and feel, so I tend to buy the best possible performing tires in terms of grip, handling, ride and quiet. At most, the price delta is usually less than a few hundred dollars among similar categories of tires (here, max performance summer), which amortized over 20k miles, is only a few cents per mile. Often the best gripping/handling tires are noisier or ride less comfortably. Not so here. Michelin managed to improve all aspects without sacrifice.

My wife immediately noticed the ride and quiet difference. I immediately noticed the increased grip, even though brand new tires tend not to develop their maximum grip until worn-in a few hundred miles (new tires have residual mold-release compound on them, which can make them a bit slippery until its worn off).

 

OK......I did the same thing and noticed the same results......except the gas mileage.! I drive an 09 XF-SC and the mileage dropped 1-2 mpg no matter what I did. I had the Pirelli P Zero before and did not like them for ride and handling. These Michelins do grab better off the line.....great acceleration. Jagular said these new tires have softer rubber that explains a lot except the wear factor.....the Michelins are supposed to get better miles (longevity) but his statement doesn't coincide with the "softer rubber " theory.

 

Michelin claims their tire carcass benefits from endurance racing such as Le Mans. If the carcass is stiffer the tread compound can be softer and rolling resistance kept low.

Michelin Supersports are the best street tire currently available and nobody who fits a set says anything bad about them. The new Pilot Sport A/S 3 is supposed to be just as magical in that category.