Brake problems

[clcollins]

I had the Porsche brake kit put on my TDI Quattro, and lets just I'm really disappointed. The kit comprises of Porsche Boxster callipers and TT disks, the pads come with the kit, but I don’t know what they are.

My thoughts at this moment are that it has been a complete waste of money /ubbthreads/images/graemlins/cry.gif

They are no better than what was already on there, and just to compound my misery there is a significant judder under breaking, it can be felt through the pedal and steering wheel. It is very un-nerving and gives me no confidence at all in there capability, which when your talking about breaks is a really bad thing. On my previous A3 I just did a disk and pad upgrade and the results were better than this.

I have had the car back to the garage twice, stripped them down, checked them and reassembled them, there is nothing physically wrong with them, but they do agree the feel ‘different’. Apparently TT owners have mod done frequently without problem, which is of little consolation to me. The garage has intimated that pad upgrade may be required but am I wrong in thinking that this kit should really be right from the start?

Has anyone got any experience of this type of problem, any suggestions, anyone recommend a break specialist that may be able to help? Last question, real shot in the dark, but does the fact my car has a diesel engine have any possible effect /ubbthreads/images/graemlins/confused.gif

 

[s8n]

Are the discs warped? did you run them in correctly?

Your engine would effect it in no way...

 

[DavidR]

Sounds like some / all of the problem could be due to the pad / disc break in procedure.

There are 2 schools of thought on this issue, but the most convincing is that in order for a high performance brake system to work as the manufacturer would have intended, a new disc / pad combination must be subjected to a fairly vigourous break in to allow the pads material to heat, smoke and then fix, and also to allow a thin layer of pad material to be deposited on the disc.

Brakes work (i'm told) most effectively when there is a meeting of pad material, with disc + pad depost, rather that a the simply abrasive properties of pad against bare metal - so if you haven't successfully transferred pad material to the disc, the overall efficiency is likely to be less than expected.

Secondy, if you overheat brakes that have not been properly broken in, the pad transfer is likely to occur in an unequal manner, rather than the desired uniform deposition. This can lead to hot spots on the disc, resulting in initially temporary and resolvable vibrations but ultimately permanent high spots on the disc and permanent vibrations reqauiring new discs.

Also worthy of mention is the pad material itself and the useage expected of it. It is difficult to use a road pad very fiercly on road or track without it overheating, causing unequal deposits and therefore vibration. It is difficult also to find a track pad that works everyday on the school run. There will always be compromise.

Suggestions for you would be to find out from the supplier the preferred break in procedure for the pads and follow them. (usually this involves 10 stops from 60-10mph with a complete cool in between, and this repeated a few times). Dial guage the discs on the car (it is unlikely they are warped - but they may have been fitted incorrectly or the hub may be corroded resulting in disc variation). I cured a vibration on stoptech discs using an abrasive race pad running cold, it literally scraped the deposits from the disc following an ill advised track session). There should be no issue with your car being diesel as far as I know. Also worth rebleeding brakes to ensure no air is trapped in the system deterioratin pedal feel (some less reputable dealers fail to cycle the ABS pump on brake bleeding, so the first time ABS is activated old fluid and potentially air is put into the system)

Finally, the key to a big brake upgrade is not the overall power (i.e. the ability to generate more braking g force and shorten the distance from a set speed to rest) but the ability to dissipate heat and resist fade. This means that the car can stop from 100mph time after time without overheating. Often brake upgrades do not provide extra stopping power, but better feel and resistance to heat. A recent test on a 350Z with OEM vs upgraded brakes showed only a minimal difference in the 1st stop from 100mph to standstill, but subsequent stops were less prone to fade.

 

[clcollins]

Wow David, that was a comprehensive answer, thanks /ubbthreads/images/graemlins/grin.gif

As for who supplied and fitted the kit (peteTDI), I don't know if I should say right now, give them a chance to put it right, do you agree or not, I'm not sure.

I know, if you want PM me the question and I'll reply, I don't want to be seen to slag off a normally reliable garage.