I'm using Godspeed standard size grooved front and rear discs (4pot front, 2 pot rear) with carbone lorraine RC5+ pads and although they work well when cold I've now got judder when braking at high speed.
This is road use only at the moment. I have no issues with low/normal speed braking where there is no judder present or anything felt through the pedal.

I've checked the discs which are definitely flush and cleanly mounted on the hubs and the only visible signs on the discs are pad shaped marks where it has been stood for a while.

Would these marks on the discs be enough to cause judder at speed?

I'm pretty sure there is no issue with any worn components at present too.

Do I clean these marks off the discs with something abrasive or just keep using them until they sort themselves out?

 

Yes the Mark's could be enough to do it , they should clean off with use , you could clean them off with some fine Emery cloth

 

Cheers Ian!

I will see if they clean up themselves. I don't do many miles so it could take some time.

 

What about worn wishbone bushes? This definitely occurs on the Legacy/Hatch wishbone, may explain high speed judder?

 

With the CL pads , if the car has been left standing , they can stick to the discs because of rust , there is a metal content in the pads , and with the discs being very corrosive , the pad shape is probably where the pad has rusted to the disc , we have seen extreme cases where cars have been left for months , and when people unstick there pads , the pads have pulled themselves apart !
If at all possible , if you plan on parking it up outside , run it around the block every 2 or 3 days , it's not generally an issue with lower spec pads , but can be with some of the better pads
Cheers Ian

 

Might have to do that. I've only done 4k in 7 years so it does stand a fair bit. New engine means it's likely to get a bit more use.

 

I have this problem quite frequently as my one sits still for several weeks at a time. I did start using Bilt Hamber Atom Mac as a way of preventing it but it seems to kill the bed in between disc and pad and leave you running out of brakes as though the pads hadn't been bedded in properly. I'm assuming this is down to a chemical transfer layer being removed/altered by its use. Just thought it worth mentioning in case you found yourself thinking it may be the cure. I mean it might be, it just depends which is the lesser of two evils! For you it might be that the Atom Mac is the lesser...

 

A little update on the problem.

No visible issues with the discs or hubs and I've checked them with a dial gauge.

No deposits on the discs to call anything.

1 stuck piston in each of the 4 pots. Both being the lower inside piston. I'm going to refurb them with stainless ones from Ian.
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​​​​​​The pads however are a different story. The front and rears all had significant pits/holes on the surface of around 1 to 2mm deep. I've managed to resurface all of them and we will see how they go.

I'm assuming it's either a bedding in issue or they have corroded due to being stood.














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