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Discussion Starter · #1 ·
So far this modest financial investment has been a good upgrade to the car's braking - apart from an odd behaviour...

If I brake reasonably hard (not emergency by any means) from silly speed xxx - say a drop of 60mph more than about 3-4 times, the brakes start to shudder a bit and make a horrible groaning/thrumming noise. There is some vibration.
What I find strange is once they cool down, everything is fine - totally smooth again at all speeds.

Any ideas? although I only do this very occassionally, it makes a cross country blast pretty pants. First thought is warped discs but I wouldnt expect the recovery in that case.
 

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Did you naturalise(various other terms are used) the disc's when first fitted ??
I had a set of Brembo disc's on a CX GTI turbo and they warped badly due to the fact that i didn't bed them in for long enough and then had to show a bloke in a Golf GTI that it may look like a long black french shed on wheels but it still goes quite fast
and did after various modifications stop quite quickly.
This is the car me and my brother drove from hereford to london with a flat rear tyre at speed with out noticing apart from various people waving at us on the Mway who i waved back at using a single finger
 

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Discussion Starter · #3 ·
they were treated with kid gloves for about 500 miles... would be surprised/upset/tearful if they warped due to me not being careful. hmm
Still dont understand why they only feel like they are warped when the they get a good roasting (so to speak). All other times OK.
 

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Not nice to say but true, all disc's are treated and real time tested i.e. spun at variuos revs for harmonics, cracks etc. Some disc's that are boarder line can get through this check but then give less than excelent performance when used. (used to get brand new ones them returned when i worked for a parts factor). It may be worth getting them off having them skimmed and checked (costs ) or just leave them on for a while longer and see if they do bed in. HTH not realy a brake expert
 

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One other point related to disc's we had 1 shipment ~20 discs and a guy came in to measure them up for a project, we checed the side markers for info and found 6!!! different foundry codes. Makes you wonder
 

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It might just be a feature of the disc/pad combo. I have had the same in the past, a particular type of pad that would start to make grumbling noises when it got warm, but would be silent when cold. Annoying, but it still stopped.
 

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I have also noticed a rumble from high speed braking, I also put it down to the brakes not being bedded in properly, as they were fitted before I bought the car, it is a little disconcerting although she still stops, I put it down to being a fair lump to bring to a stop from that speed.We are currently looking into a brake set-up for a track day car using the standard callipers but replacement discs and pads, it would be nice to perhaps try a different pad to see if that was any different? Will keep you posted.
 

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Discussion Starter · #9 ·
Thanks folks - nice link sgould - sounds very close to my problem. The issue being that my first couple of stops are always smooth at any speed. I reckon there is pad material patchily attaching to the disc when things get very hot - this causes the warped feeling.
After a bit of lighter cooler use, it seems to clean off again. This is theory 1 - the resolution is probably trying different pads/disc combo.
 

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faero, rather than thinking that you need to spend more money on a different setup, i might try the 'bed-in' procedure that is talked about, 2/3 of the way down the page for the link that sgould posted.
 

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i run the brembo hc discs with ferodo ds2500s on my st1 2.0lpt 9-5, i have found that the pads do need a few applications to get heat into them, but afterwards perform very well, although after an enthusiastc drive they can squeel for a while afterwards when applied
 

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I'm thinking of getting new disks and pads for my 9k Aero soon. I will probably go for Brembo Disks and C-Tech Mintex Fast Road pads. I don't want some insurance pleb knocking on my door asking about my 'groovy' disks...
 
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