2005 BMW 645ci convertible track day pad / disk /fluid combo

[peterh2]

Impossible question possibly but can anyone make a decent suggestion as to what combination of disk / pad / fluid I should be looking for?

It’s my daily driver and 75% of driving will be stop / start traffic unfortunately. 20% fast road and 2 – 3 track days per year.

The standard setup gave fade within a lap and within 2 laps was pretty much useless.

I’d prefer to keep the standard caliper setup if possible? Ideally after something that will be OK for a 6-8 lap session yet still usable for the commute.

I know this is a bit of a big ask for a 1,900kg car with a limited set of pads available in the standard size?

Thanks!

[GreenV8S]

peterh2 said:

The standard setup gave fade within a lap and within 2 laps was pretty much useless.

I've drive cars with woefully inadequate brakes that lasted longer than that, and I think fading that quickly shows that you will need a substantial upgrade to survive. How much scope do you have for increasing the rotor diameter i.e without the calipers fouling the inside of the wheel?

I expect the front brakes will be the limiting factor, can you confirm?

If the existing brake balance is about right you should bear in mind how any hardware changes are going to alter the brake balance and may need to take steps to correct that. This may entail upgrading both ends, in which case the rears are likely to be harder to sort out.

[aaron_2000]

You track a 645ci? What's it like on a track?

[MrOrange]

Maybe it’s your track driving style? Brake harder for less time, carry more corner speed, and sort out the cooling to the brakes.

[peterh2]

GreenV8S said:

I've drive cars with woefully inadequate brakes that lasted longer than that, and I think fading that quickly shows that you will need a substantial upgrade to survive. How much scope do you have for increasing the rotor diameter i.e without the calipers fouling the inside of the wheel?

I expect the front brakes will be the limiting factor, can you confirm?

If the existing brake balance is about right you should bear in mind how any hardware changes are going to alter the brake balance and may need to take steps to correct that. This may entail upgrading both ends, in which case the rears are likely to be harder to sort out.

Yes I the fronts are the limiting factor.

I'm not really sure what pads are on it at the moment - I bought the car 2nd hand with the current pads fitted so I'm hoping they're some really cheap options that are worse than OEM combined with old fluid.

There's very little space inside the wheel. It's on 18" and the rotors look massive which is why I was surprised that they're so poor.

Keen to keep to standard size rotors and pads if possible. I've tracked clio sports and MX5's before both of which were made completely fade free for my use by simply changing the pads and fluid but I'm struggling to work out what pads are available / suggested for this.

[peterh2]

aaron_2000 said:

You track a 645ci? What's it like on a track?

Apart from the brakes it was good! It has the electric suspension so stays very flat and you can really play about with it my moving the weight around between the axles using the power or trail braking. It's no Elise but surprisingly competent in the corners when running MPSS tyres.

[GreenV8S]

peterh2 said:

I'm hoping they're some really cheap options that are worse than OEM combined with old fluid.

Have no idea how easy it will be to find fast road pads for those calipers, but it seems like an obvious starting point, together with a good brand of DOT5.1 fluid. You could also invest in a thermometer to see what temperatures the rotors are reaching after a run.

If it's any consolation, in my experience once a set of brakes have been cooked once they feel like cr@p afterwards even when they aren't getting particularly hot, so a brake service might help more than you think.

If the brakes are marginal, brake cooling ducts can help a bit. If you have a wishbone or leading link at the front, I've seen a channel clamped to that used as a simple and apparently effective way to improve brake cooling.

[E-bmw]

Partly agree with most of that apart from the dot 5 bit.

I have used ate superblue (now called type 2000) on track cars with never a fade/cooked fluid in site.

Get some proper pads, good fluid, braided hoses remove a bit of lever travel which can help the feeling but above all else get some proper brake cooling fitted.

I fashioned some 3" concertina hose from the front grille right to the calipers which made a huge difference in the early days of tracking cars.

[GreenV8S]

E-bmw said:

Partly agree with most of that apart from the dot 5 bit

DOT5.1 (the '.1' is important). Stay away from DOT5.

The Super Blue fluid you mentioned is labeled as DOT4. Good DOT4 fluid often meets the DOT5.1 temperature standards too, and their site suggests this one does. Any fluid meeting the 5.1 spec should have similar or better temperature performance.

[CarsOrBikes]

try it on genuine pads, chances are someone put an OE version or lesser version in, OE equivalent or spec often means naff all and leads to poorer opinions of genuine stuff that was never actually used. Only my2p, but having done a full set of OE quality Brembo pads at Oulton, I put genuine pads in that were barely touched next time there, or the next day. Just been again with completely different brakes but genuine pads, superb and barely touched.

My car isn't a 645 though, only a Mini Cooper S, but never underestimate a Mini ha.