Hi, after renewing both front discs and pads (both Bosch, about 170 Euro) because of judder while braking I was initially happy and everything was smooth, even when braking hard at speed.

I should mention that immediately after fitting I went through the process of embedding (after reading that this can help to prevent such judder reappearing). About 5 braking stops from 100 Km/h to 10 km/h with normal acceleration between the stops, then, after letting the brakes cool for about 30 minutes, 5 stops with harder breaking from 160 km/h to 10 km/h. All seemed fine after this for about 800 km. I try not to keep my foot on brakes after stopping and especially not after harder braking stops.

In spite of all these efforts the juddering came back a few weeks ago and I am really pissed off about it - never have this on our Ford Galaxy, even when loaded full (as heavy the the XF for sure...) using Bosch discs and pads.

I am wondering if it is due to the apparently large amount of break dust generated by my XF - significantly more than other cars I am used to if I look at wheels. Does this dust aggravate the build-up of break residue on the heated disks?

I have ordered new Bosch disks again but have also ordered "Jurid White" low dust ceramic pads.

I tried to get my local garage to machine the shuddering discs but they cannot and closest place that does is too far.

Does anyone know if my logic makes sense and if I need to embed the ceramic pads as well?

Any other advice?

I unfortunately do not have a micrometer to measure if my wheel hub/bearing assembly has run-off but I think it must be fine considering everything was good to start with after installing the new discs.

I know this is a well discussed topic and indeed even somewhat opinionated after reading different sources.

 

Sorry to hear that. Unfortunately it's most likely due to improper mounting. Either the wheel lugs were over torqued or the disc isn't flat against the hub. My guess is the latter - if there is surface rust on your hub, when the disc goes on it it will sit at a slight angle due to the rust / debris behind it. All will seem ok at first but after some distance (usually a couple of thousand miles) the uneven wear on the rotor will give you a high and low point on the rotor and the pedal will pulse. Have whoever fits them thoroughly clean the hub mounting surface first

Also possible that you have a caliper sticking - that would generate excessive dust and heat and can similarly cause uneven rotor wear

 

Thanks a lot for your reply!
You may be correct and indeed I wondered about this myself, although I cleaned with small wire brush and brake cleaner (as always).
I fit all break related items myself - have done for years with various cars and never had problems before with brake judder.
Can it be that the Jaguar is so extremely sensitive to this that I should use e.g. sand paper to carefully polish the hub before mounting the disks?
I assume from your thinking that changing to ceramic pads will have little effect?

 

I should also mention that I always torque lug nuts to 120 Nm after first fitting nuts with a airgun.

 

Impact wrenches should never go near wheels, ever, unless you are in the pits of a racetrack. Very annoying that tire shops use them for the wheels on a regular bases.

The fast spinning socket scratches the pockets, and you can't control torque on them.

I watched a DiscountTire guy put on wheels with an impact wrench. He gave it all he could on each lug nut over and over. My impact wrench can do 800 ft/lbs, and it's not even a pro unit. And after he used the impact wrench, he went over them again with a torque stick! How much use it is to tighten a lug nut with a 100 ft/lbs torque stick after using an impact wrench that just overtorqued the lug nuts to the point that the car will probably have broken studs when they try to remove the wheels again??

 

OK, thanks for sharing that surprising information - I always use my (relatively low power) impact gun to remove and reattach the lug nuts. As you correctly point out all the professional tyre garages I know of use impact guns first and then torque with a stick. I always presumed this was the best way. Perhaps they use a lower power setting for attaching? According to what you say, however, this practice may damage the pockets for the lug nuts on the wheels. I will inspect the pockets and lug nuts carefully the next time.
Is there any evidence to back up your claim that impact guns overtorque lug nuts - I do not necessarily doubt your claim I just want to understand what the most likely reason(s) are for my brake judder so that I can try to make sure it does not happen again when I replace the discs and pads.
I appreciate all the feebdack as it does helps me make informed decisions!

 

Just got back from Discount Tire having 4 new tires mounted on the white Jag. I was watching them do another car. He had the air impact wrench on the most powerful setting for that car. When I got my car home, I checked and the lug nuts are too tight. I will redo them all with the car off the ground.

In the past they have torqued them so much that I had to bounce my 200+lb weight on the end of a 2ft breaker bar to get them loose.

 

Yes - hand tightening and torquing accurately is certainly important. You may also be right that the wheel setup is quite sensitive. I fit mine myself too and I had a set of rotors that gave me significant vibration on braking

Not sure about polishing but I'd clean them up well, hand torque (before you lower the car) then re torque about a week later

Not sure ceramic pads will help with this specific issue but I would highly recommend them as an improvement over the stock ones