I run very dished Borranni steel wheels that run incredibly close to my calipers - so maybe this is why "adjustments" have been made to your calipers?

I'm trying to fit discs to my 500.
I don't want to buy a kit as I prefer to do my own work even if it does cause a number of headaches!

Finding a caliper which will fit under the 12" wheels is proving tricky. I understand a mk1 / mk2 fiesta caliper will fit, but they're a bit tricky t get a hold of. I'm looking towards small pre 2000 Japanese vehicles for some inspiration. I'm hoping to find a set from a suzuki alto to see if they will fit.

I've also been looking into motorbike calipers. Fixed calipers with opposed pistons are too wide. I've found few types of floating calipers which may work. One advantage is twin pistons. 2 x small pistons is shorter than 1 x large piston. Motorbike discs are generally too thin but there are a few exceptions. I have a set on their way to me which I'm hoping will fit into the wheel.

If anyone has any caliper suggestions I will happily take any advice!

Fiat cinquecento calipers are used along with Fiat punto ones...

MOD500 said:

I'm trying to fit discs to my 500.
I don't want to buy a kit as I prefer to do my own work even if it does cause a number of headaches!

Finding a caliper which will fit under the 12" wheels is proving tricky. I understand a mk1 / mk2 fiesta caliper will fit, but they're a bit tricky t get a hold of. I'm looking towards small pre 2000 Japanese vehicles for some inspiration. I'm hoping to find a set from a suzuki alto to see if they will fit.

I've also been looking into motorbike calipers. Fixed calipers with opposed pistons are too wide. I've found few types of floating calipers which may work. One advantage is twin pistons. 2 x small pistons is shorter than 1 x large piston. Motorbike discs are generally too thin but there are a few exceptions. I have a set on their way to me which I'm hoping will fit into the wheel.

If anyone has any caliper suggestions I will happily take any advice!

Click to expand...

Hi Mod, If you check back through this thread it will show you what I have fitted and give you the details, all parts are available.
Ian.

Hi Ian,
I read through a few times before posting. Your calipers are fiat X19 family but I understand they have been modified to fit. I would like to find a caliper that doesn't need to be modified. (I guess I'm looking for the moon on a stick!)

I've managed to find some brake disc catalogues which allowed me to narrow my search down to a few caliper types, but so far I've been unable to find a catalogue of calipers to compare dimensions.

Cheers,

Michael

Greetings All, Just waking this thread up to report that the change of brake pipes from standard to BF goodridge braided examples has transformed the braking on my car I have yet to use them from high speed (that's a relative term ) but they now perform without any spongy pedal feel
and although it's a good shove on the pedal my leg muscles can cope !!!!
The pads are still the GALFER 139 FF as fitted from word go, but I will be fitting Mintex M1144 pads as a test to see if the feel and bite can be improved. I'll get back with any results re pad and disc wear.

Ian.

I have 13in wheels on my 500, and the disc-brake "kit" that I built up utilises Cinquecento front calipers. These are, in my opinion, more that a tad OTT, so I am looking around for something more realistic. I have managed to obtain a pair of 210mm front discs, have a technical drawing for the adaptor plate (for Punto/cinquecento/etc. calipers) so I am also looking at smaller calipers ---any body given thought to Morris/Austin 1100 calipers, which were designed for fitment inside---12in wheels!

the hobbler said:

I have 13in wheels on my 500, and the disc-brake "kit" that I built up utilises Cinquecento front calipers. These are, in my opinion, more that a tad OTT, so I am looking around for something more realistic. I have managed to obtain a pair of 210mm front discs, have a technical drawing for the adaptor plate (for Punto/cinquecento/etc. calipers) so I am also looking at smaller calipers ---any body given thought to Morris/Austin 1100 calipers, which were designed for fitment inside---12in wheels!

Click to expand...

