I’ve now replaced the front rotors with OEM rotors twice, new pads and now a left front caliper. I’m still getting a shudder braking at speeds above 50 especially taking an exit. Has anyone had this issue, Without question it’s coming from the front. I’ve also replaced the two rear rotors and pads but I can feel it in the front end.

 

Not much to work with here. Can you tell us...

shudder where? in steering wheel? seat? brake pedal?
mileage?
tires type and condition?
suspension all original? anything replaced yet?

 

Also, we need to know the year model and engine as there are different brakes for the models (i.e. V6 AWD, NA 5L V8, and SC 5L V8

 

2015 xjl supercharged 27k on it. Shudders only when braking and I can feel it in the steering wheel. Doesn’t do it at all other than stepping on the brakes at speeds greater than say 55. Front end I’ve got all OEM rotors, actually 2nd set of OEM rotors. Their thought was maybe a wrapped rotor. It really feels like it’s coming from the left front. All new pzero tires

 

2015Jag, I know this may sound funny, but, fill your front tires up to say 42 psig and then try braking again. Is it better? I have noticed my car has a quirk about it that when the tire pressures are down around say 28 psig, I get a little wobble in the steering wheel. But, I bring the pressures up to say 40 psig, the wobble goes away.

After that, have you gone with an aggressive pad (say EBC yellow pads)? This could possibly cause a wobble because the pads are getting warm and sticky which would then with the ABS, potentially cause a shudder.

After that, I am running out of ideas. When was the last time the caliper pins were greased?

 

+1 on checking and maybe greasing the caliper slide pins.
Lots of discussion about brake judder on the Pommy XF forum and in many cases it is/was caused by sticking caliper slide pins.
Another common cause is brake pad material deposition (often incorrectly called "warped rotors") which in turn is caused by not bedding the new pads in properly.
If all else fails a cheap / free possible fix is to give the brakes an Italian tune up - hammer the bejeebus out of them a few times (but don't stop) - which just might de-glaze and bed the pads in.

 

Appreciate the reply. So I just replaced all the tires all the rotors. Took back the fronts rotors ( they warranted and replaced) thinking I may have gotten a warped one. Years ago rotors came in wood crates of two and now they come in all stacked on a pallet. New pads from the dealership and now a left front caliper because when I brake at speed the wobble literally feels like it’s on the left front. Only thing left is the right front caliper, I ordered it. After that I drop back and punt.

 

Maybe try swapping the sides of front tires and see if problem/feeling moves with tire. I have read where belt separations can be most noticeable during braking. That could give you the feeling you describe.

Also do not remember reading that all suspension has been inspected closely and ruled out, particularly inner/outer tie rod ends. ??

 

also a suggestion, make sure your rims dont have bends or dents

 

Not with most tires for the Jag XJ - most are directional. If you put a left side tire on the right, you certainly will separate belts & get wobble.
I don't trust the Perrelli P-Zeros. Had a set when we bought the XJ, hated them, and never bought them afterwards.

 

I'm not aware of directional tires for our XJs, but there are a lot of asymmetric tires like the (arg) Pzero and the Michelin PS4Ss

 

+100 on comments above. I had similar problems. Recommend following steps.

1 - check for bent rim/ wheel balance issue
2 - check alignment/ suspension
3 - clean and grease the slide pins
4 - check for runout or uneven hub-rotor mating with a dial indicator.

I think 1 & 3 are most likely culprits. Step 4 I do every time I do the brakes. Steps 1 & 2 are easy to do together at a tire shop.

 

When you replaced the rotors, did you clean the hubs of rust and build-up? If these are not cleaned, they can cause vibration when braking.

 

Simply Rotors are bent. that is it. unless you have something losing.

 

They're not. So I just replaced the right front caliper, everything is new and it's finally smooth. I'm cautiously optimistic.

 

Not sure how rotors get bent?

Thanks for reporting back what fixed it. We guess a lot and don't always hear the solution.
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clubairth1, rotors can get bent 2 different ways that I am aware of. The first being simply that you do a hard braking and then while the rotors are hot, you splash a fair amount of water onto one half of the rotor and not the other. This will cause one side of the rotor to cool a lot faster than the other. Because metal expands and contracts with temperature, as one side is hot and the other side is cooler, this induces a stress into the rotor that will cause it to bend side to side, resulting in the warp. The other way is simply not torquing the lugnuts evenly. The act of the rim not pressing evenly against the rotor again introduces a stress into the rotor. With repeated heating and coolings, this transfers the stress into the rotor structure (think at the atom level). This then leaves a permanent warp in the rotor. This is why having all your lug nuts at about the same torque is critical. This can also be created by having a little imperfection between the hub and the rotor, introducing the stress that way. Same cause and effect as not having the lugnuts tightened evenly.

 

I agree with this explanation, but I'd like to add one thing. This is especially important when first installing new pads and rotors. They have to be "bedded in" properly. What I've done, with success, is install the new pads and rotors, then go someplace where you can accelerate to 45-50 MPH, then brake SHARPLEY down to about 10 MPH. Do not stop, but then accelerate to 45-50 MPH, and drive for about a mile or so, to cool the brakes. Then repeat whet you just did, slowing briskly, to 10 MPH, then accelerate to 50 MPH again, and cool the brakes. About this time, head back home, approaching your driveway slowly, so you don't have to apply your brakes. Coast to a stop, and gently slide the shifter into "park". Again, DO NOT TOUCH THE BRAKES!

Let the car sit for an hour, or so, to completely cool the pads and rotors, and then enjoy your fresh brakes, for a long time.

The purpose of this is so that you "heat cycle" the rotors, heat off the gasses from the pads, and by not applying the brakes when you park the car, you don't get ant pad transfer to the hot rotors. In most cases, what you feel and think is warping, is actually is "shudder" from the pads alternating between clean rotor surface, and "dirty" sections of the rotor, the "dirt" being pad material that stuck to the rotors, from that hot stop when the pads were new.

 

none of this worked, i also replaced both front calipers now plus had both front tires straightened. Cars going back in tomorrow to check on the suspension

 

Have you managed to find the fault?