Brake judder when hot on track??

M

Mikey_Boy

Member
Hi Folks,

Hoping you can help me out with a bit of advice. I've just got back from A glorious couple of days at Spa getting to know my M coupe a bit more - I've done a few mods (post with pics to come soon!) but the brakes are bone stock OEM all round.

I frankly thought they were appalling on track - serious brake judder after only a couple of laps - on the road they were fine and on the drive back they were fine as well, just as soon as the duty cycle went up they wilted.

I've read a couple of threads stating pad choice is critical, but wondering if going AP is the only choice?? A single piston caliper on an M car seems a bit out of place to me!!

Be good to get some opinions before I bite the (expensive!) bullet!

Thanks all!! :driving:
 
Hmm, so many things to check:

firstly state of pads and discs? Possibly pad deposits on disc?
when was the last brake fluid change?
Caliper moving smoothly?
Piston OK in caliper?

I don't have the standard brakes (APs all round for my car) but from memory there is an upgrade to the caliper pins or bushings or something that can be done to prevent the caliper deflecting under heavy load.
 
the stock brakes were ace from my memory and always impressed me, my APs just allow me to keep doing it for much longer before they start to suffer....

with the right parts the stock brakes are very effective, the may not look super bling but offer serious performance.
 
Thanks guys! :thumbsup:

That's really helpful - the fluid was changed about 9 months ago as part of an Inspection II service so I know that's ok. There are a good few unknowns in the car - my assumption is that the pads and disks are all OEM, at least that's what the receipt said when I bought the car! :wink: Plus I haven't checked the operation or health of the calipers so that needs to go on the list.

I really think the solid bushes will be a big help so thanks Exdos for that! That makes a lot of sense, especially as the judder got progressively worse with more heat. I've read that Pagid (RS29??) pads are a worthwhile upgrade to do, but I will also have a look at the yellow stuff pads too..

Suspension is ok as I've just changed all that to Bilstein PSS10 and fitted new front and rear bushes too.

And of course braided hoses make excellent sense.. :D

Good to know there are some things to do to the OEM brakes to make them better - whilst I like the idea of the AP kit, the cost of it makes me wince!!
 
The judder is probably adhesion, which is why it's much worse when the brakes are hot.

You might get away with new pads, preferably a decent compound (not anything ebc) which will clean the deposits off the disc. But if they've been heat cycled a couple of times you'll probably find that the discs wear unevenly (they'll wear more wear the adhesion didn't happen) so new discs will be required.
 
Welcome to the club fella! The brakes as others have said and a few will testify are just fine for track if 1. they are in good condition and 2. you look after them.That means you bed them in correctly and do long cooling lap at decent speed. Remember they are the same brakes as on the M3CSL which is track focused. HOWEVER:

Like most, not being a great driver I fried my already tired OEM set up on the 2nd trackday. Solution was simple and cheap: New discs all round, new decent pads Pagid etc. Goodridge stainless steel braided line, DOT 5.1 brake fluid. Then you'll be amazed at the difference it makes. just be careful on you choice of pads. Not saying A&P kit is over-kill but unless you'r really going to use it its way too big investment unless looking at it as a long term project (suspension, lightening, engine mods etc).
 
First: Extra brake cooling

Because the OEM Z4M brake ducts are not the greatest in cooling the brakes I looked for something extra. I never had fading with the AP & Pagid set-up. But on some tracks the Pagid brake pads and AP disc were getting really hot. Sometimes I had a vibration steering wheels after some intensive hot laps (the brake pads get a little to hot and some pad material got stuck on the AP discs) . The extra cooling helps to address this problem… Even with my full AP racing kit the extra brake cooling had some really positive effect (on track)… At the picture you can see my extra cooling holes beside the original ones.

z93w.jpg

Second: Modify OEM brakes
Get some decent Pagid Pads, steel brake linings and some better (high temp) brake oil… This will upgrade the brake's a lot and let them work rather good on track. jpeeters (on this forum) drives his blue Z4M coupe on Spa and the ring with this brake set-up and he is a very good driver. He thinks the braking is OK, but only a AP kit will completely satisfy his braking needs and bring the braking to the level of awesome...