Hi Tom, I've had another look at my front brake arrangement and can say that there is now 24mm from the inside face of the wheel to the 'adjusted' caliper body I am unaware of the original wheel fitment on my car, but I feel that almost an inch of clearance is plenty I will be obtaining some new calipers (x1/9) and disc's in the near future and will be able to comment on the clearance with an 'unmodded' caliper then. A past car of mine ran with Brembo 4 pot calipers and they were only a few mm from the wheel. I have a slight hi spot on one of my disc's which has been exacerbated by the braided pipe fitting (I can feel it more through the pedal!!!) so a new set of disc's will sort it.

Ian.

dragonwagon said:

With the 500 being so light at the front it may not really benefit from having a disc conversion as good initial bite may translate into premature lock up....anyone remember the early Lancia Montecarlo? Personally, I'll be looking to upgrade the drums to improve their performance, which when all is said and done will be quite sufficient to tame the fearsome 30ish bhp I have in mine !

Click to expand...

Yes, I remember the Lancia Montecarlo. Didn't Lancia (Fiat!) remove the servo to try to fix the problem and then withdraw the model for a while (and a re-think!). Absolutely lethal in the wet. But, then again, I was always wary when driving an X1/9 in the wet.

I'd tend to agree that the original drum brakes, provided they are in goood working order, should be fine for normal road use, but can be upgraded if desired.


In the good old days, people used to upgrade drum brakes by fitting either wider shoes/drums or else the twin-leading shoe version from another model in the range. Some fitted 'harder' brake linings and possibly a brake servo. There were larger drum brakes fitted to the 850T (Van) , it was said these were the same as fitted to the early? Fiat 1100.

AL.

Bleeding Knuckles said:

-------------------
-------------------------------------
------------------------------
-------------------- I have a slight hi spot on one of my disc's which has been exacerbated by the braided pipe fitting (I can feel it more through the pedal!!!) so a new set of disc's will sort it.

Ian.

Click to expand...

Hi Ian,

If your discs have been turned down on their outside diameter maybe it would be easier and cheaper to just have the discs skimmed/re-ground in situ on the car?

Also, I see that you're using alloy wheels plus 2 of the standard Fiat wheel spacers... If you haven't already done this, could you check that you still have enough of the threads on the wheel bolts engaging with the hub?

AL.

Someone mentioned possibly using Ford Fiesta Mk1 calipers.....

Had a bit of experience with Fords, back in the day. My memory of Fiesta Mk1 callipers was that they could flex under firm braking pressure, used to feel like brakes that hadn't had all the air bled-out, i.e. slightly spongy!

Don't forget that Fiat rear brake callipers used to use smaller pistons (idk about modern model rear brakes). But they also didn't take full thickness brake pads as used on the front brakes (rear pads were approx. 1/2 the thickness). The advantage of smaller calliper pistons are reduced pedal travel and less pressure applied.

There's a company in the U.K. called, iirc, 'Big Red' who specialize in brake calliper overhaul. I reckon they might be a great source of info on brake callipers, could probably identify what a calliper was originally fitted to, and might be able to suggest suitable callipers to use on a 500 drum to disc conversion.

AL.

I have spent many an hour trawling through caliper catalogues and seeking out dimensions etc...
As I have previously said the problem with fitting disks to the front of a 500 is caused by the fact the wheel offset means that the caliper sits inside the wheel... Minis and such have an offset that means the brakes fit more "inboard" from the wheel.
As a result the main clearance issue is the overall diameter of the caliper plus disk must fit inside the wheel. Because of basic caliper design the caliper and disk diameter must be quite small, and must therefore fit inside a 12" wheel..
the inside diameter of a 12" original wheel is 250mm (approx) the inside diameter of a 13" alloy wheel is 280mm, I would have thought this should have been 25mm but 5mm extra probably due to the difference between steel and ally designs..
so if you look at disks that fit over 98pcd hubs you are looking at 215mm diameter then you must have a minimum of 5mm clearance between caliper and wheel, so think about why this means 10mm resulting in a total of disk plus caliper being 225mm that leaves 25mm of the caliper body..
This does not take into account the clearance needed between the caliper body and the hub face of the wheel...
You can get away with taking 5mm of a disk diameter but any more means the pads will need to be cut down as the disk working surface starts to become very narrow and then the associated modifications to the caliper.

