If I was to delete the boosters, should I stay with the standard alfa master cylinder or go to something bigger like a tilton with bias adjust?

If you delete the boosters, you want to substitute a smaller MC - not a larger one. Alfa used a 22mm dia MC on cars with boosters, and a 20mm dia MC on unboosted cars (at least on 105's with standing pedals).

For a given force applied to the pedal, a smaller MC will produce a higher pressure, since pressure = Force / Area. So, if the MC diameter is reduced by 10% (1 - 20 / 22), it will produce 1 / (.9 x .9) = 123% as much pressure

 

To be honest the Brembo calipers won't do much to improve the brakes, they're pretty much the same size as the original brakes, they just weigh a load less because they're aluminium. As far as trackday upgrades go, a set of Ferodo DS2500 pads in the front will give you decent stopping power without having to get them red hot to work so you can use them on the road too.

As you're in Oz I guess you have a floor pedal car with twin servos? If you do, you can't remove the servos without ending up with a rock hard pedal that does nothing to retard forward progress. Smaller cylinders aren't available for dual circuit cars so unless you convert to single circuit brakes you won't be able to fit the 20mm m/c you need to ditch the servos.

We make a dual circuit adjustable bias pedal box for right hand drive cars that does away with the original master cylinder and both servos. It's not cheap but works out at less than the price of two new servos and a new master cylinder so if you're planning on replacing all of them it's the way to go.

 

Whether a car needs a booster or not depends on the MC size, piston sizes, and leverage built in the pedal mechanism.

Going to a smaller MC will compensate for the removal of the booster (applied force divided by smaller area = higher pressure) but to displace the pistons in the calipers by the required distance to apply the brakes, a given VOLUME of fluid is needed. Smaller MC = longer stroke. Going from a 22 mm to a 20 mm diameter woujld increase the stroke by 20%. The longer stroke is likely to be a nuisance and may become a killer when brakes start to fade under load.

Playing with calipers is tricky. Changing the pad size and/or piston size at one end will alter brake balance. Usually race cars are built with twin master cylinders an a balance bar which allows the brake balance to be adjusted experimentally.

 

Thanks for the feedback.

Yep, floor standing pedals, twin boosters.

I thought upgrading to the 75 calipers would give me something of an upgrade from the small 1300 ones. Arent the pads much bigger for the 75 calipers? Im already using ferodo pads with the small calipers.

I wanted to avoid going to a new pedal box, would be overkill for my occasional track day use Im thinking. Assuming I go to the 75 calipers, If I was to delete the boosters could I swap out the master cylinder (to something like the tilton 76 m/c) and use a proportioning valve like the tilton or would I need to go to twin master cylinders and/or a pedal box?

Tilton Engineering

 

The Brembo pads are bigger than the 1300 ones but not by enough to make that much difference. And you'll need to remove the spacer and fiddle around with shims to get the caliper onto the upright. Then you'll need a set of 1750/2000 brake discs. It's all do-able but I don't think it's worth the effort.

My understanding of the Tilton setup is that it's dual cylinder (yes/no?)

If it is then you won't want a bias valve as it should have adjustment built in like ours has. I'll bet that unlike ours it doesn't just bolt in using the same mounts as the Alfa one though!

Assuming you mean a dual circuit master cylinder then you'd need to find some way of mounting it to the underside of the car. With repro ATE dual cylinders the price they are I'd be surprised if the solution was as easy as that or everyone would be doing it!

 

My understanding of the Tilton setup is that it's dual cylinder (yes/no?)

If it is then you won't want a bias valve as it should have adjustment built in like ours has. I'll bet that unlike ours it doesn't just bolt in using the same mounts as the Alfa one though!

Assuming you mean a dual circuit master cylinder then you'd need to find some way of mounting it to the underside of the car. With repro ATE dual cylinders the price they are I'd be surprised if the solution was as easy as that or everyone would be doing it!

I think the tilton ones are single cylinder only. Theyre meant to be used in a twin cylinder setup with their pedal boxes I suspect. I see what you mean about the cost issue with the repro ATE, thats one thing, the tilton stuff is a different thing altogether!

Makes the alfaholics twin cylinder setup seem very reasonable.

Need to talk to some of the racing guys locally, find out whats going on in their cars.

 

The Alfaholics one being referred to seems like the obvious choice to me, the pounds is taking a beating against our mighty iron-ore clad aussie dollar so it might be time to fill up an alfaholics container or two
While you are at it get a pair of their 4-pots too.

 

I had exactly your proposed set up on my car for two years -- 1300 uprights, 2litre discs ( easy to fit small amount of machining ) Brembo's standard dual circuit m/c , no servos, worked great , pedal was a bit spongy but I think everything was really due for a rebuild.
I now have 7/8 bonaldi m/c with outlaw calipers no servos and it works great but is still a bit spongy so I now wonder if I should have used a 20mm m/c ?
I'll certainly be using the brembo setup on another of my 105's

 

I have the Brembo's on my '67 GTV, with vented rotors on custom hats, using the single booster. I also have a Tilton proportioning valve. The brakes are fine, with one disconcerting exception: after the brakes have been used a couple of times, the pedal drops significantly. It pumps right up with one tap, but you never know when it's going to do its thing, and that's no fun when trying to get through a curve quickly.

I've gone through a long list of possibilities and haven't found the cause. If I were to do it over, I'd save up and buy one of the bigger, better front and rear brake packages now available from several suppliers.

