Track pad advice please

[ga41]

Is the real benefit of the BBKs that only the expensive/best pads will fit?

It's a giant con!

The real benefit is higher thermal capacity because of the bigger, thicker rotors and callipers and superior braking feel. To that extend i saw a huge improvement. Not much more stopping power, if any improvement at all, but very good braking feel and stamina. If you want better stopping power then you need a more aggressive pad, not more pistons/larger disc.

 

[BMWZ4MC]

Thanks, I'll have a look at their site later.
If there is but one benefit of a BBK I think it lies in the ability to dissipate heat. The OEM set up works really well, until the fluid fails. The pads themselves do develop fade but not alarmingly so. I'm 90% happy with the setup I have in terms of performance - although being able to brake slightly later would be nice, it's the susceptibility of the yellowstuff to heat damage and rapid wear that bothers me.

 

[BMWZ4MC]

ga, great minds think alike!

 

[exdos]

The stopping power of OEM brakes can be easily improved by more "aggressive" pads which create more heat, but then this will reduce the "duty cycle" for repeated braking events with short periods for cooling in between (as on track). The simple and cheap solution is provide auxiliary brake ducting directly to the centre of the rotors so that cold air constantly blows through the discs. Job done. I'm not saying that this is better than an alloy BBK, just that it's an alternative to spending £1.5k or so.

 

[ga41]

It is a good solution and one that i'd be interested in but there is no readymade brake duct kit out there for our cars. I've only seen 1 retrofit that they had to cut 2 holes in the front bumper and slightly reduce the max steering angle so the wheel would push the ducts.

 

[exdos]

It is a good solution and one that i'd be interested in but there is no readymade brake duct kit out there for our cars. I've only seen 1 retrofit that they had to cut 2 holes in the front bumper and slightly reduce the max steering angle so the wheel would push the ducts.

You wouldn't need to cut any holes in the bumper or reduce the steering angle. I'll make some and test them and I could get the appropriate parts professionally made in aluminium if there's enough interest in the idea.

 

[ga41]

Post or PM me some pics when you do and i might buy a set.

 

[BMWZ4MC]

Post or PM me some pics when you do and i might buy a set.

x2

 

[ChawenHalo]

Post or PM me some pics when you do and i might buy a set.

x2

x3

GA41. Really? not much point on a BBK? just increases stamina? Could help explain BMW's facination with single piston floating whatever calipers.

AP BBK is 4K over here which is a hell of a lot so any iomprovements avoiding that need is whelcome.

Exdos: do you have any pics of yoju brake duct cooling thing or was that in you Z3?

Cheers

 

[ga41]

Really, you only get more stamina and better brake pedal modulation. In my case i'd done everything else, racing fluid (tried both Motul RBF660 and Endless SR650), braided brake lines and decent pads and still found the stock system's stamina lacking. The Stoptech BBK i now have is rock solid and does not fade even after 3x20min track sessions with 20-30min rest periods between.

 

[exdos]

GA41. Really? not much point on a BBK? just increases stamina? Could help explain BMW's facination with single piston floating whatever calipers.

BMW have used the one pot caliper on most of its cars, even the heaviest of them. I don't think stopping power is the problem, only the duty cycle, and this is where auxiliary brake ducting comes to the rescue.

Exdos: do you have any pics of your brake duct cooling thing or was that in you Z3?

I already have brake ducting on my Z3MC and have photos of that which I think I've previously posted on here. However, I've spent a couple of hours this afternoon with the front wheels off my Z4MC and I've come up with two different ways of making auxiliary brake ducts and I've just come into the house to scan the cardboard template I've made for the idea that I think could prove to be the best and neatest solution, so that I can cut some aluminium to fabricate a part.

 

[exdos]

ga41, BMWZ4MC, ChawenHalo,

Here are some photos of the two different solutions that I've devised.

The first photo shows a typical brake cooling duct solution, although not with any fittings onto the ducting. I simply attached a spare length of ducting to test for clearance and it is possible to attach a length of ducting onto the tie-rod which permits lock-to-lock turning. So this is a possible "goer" and will be developed further.

The other 4 photos shows a fitting which I've devised and fabricated as a basic prototype, which should direct more air towards the brake discs and which needs no ducting. The fitting allows lock-to-lock turning. The part shouldn't weigh much so not adding much to unsprung weight. As I see it, if the forward-facing vents in the OEM disc-shield are designed to allow the passage of air towards the brakes, then fitting a large forward-facing funnel over these vents should make the vents even more effective because they will capture air coming through the OEM brake ducts in the bumper and air passing underneath the car. We'll see.

I intend to test both versions by fitting them to one wheel only, leaving the other side OEM, and then taking temperatures with an infra-red thermometer, after braking. It is, of course, possible to make this into a hybrid solution, where there is auxiliary ducting with a forward facing inlet and uses a hub-mounted outlet, like my prototype in the photos.

