Fiat 500 Abarth Brakes installed on X1/9

FYI, 500L rear calipers are 38mm and are manual (ie not electrically actuated like the 500X). I have not looked into this more completely yet but one should be able to use Mototroopers technique to apply these to the X rear upright switching a ‘left’ caliper to work on the right side as the 500L mounts the caliper behind the axle centerline where the X mounts it forward of the axle centerline.

Regarding 500X, Jeep Renegade, Jeep Compass rear calipers (all the same) which are electric e brake, if the Tesla controller would work with 500X calipers we could get rid of an entire mechanical system on our X’s. Just a thought.
 
TonyK said:
I have some pictures of the installation of the Fiat 500 Abarth Calipers and Fiat 500 Vented Rotors installed along with stock Abarth brake hoses. All of it seems to bolt up once the mounting holes are enlarged from 10MM to 12MM.
Click to expand...

I apologize for jumping in to an old conversation, but I am curious.

The original post in this thread is about installing 500 Abarth calipers with standard 500 rotors on an X, correct?

Years ago, when I temporarily had access to X1/9s and to a 500 Abarth that I was dismantling for parts, I had a look at how the Abarth rotors and calipers might fit on an X1/9 knuckle. The rotor fit like factory parts, but the hat offset placed the caliper carrier's mounting face to the knuckle flush with the outboard side of the knuckle's carrier mounting tabs. In other words, roughly 10mm away from the surface it needed to face. Unless my memory is faulty, the Abarth rotor and the base rotor must have a different offset.
 
Longitudinal said:
I apologize for jumping in to an old conversation, but I am curious.

The original post in this thread is about installing 500 Abarth calipers with standard 500 rotors on an X, correct?

Years ago, when I temporarily had access to X1/9s and to a 500 Abarth that I was dismantling for parts, I had a look at how the Abarth rotors and calipers might fit on an X1/9 knuckle. The rotor fit like factory parts, but the hat offset placed the caliper carrier's mounting face to the knuckle flush with the outboard side of the knuckle's carrier mounting tabs. In other words, roughly 10mm away from the surface it needed to face. Unless my memory is faulty, the Abarth rotor and the base rotor must have a different offset.
Click to expand...
That sounds like how I remember it. The Abarth rotor's offset won't work on the X with 500 calipers, but the standard 500 rotors will. And it is the Abarth caliper carriers that's needed, either the Abarth or the standard 500 calipers will work. Although it is most likely you'll find the Abarth calipers along with their carriers together.

With the right selection of rear calipers (not 500 ones) this should make for a very powerful braking setup, say for a K20 swap or such. I'd say the master cylinder size would need to be increased though, as discussed in the other thread.
 
Dr.Jeff said:
That sounds like how I remember it. The Abarth rotor's offset won't work on the X with 500 calipers, but the standard 500 rotors will. And it is the Abarth caliper carriers that's needed, either the Abarth or the standard 500 calipers will work. Although it is most likely you'll find the Abarth calipers along with their carriers together.

With the right selection of rear calipers (not 500 ones) this should make for a very powerful braking setup, say for a K20 swap or such. I'd say the master cylinder size would need to be increased though, as discussed in the other thread.
Click to expand...
In Bob Martin's build he has Abarth calipers and Fiat 500 rotors and the holes on the strut mount need to be drilled out to 12MM. It all works fine. On my car I have Uno Turbo Mark 1 calipers and rotors and 2 Lockheed brake boosters with Willwood proportioning valves on each circuit to dial in the amount of boost for front and rear calipers.

TonyK with Bob Martin in The Woodlands Texas
 
TonyK said:
In Bob Martin's build he has Abarth calipers and Fiat 500 rotors and the holes on the strut mount need to be drilled out to 12MM. It all works fine.
Click to expand...
Thanks Tony. I think that has to be the most cost effective and easiest front brake upgrade available. :)
 
Going off on a tangent here, I wish there was a practical way to add ABS once larger brakes & higher output are a factor. The problem I have is that rapid braking from the easily and rapidly reached triple digit speeds can easily lead to lockup potential, as I don't instinctively modulate the pedal as I used to when my cars were all non-ABS steups.
 
lookforjoe said:
Going off on a tangent here, I wish there was a practical way to add ABS once larger brakes & higher output are a factor. The problem I have is that rapid braking from the easily and rapidly reached triple digit speeds can easily lead to lockup potential, as I don't instinctively modulate the pedal as I used to when my cars were all non-ABS steups.
Click to expand...
It's true, we've become spoiled with ABS and no longer have to modulate brakes manually. The opposite of when ABS first become mainstream and we weren't accustomed to allowing it to do the thinking for us. ;)
 
TonyK said:
In Bob Martin's build he has Abarth calipers and Fiat 500 rotors and the holes on the strut mount need to be drilled out to 12MM. It all works fine. On my car I have Uno Turbo Mark 1 calipers and rotors and 2 Lockheed brake boosters with Willwood proportioning valves on each circuit to dial in the amount of boost for front and rear calipers.

