Potential Warped discs? Shudder when very hot

da.murf

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Fitted mintex grooves and drilled discs in the zed back in March.
Car maybe done 2.5k since. Brakes where bedded in correctly (late night carriageway 70-80mph hard braking a few times, then from 40-60mph etc, careful not to have brake on whilst static)

recently when the brakes get decent heat into them (back road run for example with braking hard etc) there is a shudder appear in the steering wheel and a little in the pedal.
It goes when the brakes cool again.
Few questions:

Firstly idea how discs n pads so new could warp? Is this even a warp?

Secondly would something like that be warranty covered?

Should also add normal driving there is zero issues.

did notice yesterday when I’d wheels off I could turn the left disc pretty freely by hand but there seemed a tight spot.

Thanks
 
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mrloaf

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I'm having a little shudder in my 350z brakes as well, took the front discs (only couple of k on them) off as I'd read about pad material transfer onto the discs, fully cleaned the surface with brake cleaner and a dremel thinking that would help but shuddering was still present.

Changing a worn bearing on front drivers side helped a lot but still getting a slight shudder so going to repeat that process on the rears and check for bearing noise too.
 

da.murf

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da.murf
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I'm having a little shudder in my 350z brakes as well, took the front discs (only couple of k on them) off as I'd read about pad material transfer onto the discs, fully cleaned the surface with brake cleaner and a dremel thinking that would help but shuddering was still present.

Changing a worn bearing on front drivers side helped a lot but still getting a slight shudder so going to repeat that process on the rears and check for bearing noise too.
Was this at any speed?
 

mrloaf

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Really noticeable at higher speeds with heavy braking, light braking at town speeds was fine @da.murf
 

FM155

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I've frigged discs/pads on my daily due to lack of use March - June and rust pits in the disc surfaces.
Same sort of symptoms..
 

da.murf

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da.murf
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I've frigged discs/pads on my daily due to lack of use March - June and rust pits in the disc surfaces.
Same sort of symptoms..

For my case i wonder would an air line help blow any crap outta the grooves in the disc etc

Also can you skim grooved and dimpled discs ?
 

FM155

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Probably more like a wire brush. I used to get that problem with grooved discs. That's why I haven't bothered with them on the MX.
 

-Pete-

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had the exact same thing on a previous car running grooved discs, and the grooves were filling up with pad material and thats what was causing the judder. were fine when you picked out the material from the grooves and gave them a clean but within 10 minutes or some heavy breaking it was back again. total PITA. put me off grooved discs completely.
 

quattro Rick

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Had the same crappy experience with cheap Brembo grooved discs, could be the pads tbh but once I swapped to solid discs with ds2500 pads I had a much nicer pedal feel

RS6 with AP racing grooved discs didn't seem to gather up as much in the grooves and they were arguably abused much more and done similar miles.
 

da.murf

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da.murf
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Had the same crappy experience with cheap Brembo grooved discs, could be the pads tbh but once I swapped to solid discs with ds2500 pads I had a much nicer pedal feel

RS6 with AP racing grooved discs didn't seem to gather up as much in the grooves and they were arguably abused much more and done similar miles.
Hmmm they came with cheaper brembo pads.... wonder if it’s worth changing the pads first and giving discs a clean down
 

veedubnoodle

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Will definitely be covered under warranty and you are entitled to get your money back and opt for normal discs if you prefer.

I've heard of this issue many times (infact had it on my Mitsi with EBC greenstuff pads and drilled discs) and it was caused by a build up of braking material in the drilled discs.

You can get a disc run out tool to measure if the disc is warped but I'd only buy one if you do a lot of home mechanic-ing yourself.

Also changing pads won't solve your issue. A judder will come from the disc or play in something around that area. It is worth checking everything connected to the hub just to be sure incase you have a wheel bearing on the way out or play in something but from what you are describing it sounds like either a warped disc or pad material build up.
 

Jrooney06

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Just a couple of things i would also check. First would be a sticky calliper second would be ball joints. Worn pin sliders can also cause issues. I always check with a dti gauge after fitting there have been times when I’ve thought the disc was perfectly square and it wasn’t, so always a good investment. Lazer sell one for £50 or so which isn’t too steep for the DIYer.
Should also add the old do a few heavy braking procedures to remove pad build up on the surface is a short term fix. The pad material impregnates the surface of the disc and the judder will return.
 

da.murf

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Bit of a resolution to this

@sam_9n kindly skimmed the discs for me and seems to have sorted it.

both discs where moderately warped & with only 2500 miles on them I can only put it down to me over bedding them in initially using an overly aggressive bedding in procedure.
Long story short I was given brembo pads (I assume budget) with the discs.
Then I went onto use stoptechs bed in procedure, which I now realise is for a pad with a much higher temp and performance rating.
I think they have overheated and temp transferred to the discs.

