@20k My service adviser told me that my rear brake pads need changing and that rotors were too thin. When have you changed yours?

 

Get a second opinion. Service Advisors are commissioned salesmen, and they're good at getting little old Jag ladies' trust--and then sell'em a $1K set of brakes--including new rotors.

Jag brakes are completely conventional, and very easy to work on--at any mechanic's shop.

My XK8 is a different animal than your XF, and I got 59K out of my original brakes.

Many of the newer cars are in competition with other luxury brands for who can make the shortest stops on magazine road tests. My Lexus IS brakes were not supposed to last more than 15K--in competition with the brakes from a BMW 325. Some luxury car tires are also very expensive, sticky rubber--20K miles expectancy. It's almost a crime to put quick wearing rubber and brakes on a new $40-80K car.

I would caution you to have someone keep a close watch on your brake pads as they're wearing. The rotors are pretty expensive replacements, and they may can be turned once if you don't wait for the pads to be 100% used up.

 

Good advice. Thanks.

 

This thread is very similar
https://www.jaguarforums.com/forum/x...arranty-56006/

 

I disagree in that it depends on what your criteria are. The XF is a fairly heavy car, and if you are concerned with optimizing braking and handling performance, it often comes at some expense to longer wear characteristics. Some mfrs manage the tradeoffs better than others, but until someone discovers miracle friction materials that grip like crazy AND don't exhibit much wear (carbon ceramic rotors come to mind for that application) AND have costs within reason (carbon ceramic rotors don't meet that criteria currently, unless you consider rotors that cost $2-3000 each within reason), shorter stopping distances/better grip in turns usually comes at the expense of more rapid wear.

That said, I can see a XF owner expecting his/her car's brakes and tires to go 20k+ miles, while an XFR owner thinking that's pretty good.

I would say that for most higher performing cars in the 4000 lb. range with sticky tires and strong brakes, 20k miles between brake and tires changes is average.

I question the need for new rotors, however. If the rotors have only been through one set of pads, chances are that they are still within spec for minimum thickness. You can only make that determination by measuring that.

Dealers often want to change both pads and rotors at the same time because they worry that some time during the life of the second set of pads, but before the pads are worn out, the rotors will have already been worn below minimum thickness. If that happens and the rotor fails (e.g. cracks) causing an accident, well, you can understand why the dealer might err on the conservative side.

On the other hand, changing out rotors with every pad change is also very profitable for the dealer, so there's no real incentive for the dealer to take some risk by not changing the rotors at every pad change.

You could opt for longer wearing pad material and/or tires that are optimized for longer wearing, but the most likely result is longer stopping distances (or the need to apply more pedal pressure) and poorer handling.

People who say there are "no problems" with longer wearing pads (sometimes going to materials that produce less dust as well) haven't tested stopping distances between the OEM material and aftermarket longer wearing pads. Maybe there is no difference, maybe there are differences but only under some conditions (like when the pads are cold) or maybe the difference is 10-15 feet but that isn't important to you (figuring you'll just follow other cars further away). If you opt for anything "longer wearing," that's up to you. Just go in with your eyes wide open.

 

Our XF, when not sitting at the airport, is usually running around in Dallas rush-hour traffic. Our rear pads were replaced at 13k. They may have had another 2-3k left but we did not want to risk the rotors, which did not need replacing. For what it is worth, the "inner" pad (behind the rotor) was worn more than the "outer" one. High quality braking on a heavy vehicle comes at a price. All that brake dust that quickly builds up on the wheels (front and rear) just after being washed has to come from somewhere. The XF produces the most brake dust of any vehicle we have owned and is the only vehicle we have had the gets significant brake dust on the rear wheels. Likewise the XF wears the pads the quickest as well.

 

That seems the consensus. I'll point out that many BMWs and Mercedes dust a lot, too, though I don't recall if they go through pads more slowly or not. For us with Jag's Platinum/Premium (or whatever it's called) included maintenance, it's really not an issue (at least not until we reach/exceed 5/50k) apart from inconvenience of having to take the car in. Overall, I think slightly more frequent pad changes are a relatively small price for the performance.

Inner pad wear faster than outer is fairly common, btw, in floating caliper, inner piston designs (I haven't checked to see if this is the design applicable to our cars). Multi-piston designs, e.g. those having 2 pistons on the inboard side and 2 on the outboard side, tend to wear the pads more evenly as between inner and outer pads.

 

Minimum thickness is usually quoted in the technical data; you could ask your mechanic what the minimum is to check. Also you can check yourself with a micrometer. Also there is normally a chamfer on the disc edge to indicate minimum has been reached. If this chamfer has disappeared it's time for new discs.

 

Disc specs are supposed to be encoded on the rotor itself also.

If you elect not to change the discs when new pads are installed then you should ensure the rotor thickness is checked regularly to ensure it remains above minimum. Generally, a rotor should last for two sets of pads, but not always. Thinner rotors hold less heat for any given temperature so are a bit of a false economy as higher temperatures wear street pads more quickly. The relationship is almost linear between volume of metal in the disc and temperature (thinner discs also cool a little more rapidly due to higher surface area to volume ratio).

It is very difficult to improve on factory brakes in most cases. I doubt there will be an aftermarket brake kit for the XFR, for example. The most important thing about street brakes is the first emergency stop of the drive which can occur at any time, before the brakes are warm. Disc brakes pretty much eliminate any meaningful fade in normal street use, i.e. off track.