At the time of the movie, this was the set-up of both cars:
Z4M coupe / blue: extra brake cooling, OEM Brakes with with modification, Pagid RS-14, CSL wheels, Supersport tyres, OEM suspension
Z4M roadster / silver: extra brake cooling, AP kit, Pagid RS-14, CSL wheels, Supersport tyres, OEM suspension with Eibach springs

[youtube]dRWZxmI0AYY[/youtube]

https://www.youtube.com/watch?v=dRWZxmI0AYY&feature=youtu.be

Third: Still not happy? If you want awesome braking and are planning to do a lot of trackdays and keep the car a long time get a BBK.

BMW does makes brakes that work on there cars....if you stay on the street! On a track it's a totally different story and the OEM BMW M brakes are not 100% up to the job (even on a purpose build car like a M3 CSL= same set up Z4M). Remember; there are only a small amount of M owners who drive their cars on a track (even M3 CSL owners); so why would BMW put more expensive brakes on their cars? From a commercial view there is no point for BMW. It will only make the cars more expensive and not everyone needs brakes that also work perfect on track. It's not only the brakes, the pads themselves make a really big difference

It's true; other brake pads and high temperature brake oil will improve the standard OEM brakes. But a BBK is another cup of tea and brings the braking to a higher level (no fading, brake balance, better modulation, etc). It all depends how much you are willing to spend and how much trackdays you do. In my case; I do at least 1 trip to the ring a month (+ additional trackdays). IMO the investment in a BBK is only worth if your car sees a lot of track. From day 1; I wanted the best braking I could get on my Z4M…so I invested 0 money in upgrading the OEM set-up and went straight for AP racing kit. It's not cheap, but a BBK is in another league then the OEM set-up. Also spending 0 money on modifying the OEM brake set-up and going straight to a AP BBK saved me some money in the long run.

When I first got my AP kit under my Z4M, then I was not so happy with my purchase (you can find the topic on the forum). After some fine tuning (bleeding the brakes) from my specialist and driving some more miles the AP became good... Then after one year of driving with the Pagid RS4-2 (blue) I switched to Pagid RS-14 Front & RS4-4 Rear. This change in brake pads totally transformed the AP brakes. The AP kit went from good to totally awesome!!! Initial bite, fade resistance, modulation and feel is now great and everything I wanted from a BBK on track. Whatever you do with your brakes, the type of brake pads also makes a really big difference... Personally; I don't recommend Pagid RS4-2 for track work!
 
Franzino said:
Z4M coupe / blue: extra brake cooling, OEM Brakes with with modification, Pagid RS-14, CSL wheels, Supersport tyres, OEM suspension
Z4M roadster / silver: extra brake cooling, AP kit, Pagid RS-14, CSL wheels, Supersport tyres, OEM suspension with Eibach springs
Click to expand...

I also upgraded to the solid caliper bushing as tertius suggest in http://www.z4-forum.com/forum/viewtopic.php?f=24&t=45293 . Bought mine on http://www.turnermotorsport.com/p-4118-caliper-bushing-upgrade-kit.aspx
 
Thanks everybody!! :thumbsup:

I have been rather spoilt up to now with brakes - my BMW E30 track car has 330mm 8 pots at the front and 300mm 4 pots at the back and having also owned Porsches whose OEM brakes are SUPERB and even my little MX5 has Wilford 4 pots with big discs... :evil:

I guess I am still learning and adjusting to the Z's character....!

It's good to know that the standard brakes can be tweaked to suit - when I bought the car the assurances were that new OEM stuff had been fitted all round, but of course, you only have the vendor's word and you don't know what other underlying problems could be there (e.g. sticking pistons etc).

Those 'Ring laps look like a lot of fun!! :driving:

I shall do some more investigating and make a decision soon...! :wink:
 
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