BREMBO

[Special]

Well , you all know how original Fiats breaks suck.
So , I am working on a Brembo brake system for my Fiat .
I have some progress and I think it might be interesting for somebody else.
It is far from over - but here it is.

Front - Porsche 944 Turbo
Back - Lancer Evo



I chose them because they are the smallest calipers of the Brembo's line -
Rear - row 4 , line 5
Front - row 3 , line 5



On the back I had to modify mounting holes to fit Brembos , since it is a 5mm difference.





Caliper fits right on





Back guard painted and installed



Rotor took its place



High temp header paint







Wheel fits without problems





And to compare old and new rotors







For the front I had to fabricate an adapter plate out of 10mm steel.
It took me about 6-7 hours , since I don't have any fancy machinery and everything was done by simple hand held tools.
The second one should be easier , I'll just copy the first one.

















Well , that's all for right now.
To be continued ...

[djape1977]

nice job but a little objection about the spacers: there's nothing to hold the wheels centred

[Daniel]

I think it's cool that you did a custom fab on your own but there are a few aftermarket brake kits
already out there maybe you know this already and wanted a challenge ? any how 2 thumbs up
for making something better then stock ...

[Redline]

Well , you all know how original Fiats breaks suck.

In good condition, on vintage tires, the "poor" Fiat brakes would pull up with about 0.8g. Not bad at all. My original Fiat brakes can be provoked to lock modern, sticky rubber with a 205 section. I'm not so sure there is anything wrong with them if you keep them well maintained; going to bigger brakes will not decrease your stopping distances if you can already lock the wheels with the standard system. Now, it may improve fade performance (relevant for the street?), modulation (doubtful) etc., but I would wager a decent set of pads would get you most of the way there.

What makes me more nervous than the "poor" original Fiat brakes are original hubs that are drilled to accept rotors with a bigger PCD; it looks like you have very little metal, also on your caliper adapter plate. Are you sure you trust them?

[Daniel]

redline have you measured the Gs during braking on your fiat ?

[divace73]

redline have you measured the Gs during braking on your fiat ?

that's easy enough to do now with GPS gear...

[So Cal Mark]

it's hard to tell from the pics, are the rear rotors centered?

[spiderrey]

The rear set up is interesting. Is there still a parking brake? Dont like all the spacers on the front though. Also , I dont see where the hubs were redrilled, unless I missed something. Kind of skimmed thru it. Personally, I dont think the stock brakes are bad. Mine only failed me once. I have way over stock horsepower, and was on a run with other spiders running down a winding canyon. They overheated to the point of being useless. Nothing some minor mods and maintanince couldnt cure Im sure. Not knocking your efforts at all here.

[Special]

Bunch of spacers is to temporarily hold down the rotor while working on the adapter plate.
Hub-centric bolted spacers will be installed later.

The hubs were never drilled , rotors were drilled to accommodate 4x98 bolt pattern.
It was done on the CNC machine with great precession , they tightly fit over the studs , so where is no play at all.
Parking brake will be hydraulic with adjustable proportioning valve for the back.
And if you guys think this system is not going to stop better then stock - well , then I am doing all this just for looks.
I'll measure my brake Gs when done

[So Cal Mark]

I'm sure it will be a huge improvement, I was concerned because the angle of the rear pics look like the rotors can be mounted off center. It sounds like you anticipated that situation. What is the diameter of the caliper pistons? Are you using the stock master cylinder?

[manoa matt]

"What is the diameter of the caliper pistons? Are you using the stock master cylinder?"
That was one thing I was also thinking, keeping it proportional and the pedal feel/travel.

Considering the power and weight of the spider and how the brakes are proportioned front to rear I think you could have gotten away with intalling what you came up with for the rear on the front axles and keep the stock rear brakes.

What is the unsprung weight difference between the new rotors and spacers vs. the stock setup?

[Special]

Front calipers - 2X36mm and 2X40mm
Rear - 2X36mm
Master cylinder is stock for now.
I want to take it on the road and check the performance.
If I'll fill I need more - I might start looking for an upgrade.
Do you have any suggestions ?

And I did not not have a chance to weight anything yet.
I'll do it later and let you know.

[Redline]

redline have you measured the Gs during braking on your fiat ?

No, just calculating from old magazine tests of the day (1960s). Simple physics. Car & Driver had it as high as 0.88g in their first test. Sport Car Graphic had it consistently above 0.8g. in real numbers, that was 60 - 0 mph in about 135- 140 feet, on rock-hard hockey-puck tires. A Miata does 60 - 0 in about 125 - 130 ft on modern rubber. You draw your own conclusions or you can roll your eyes. In my book, it's a good idea to identify the real deficits first before trying to find a solution.

[maytag]

In my book, it's a good idea to identify the real deficits first before trying to find a solution.

Always good advice. BUT: I think MOST of us have found that the brakes on these cars SUCK. Could very well be due to their age, but as long as we are replacing, we might as well upgrade, right? I mean, why put back on decades-old stuff that was marginal THEN?

[Redline]

The numbers above would indicate that they do not, in fact, suck. 30 years of neglect can make them suck. Porous lines, water-soaked fluid, grotty caliper pins, cheesy pads, a rusty master cylinder. Those can all make them suck. I'm pretty sure the factory rally effort (the first BS-series cars) didn't even upgrade the brakes.

I certainly don't want to rain on anyone's parade, and I think it's great when someone takes the initiative to do something. I really like this particular car, to be honest. But I also think that "big brakes" are a panacea that everyone quickly reaches to, and then there is the surprise that, in fact, those big discs and multi-pot calipers didn't really bring anything. We're talking about an 800kg car.

I retract my concern about the hubs. I had assumed they were re-drilled. Now I see that the OP has "only" made slotted holes to hold the caliper bolts. Interesting. I mentioned it because I think sometimes people don't realize the kind of "power" that is going through these components under braking. Everyone spends a lot of time trying to beef up diffs and driveshafts to take an increase in engine power. Quite often hubs, rotors and caliper backing plates get overlooked. Let's look at some rough calculations (and I may be way off, as I'm just hand-waving it, so feel free to correct me or my logic):

On original brakes the 124 can pull 0.8g of deceleration, so that's about -7.85 m/s^2

If it weighs about 850 kg, then that means an average friction force of 6670 N to slow it down.

If the brake balance puts 75% of the braking on the front, that's 5000 N on the front axle, or 2500 N per wheel.
(As an aside, I guess the corner weight on the front is about 2500 N per wheel, so that's an effective friction coefficient of about 1, which is consistent with many estimates, so so far the rough calculations aren't complete nonsense)

The rolling radius of a typical 124 wheel is about 295 mm, so the effective braking torque per wheel is about 2500 N x 0.295 m = 735 Nm (540 ft.lbs!)

Now, divide that braking torque by the bolt circle of the caliper adapter plates that have been fabricated and you start to see why material strength and the amount of material you've left are rather important...

Probably they're ok, but don't just eyeball it.