colin hewetson

XF excessive brake wear

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Reading many Jaguar forums I noted a large majority of complaints concerned excessive disc rotor and pad wear on both front and rear brakes. I had my XF V6 S Portfolio from new and in 4 years have had 5 sets of rotors and pads replaced in 80k odd miles. The rear rotors and pads seemingly are subject to the greatest wear. Some forum posts stated owners had been advised by their Jaguar dealers service that rotors and pads needed replacing from 6k-10k miles which is really totally unacceptable, especially when Jaguar charge £600 odd for each front and rear set,

I had my rotors and pads replaced some 8 months back (8K miles) from an independant Jaguar specialist at half the price using Brembo/Mintex parts. Last week I had no choice but to visit Marshalls in Didcot to obtain two replacement rear exhaust box rubber heart shaped hangars as one had failed and the box was hanging down. These cost £24 each and checking on the internet was annoyed to find I could have obtained an identical part for £7!! Anyway I got Marshalls to fit the hangars whilst there as its !Removed! difficult if not impossible to install them without the car raised on a ramp. On paying they provided me a "free health check" which was okay except for the rear brake rotors and pads; fronts were noted as 10% worn and rears 80% worn and service advised me they could change them for £350 under 3+ plan in lieu of the normal £660! I politely declined. Of course the purpose of the "free health check" is to find something wrong that needs replacing, its not a health check at all its a 10 minute visual of brakes and fluid levels.

Any way the point of this post and above background is to advise other forum members who suffer excessive break wear and constant replacement costs why they wear so quickly. Being !Removed! off to learn the rear brakes needed replacing having only replaced them 8 months previously I dug around to find what could cause such excessive wear. Marshalls could not explain it merely suggested the wear must be down to excessive hard braking. So I checked with my specialist Jaguar service outfit, they too had no explanation except the same line, excessive speeding and braking.

But the real reason for excessive brake wear is down to a technical issue labelled as car safety "DSC" Dynamic Stability Control" for the unitiated, which is constantly engaged unless you switch it off, which like me no one bothers. Jaguar cars and probably many other makes include under the label DSC, ABS (Anti Lock Braking) EBD (Electronic brake force distribution, ASL (Automatic Speed Limitation) Traction Control. All of these are controlled via the engine management computer which via sensors measures speed, Yaw, wheel slip, wheel speed, vehicle loading and applies a braking force to any or all wheels if it detects what it considers a dangerous situation e.g. rear wheels locked up, as part of its "safety program". 

If you use cruise control (ASL) as I used to, the set point speed is maintained say on hill or slop descent by applying the brakes, if the computer senses a front or rear wheel locking up it will apply a braking force to the opposite wheel to prevent a skid, similarly if a wheel is slipping. A little know and understood Jaguar "safety feature" is EBD, which electronically applies brake force pressure bias between front and rear wheels depending on vehicle loading. Brake bias is a vital safety issue, particularly for racing drivers, to much pressure force on the fronts and the vehicle wont turn in to a corner at speed and too much pressure force on the rear brakes entering a bend could result in a skid. Brake bias is impossible to program into a computer as there are so many variables, which is why racing drivers have an adjustable hydraulic control on the wheel or dash so they can set the bias towards the front or rear depending on whether the track is wet or dry, whether tyres are hot or cold and tyre wear. For the average family salon and driver manufacturers included a hydraulic fixed ratio pressure bias proportioning valve between front and rear brake circuits, 55% front 45% rear or thereabouts. Now they use EBD which does the job electronically (supposedly) sensors measure the loading in the vehicle and speed/yaw when braking and apply a greater braking force to the rear or front dependent on circumstances. Generally if no passengers, the greater braking force is applied to the front brakes but if it senses passengers in the rear (presumably via seat sensors) it applies a greater braking force to the rear brakes.

For all this computing power and sensors though, I have never in 4 years seen the bonnet dip down under heavy braking which means the greatest braking force is regardless always applied to the rear brakes.

So the answer is after much study simple, SWITCH OF DSC AFTER STARTING CAR (this requires pressing the DSC button below the rising gear knob and holding it down for 10seconds). In essence if you are an experienced driver and drive normally or even sometimes spirited, you do NOT need ABS/EBD/Traction Control/speed control.

Since early this week I have always had DSC switched off and now note the greater braking force is on the front brakes as I can see the bonnet dip down when braking and I dont use cruise control any longer. Hopefully this will save me spending £3-600 every 8-10k miles.

(As a matter of interest in researching reasons for Jaguar excessive brake wear I contacted Jaguar Engineering services, the chap I spoke to couldnt explain what might be causing excessive brake wear nor could he confirm if  EBD was included on the XF or if the function was included in DSC, but "if I would like to hold on for a minute" he would ask one of his colleagues who might know more. 10 minutes later he returned to advise "no his colleague couldnt answer the questions either". So much for Jaguar Engineering Centre!!)

Edited by colin hewetson
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Hi Colin,

Interesting post! I think I'll give your suggestion a go, always prefer to be in control rather than controlled (unless it's wet or icy!!!).

My 2011 XF-S brakes well, but when the brakes have warmed up, I get a slight shudder and rumble from the front. I assume that means I will soon need new disks - not looking forward to that bill!

Cheers,

Jon

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My 2012 XF S has had 3 complete sets of discs and pads and the car has only done 80k.

A very expensive outlay for non expensive parts on all too regular basis.

Jaguar, I am certain know of the issue, its just one of their trade secrets.

You can of course buy the brake components a lot cheaper and have them fitted at a local garage for a quarter of the main dealer price.

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https://www.buycarparts.co.uk/jaguar/xf-j05-cc9/31361/10132/brake-disc?line=coated

This company is spot on for prices and quality parts. Dont be led by the nose on replacing with Genuine Jag parts, these Brembo parts are fully coated and i have had no issues with quality so far.

WIth regards to the rear discs and pads, from my tinkering on the Web prior to buying my XF, it was suggested that the friction material on the rear pads is softer than normal to accomodate for the EPB. There have been instances in the States whereby the EPB would be applied after a run, hot discs, hard material, discs cool down, run you over... Hence the change to the softer compound.

Sure enough, on my inspection yesterday, the rear pads are down to 50% of their originally fitted thickness after 10 months, but at £24 a set, i am really not complaining.. They are easy enough to fit without any special tools or SDD.

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