SP20 big brake kit - Update, date etc

[preeman80]

so a positive way I am guessing?

[Cosmo Dude]

Any pictures?

[twilightprotege]

not in any positive way either....sort of.

see with abs equiped cars, in-built into the abs computer is a predetermined maximum deceleration rate, ie the rate at which the stock brake setup can decelarate at a safe rate without locking up etc.

when you increase the braking force, the abs still thinks you have the stock setup and wont stop any quicker than before.....but this is where the big brake setup is better.

because the big brakes are much larger, they hold much more heat and can dispurse more heat, so stopping from 200kph to 0, your stock brakes will be redhot and farked at 150kph (example this is ofcourse) and will dramatically loose braking effect. your new kick-arse brakes mightnt loose that maximum braking force the abs can allow at all!

so summing up? around town at 60kph, you wont stop any quicker, but you'll most likely have a crisper initial bite. driving like a maniac and getting the rotors red hot, big brakes will give you a smile from ear to ear.

[SFC01]

Are you sure you are right on this twilight? Does the ABS system run off tone rings on the rotors/hubs or on an accelerometer?

The tone ring acts like a hall effect sensor (i think) to get a rotational rate off each wheel. if that rate heads to zero (wheel locking) i thought that was when the brains kicked in and operated the hydraulic circuits?

I would have thought that with the identical tone ring and sensor the ABS system would act like OE.

But then again it wouldn't be the first time that I was wrong (ask my ex-wife!) :roll:

[Cosmo Dude]

The ABS have both individual wheel sensors and a G-force sensor, I'd hope the individual wheel sensor would correct one or two wheel lock-ups while acknowledging the speed from the still rotating wheels and correct. The G-force sensor would activate if all wheels locked and their was no speed info to make a decision.
When the car is stopped at the lights the brakes are effectively locked up and ABS isn't required.

Just my thoughts :roll:

[twilightprotege]

yes abs does have teeth like ring sensors on each wheel (is fixed to the hub, not the rotor), but abs is smarter than just stopping the wheel speed dropping to 0.

abs knows that in perfect conditions (surely tested by mazda A LOT) the car can only decelarate at xx m per second. so that's plugged into the abs system.

if the wheel starts to decelarate at xx + 1 m per second, abs (and this is done like 20 times per second), goes ok, that wheel is slowing a bit quick, let's watch it. then on the next 20th of a second it's decelarating at xx + 3 m per second, so abs goes ok, it's locking...and then it releases some brake pressure...and we get that nice abs shudder feeling.

so what happens when we get a big brake system? we can now stop at a rate say xx + 10 m per second. abs doesnt know this, so we're still stuck with xx m per second.

to my knowledge there is no g-force sensor, only that stock xx m per second locked into the computer. and with the stopped at lights issue, the abs system knows the car has already stopped (20 reading per second) so the abs doesnt activate

but like i said, with a big brake kit, we can stop at xx m per second for much much longer than the stock setup.

does that make sense?

[dfvadr]

guys from what ive been told any abs system has to have a g-force system to work properly , an as for wat ur saying about the computer just reading xx - m that is never the same under different sercumstances thats wear the g-force sensor comes into play
so bottom line is bigger brakes better braking even on abs

[twilightprotege]

ofcourse xx m per second is never the same under different circumstances. the xx m per second in built into an abs system is for optimum conditions. the abs system then knows there is no way in hell the car can stop quicker than that. have you ever noticed that the abs pulses are much much greater on wet roads than dry roads? that's because 20 times per second, the abs is reading what decelaration rate each wheel is doing. it knows that at 100kph in perfect conditions it takes say 35m to stop. mathematics will tell you how long that'll take. so therefore, why spend time and money developing a g-force system (remember, this has to be extremely accurate) when they can just take speed readings from the wheels?

i agree bigger brakes are better on ALL applications, but i'm just trying to point out the reasons why it is better and not better on abs applications.

[Cosmo Dude]

http://auto.howstuffworks.com/anti-lock-brake.htm

[dfvadr]

ur missing the piont here i think as i said earlier all abs has g-force controlling that is what tells each wheel not to lock. not a counter as you have put it a counter doesnt tell weather its a slippery rd, wet rd , or dirt this is were the g-force comes into play
as u no abs is desinged not to lock a wheel so a counter on each wheel will not read until it has locked, ie too late the g-force sensor gets the reading off what the wheel is doing when braking hard the wheel is about to lock then the g-force sensoer sends the signal to the control box telling the brake pressure on each wheel to release an bite thats where the anti lock off the wheels comes into play an the pulsating through the pedal

[twilightprotege]

wrong.

a counter will NOT not read until it is locked, it reads 20 times per second. when a wheel is decelarating FASTER than what the abs system knows it can do (ie on it's way to locking up), it will releive the pressure to that wheel, way before it even comes close to being locked up. the counter (it's not actually a counter, more like a toothed washer) is constantly reading the speed of the wheel.

have a look at the link cosmo put up. notice it doesnt even say a word about g-force? that's because there is no g-force meter in an abs system

[dfvadr]

ok ill read through it over the next week or so try an understand it more mean while ill get back too mazda an pick there brains again too seems there is misleading info somewhere

[Cosmo Dude]

Damn,
If their is no G-sensor how does the ABS know when the vehicle speed has matched that of the road (ie - stopped)?
The ABS is a complex system that uses many inputs over a various array of situations programmed into the unit.
At worst the ABS will work as normal, at best you have one hell of a set of stoppers. I guess it's a compromise, with the big brakes their will be much less fade and more predictable braking

[twilightprotege]

cosmo, like i said earlier, because of all the readings the abs is taking, it knows it's stopped because since the wheel was moving, it decelarated. the abs knows that if you are doing 90kph and decelarate at 5m per second, you'll take so many seconds to stop. obviously the stopping rate changes and the abs takes that into account.

i'm not sure, but maybe under a certain speed (like 2kph), the abs becomes inactive

but like you said, your last part of your last sentence says it all.... "with the big brakes their will be much less fade and more predictable braking". that's the advantage of big-brakes on abs equiped cars. the rest is the same

[chipa]

Just been talking to the guys at DBA and their story is that our ABS system (in the SP20's) will automatically adjust to the different braking setup...

Of course they could be wrong, but I'm happy to believe them anyways. :lol:

[twilightprotege]

i'm a bit skeptical at that. as far as i was aware, the abs system is hard coded and cannot learn, that's why you hear car companies every now and they say that their abs is designed for australian conditions (ie dirt and crappy roads)

[Cosmo Dude]

It would need an adaptive component due to different surfaces, tyres, shocks, springs, wear and tear and even brake components.
The worst thing about australian roads is the distance, they are plenty wide enough, relatively free of potholes and very few are paived with cobble-stones.

[chipa]

That could still apply, I take it to mean that the ABS system will simply adapt to the difference in braking power. i.e. so when the ABS is disengaging/reengaging the brakes it will actively learn how to apply them correctly without any adverse changes from the original. As Cosmo just said, it has to be able to adapt to worn brake & suspension components, so even replacements should work ok.

[Cosmo Dude]

I think 'adapt' would be a better word than 'learn' as every situation will be different.

[BigMal]

Never having ABS are you telling me that ABS will release earlier on dirt roads
than on normal roads. I can understand that the system would recognise that
if the car is moving that a still rotor means lockup and would start releasing
or pulsing but from that point does it continue to release more from there
or once it starts pulsing thats basically it, ie on or off ??

Ta

Mal