Loud clunk when braking (Everything is tight and looks good)

MrTrendizzle · September 29, 2023

Hey,

So when I'm driving down the road and hit the brakes there is a single loud clunk from the passenger side wheel. I've checked the calliper, pads, all the control arms and mounts which all appear good and or are brand new.

I have noticed the brake disc holes (The ones that slot over the wheel hub bolts) are more oval shaped than round leading me to think when i apply the brakes the disc stops but the wheel hub continues to travel slightly which is hitting the wheel bolts on the disc making the clunk. I'm not entirely sure this is possible due to the wheel being bolted down to the hub sandwiching the brake disc between them so no play should be there right?

The diff, prop, axle shafts are all good, the subframe looks good although the roll bar? Sway bar? looks a little rusty (More surface rust) Could the handbrake shoes be loose and moving while under braking? They're cable driven not hydraulic right?

I'm surprised this wasn't picked up on the MOT and even having the car on a ramp with a large prybar nothing seems loose or moves. It dosn't affect the braking or handling of the car, just "clunk" every time I press on the brake pedal. Now as i type this the only part i haven't checked is the suspension top mounts but i would assume that would be picked up quickly during the MOT right? Right? Halfrauds, You did check the suspension right?

I'll be outside tomorrow giving the car it's weekly shower so i might pull the boot lining out to check the top mount of the suspension but in the meantime is there anything anyone could think of that could cause this rather annoying clunk sound?

Linas.P · September 29, 2023

5 minutes ago, MrTrendizzle said:

I have noticed the brake disc holes (The ones that slot over the wheel hub bolts) are more oval shaped than round leading me to think when i apply the brakes the disc stops but the wheel hub continues to travel slightly which is hitting the wheel bolts on the disc making the clunk

That would do it... not difficult to check - take the wheel off and move the disc backwards and forwards... if as you say holes are oval and disc turns backwards and forwards when bolts stay in place, then surely that would result in quite horrible clunk under braking.

The disc tolerance over bolts should be quite tight, not sure exactly but like 0.2mm or something like that, so there could be very little movement...

NemesisUK · September 29, 2023

Surely the disc is clamped tightly between the road wheel and the hub when the wheel bolts are tightened?

Have you checked the disc holes on the other wheels?

MrTrendizzle · September 29, 2023

8 minutes ago, Linas.P said:

That would do it... not difficult to check - take the wheel off and move the disc backwards and forwards... if as you say holes are oval and disc turns backwards and forwards when bolts stay in place, then surely that would result in quite horrible clunk under braking.

The disc tolerance over bolts should be quite tight, not sure exactly but like 0.2mm or something like that, so there could be very little movement...

I'll give that try tomorrow. The oval shaped holes are definitely much larger than 0.2mm (At the sides but most likely that top/bottom) Even with the wheels bolted on tight could the disc slip slightly? I would've assumed with the wheels tight the disc is held between the wheel hub and wheel so tight that no movement would be possible? I guess there's a lot of force 3T of car movement and all the braking pressure yanking things about so it could be possible.

1 minute ago, NemesisUK said:

Surely the disc is clamped tightly between the road wheel and the hub when the wheel bolts are tightened?

Have you checked the disc holes on the other wheels?

That's exactly what i thought also. If the wheel is bolted on the disc shouldn't be able to move at all which is why i'm at a loss. Altho like i said above 3T of car movement and all the braking pressure i'm sure movement would be possible compared to a long prybar etc...

Tomorrow will be a fun day explaining to my wife how i need new discs... It's good that grooved discs are "much" cheaper than Lexus branded OEM discs right 😉

Linas.P · September 29, 2023

It all depends on how "oval is oval", yes discs are clamped, so with wheel bolted on it most definitely should not be slipping, but if they have 5mm slop each side then eventually they will start moving...

MrTrendizzle · September 29, 2023

2 hours ago, Linas.P said:

It all depends on how "oval is oval", yes discs are clamped, so with wheel bolted on it most definitely should not be slipping, but if they have 5mm slop each side then eventually they will start moving...