So those are the basic problems....
I personally do not like those single piston floating calipers that exist because they are cheap for modern cars, I have a selection of calipers, and have a set of mini cooper calipers for 7.5" (about 190mm) disks, which one would think would fit, but they are in fact "huge" when you try to fit them in a fiat 500 wheel.

So the problems are caused by the caliper/disk diameter and the internal diameter of the 500 wheel... a Fiat disk cannot be substantially turned down to reduce this diameter as the Fiat disk "slip over" the 126 hub..
I will not go into over braking and fluid volumes.....

The original Abarth solution used a custom cast hub and an almost flat disk that mounted with more offset from the wheel hub face, allowing more clearance for a twin piston caliper to be fitted.... I cannot ascertain what make of caliper was originally used but have a suspicion..... as they use Mini cooper 998 Pads...
(now the mini guys here may jump in...) I have been informed that there was a popular modification the the useless early small piston 99/998 Mini calipers, that is to have them bored out to take the larger pistons and thus make them more efficient...
The plus point is these these calipers are very small....
the minus point is... rare/expensive..

Solutions....

The disk is the first issue....
the only workable solution wold be to find an off the shelf disk that is small enough that does not need modifications... (there are other factors such as center bore etc)
Trawling through disk catalogues I located two possibles, one would need a modification when produced (yes possible) in that the mounting holes pitch would need to be changed. the other is very interesting!!!
These disks are 180mm and 210mm respectively... and 8mm thick (these are car disks) both would allow fitment on a suitable hub.
Factors to consider..... center bore to fit over a hub that would allow std Fiat (or other std.) bearings to be used.
Calipers are still a problem.... as car calipers are huge in reality, given so few modern cars have such small wheels, I have tracked down a Daewoo that has small disks/calipers and the calipers are popular in Poland... but hard to get in the UK.
So lets look at AP, Willood etc... yep they make them small enough but £250 each and not Road use approved.
So unless someone wants to manufacturer something or find where the various Abarth kits source the calipers from we have to look at motorbike calipers... The selection is amazing and if they will stop a 180mph super-bike (60-0 in 2-3seconds) I'm sure they will stop a 500..

Factors that must be considered, availability off the shelf of all
parts and minimum custom components.
Fiesta calipers were a popular conversion.. but try to find some!

I will leave it there or it will be a novel....

Bigvtwin996 said:

I will leave it there or it will be a novel....

Click to expand...

...it's already a novella!

Very good that, full of facts and figures and exceedingly logical.......generous of you to share your research.

Re:- locating small calipers?

As suggested earlier, maybe contact a Co. such as Bigg Red Ltd., (Brake caliper refurbishment specialists in Worcester) and ask for suggestions. They should be able to at least tell you what are the smallest calipers they've handled and what car they came from.

Al.

F123C said:

Hi Ian,

If your discs have been turned down on their outside diameter maybe it would be easier and cheaper to just have the discs skimmed/re-ground in situ on the car?

Also, I see that you're using alloy wheels plus 2 of the standard Fiat wheel spacers... If you haven't already done this, could you check that you still have enough of the threads on the wheel bolts engaging with the hub?

AL.

Click to expand...

Hi Al, did a check on the wheel bolt length as you suggested and found that I have 27.3mm of bolt from the inner wheel surface, the spacers are a total of 10.3mm so I have 17mm available or ????
Never thought about this before and thanks for the notice, never had a wheel bolt come loose, but that's not to say it cannot happen
As an aside I cleaned up my callipers and applied some copper grease while the wheels were off and greasing the kingpins, went for a drive and can say that the hi spot feeling seems to be less ???? Or maybe that's wishful thinking

Ian.

Bleeding Knuckles said:

Hi Al, did a check on the wheel bolt length as you suggested and found that I have 27.3mm of bolt from the inner wheel surface, the spacers are a total of 10.3mm so I have 17mm available or ????
Never thought about this before and thanks for the notice, never had a wheel bolt come loose, but that's not to say it cannot happen
As an aside I cleaned up my callipers and applied some copper grease while the wheels were off and greasing the kingpins, went for a drive and can say that the hi spot feeling seems to be less ???? Or maybe that's wishful thinking

Ian.