For track use it is wise to consider swapping in competition grade pads rather than compromise street performance by putting harder pads in for daily use. Hard pads do not stop well when cold. Soft pads usually stop pretty well when very hot, once or twice, but wear very quickly and fade rapidly if temperatures keep rising due to repeated braking events with insufficient recovery time between applications. Street pads need cooling off between hard brake applications.

Like tires, brakes are a compromise. There is also absolutely no point "improving" the power of the brakes if the tires are not up to delivering the extra grip required to improve stopping distances. Brakes just stop the wheels, it is the tire that stops the car.

 

Well put!

Street and track have somewhat different requirements. On the street, as noted above, you want and need instant maximum brake torque, regardless of temperature, e.g., when that neighbor pulls out of his driveway unexpectedly a block from your house and nothing on the car is warm yet, or when freeway traffic suddenly slows or stops and you haven't used your brakes much in miles of driving. On the track, you want and need fade resistance, i.e. consistent braking performance with lap after lap of hard use.

One does not necessarily provide the same as the other. Street bite when cold often involves higher dusting, softer pads. Manufacturers know that many people with performance cars drive their cars hard, too, so they also need to have a good heat range envelope (Maximum Operating Temperature or MOT), too. Hard to get that formulation "right" and also keep people from complaining about dust and squeal, and evidently, lack of long wear. Move the balance in favor of low dust, for example, and often something else suffers, such as cold bite, or fade resistance.

Move the balance in favor of cold bite and maybe long wearing suffers. In the bicycling world, they often say, "light weight, high strength and low price, pick any two," because of the tendency of these factors to be mutually exclusive. A high strength, low priced bike is likely to be heavy. A light weight, high strength bike is likely to be very expensive, etc. Similar idea with brakes.

Track pads are often harder and may not bite as well when cold. The key to track performance is also larger rotors, pads and multiple pistons, to deal with the heat. That's what "big brake" kits are all about. They are not necessarily about stopping in shorter distances, or providing that short stopping ability when cold, as when you need it on the street. They are about absorbing the high amounts of heat generated from the repeated heavy use they see at the track. Thus, big brake kits are not necessarily "better" for the street, unless you live at the top of a mountain and your stock brakes fade by the time you reach the bottom.

 

20k for rear pads on a XF is normal, rear discs then are not. Some tech ONLY do rotors and pads. I go on the second set rule as normal. 2nd set of pads replace the rotors

 

Hey, we agree on one thing. Excellent.

Oh, maybe two things.

 

My 2010 XF Premium has 14k on it and the "low pads" light goes on and off. I had a mechanic look at the rear pads and he told me that they were between 2/32 and 3/32. Both rear rotors have a "lip" and according to him, should be replaced. I find it awful odd that the rears need replacing so soon.

The dealer replaced the front pads and rotors, under warranty, at about 10k miles, because the brakes constantly were squeeking since the car was new.

So now I am bringing the car to the dealer on Wednesday so they can assess the "damage". Any ideas on what rotors and pads might cost. I am guessing between $500 and $700.

Thanks

 

The pad light on the rear (Right Rear to be exact) will come on when the pads are at 4mm. I would measure the rotors. Also remember that annular grooves on the rotor,especially rears, are normal and just because they are grooved that doesn't mean they need replacing.

 

The "lip" is an indicator of disc wear.

Modern brakes without asbestos in the pads are made of harder materials so the pads wear the discs much faster than in the olden days.

Brake wear is very much a personal issue. Some people brake a lot and some not much at all. Automatic equipped cars wear brakes much faster than manual shift cars. The ZF transmission in the XF utilizes engine braking but only if you let it. Many drivers accustomed to old style automatics actually ride the brakes much more than they need to. I notice because the XF is the first automatic I have owned and I notice now how often most drivers use their brakes whereas I drive the XF like it has a manual shift and hardly need to use the brakes at all in normal Canadian style traffic.

My "like a manual shift" I don't mean using the paddles, though I do occasionally do that also. I find the automatic programming in the ZF allows you to drive as you would a manual shift and the automatic does a pretty good job of gear selection and will hold a gear when you lift off the gas. It also holds the gear in corners and if the traction control senses wheelspin.

 

 

Thanks for all the great advice. My rear rotor was at 4mm and the car was already at the dealer... so I replaced. Total damage $335 parts $190 labor.
I thought about using a set of slotted and drilled rotors for added performance. EBC comes up in Google. Maybe next set. Anyone know if the front and rear rotors are different? I see them listed separately on some sites.

 

I have started to get the message light saying mine are too thin! 36000 klm. I had an x-type that last 80k, and a hummer h3 that was done at 60k Seems like a money grab

 

My 2009 S/C rear brakes lasted for 48,000 Km and the dealer replaced only the pads. They said that if the rotors were smooth and not warped they can usually be reused for one pad replacement. The front brakes were never replaced and were still good before I traded the car at 61,000 Km. However, I used the paddles a lot to bleed speed when applying the brakes.

 

The one thing as I read thru everones post that was left out. Your rear brake pads will wear out faster because your traction control uses your rear brakes to control wheels spin. So if your have a heavy foot and like to spin tires when your dsc is on you are going to wear them faster. Or if you drive in the snow and have lots of wheel spin.