Advice on brakes please

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Deano1712
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Advice on brakes please

Post by Deano1712 »

Apologies for my naivety on my MR but I need a bit of advice. I am fancying a brake overhaul since my discs look a bit rusty and Im not getting a full contact between pad and disc. Options are new discs and pads or skim up the old ones. The present discs appear cross drilled and grooved F+R and I don’t know whether these are standard for the car. I they are non standard (ie upgraded) its probably best to get them skimmed rather than taking the backward step of fitting standard parts. What are the standard discs like?

Mark
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TonyCal
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Post by TonyCal »

The discs you have are not MR standard ones, Im not sure it would be a good idea to have grooved discs skimmed. So far better to replace them. The standard M discs with standard pads work extreemly well in the majority of situations. I had no problems with mine on a track day at brands hatch in june, no fade etc. Even fast road use does not affect them, the only problem is tha amount of brake dust they produce.
It really your choice as to go standard or replace the grooved and drilled with similar. Personally I would not say it was a backward step to go to standard brakes.
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SpunkyM
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Post by SpunkyM »

Completely agree with everything Tony says apart from one of his points...
The standard M discs with standard pads work extreemly well in the majority of situations. I had no problems with mine on a track day at brands hatch in june, no fade etc
..I found the standard pads sadly lacking on my car. Even 'spirited' road driving would have them grumbling like an old man. You had to push them a fair bit further to get them to fade but I guarantee they will be like wood after 5 consecutive stops from 100 - 30 mph. I'm surprised you didn't notice any degredation on your track day Tony - are you absolutely sure you have standard pads?

The OEM discs are another matter entirely and are more than up to the job. They are a posh semi floating construction which reduces the thermal potential between the rotor and the hub - the result being they are incredibly resistant to warping. They are probably more expensive than your posh looking grooved and drilled jobbies though so a difficult decision.

In terms of pads, I would consider (in order of price, cheapest first):

Mintex Xtreme
Pagid Fast Road
Ferrodo DS2500
Pagid Blue (4-2)

I've only got the Mintex Xtreme on the rear of my car so difficuly to judge just how good they would be on the front. Great value though.
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Deano1712
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Post by Deano1712 »

Thanks for the advice guys. I can get the discs skimmed at work for free so may try that as first option. I cant see a problem, there is plenty of meat on the discs and there is no judder so they must be true. They just need a lick on a grinder, maybe 0.2mm off. If they dont come up right I can buy new standard but prob a few hundred. Fast road pads sound good, I will give it a go. With the brakes sorted and a strut brace fitted I will feel a more comfortable driving it hard through the twisty stuff. :twisted:
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Disc Wear

Post by Guest »

Your discs look like Black Diamond, which seldom seem to have that nice bright finish seen on most discs, but they work fine.

Your discs do not look as if they need replacing - just a lot more serious use! Unless your pads are worn out, just go for a decent drive and use the brakes firmly and regularly, but not to excess - no marks for funny smells!

I have Black Diamond discs like yours on my 2.8, and as most of one's braking is quite gentle they often show the same type of marking, but after a bit of serious use always show a nice full-width bedding. I think the basic problem is that the calipers are not 100% rigid, being stabilised by the big spring clip, so under light braking pressure the pads are not being fully forced against the disc surface.

After a trip around the best alpine passes last month the discs showed full pad contact - and the brakes felt better, too!

The rust around the edge is a normal thing on any disc, other than the stainless steel type fitted on motorcycles for cosmetic reasons. If it worries you, scrape off the crusty bits with a file. It will come again, and will do on any cast iron disc, but is nothing to worry about.

I have heard of several BMW dealers 'Advising' after an MoT that the discs should be replaced due to this uncosmetic effect. I think their motto is something about 'A fool and his money!'
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Mster
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Post by Mster »

The standard ///M discs are fine (as they have decent cooling ducts) but as has been said the standard pads are lacking. I experienced fade with standard pads on a handling day, on the road you probably wouldn't notice.
A simple upgrade to DS2500 cured the problem and they were excellent at Bedford all day with no fade and Bedford is known to be hard on brakes.

Mike's right, just go out there and bed them in again, no need for skimming in most cases unless warped, they just need to be used hard.

To bed them you just need apply half to three quarters of maximum pedal for about 4 seconds at a time and repeat about 20 or thirty times with about a 30 second break in between (so not to overheat the discs).
board
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Post by board »

I have gone down the tarox route. They do a set for the front for track use. I found the standard discs only lasted 4 laps of Cadwell Park (heavy on the brakes) before they faded badly. Also under the more extreme conditions there i found the front end all over the place as if the brakes were warping but i think it was more a build up of dust.

I don't think i'll go down the standard route on the front again. the back end is fine with the standard discs but if i upgrade further (calipers etc) then the lot will go.

I'm very happy with the Tarox solution (ordered direct from them) and have had a few moments (ie. van coming out of the services on a dual carriagway straight to the outside lane without looking) going from 70 ish to 40 with in a car length.

They are a bit noisy around town but that doesn't bother me, i would rather have something that stops ;)
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Deano1712
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Post by Deano1712 »

I went out for a spin today and did as you suggested Mike - used them a lot harder. The discs look better and the brakes certainly feel a lot sharper. During the last service (just before I got the car) the dealer said they needed changing but perhaps that is a red herring. I will spend the next few weeks driving it like a mad nutter and hope the brakes continue to improve :wink:
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SpunkyM
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Post by SpunkyM »

I found the standard discs only lasted 4 laps of Cadwell Park (heavy on the brakes) before they faded badly
I would say the blame lies much more with your pads rather than your discs there.
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Post by board »

I would agree but the instability caused by the build up of dust was quite alarming so made more sense to go down the grooved route to make sure i didn't experience that again
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c_w
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Post by c_w »

board wrote:I would agree but the instability caused by the build up of dust was quite alarming so made more sense to go down the grooved route to make sure i didn't experience that again
A grooved disc might help in some situations but try and get discs that are grooved only rather than drilled and grooved (as most aftermarket discs seemed to be).
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Post by Guest »

Anyone interested in changing their brakes should rally take a look at this. - http://www.zeckhausen.com/avoiding_brake_judder.htm

VERY intersting reading.

Simon
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