Click to expand...

Hi Ian,
So if I'm understanding you correctly, you have 17mm available....
Minus the thickness of the brake disc? (not sure of the thickness of a disc mounting, would estimate c. 6mm?) so you'd have approx. 11mm of thread engaging with the hub threads? The usual rule of thumb is afaik to have 1-1/2 times the thread diameter in thread length for maximum strength. But as the bolt goes through the hub, I think once you have the bolt engaging with all the hub threads plus protruding by maybe 1 thread, you'll have maximum strength. So if my figures/assumptions are correct, you should be fine.

The reason I mentioned checking the bolt engagement with the hub is that many people fit alloy wheels and just use the original wheel bolts. There are different types of bolts used on alloy wheels, some use a standard taper/cone, others use a rounded cone, yet others use a flat washer plus a bolt. It's vital that the bolt matches the seating on the wheels. It's advisable not to use any lubricant (incl. copper grease) on this seating, as it's the friction here that mainly stops the wheel bolt from loosening. It's OK to use e.g. copper grease on the bolt threads but you need to reduce the tightening torque (by approx. 40% iirc) if you do so.

Re: bolt length - usually, alloy wheels are thicker at their mounting face so longer bolts are often needed. In the '70's, Fiat used longer bolts if fitting alloy wheels, some people fitted s/hand alloys and used the shorter bolts that came with steel wheels, I don't know if they had any problems.....

An easy way to check how much bolt thread is engaging with the hub without stripping things down? Clean a bolt, apply some copper or ordinary grease to the threads, screw the bolt home, then remove and see how much grease has been 'wiped' by screwing the bolt home. As long as you have at least the thickness of the hub threads 'wiped' from the bolt threads, you should be fine.

Re:- the braking hi-spot possibly diminishing? Anything is possible. I wouldn't rush into replacing the discs or having them reground/turned. My approach is to clock up a bit of mileage and see how things work out. (as long as the car is safe to drive!). Oftentimes, things settle down with a bit of use.....

Regards,

AL.

So if my figures/assumptions are correct, you should be fine.

Hi Al, Yep all OK, checked the hub thread depth and found that it's 10mm so my bolts are able to use all of that without protruding - the bolts have been cut to fit I think.

Ian.

I am looking into this further, but I have found out the Minis from 1985 onwards used un-vented 8.4in (213.3mm) front discs--fitted inside 12in wheels! This means that the front calipers for a post '85 Mini might just be the answer for those people looking into fitting disc brakes inside 12in wheels. And to make it even better, the minimum thickness allowed on the discs is 8.6mm, which means that they must start off at about 9.5mm. This means that only minimal skimming would be required (the solid front discs for a Fiat X19/Punto start at 10.9mm, and are 227mm in diameter). I am going to try and lay my hands on a post'85 Mini front caliper, and take it from there. :bang:

the hobbler said:

I am going to try and lay my hands on a post'85 Mini front caliper, and take it from there. :bang:

Click to expand...

I will when I get time post pictures etc of the calipers I have including a mini caliper... and the disk pictures, if I get time I will post some shots showing the clearances within a wheel..
A mini Caliper (unless a 997 one) will not fit inside a 500 wheel, as I said this is because mini wheels/hubs mean that the caliper sits further inboard away from the wheel.
Also the disk has to be as close to the adapter plate as possible to allow the other side of a twin piston caliper to clear the wheel, an x19 disk does not have sufficient offset to do this.
This is why Fiesta, Punto etc calipers seem to be the favorite choice because on a floating caliper there is very little of he caliper outboard of the disk, thus allowing shallower disks to be used.

What about using 600/850 drums ?
If you must have discs some 850 Specials and the Coupe / Spider had discs on the front with uprights that are in theory a straight swap for 500 ones. If you choose the 850 route, you will need late 126 rear hubs or carry 2 spares.