I fitted the new stoptech sport pads (light track/fast road) yesterday and quick test last night seems positive. Already I think I notice a heavier bite once they heat.

Think ill just run them in gently over a period of time with a few 60mph stops rather than really heavy heat cycle procedure.

Again thanks to @sam_9n for sorting discs.
 

DC.

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Modern discs seem pretty poor. Maybe it’s the quality of the disc or new cars are getting bigger/heavier either way they are dung.
 

stevieturbo

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Modern discs seem pretty poor. Maybe it’s the quality of the disc or new cars are getting bigger/heavier either way they are dung.

Aftermarket discs are generally pretty poor....hence why I say if you have problems, fit OEM discs. They are not the same even if some claim OEM quality etc.
 
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Ghisallo

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I had badly pitted discs earlier in the year, I started a thread on it.

Although the parts were Ford motor craft items and not had many miles on them, the service manager at Ford reckoned that in his experience that the first set of discs and pads a car has from the factory last the longest by far, with subsequent ones never having the same longevity.

He also mentioned that keeping the brakes on for a long time when stopped can cause damage to discs. Though I thought holding the foot brake on was what you were supposed to do with automatics while stationary at lights etc.
 

stevieturbo

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I had badly pitted discs earlier in the year, I started a thread on it.

Although the parts were Ford motor craft items and not had many miles on them, the service manager at Ford reckoned that in his experience that the first set of discs and pads a car has from the factory last the longest by far, with subsequent ones never having the same longevity.

He also mentioned that keeping the brakes on for a long time when stopped can cause damage to discs. Though I thought holding the foot brake on was what you were supposed to do with automatics while stationary at lights etc.

Technically when stopped, any teachings would say put it in neutral and apply handbrake.

Although clearly with modern cars and electric handbrakes, it would be yet another aspect of highway code etc that is far outdated and impractical.

But applying and holding the brakes onto very hot discs can apparently cause some issues...normal driving, perfectly fine. And probably even then 95% of the time perfectly fine.
 

Mark_C

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How is the disc "warping" being measured? Runout is not an accurate measurement, to use runout you would need to measure face and rear of disc at opposite points with similarly mounted gauges and record a negative displacement on one needle equal to the positive displacement of the opposing needle.
 

sam_9n

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How is the disc "warping" being measured? Runout is not an accurate measurement, to use runout you would need to measure face and rear of disc at opposite points with similarly mounted gauges and record a negative displacement on one needle equal to the positive displacement of the opposing needle.

Used a DTI on them. Initially made a mandrel up to locate disc on, bolted disc to that then clocked were the disc actual sits on the hub, little to no variance or at least nothing to worry about. Touched on the face of the disc after a good clean, found the low point And high point which was 0.28mm difference. Basically the same as the other side of the disc. Skimmed just over 0.55mm in total and checked the faces of the disc to the area sitting against the hub, still well within the disc operating thickness.
 

da.murf

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da.murf
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Used a DTI on them. Initially made a mandrel up to locate disc on, bolted disc to that then clocked were the disc actual sits on the hub, little to no variance or at least nothing to worry about. Touched on the face of the disc after a good clean, found the low point And high point which was 0.28mm difference. Basically the same as the other side of the disc. Skimmed just over 0.55mm in total and checked the faces of the disc to the area sitting against the hub, still well within the disc operating thickness.
Yep Yes GIF by zoefannet
 

Apis

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That assumes there is no run out on the hub itself.

Clocking the disc on the hub and using an on-car brake lathe is the best way to guarantee a good outcome, be it run out, "warping" or most likely, disc thickness variation.
And if then if the disc is ever removed, it needs to be refitted in same location. (usual for most discs anyway.)
 

sam_9n

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In an ideal world of course machining in situ is best, but alas it’s not an ideal world. And considering the hub area of the disc was clocked before machining, is the best outcome you can hope for. Likelihood of a hub being out is slim, and he sure would of noticed it before these discs. 99% of warped discs I’ve seen always get taken to a machine shop (OD cars included use lathes) or replaced due to ease, yet to see a mechanic with a disc lathe. Likes of a Pro cut albeit mostly american are great for on car machining.
 

-Pete-

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nothing wrong with using a lathe to skim the discs at all. After skimming off that 0.28, if you could feel any run out via pulsing on the pedal you would need to be at the resonant frequency to have a hope. its all splitting hairs for diminishing returns too. pointless to do anymore than just skim the discs and makes sure the pads aren't knackered and seat the disc back on a clean hub with no gunk on the back side. Also making sure the pads can float freely away from the disc when the pedals lifted, usually well overlooked. I nearly always find I'm buffing the edges off the backing material to make that happen when fitting new.
 
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