TonyK with Bob Martin in The Woodlands Texas
Click to expand...
Thanks to the info in this thread, I matched the Stilo front calipers that are fitted to my X, to these ventilated Fiat 500 discs:
0161df2734 (2).jpg

The radial and axial offset on the Stilo are both different (the Stilo discs are 284mm), but the only thing I had to do was drill the bracket mount holes on the X1/9 wheelcarriers from 10 to 12mm, and make new flares on the hard brake lines to fit the M10x1 of the new calipers), then it all mounted as if it came from the factory that way (except perhaps the fact that the 13 inch steel wheels didn't fit anymore ... 🤫).

Best regards,
Marc
 
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I should also add that the rear brakes are 38MM with custom pistons that I turned on my lathe.

TonyK with Bob Martin in Lonoke Arkansas
 
Hi Tony, are the 38mm oversize piston rear brakes on Bob Martin's car? Does that car have a proportioning valve, or was the increase to 38mm enough to keep an adequate brake bias?

I have installed Fiat 500 1.2 front calipers on the rear, matched to these solids discs:
download.jpeg

Again mount as if from factory.

The downside is that it kind of forces me to have a hydraulic handbrake and also a proportioning valve. The latter because the 500 1.2 calipers have 48mm pistons, so I expect it to shift the brake balance too much rearwards without. I might find out that the brake master cylinder is not big enough for 54mm plus 48mm pistons, but assume I will find a solution if so.

Anyway, the point I actually wanted to make is that if someone was looking for a moderate front brake upgrade from 225 to 240mm and have modern sliderpin / easy brake pad exchange set-up, getting the 500 1.2 calipers (and brackets plus the discs above) is a 99% bolt-on, no drilling solution. It only needs a solution for the brake line hose (M10x1,25 to M10x1)

Best regards, Marc
IMG_20221005_220715.jpg
 
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I am still at Bob Martin's house in Kentucky, Bob has 34MM rear stock calipers. I have 38MM rear caliper pistons and I noticed the change when I installed them. It was controllable and a good choice of upgrade. That being said, it still required a lot of braking force to slow the car. The issue at hand is that with 177HP tune on the Abarth engine the car gets going very fast in a short time and now the distance to stop is very short as well. Hence the reason I went to power brakes. The down side is that the car stops so fast that the car behind me will run into me so I have to be aware of that constantly. I would suggest that you install a Wilwood brake proportioning valve in the car beside the column as I have done for the rear brakes so that you can dial in the amount of pressure to the rear wheel brake calipers. Also at Freak Out Matt Brannon from Midwest Bayless stated that they sell a 20mm master cylinder to apply more volume to the braking system over the stock 19MM brake master cylinder.


TonyK at Bob Martin'S in Radcliff Kentucky.
 
My1stCar said:
I might find out that the brake master cylinder is not big enough for 58mm plus 48mm pistons, but assume I will find a solution if so.
Click to expand...
I suspect that will be the case. The size increase in all four caliper seems like a big overall change that will require a larger master cylinder.

My1stCar said:
getting the 500 1.2 calipers (and brackets plus the discs above) is a 99% bolt-on, no drilling solution. It only needs a solution for the brake line hose (M10x1,25 to M10x1)
Click to expand...
That sounds like a good option. I don't have much interest in the 500's, does the 1.2 version exist in the US?
 
TonyK said:
it still required a lot of braking force to slow the car.
Click to expand...
Tony, what master cylinder is that with? Because a different ratio between master cylinder size and total caliper sizes will change the amount of effort needed and pedal travel. So I'm wondering if the high effort is a function of the master cylinder size for the calipers you have?
 
I am unsure if you are talking about my car or Bob Martin's car. So I will give the run down. My car Uno Turbo 38MM front calipers and vented rotors, rear 38 MM rear calipers. Then 2 Lockheed brake boosters 1:1.9 ratio for the front and rear circuits. Because this is a seat of the pants engineering and I could see that their was a chance that the balance between front and rear braking could be off I installed 2 Wilwood proportioning valves each in the output of the X1/9 stock master cylinder which is acting as a pilot for the brake boosters. Once dialed in, there is little to do with the system. Bob Martin has Fiat 500 Abarth 54mm front calipers and brake pad carriers and Fiat 500 vented front rotors. Rear brake calipers are stock and so is the master cylinder. Bob was at Freak Out and drove his car, fast and said he has no issues with the braking system. In this build we felt that we may need to add brake boosters and proportioning valves but currently that does not seem to be required. While at Freak Out Bob drove with me and let Matt Brannon from Mid West Bayless drive his car to the meet and greet. Matt never commented that there was a problem with the brakes.

TonyK at Bob Martin's in Radcliff Kentucky.
 
Dr.Jeff said:
I suspect that will be the case. The size increase in all four caliper seems like a big overall change that will require a larger master cylinder.


That sounds like a good option. I don't have much interest in the 500's, does the 1.2 version exist in the US?
Click to expand...
That's also what I thought, but one can't be sure without trying, I'll report back once the car is running (which will be in due time). For now I need to correct my mistake, the Stilo front calipers are 54mm pistons (I wrote 58mm, now corrected in the original post)
 
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