 

... The brakes are fine, with one disconcerting exception: after the brakes have been used a couple of times, the pedal drops significantly. It pumps right up with one tap, but you never know when it's going to do its thing, and that's no fun when trying to get through a curve quickly.

What brand of MC are you running? To me, it sounds like the problem is in the master (because I'm guessing that you have already addressed loose wheel bearings, bleeding, etc).

 

Low Pedal with floor M/C

I have have seen this low pedal symptom before. Assuming all the other possible causes have been ruled out: Warped Rotors, Loose Wheel Bearings, Air in the system...etc. Has anyone tried a residual pressure valve? Willwood makes one.

Just a thought.

David Alexander
Riverside, IL

 

Thanks, guys. Yes, several excellent excellent mechanics and I have been over all you list and more. I have a stock 22mm Bonaldi MC, the third since the problems began. In fairness to Bonaldi, the first got cooked before I realized the need to insulate my brake lines from heat off the fancy headers and the third was desperation to cure the pedal problem. But the soft pedal predates the cooked MC; it began as soon as I put the Brembos on the front and new calipers on the rear.

The residual pressure valve is interesting. I printed out a report about using one ages ago, but filed it so well I have never seen it again. As I recall, it said the soft pedal issue sometimes occurs when a brake MC is at a low point in the system. But the MC is there on a lot of 105s whose brakes work fine.

I wonder if it's as simple as a caliper that sticks, but only in a way that's hard to find when the car is on a lift. I have kits to rebuild everything, just hate having to rip them apart when I'm only guessing.

 

I have a stock 22mm Bonaldi MC, the third since the problems began. ....But the soft pedal predates the cooked MC; it began as soon as I put the Brembos on the front and new calipers on the rear.

AHA! See the thread I posted about a month ago at http://www.alfabb.com/bb/forums/sus...rums/suspension-brakes-wheels-tires/162135-master-cylinder-conversion-105s.html I had similar, though not identical symptoms, and solved it by switching to an ATE cylinder. It was a bolt-in replacement.

Is the Bonaldi designed like the Dunlop MC? That is, with the fluid supply at the rear of the cylinder (as it mounts in the car), and the outlet in the middle? If so, the design is suspect, in my opinion.

Did your Bonaldi cylinder work OK before putting on the Brembo calipers?

 

Im in the process of planning a braking system upgrade for my 105. The car still has its original 1300 small calipers and small uprights and twin booster setup.

As this car is setup for road/track use I was planning to go to 75 brembo calipers/rotors in the front and probably leave the rears standard.

Cheers.

Hi blacklotus99,

If you're planning to use Alfa 75 Brembo calipers on the front, as I'm doing on my GT1300 Junior, there's a company in Adelaide (see below link) who can supply custom disc rotors that will fit your car. They're ventilated and 22mm thick, which means you don't have to open up and take the spacer out of the Brembo caliper.

You'll end up with the slightly bigger Brembo pad surface area, slightly larger diameter disc (ie custom disc rotors are about 5mm bigger diameter), the benefit of lighter Brembo calipers, and, perhaps most importantly, ventilated and better cooling front disc rotors.

Alfa Romeo Service | Eurosport Automotive

As for other modifications required:

1. you'll need to trim the 1300's disc splash guards to fit around the Brembo calipers... a fiddly trim-fit, trim-fit job which is best done with the guards still on the car.
2. the hard brake line on the inboard side of the Brembo caliper will need modifying to fit up to the 1300's flexible brake line position.
3. you will probably need to fabricate and install a shim (1mm-3mm??) between the upright mounting points and the Brembo caliper to ensure that the inboard pad clears the disc rotor.
4. the wheel stud holes on the custom disc rotor may need to be drilled out slightly so as to accept installation of the 1300's wheel studs. The studs need to be pressed out of the original 1300 rotors and then pressed in to the new custom rotors.

Regards,


Nick

 

My Dunlop M/C will sometimes hang the piston up while bleeding the system - I haven't been able to pin down the cause - adding an additional return spring inside the master didn't help much, and I'm loathe to try honing it out to try aleviate the sticking issue (it's been re-sleeved at some point, I wonder if the bore is slightly tapered).
Might have to try the ATE master once it's back on the road, although I'm tempted to get rid of the booster and fit something like the Alfaholics twin master kit with new lines.

 

One of the key reasons for using a balancing bar instead of a proportioning valve is that the valves can stick, not under pressure but after your foot comes off the pedal.

Take out the proportioning valve and see if she still sticks.

 

It stuck before the proportioning valve went in - it's something with the stupid Dunlop M/C.

 

Hi Jay and other Alfa friends:

I haven't checked AlfaBB for a while, been busy selling our house and getting the "treasures" accumulated over the past 42 years of marriage moved from our former Olympic Peninsula home. Conclusion born of doing it wrong: Don't collect so much stuff, don't ever move, or hire young guys to do the heavy lifting.

Regarding the car, thanks for your helpful suggestions.

The thoughts on how to cure the Alfa's brake woes are appreciated, as is the link Jay posted in March. Once I can actually move around in my garage again, the brakes are a high priority.

And yes, the brakes worked fine until I decided to "improve" them. Where it all went wrong was actually before the proportioning valve was installed; it was when I put on the newly rebuilt Brembos and a set of new rear ATE calipers meant for a Spidy.

The new brakes lines, Tilton valve, and pedal box from a '69 car came later.