How Big is too Big?

[cwatt]

I'm going to be doing a e36-based 5-lug swap which will offer new possibilities of larger brake options. Wilwood (amongst other manufacturers) offer four and six-piston options.

So how big is too big? Four piston enough? Six-piston overkill on such a small car?

If it helps, I intend to do an S54 swap and want some bite with that bark.


- Colin

[Roysneon]

When you can lock up your tires, they're too big.

[jlevie]

With the right pads, the stock brakes can lock up any R-comp tires you can fit in the fender wells. The point of a BBK is more for better cooling and greater thermal mass. So in that sense they can't be too big.

[cwatt]

That's a fair point about pads. I don't want to buy high-performance pads so that I can replace them every second week of daily driving. My intent for larger brakes is everyday performance and aggressive driving. I want the car to stop like a freight train without looking like a goon who bought the largest brakes he could afford. I'm just after the right balance.

[jlevie]

Well there's another thing to consider with pads. That being the Maximum Operating Temperature (MOT). A street pad, and especially a low dust pad, will have a low MOT as well as a low friction coefficient. A BBK could compensate for the friction with greater swept area but that won't help with the MOT problem. If the pads get hot enough, as they can with aggressive driving, you get brake fade.

There are race pads that have pretty good life, like PFC 06/08's. Probably way more than a couple of weeks of aggressive street driving. I usually get about 10 racing days out of a set of front PFC 01 pads (and about twice that out of the rears) and the 01 compound is not a long life type. That probably corresponds to six months or more of pretty aggressive street driving.

If performance is purely the goal, a 5-lug swap, bigger brakes, & bigger wheels is working against you as that increases unsprung weight. One pound of additional unsprung weight is equivalent to making the car weigh 6-8 pounds more. The lightest 4x120 wheels you can find and stock brakes with good pads is hard to beat.

Colin Chapman got it right when he said, "The way to go fast is to add lightness."

[jalopi]

Hit up Massive or Ireland - they both sell BBK's for our stock four lug setup. I left out UUC because I've read too many complaints about them.

No idea how either of their products perform, but Lee's stuff is a bit prettier IMO. It's also more expensive, so there's that. Talk to them and see what their suggestions are.

[Gertech]

I talked to Lee at Massive about his 332mm kit for the 4-lug set up. Could be a good option for you if you decide to stay 4-lug. Anybody running this? Thoughts?

[Todd TCE]

Too big? It has nothing to do with piston quantity. One, two, four, six, eight....could well be all the same. More quantity alone has no direct connection to braking performance. You can have less piston qty and more clamping (power).

The issue you need to be aware of it not qty but AREA. Total piston area. For comparative purposes that means 1/2 the caliper body thus allowing comparison to single piston floaters/sliders.

Area of a small body four pot caliper could easily exceed that of a larger six pot model thus make more torque.

Pad size is relative to the required fit of the caliper body and does not have much to do with the torque it creates. A larger pad with the same piston area behind it generates the same values as one that's smaller. It just lasts longer.

...just all FWIW

[Roysneon]

Too big? It has nothing to do with piston quantity. One, two, four, six, eight....could well be all the same. More quantity alone has no direct connection to braking performance. You can have less piston qty and more clamping (power).

The issue you need to be aware of it not qty but AREA. Total piston area. For comparative purposes that means 1/2 the caliper body thus allowing comparison to single piston floaters/sliders.

Area of a small body four pot caliper could easily exceed that of a larger six pot model thus make more torque.

Pad size is relative to the required fit of the caliper body and does not have much to do with the torque it creates. A larger pad with the same piston area behind it generates the same values as one that's smaller. It just lasts longer.

...just all FWIW

That is the best first post I've ever seen.

My opinion is that if the OP is getting his brakes so hot on the streets that he needs bigger brakes for more heat transfer ability, he should hang up his keys and buy a bus pass.

[Todd TCE]

I cheat a little bit; you might say I've been around the block a bit. But thanks.

A more durable pad compound would help. Or some beefier (wider) rotors perhaps. But that will lead to the need for thinner pads or alternate calipers.

All things being equal and designed properly the BBK option could meet the needs by way of a lower duty cycle of sorts. Like most BBKs the intent is not so much about stopping shorter as it is repeated stopping. Or at least is should be. But I agree street overheating would be pretty extreme...

[2002tiiguy]

Lol I know what you meant but last time I checked, freight trains take like a mile to stop:D