Severe shuddering when braking between 40-60MPH

[robxenotech]

LS400 1999 Had the brakes changed on the front a few months ago and the problem was rectified. Then it slowly started coming back, so I mistakenly ordered some new front brakes to change them and see if it fixed the problem and lo and behold it shakes so incredibly much between 40-60mph it’s almost dangerous. Wheel shake, body shakes a bit now and the brake pedal judders. It’s way worse than the old ones which only had 1000 miles on them. Any ideas as to what it could be?

[NemesisUK]

Pad material deposited on the discs can cause a brake judder. A couple of hard stops from speed can remove this but depending on driving style and where one drives can cause a build up again.

When you say 'new front brakes' what exactly did you change? If you replaced the discs you may have introduced some dirt or rust between the disc and hub mounting face. The smallest amount can cause a very bad judder.  The mounting faces must be scrupulously clean.

I'd recommend getting a good garage to check over the brakes, if it is that bad a quick test drive by the technician will illustrate the problem.

[Jon Dee]

jack the car up until the front wheels (wheel if you do one at a time) are off the ground. Rotate the wheel by hand and listen. If the disc has excessive runout you will hear a definite metallic rubbing sound that occurs with the valve stem (or a chalk mark) in the same position each time. If the runout is normal you will only hear a very light continuous rubbing sound, or a light rubbing that is present for most of the wheels rotation.  If the runout is severe, the wheel maybe difficult to rotate and after half a rotation it will make a scraping noise and stop as if the brake had been applied lightly. 

If the runout is in spec then as mentioned above, and you didn't follow the approved "break-in" procedure for new discs and pads, you may have pad material transferred unevenly onto the surface of the disc. You will need to inspect the discs for uneven patches of discoloration. Excess pad material can usually be removed by flat sanding the braking surface, cleaning the disc with a spray-on brake cleaner, and repeating the correct break-in procedure.  

Post up what you find after inspecting your brakes. 

Cheers...

[Malc1]

17 hours ago, robxenotech said:

LS400 1999 Had the brakes changed on the front a few months ago and the problem was rectified. Then it slowly started coming back, so I mistakenly ordered some new front brakes to change them and see if it fixed the problem and lo and behold it shakes so incredibly much between 40-60mph it’s almost dangerous. Wheel shake, body shakes a bit now and the brake pedal judders. It’s way worse than the old ones which only had 1000 miles on them. Any ideas as to what it could be?

Is it really a brake problem ?

Have you checked and double checked the tyres for bulges or summat not right that's throwing it all awry ?

Malc

[robxenotech]

33 minutes ago, Malc1 said:

Is it really a brake problem ?

Have you checked and double checked the tyres for bulges or summat not right that's throwing it all awry ?

Malc

Brand new set of premium tyres a few months ago too, can’t be those

[robxenotech]

6 hours ago, Jon Dee said:

Jack the car up until the front wheels (wheel if you do one at a time) are off the ground. Rotate the wheel by hand and listen. If the disc has excessive runout you will hear a definite metallic rubbing sound that occurs with the valve stem (or a chalk mark) in the same position each time. If the runout is normal you will only hear a very light continuous rubbing sound, or a light rubbing that is present for most of the wheels rotation.  If the runout is severe, the wheel maybe difficult to rotate and after half a rotation it will make a scraping noise and stop as if the brake had been applied lightly. 

If the runout is in spec then as mentioned above, and you didn't follow the approved "break-in" procedure for new discs and pads, you may have pad material transferred unevenly onto the surface of the disc. You will need to inspect the discs for uneven patches of discoloration. Excess pad material can usually be removed by flat sanding the braking surface, cleaning the disc with a spray-on brake cleaner, and repeating the correct break-in procedure.  

Post up what you find after inspecting your brakes. 

Cheers...

Thanks, will take a look later on and inspect

[Malc1]

45 minutes ago, robxenotech said:

Brand new set of premium tyres a few months ago too, can’t be those

But are the pressures right, valves ok, any “ flat spots “ on the treads, wheel balance correct ???  Stones stuck in the tread too 
Might be worth re-checking at some stage 🤔

Just coz the tyres are Premium and new …….. 

Malc 

[Boomer54]

My Zimmerframe has this same "shuddering" problem when I brake sharply from 3mph.

[robxenotech]

1 hour ago, Malc1 said:

But are the pressures right, valves ok, any “ flat spots “ on the treads, wheel balance correct ???  Stones stuck in the tread too 
Might be worth re-checking at some stage 🤔

Just coz the tyres are Premium and new …….. 

Malc 

All right and spot on. It’s 100% the braking area somewhere, can feel the car swaying as if the discs are wonky and the shuddering and shaking is very loud at 40-60. Perfectly smooth when driving normally no braking

[Razor61]

Let’s assume new brake discs and pads are correctly fitted. I would fit genuine Lexus OE stuff, make sure the anti squeal plates and spacers are present.
What does that leave? That leaves the brake calipers, a sticking piston or 2 and warping the discs over time. That would be my guess.

[steve2006]

I remember ( just) having very similar symptoms on my old 1994 Celsior which went away after replacing the LBJs which had play in the ball joints.

It may be worth checking these with a pry bar for excessive play.

[Razor61]

55 minutes ago, steve2006 said:

I remember ( just) having very similar symptoms on my old 1994 Celsior which went away after replacing the LBJs which had play in the ball joints.

It may be worth checking these with a pry bar for excessive play.

Good shout, not difficult to replace either and ‘relatively’ inexpensive at £95 each from LPD.

[Exdee]

If the wheel balancing was done when the tyres were changed, and you don't have a sticking piston (which I think if you did you would smell it), I would also guess that this is an issue caused by rust, either behind the rotor or somewhere in the region of the brake hardware.

If your car is not driven frequently, it could just be glazing on the rotor and brake pads which can be fixed by doing some hard braking at high speed (don't come to a complete stop).

 

[robxenotech]

Adding to this - put my old (only 1000 miles worn) brakes back on and the shuddering is far less and much better. But I’m now getting  brake pedal judder all the way from 70 down to 0MPH and the wheel shakes (when not braking) at 60 -70 mph. Cannot for the life of my figure it out, we’ve inspected the braking system well. Could it be suspension related? Tyres have been balanced.

[Barry14UK]

Don't know if all tyres are the same size/directional but if same size you could try transposing front and rears to see if that makes a difference. Assume wheels are being gradually tightened in prescribed pattern.

[Jon Dee]

3 hours ago, robxenotech said:

... put my old (only 1000 miles worn) brakes back on...

Rob, when you say that you changed the brakes, do you mean that you changed both the discs and pads, or did you just change the pads ? If it was just the pads, are the discs fairly well worn with a bit of a lip at the outside edge of the braking surface ?