I will definitely have to check in the morning. I would guesstimate the gap in total would be around 5mm (2ish mm either side of the bolt) i could fit a typical washer in the gap either side.

Time to get slightly better discs along with new shoes, front pads and tyres.

J Henderson · September 29, 2023

Got this old pic showing the "slop" on an OEM disc after about 50k miles.

It could be that the pads are moving around, or worse, the top and bottom locating pins, if any of those little retaining clips are missing. The ones that look like they're made out of a wire coat hanger.

MrTrendizzle · September 30, 2023

8 hours ago, J Henderson said:

Got this old pic showing the "slop" on an OEM disc after about 50k miles.

It could be that the pads are moving around, or worse, the top and bottom locating pins, if any of those little retaining clips are missing. The ones that look like they're made out of a wire coat hanger.

My discs look just like that, A little more oval than round with a gap the same size as your top left bolt. Imagine that gap but on both sides. Was that a cause for clunking for you?
My rear pads have 2 wires holding them in. One that hooks over the pin and clips in to both pads and another that runs up the closest pad from pin to pin.

eightk · September 30, 2023

Try hard and soft braking to see if there’s a difference - if it’s just hard braking clonking and making the nose dive it could be suspension eg drop links or roll bar bushes or lower arms moving about… plus find a deserted bit of road and do walking pace forwards brake, backwards brake cycles to see if it’s the pads moving in the callipers.

J Henderson · September 30, 2023

8 hours ago, MrTrendizzle said:

My rear pads have 2 wires holding them in. One that hooks over the pin and clips in to both pads and another that runs up the closest pad from pin to pin.

Sounds like nothing is missing then. What about the shims for the pads? There should be 2 sets. The outer silver one that you can easily see in that picture. Plus, there's another black one that fits underneath.

MrTrendizzle · September 30, 2023

7 hours ago, J Henderson said:

Sounds like nothing is missing then. What about the shims for the pads? There should be 2 sets. The outer silver one that you can easily see in that picture. Plus, there's another black one that fits underneath.

For the rears i don't have any shims on the back of the pad Just looks like a black shim that's attached/embedded to it but no silver shim like yours. I do have a couple of clips holding the tabs(edge) of the brake pads tho.

I didn't get around to having a wiggle this morning. I ended up being taxi for the kids birthday party's they've been invited to and only told about this morning and the fetching the wife to rugby and back. 🤣 Tomorrow i'll be under the car replacing an axle seal for my diff so can get a bar and see if it's 100% the disc bashing on the wheel bolts. But everything is in my basket ready to order regardless.

ColinBarber · October 1, 2023

Normally this type of noise is pads moving from one end to the other, and typically happens once if you reverse out of your driveway which will move then pads on one direction and then you hear it when you make you conduct your first forward stop. As eight has mentioned, easy to check - do low speed heavy braking going both forwards and backwards a couple of times. The cause is missing end clips, no brake grease on the ends of the pads or worn calliper. Another common cause is the sliding pin with the bushing on it - someone forgot to put the bushing back on so there is play.

MrTrendizzle · October 2, 2023

I've checked all the brakes and control arms. Everything seems ok. Here is a video of what i suspect the knocking is from.

@ColinBarber my pads have the clips that hold the edge of the pad in to the calliper but they don't have the back plate as @J Henderson has shown on his.

J Henderson · October 2, 2023

Not sure how you can prevent that noise then since new discs will also have a bit of play in the holes.

I'm still confused how the movement is even possible with a wheel bolted down on it. I've tried to work it out, but I can't! 🤔

Perhaps adjusting the parking brake shoes so they're dragging ever so slightly might help.

ColinBarber · October 2, 2023

1 hour ago, MrTrendizzle said:

@ColinBarber my pads have the clips that hold the edge of the pad in to the calliper but they don't have the back plate as @J Henderson has shown on his.

The plates stop squeal so that isn't your issue.