If both these solutions offer the same cooling efficiency, which, if any, would you prefer to fit on your Z4MC?

 

[ga41]

If they're equally effective i'd go with the second solution for simplicity's sake. Would any of these interfere with the thicker rotors of a BBK? Might i suggest a dedicated thread as well?

 

[inkey$]

Just realised what ridiculous geek I must be. Read the title of this thread and was going to recommend Apple.

(Thanks for buying me that ZX81 back in the day dad. You've made me the man I am today)

 

[exdos]

If they're equally effective i'd go with the second solution for simplicity's sake. Would any of these interfere with the thicker rotors of a BBK? Might i suggest a dedicated thread as well?

The second design is also my preferred option; it's also more akin to the brake ducts on F1 cars. The prototype I've fabricated will fit any Z4 MC/R provided the OEM disc-shield remains in place. I've made the prototype from a scrap piece of Aluminium/manganese alloy just because I had this to hand and it is thicker and heavier than the aluminium from which I'd fabricate the finished part, and the prototype presently weighs 150gms, so I reckon a finished piece would weigh around 100-120gms.

 

[ChawenHalo]

Just realised what ridiculous geek I must be. Read the title of this thread and was going to recommend Apple.

(Thanks for buying me that ZX81 back in the day dad. You've made me the man I am today)

LOL :lol:

Just for comparason's sake, how do your respective women cope with you car's obsession?

 

[ga41]

If they're equally effective i'd go with the second solution for simplicity's sake. Would any of these interfere with the thicker rotors of a BBK? Might i suggest a dedicated thread as well?

The second design is also my preferred option; it's also more akin to the brake ducts on F1 cars. The prototype I've fabricated will fit any Z4 MC/R provided the OEM disc-shield remains in place. I've made the prototype from a scrap piece of Aluminium/manganese alloy just because I had this to hand and it is thicker and heavier than the aluminium from which I'd fabricate the finished part, and the prototype presently weighs 150gms, so I reckon a finished piece would weigh around 100-120gms.

I think the dust shields are removed on my car because of the thicker rotors and larger callipers. I didn't do the install myself so will have to check to confirm.

 

[Lower]

Stripes of heat paint on the discs is the best way to measure brake disc temperature. Then you know the peak temperature the disc reaches which the key figure.

The flexi ducted route is going to be more effective at cooling the discs than the scoop. Most of the airflow inside the wheel and wheel arch is rotational and driven by the tyres so getting the airflow from outside the wheel arch is going to be much more beneficial.

If possible, the best place to duct the air to is the centre of the hub so that it assists the flow of air through the disc which is what gives the greatest cooling.

 

[Lower]

The stopping power of OEM brakes can be easily improved by more "aggressive" pads which create more heat, but then this will reduce the "duty cycle" for repeated braking events with short periods for cooling in between (as on track). The simple and cheap solution is provide auxiliary brake ducting directly to the centre of the rotors so that cold air constantly blows through the discs. Job done. I'm not saying that this is better than an alloy BBK, just that it's an alternative to spending £1.5k or so.

Brake pads with a higher coefficient of friction won't necessarily create more heat as the pressures applied by the pad to the disc for the same retardation is lower and can be applied for a shorter period. Logic tells you that the same amount of kinetic energy will be converted to heat but reality is different, certainly in regard of disc and pad temperatures.

There are a number of key qualities to a high performing pad. it will have a higher coefficient of friction than standard with high initial bite. This will enable the driver to brake for a shorter period of time with less pedal pressure which helps keep disc and pad temperatures down. The lower pedal pressure will also enable the driver to modulate the brakes closer to the tyre lock up point, thus increasing the retardation performance. The pad will also act as an insulator, absorbing as little of the heat generated during braking as possible so that the pad itself doesn't overheat and also preventing heat transfer into the calliper and consequently the brake fluid. Lastly (for this simplified post) the pad will also have as constant a coefficient of friction as possible throughout its temperature range so that braking performance remains constant.

Brake disc cooling is particularly important because if the disc temperature is controlled then the pad temperature is also controlled and consequently the brake fluid is less likely to overheat. Combine that with a really good performing pad and a BBK becomes overkill for normal driving or trackday use.

Most of my experience of brakes comes from testing a wide variety of pads and discs on my previous honda S2000s which also have a single piston calliper. The best solution (and that used by the people that race them) is the OEM caliper, an upgraded disc with curved cooling vanes and Dixcel pads. Unfortunately you can't get the same pad for the Z4M and different makes and grades of pads do perform differently on different cars.

EBC yellowstuff pads are R90 approved which means they are road legal and their friction coefficient is within 10% of the performance of OEM. They are more hardwearing and heat resistant than OEM which means you can use them for longer before they fade but that they won't give you an actual improvement in retardation. It also means that they will overheat before they fade which is why the pads wear so quickly. You are overheating them, you just don't notice it when driving.

 

[ga41]

Good post Lower

exdos, looking forward to even more detail. Be happy to help any way i can.