In a bit of a rush this morning to get my wife to the airport, so was doing somewhat illegal speeds on an empty dual carriageway. Went to brake, and the whole car started shaking violently (consequently so did my bum!). Only happens at high speed, under light or heavy braking, and only happens under very hard braking below 60mph.
Is it time for new discs and pads, or does it sound like something more? I have a slight squeal sometimes when not braking, which I'd put down to cheap pads in Brembo calipers, and was waiting for them to wear down a bit before changing them.

2007 4.2 SC, 105k

I had this with warped discs - I don't think the previous owner had genuine discs and the last pads I put in were non-gen.

Switched to Gen discs and pads and my problem went away - not cheap for the Genuine parts though :'( 

Do you get pulsating back through the brake pedal? Warped discs will normally result in that because as the disc isn't true it pushes the pistons in and out as it rotates pushing fluid back into the reservoir and master cylinder - pushing the brake pedal.

You should be able to feel it at slow speeds under all braking conditions - it will just be slower and not quite as noticeable. Ed

This is what slightly confused me. There seems to be a definite point of brake pressure at which it starts to shake, and this depends on speed. So at low speed you never really get to the "shake-point", but at 100mph+ the shake-point is almost at the top of the pedal.
I suspect it is warped discs, and this odd behaviour is down to the damping effects of the brake pump, ABS, and massive servo between pedal and caliper.

I've only experienced warped (or extremely rusty) discs in stuff with no fancy braking system so don't have any first hand experience.

Probably worth checking the state of the bushes. Different steering geometry completely but I had a violent shake on the Defender, replaced the panhard rod complete with bushes which improved the shake, it was still there but minor. Then about 2 months later when I finally had some time I replaced the radius arm bushes. The shake was back worse than before. Turned out the new panhard rod (with polybushes) was shot (replaced with genuine took more time and the manufacture of a press - why I didn't do it before) and cured it.

That episode had some interesting side effects on braking and so on so could be bushes rather than discs but I can't see how the geometry of the FFs suspension would be affected by braking.

Discs and pads are cheap and easy to replace so probably best to start there. You might be able to see if they're warped by taking the wheel off and using something like an engineer's ruler to see if it's not flat. Ed

Could it not be down to the fact the tyres aren't balanced properly for the speed your doing.
Or even the tracking is possibly out?

Normally the front brakes go on first when applying low pressure.
The harder you push, the more goes over to the rear brakes.

Pulsating/wobbling can be:
Warped discs
Spots on the discs (caused by rust or heat)
Wheelbearings
Bushings for the a-arms
Oval tires
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Blair,

you may try "cleaning" disks while driving. bring car to 75-80mph and press brakes first light and then smoothly increase pressure till you come down to 30-35mph and repeat that 4-5 times. somethime brake pads leave deposits on the disks and it feels like they are worp.

Front or back? Check the rears for lots of heat. is one hotter than the other etc, could indicate a sticking caliper at the back, which is quite common and a cheap fix, DIY with a bit of help with bleeding.

its worth having the front callipers off to have a look whats going on. I had a problem where there was a hole in the CV boot and it was letting a bit of grease onto the braking surface. Caused a judder under high speed braking. Contaminated the pads though and it was eventually solved with new pads and discs.

Also while the callipers off have a look at the seals on the pistons. They can deteriorate over time and if you are on original callipers then you may be looking at replacing the outer seals. There is nothing that can't be fixed with a hammer😜😜
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deleted---double post There is nothing that can't be fixed with a hammer😜😜
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Have your hubs checked, these can go out of 'true' and cause this vibration and you can end up swapping discs loads of times with no positive results. A decent mechanical garage should have the equipment to test the run-out. Discovery 4 HSE
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