Master cylinder sizing

[Timmyevo6]

i've had total brake loss on my current system, but that was through boiling the fluid, however i was lucky enough to be at the end of revits straight and nobody was near teh escape road. it was scarey! pedal simply fell to floor and didn't do anything!

i understand that bias box with bar and 2 master cylinders certain does have its short comings but i'd like to think those situations can happen to any part of a race car, its just not so bad when the throttle cable falls apart and you lose drive.

[phoenix]

Originally Posted by Timmyevo6

its just not so bad when the throttle cable falls apart and you lose drive.

It is if it jams the throttle wide open - which is what happened to me once!

[GORDON STREETER]

Originally Posted by Tim Falce

Gordon, I fully understood the meaning of your first post on it but I was just pointing out that having two system doesn't mean it's a fail safe. What happens when one side of a tandem cylinder system goes down, do you still have any stopping power with that? After all when you bleed one brake on this type of system the pedal will go straight to the floor won't it.

Yes Tim that's exactly what happened to me. I had a front caliper union snap off and the pedal went straight to the floor.
Unfortunately my hydraulic handbrake also works on the front so I had nothing at all.
As I know the car so well after years and years I scrubbed the speed off sideways, and was lucky not to hit anyone else !

[GORDON STREETER]

http://tentenths.com/forum/showthrea...=brake+failure
Timmyevo6 this might be worth reading for the pro's and con's of bias boxes.

[Belatti]

Originally Posted by phoenix

It is if it jams the throttle wide open - which is what happened to me once!

Neutral and pray

[phoenix]

Originally Posted by Belatti

Neutral and pray

No. Turn the ignition off, leave it in gear for engine braking - and brake hard!

In fact this happened to me coming into the second corner on a tarmac rally stage - and I managed to complete the whole stage and get a reasonable time!

[phoenix]

Either a 0.625" or a 0.700" master cylinder will work well on the front - the 0.700" giving a slightly harder pedal with less initial movement. 25.44% more 'leg work' will be required for the same braking effort if you choose the larger cylinder.

I am unable to work out the correct master cylinder for the rear without knowing piston size and pad area in the two-pot Brembo's. Does anyone have that information?

[Timmyevo6]

Originally Posted by GORDON STREETER

http://tentenths.com/forum/showthrea...=brake+failure
Timmyevo6 this might be worth reading for the pro's and con's of bias boxes.

thankyou for the above gordon, interesting read. i don't know what to make of it really.

this is what i've come up with so far, people, please feel free to correct me where i may have got myself 'mis-guided'.

i've had brake failure before, ok it was due to incorrect pads, boiling fluid and so on, but none the less it made the pedal drop to floor like it had fallen off the bulk head.

all i know is that when it happens, it happens fast and there isn't much time to react, if you're lucky you at least manage to pull a daft face within your lid. if you're really lucky you hit something not too hard. if you're REALLY REALLY lucky, you hit nothing.

It also happens for many differnt reasons, mechanical failure of parts, ill fitment of parts, poor choice of parts ETC.

SO, with all that in mind, can we say that the fitment of a single push rod brake pedal and dual master cylinder isn't a cure but simply a potentially less likely item to cause issue? but only really if the rear has a issue because if the fronts have a issue, the likely situation is that there still isn't much braking ?

ALSO, bias bar set-ups, 2 cylinders, 2 circuits, front circuit fails, NO BRAKES? rear circuit fails, NO BRAKES??

at what point do we just say "this is the best i can manage regarding brake setup, if after this point it goes 'pete tong' then so be it"?

[JohnD]

timmy,
You have a rack of gurus lined up to advise you, but why have you chosen to go for twin masters and a balance bar? Your problem was NOT an imbalance between front and rear, it was, by your own admission, the wrong choce of pads that over heated and faded. Surely you should be addressing that, by barke material with a higher temp rating and means of cooling the brakes, either by air flow, brake fluid recirculation or water cooling.

AS part of my own brake mods in the face of similar circumstances, I experimented with a water spray into the internal passages of a vented disk. It made no difference, as the extra air supply I had made at the same time provided optimal cooling. but you have a much heavier car, so might need evaporative heat loss as well as convection.

John

[Tim Falce]

Have you tried looking at your driving style, could that be anything to do with it?

[Timmyevo6]

the thing is with the people who advise me is that although their capable tuners, they've not been involved in racing evo's, they know how to get the max out of the engines/drive train and thats great, but its the little tweeks/adjusments that comes with experience from myself, experience that currently i don't have much of, only having done 1 seasons racing.

regarding the pad choice that went badly wrong, well, they were free on offer from a supplier, the supplier was the guy who claimed to know all about choice of pad, it didn't work! you live and learn!

i now run carbon lorraine RC6+ pads and have no issues with brake fluid boiling. next years car will have full under body ducting to brakes, currently there is no 'caliper cooling' other than a crude tube.

my driving style is improving, i tend to be uber late on the brakes when there is no need for it, i often push myself when i know there isn't a need, the guy behind can't catch/pass me without a mistake from myself, but i just wanna go faster! not the correct attitude i understand but that is something that is moving away with experience, the latter part of my rookie season saw times when i was leading the race and i simply took it steady enough to give the guy behind me no real chance to pass. my tutior does give me a rollocking when i 'get out of my rythem' and simply get 'aggresive and trackdayish'.

my decision to use a pedal box over the OEM setup was mainly so i could get a better driving position, i can't get myself close enough to the pedals without my seat needing to be quite high, and that is with us already cutting and boxing a part of the transmission tunnel.

what is brake fluid re-circulation?

my car weighs all up including me/fuel/oils just under 1200kilo and is just under 500hp ATF

[JohnD]

It's an idea, I think from NASCAR, whereby there are two lines to each caliper and the fluid flows one way. There need not be any specific attempt to cool the fluid, but its whole mass is exposed to the caliper heat, and it can loose heat from lines and reservoir, so it avoids localised over heating. It also self-bleeds!
See: http://www.dpiracingproducts.com/sto...DPICatalog.pdf page 10

[Timmyevo6]

Originally Posted by JohnD

It's an idea, I think from NASCAR, whereby there are two lines to each caliper and the fluid flows one way. There need not be any specific attempt to cool the fluid, but its whole mass is exposed to the caliper heat, and it can loose heat from lines and reservoir, so it avoids localised over heating. It also self-bleeds!
See: http://www.dpiracingproducts.com/sto...DPICatalog.pdf page 10

can anyone confirm if these DTI products are allowed in MSA events? are they FIA approved?

[JohnD]

My reading of the MSA Blue Book does not prohibit the use of such a system. It merely insists that brakes should comply with Construction and Use statutes. The relevant law is the 1986 Statute, but that is not available online - unless anyone knows where.
Of course, your series regulations may include such a prohibition, or the general one, "You can't do it, unless these regs say you can"! Which is a b*gg*r, in my opinion. John Cooper and Colin Chapman would have hated the stifling of innovation!

John

[GORDON STREETER]

It sounds OK but its another thing to go wrong IMHO, especially for short clubbie races