Brake BOOSTER - How necessary for street use ?

[abently]

Do I really need to say what car it is ?

1988, RWD, 1250Kg (Weigh bridge minus driver/passengers), 276mm Ventilated Front discs - Twin Piston Calipers, 264mm Ventilated Rear discs - Single Piston Calipers.

Current M/Cyl Internal diameter is 1"

Just one thing I haven't got my head around, do the Front calipers in particular, automatically re-position themselves as the pad wears down ? And how does that generally happen ?

[The Real Roadrunner]

think of it more like " do we really need to answer your qustions? "

if we know what it is we may be able to help, if we dont its like asking someone to fix an engine without being told the reason it needs fixing.

please tell me how you go from knowing everything about race engines to " how does a caliper compensate for pad/rotor wear"

[Joshstix]

Brakes only need to work and be biased front to rear so the fronts lock first. There is no legal requirement for a car to use a booster. Of course a car that was ADR'd with a booster would need to be tested to confirm that the braking ability has not decreased and the bias is ok.

In NSW we need a brake test for a pink slip each year and it measures required pedal pressure. If the pedal pressure is too high then the test is failed. Getting a low enough pedal pressure without a booster is going to be a good effort.

I assume this is for the super secret Mitsubishi race monster with secret squirell spec single cam head that needs porting???

[abently]

In NSW we need a brake test for a pink slip each year and it measures required pedal pressure. If the pedal pressure is too high then the test is failed. Getting a low enough pedal pressure without a booster is going to be a good effort.

I assume this is for the super secret Mitsubishi race monster with secret squirell spec single cam head that needs porting???

Nice to know that you allocated a special spot in your brain just to remember that.

[Joshstix]

No problems.

I'm a moderator so it's my job to keep an eye out for anyone acting like a clown.

[oldcorollas]

Do I really need to say what car it is ?

1988, RWD, 1250Kg (Weigh bridge minus driver/passengers), 276mm Ventilated Front discs - Twin Piston Calipers, 264mm Ventilated Rear discs - Single Piston Calipers.

Current M/Cyl Internal diameter is 1"

Just one thing I haven't got my head around, do the Front calipers in particular, automatically re-position themselves as the pad wears down ? And how does that generally happen ?

oh dear........

lets see.... take away master (curious to know how you found it has a 4.1:1 ratio )and increase master cylinder ID by 25%..

4.1 x 1.25^2 = 6.4

so.. say you needed to push with.. maybe.. 50kg force before... (reasonable for full braking?) you now need to push with 320kg force....

i think it would be physically impossible for any human to do that... can anyone squat 640kg yet? (seems max is 550kg)

if you decrease by 25%, then you need 115kg force.. but you almost double the pedal travel over what you have now (well.. the master cylinders piston travel anyway)

you can run no booster BUT, you need to have larger discs, and the correct size master and pedal leverage, to still get good feel without having to have a popeye leg.

basically.. bigger disc is what makes the difference.

changing the pdeal ratio and the master and calipers and everything else... is only adjusting the tradeoff between pedal travel and pedal force.

think of it like this....
pedal force x pedal travel = CONSTANT
CONSTANT x brake disc size = braking force.

oh, and the "secret squirrel" bullshit about what type of car just makes you sound like a gunna

[GA61XX]

Good question..
The '71 chrysler charger, had two options with or without...
The "RT" charger didn't have the booster, nor did the "L" model have it..
The "XL" & 770's had a booster...
The reason, for non boost, "L" cheep model.. the "RT" on the other hand, was a race car, & under heavy de-acceleration, & large vac' from the manifould, it pulls the brakes on hard...

I've found this out, after having my brakes lock up, on me under the same, heavy de-acceleration. "i wish i didn't have the booster" & had the same prob' with my RA40... "i hate brake booster's"

The "RT" also had, a front to rear bias, the same as the, "GT" Celica's..

All brake sizes, are the same, just the "RT" was non boost..
As for street use, it would have to pass, a braking test ...

[Mos]

GA61XX - were the brake pedal pivots/lengths and piston diameters the same with or without booster?

BTW, your punctionation is fkn hard to read

Mos.

[GA61XX]

Ok. i went to the, '71 -'73 Chrysler parts catalogue, to check, & yes, the same pedal, & piston diameters, are used on both, boost & non boost...

PS. i failed englush..
PPS. "punctionation" is spelt punctuation..

[SillyCarS]

No problems.

I'm a moderator so it's my job to keep an eye out for anyone acting like a clown.

baboom tish

you're getting a lot of free advice from both professionals and enthusiasts who have paid a lot of money to aquire that info, so dont waste their time being vague/a smart arse, also you'll get a better answer the better you come across

i personally like to keep things simple, cos im a simple kinda guy and when things fuck up in the middle of the desert while travelling back to adelaide from canberra i know i'll be able to fix it with cable ties and electronic crimping thingoes and not get abducted by uncle chop chop (this is the kinda of unecessary info that people dont really give a shit for)

so to avoid such a situation i would suggest recoing the booster or getting another one from a wrecker

still no good

replace master cylinder for a slightly bigger one, i would recommend 15/16th or someting or maybe 1" if you have legs like roberto carlos, if the harder feel is what ur after

and you wont get defected

[abently]

4:1 ratio, is the Booster ratio. As listed on the Factory Workshop manual.

I've already settled on going for a smaller ID M/Cyl, but I think I'm going to have trouble finding one twice or even 1.5x the length of the Original to displace the same amount of Fluid.......

I really need access to the internal PBR catalogue......

[oldcorollas]

or bigger ratio pedal and same master

[abently]

or bigger ratio pedal and same master

I loose M/Cyl piston travel distance doing that, but I will try that first though and then see if I still need to step down in M/Cyl size.

[allencr]

I'm going to have trouble finding one twice or even 1.5x the length of the Original to displace the same amount of Fluid.......(

Yep, you sure are going to have lotta trouble finding one that's twice the length, but I've got no idea why you'd be looking for one that is 1/2 the area of the original, if that's the reason.

With ALL the crap that's been going on here, I just think you'll be very surprised & satisfied how well a smaller MC, 1/8in/3mm, will work, as long as there isn't a lot of compliance from shoes that need to be arc'd, tapered worn pads, those mickey mouse shims & old hoses.

[thepeter]

You'd just be better off going to a pedal box with dual masters at the same time really.

as oldcorollas stated, you need to upsize everything else to bring the compress ratio up. And still, even then when you bring it up, you need the force behind it to move it.

Ah ok - i'm done stating the obvious....