Brakedimensions and Hydraulic circuit S1 Montecarlo

[Otto-valvole-per-tutte]

Hello All,

Could someone give me the mastercilinder internal diameter from an S2 Montecarlo? Is this 19,05 mm?

And what about brakecalipercilinders? Are they 48 mm or less/more?

Final question :wink: , could someone give me a hydraulic circuit from an S1 Monte (i believe there are two versions?)

Many thanks in advance, Pieter

[Wallace]

Yes. no. The mc is definetly 19.05 or 3/4". I THINK the calipers are 38 at the back (slightly up on an X1/9 at 36 ) and the fronts are 42. Don't quote me on the caliper sizes. someone should have them and the hydraulic system from the manual somewhere ! Mine's 98 miles away !

[Otto-valvole-per-tutte]

Thanks Wallace,

Mine is also to far away to measure things myselve.

:cry:

What would be the effect :twisted: if i switch from standard Monte:

251/10/42/19,05

to Fiat Croma

257/22/54 dimensions?

The Croma uses a 22,225 mastercilinder so slightly bigger.

Will this work?

Cheers, Pieter

[Wallace]

I take it the 22 mm refers to the disc thickness - which means they're vented so they'll take "more" braking before they'll fade.

The 4mm increase in diameter will not make any noticable difference.

Bigger caliper cylinder will mean greater pad pressure for less effort on the pedal but greater travel (I think . . . . it's been a long day .. . . ). It will also make you back brakes work harder as the balance has been affected. Should reduce the tendancy to lock up the fronts though.

I'm not sure the Croma mc will even think about fitting as it's designed for a servo set-up. Fitting a larger mc on the remote servo won't change a thing - a servo only changes the effort in putting the brakes on, not the amount of fluid displaced.

This is all speculation on my part - Will, Ken anyone - please correct and add your two-penneth worth !

[Gary Severson]

Sorry Wallace, but I'm gonna have to call you on that last post. Your line pressure goes down with a bigger master cylinder all other factors being the same. For example say we are applying 100lb force to our brake pedal and our pedal lever ration is 5 : 1 we deliver 500lb force to our master cylinder piston. The line pressure developed is the amount of force delivered to the piston devided by the master cylinder piston area. so if we have 1sqare inch of piston area our line pressure would be 500psi. Now say we reduced the piston area to 3/4sq inch our original 500lbs of force delivered to the piston is now divided over a smaller area so we end up with 666.6 psi line pressure. The same principle applies to why a 747 doesn't sink into the tarmac. It have a lot of weight(force) but it is divided by a lot of wheels so that the pressure at any one spot is pretty low.
Gary Severson

[Otto-valvole-per-tutte]

Wallace,

Thanks for the reply. Actually my plan is to use standard Monte-everything (non-servod S2 spec), but switching to Croma brakediscs and calipers.

So from:

251/10/42/19,05

to

257/22/54/19,05 dimensions (presumably bigger brakepad-surface-area).


The Croma uses a 22,225 mastercilinder (servod) so slightly bigger. I'm just curious what the affect will be on:

a) pedalfeel

b) brake-effort

c) rearside braking of the car

and of course

d) stopping power :twisted:

Ciao, Pieter

[Bazza]

Pieter - you will get 65% increase in pedal travel which with a Monte your foot will be halfway through the luggage compartment :roll:

[Otto-valvole-per-tutte]

Barry,

Basemode on :D :

(54² + 38²) / (42² + 38²) = 4360 / 3208 = 1.36 = 36% more (Croma setup)

(48² + 38²) / (42² + 38²) = 3748 / 3208 = 1.17 = 17% more (HF4WD setup)

Basemode off. :P

Diameters are from front and rear calipers.

For my Autobianchi i swap from:

227/10/48/19,05

to Fiat Uno Turbo brakes that have:

240/20/48/22,225

People who race with this setup in the Coppa Mille races (Holland, Belgium and Germany) are very satisfied by this upgrade.

Cheers, Pieter

[Wallace]

Gary - I was only thinking about the effect of changing the cylinder diameter on the remote servo - not the diameter of the mc itself !!! Unless the remote servo has a seprate fluid feed - I can't see how it will change anything !!

I must admit - I've never played with one - but if you're pumping a certain amount into the servo from the main mc, then you'll get the same amount out ! My understanding of a servo is just that- it only is a "servo" i.e. it uses engine vacuum to help reduce the effort in braking.

Obviously changing the main mc WILL affect everything (or why else would I have gone to the effort of making up a pedal box to take Titlon mc's ?? !) :lol: .

What I was questioning was the effect of JUST changing the piston diameter on the servo ONLY. I still don't think this will have any effect -appart from the amount of leg muscle required. And this would be dependant not only on the servo mc diameter, but the servo piston diameter itslef, how much vacuum the engine can develop etc etc.

I think !

[Bazza]

Ah but you have a twin circuit system - this means that on the front circuit you will have 54²/42² extra travel = 1.65 but no difference on the rear circuit. Admittedly my first post was an exaggeration but a standard Monte brake pedal travel is about half way to the floor so with the bigger front calipers it will be most of the way to the floor. A good compromise is to use Uno Turbo front calipers which are 48mm. piston diameter.

[monte_giallo]

Made a start on my wacky brake M/C idea on Saturday, visiting a local scrappy looking for a suitable brake pedal and direct-acting servo. Suitable in my case means a solid-looking pedal (rejected Peugeot 205) and reasonably easy to remove (rejected VW Golf/Scirocco). So I plumped for a servo off a Rover 216: nice big capacity servo and solid pedal assembly.

I plan to retain the existing pedal box for the clutch (and possibly accelerator), modified so that I can fix the new brake pedal to the top of the footwell, acting on a push-rod through the 'firewall' to the servo in the luggage compartment. My intention is to get good brake pressure with little pedal movement, so that I can heel and toe easily. I'll pipe vacuum up from the inlet manifold via a steel pipe in/alongside the 'transmission tunnel' where all the brake pipes go.

If I get one end locking up too soon, I'll fit a balance valve.

I'll let you know how I get on!