The oversized holes on the brake disc look normal to me. There will be no movement when the wheel nuts are done up correctly.

MrTrendizzle · October 2, 2023

6 hours ago, J Henderson said:

Not sure how you can prevent that noise then since new discs will also have a bit of play in the holes.

I'm still confused how the movement is even possible with a wheel bolted down on it. I've tried to work it out, but I can't! 🤔

Perhaps adjusting the parking brake shoes so they're dragging ever so slightly might help.

I have some old rubber washer/bushing type things laying around the shed Similar to the calliper slider rubber which might fit between the bolt and the disc. I might give that a try, slide them over and push the disc back over to ease the knocking. If that's the cause.

4 hours ago, ColinBarber said:

The plates stop squeal so that isn't your issue.

The oversized holes on the brake disc look normal to me. There will be no movement when the wheel nuts are done up correctly.

That's normal? I thought that gap was excessive compared to other cars i've owned in the past. I'll cable tie my go-pro under the car tomorrow and see if i can find anything moving but like i've said i've had a 4ft pry bar on everything and nothing has any give at all and the sound is 100% from the rear passenger wheel. I did forget to check the suspension top mounts. I'll get on that in the morning. Busy busy and always forgetting something me.

ColinBarber · October 2, 2023

45 minutes ago, MrTrendizzle said:

That's normal? I thought that gap was excessive compared to other cars i've owned in the past

Normal in that there will always be a gap. If there was movement it wouldn't take long for the holes to become larger, the studs would be damaged (being softer than the disc) and everyone would always have clunk noises.

MrTrendizzle · October 5, 2023

Quick update: I can't find anything moving with the go-pro and the suspension mounts are all fine. I've torqued everything up to "**** you" lbs/ft by using my massive breaker bar to tighten EVERY nut/bolt on the passenger side including the brake callipers and the clunk has reduced severely. Now it only clunks when i press the brakes hard and release the moment my nose dips (Quick hard dab on the brakes)

The only thing left is the pads/calliper but without a suction mount with arm to hang my go-pro over the wheel to watch as i drive i'm unable to check to see what's moving.

It's driving me insane but atleast general driving the noise has stopped. I will find exactly what is causing it but it's taking a bit longer than i thought it would.

MrTrendizzle · August 28

Just to update. The clunking i was hearing was the brake pads moving only a few mm when applying the brake. I found a very old youtube video with very little views that was showing the same issue. He replaced the backing plates and it fixed the issue.
I made some plates from old coke cans which fixed my issue so ordered new plates from Aliexpress. No more clunking under braking. Honestly it has driven me insane and without finding any other issues i attempted to live with it until this random Youtube video popped up on my feed.
These are the plates i got which fixed the clunking.

zoricib · August 29

21 hours ago, MrTrendizzle said:

Just to update. The clunking i was hearing was the brake pads moving only a few mm when applying the brake. I found a very old youtube video with very little views that was showing the same issue. He replaced the backing plates and it fixed the issue.
I made some plates from old coke cans which fixed my issue so ordered new plates from Aliexpress. No more clunking under braking. Honestly it has driven me insane and without finding any other issues i attempted to live with it until this random Youtube video popped up on my feed.
These are the plates i got which fixed the clunking.

Got a link by any chance?

Toyoda · August 29

I had a similar issue with the Lexus dealership after they fitted new discs and pads. However, it was related to the pure new mechanic's experience.

The mechanic told me that the older Lexus models used thicker pad grease, and the new vehicle was moved to thinner so I had to send my car back to re-grease it and the click was gone.

MrTrendizzle · August 29

3 hours ago, zoricib said:

Got a link by any chance?

https://lexuspartsdirect.co.uk/product/lexus-is-phase-2-rear-brake-pad-anti-squeal-shim-kit/ - Lexus part

Seems the Aliexpress link i have in my emails is now invalid. But they cost me £28 with shipping which took 28 days to arrive. The store still sells pads and big brake kits for the IS250 tho.