Upgrade Brake Master Cylinder

[Mux213]

Owh and as an ontopic remark,

With a larger diameter brake cylinder you increase the volume of brake fluid you push into the system with the same travel of the brake paddle. The volume of brake fluid defines the amount of force that you excert on the brake pads.

I do wonder if this does mean you also have to excert more force on the brake paddle but I think there is a lever effect here. The force your foot excerts on the brake paddle is far less then the force that is excerted on the pads. With a lever offcourse the effect is generated because the force you excert is excerted on a longer distance then on the 'recieving' end.

Also with a powered brake you should be able to excert more force with a larger cylinder for sure.

But this is all pretty unformiliar terratory for me

Does anybody have a good site that actually explains this stuff and especially how a brake booster works? Because that is the key here I think.

[Ivan141]

The extra area of the piston makes it possible to displace more fluid with less pedal travel. When you think of it, it's pretty logical that you will need to apply more pedal force to reach the same pressures with that decreased pedal travel. It is not the volume that you displace that defines the braking force, since you already displace maximum volume with your stock system (otherwise it wouldnt work now would it?). It's the compression of the brake fluid that does the actual work.
Pressure is a function of force and area, the bigger the area you apply force on, the more force you need to get a certain pressure. The only way to really get the brakes to clamp harder is to raise the pressure, which means you'll need to press that pedal harder. With a bigger than stock master cilinder, that means that you will need to press the brakes a lot harder to get any improvement.

The advantages to having a bigger master cilinder IMO are:
-more fluid to account for flex in the brake system..
-more pedal pressure, making it easier to dose the power you put in.

Getting the car to actually brake better (not just feel better) is in theory more up to the brake pads and heat capacity of your system. And ultimately the grip of your tyres is what really stops your car.

[Rasteirinho]

Sorry, but i don't think so...

I've the firm idea that with a bigger BMC you will increase the brake power. But i'm not a guru and so i can be wrong...

It isn't the most important thing on the brake system during braking but it's an upgradable item for those who alreday have steel lines, good brake pads, discs and brake fluid.

[Mux213]

I do keep feeling this is a damn cool site. http://www.howstuffworks.com

This is about the master brake cylinder:
http://auto.howstuffworks.com/master-brake.htm

This is about the brake booster:
http://auto.howstuffworks.com/power-brake.htm

Reading this I have to agree that changing the master brake cylinder most likely will do jack shit. It would only do you any good if its leaking or something.

The brake booster on the other hand, thats the bit where extra braking power can be gained. First the big question is if the brake booster on a 23 year old hachi still works good. If its loosing vacuum somewhere it will deminish in strenght. But also the size of the brake booster effects how well it helps the braking.

A bigger brake booster, or a 2 membrame booster (basically two boosters stacked ontop of eachother) will increase the area on which the vacuum has effect meaning there is more force going into the brake system. Atleast thats the theory for asfar as I've understood it and seeing I know jack shit about this, I'm probably overlooking something

[Ivan141]

There is still some incomplete info in that howstuffworks article.
Go here if you need some better info about brake systems:

http://www.stoptech.com/tech_info/tech_w...pers.shtml

[NoHachi]

Larger BMC's do absolutely nothing besides making it more difficult to appropriately modulate the brake at the threshhold. Putting in a larger BMC isn't exactly rocketscience and is certainly something that toyota techs could have come up with in 1940 even.

This is the point: Through a well maintained stock brake system with good pads, it is more then possible to apply enough pressure to the brakepads to overcome the tires stickyness..You can apply all the pressure you want, but when the tires let go, you go. Thus the whole brake system is limited by the grip of the tires, not by a BMC or pressure. There is one catch though: the "well maintained"stock system is a coin frase that is completely unappropriate for 90% of the hachi's out there..So you start upgrading everything around the original problem, without solving it.

Happy braking!

One other example: At the volvo forums people were 100% sure that the stock 360 brake system was severely undersized for its task. They all dreamt of bigger brakes and exotic callipers. When I told them that me and Ivan drive around the whole day at the track, without ever experiencing problems they just told me that is impossible..Fine with me: the impossible little brake system is extremely easy to modulate and outbrakes lighter cars with more aggressive pads.
As always: first make sure that your car is well maintained. Then tighten the nut behind the wheel.

[Mux213]

NoHachi,

You keep forgetting the biggest point in a hachi.

The pressure you put on the brake pads at this moment is NOT enough for the tires to loose tracktion.

Only at low speeds this happens.

With fresh pads, fresh brake fluid I can only lock the brakes on my car at low speeds, at higher speeds I can not use the full braking force my tires would allow. Hence by your own description I need to improve my braking system so it can go beyond my tires stickyness.

Just to compare, if I brake with my hachi on Zandvoort approaching the Tarzan corner (after the long straight) I can floor my brake and I still don't lock the tires. Sounds to me there is room for improvement

Now with my car I still have to replace my old not to warn out brake lines. Still talking with Zax the other day, with his hachi, with fresh brake lines, fresh brake fluids, fresh mintex pads, he still has problems with his braking.

I'm slowly getting pretty convinced that the calipers and pads the hachi has are up to the task and the only worry I have with those is that they get hot to fast and start to fade. Allthough better brake fluid can do alot of good here. I also don't rule out that fading is my real problem, not the maximum braking force I can apply.

But I'm also getting convinced that the amount of force my foot can apply to the brakes is not enough to get the maximum braking power out of my car in track conditions.

Also having more power assist will make braking easier on my foot, I may not be able to increase the braking power of my car beyond the point that the tires allow, but I wont have to put as much force on my paddle to get the same braking result as the power assist will apply the force I am not applying, thats worth something aswell.

[Ivan141]

Getting stainless lines should help reduce the compliance in your hydraulic system.. it's not much, but it does help the brake response. You could also get a master cilinder brace. That stops the master cilinder from moving around and has a similar effect as stainless lines.
Making sure that everything around the calipers is in tiptop shape is also an important measure (slider pins should be straight and completely smooth + lubricated). I'm completely convinced by the mintex pads on my 360 that they should perform pretty well on an ae86 too. Last trackday I drove the damn volvo without rear brakes (badly worn out linings in the drumbrakes) and it still stopped without a problem all day long (be it a bit unstable).