Brakes for a Fiat 131 rally car

Non-engine, eg: aerodynamics, gearboxes, brakes, suspension
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miro-1980
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Re: Brakes for a Fiat 131 rally car

Post by miro-1980 » Sat Mar 12, 2011 11:00 am

Guy,

I will certainly do that , after I resolve the front disk issue I will consult with him and anyone else who I can thing of and you can recommend who has brake system knowledge and experience.

The front RS 911 300 mm (maybe plus 5mm) is a fixed element. Once this is in place I will have something to gauge the rear brake against (as a reference).

You know me Guy, I may sound stupid and occasionally jump the gun in discussion , but I will be extremely ( I mean EXTREMELY !!!) careful in building the new brake system.

Thanks

Miro
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Re: Brakes for a Fiat 131 rally car

Post by miro-1980 » Mon Mar 14, 2011 12:59 am

The rear hydraulic hand brake.

I have found a very nice an rather inexpensive solution to hydraulic handbrake conversion.
hamulec reczny 1 .jpg
hamulec reczny 1 .jpg (11.7 KiB) Viewed 2711 times
hamulec reczny 2 .jpg
hamulec reczny 2 .jpg (8.36 KiB) Viewed 2711 times
Because if its versatility you can mount the handle in numerous positions from horizontal to vertical ( and at least 3 positions in between.) It is based on a Girling pump so quality is expected. I believe I will need to used the AP shuttle valve top cut off the effecting the front brakes.
shuttle valve .jpg
shuttle valve .jpg (22.33 KiB) Viewed 2711 times
Looks like the solution we will adopt.

Miro
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TomLouwrier
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Re: Brakes for a Fiat 131 rally car

Post by TomLouwrier » Mon Mar 14, 2011 11:37 am

hi Miro,

What sort of disc sizes are we looking for?
Front: 300-305mm diameter, 20-22mm thickness (ventilated), probably standard Fiat hub (4x13.2mm holes @98mm, 59mm hub centre hole).
Rear: 250mm diameter, 20-22mm thickness (ventilated), probably standard Fiat hub (4x13.2mm holes @98mm, 59mm hub centre hole).

If you fit your calipers straight onto the hub carrier, then the size of the disc is more or less given, you may be able to play a bit with different pads, but that's it really.
Most F/L discs are in the 40-55mm range of total height, but there are many discs in the OEM catalogues that may be adaptable. Usually it's the bolt holes you need to re-drill. You may be able to shim out either the disc or the caliper by some mm's, but for more you need another disc with the correct height (or pretty close to it). It also depends on the way the caliper is mounted to the hub carrier.
The original works discs mentioned on page 2 have about 74mm total height. Is that the size that you need in order to get the disc centred in the caliper?

Can you give some more dimensions please? Pictures?

regards
Tom
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miro-1980
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Re: Brakes for a Fiat 131 rally car

Post by miro-1980 » Wed Mar 16, 2011 12:08 am

Guy ,

Several recent I made and the most recent you made on this thread keep appearing and disappearing with no apparent reason.
I have placed some test posts which I later removed but there is something wrong. ( a virus ? or maybe corrupt files on the server ?). Can you have the webmaster check it.

Miro
Last edited by miro-1980 on Wed Mar 16, 2011 2:01 am, edited 3 times in total.
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Re: Brakes for a Fiat 131 rally car

Post by miro-1980 » Wed Mar 16, 2011 12:27 am

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Re: Brakes for a Fiat 131 rally car

Post by miro-1980 » Wed Mar 16, 2011 12:31 am

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Re: Brakes for a Fiat 131 rally car

Post by miro-1980 » Wed Mar 16, 2011 1:24 am

Tom ,

"What sort of disc sizes are we looking for?
Front: 300-305mm diameter, 20-22mm thickness (ventilated), probably standard Fiat hub (4x13.2mm holes @98mm, 59mm hub centre hole).
Rear: 250mm diameter, 20-22mm thickness (ventilated), probably standard Fiat hub (4x13.2mm holes @98mm, 59mm hub centre hole)."

Actually all I can address at this stage is the front disks.
Front: 305mm diameter, 18 mm thickness (ventilated), Fiat 131 A|barth hub (4 x 98mm with holed for 12 mm diameter bolts , no hub center hole required).

The disk I got are 250 mm diameter and 65 mm height (60 mm internal depth).
final  old disk 1.jpg
final old disk 1.jpg (66.61 KiB) Viewed 2619 times

They are 5 mm too shallow.

There would be no problem if they were too deep, as this could be compensated by washers.

I need disks with respective measures :

305 mm diameter and 70 mm height (65 mm internal depth):
final new disk 1.jpg
final new disk 1.jpg (62.27 KiB) Viewed 2619 times


I have found nothing to resemble this configuration in currently stock disks.

Moreover the foundries supplying casts to manufacturers do not want to send raw casts to them . They are always pre-machined to certain model OEM determined dimensions. While final machining takes place at the disk manufacturer the pre-machined disks do not fit our specs. To top this the foundries supplying major manufacturers require a minimum order of 100 pre-machined disks.

So I had to find a small foundry doing small orders ( I need 4 disks - two to install and two as spare) ready to prepare a mold and ready to cast only 4 disks. It was not easy but it looks like I have found one (lets keep our fingers crossed!!!!).

Your point regarding the pads is very well taken !
I have no idea why my mechanic decided we need 58 mm working height while the pads I ind=trend to use are 55 mm high.

In fact pad measurement is something I forgot to take into account at all about. We measured the required depth with the pads and the height based on the pads currently installed in the RS calipers and not the ones we will actually use.

The ones on the calipers are Porterfield Racing Pads Ap45T R4S while we will use Ferrodo FCP 11 H (DS 2500).

I will now install the proper pads into the caliper and take the measurements again. Maybe the 74/ 75 height difference between data on original gr 4 disk height and our non standard 58 mm working surface height stems from measuring the wrong pads. Or maybe ( which is also likely the numbers are wrong by the mechanic taking extra margin).

I also need to find out what disk thickness were originally installed ion Porsche 911 RS with the calipers I have. This will verify the disk thickness. So far I have only found the thickness to be 20.4 mm on 282 mm disks , but the Porsche pads seem to have different dimensions , so I need to consult one of my Porsche friends who is old enough to know original RS ( LOL).

The Ferrodo pads thickness is 15 mm. height is 55 mm and width is 76.7 mm.
my ferrodo pads 1 .jpg
my ferrodo pads 1 .jpg (85.9 KiB) Viewed 2619 times
If the Portfield Racing Pads Ap45T R4S pads' have different height the working surface height will change and if they have different thickness the disk thickness will change.

Life of a limited volume produced auto restorer is tough and full of traps ...

Miro
Last edited by miro-1980 on Wed Mar 16, 2011 1:53 am, edited 6 times in total.
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Re: Brakes for a Fiat 131 rally car

Post by miro-1980 » Wed Mar 16, 2011 1:26 am

Guy , Tom,

You gents inspire my technical thinking and accelerators steepening my learning curve.

I have come back to the basic measurements and discovered some bad assumptions circulated between me and my mechanic regarding disks requirements.

Here is ts again :

The existing disks are too shallow by 5 mm. Instead of measuring 65 it measures only. ( see 60m in red circle).

top super final  old disk 4 v x.JPG
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top super final old disk 4 v x.JPG (32.29 KiB) Not viewed yet


Key measurement for developing was the distance of 51 mm marked in red.

In the new disk this must be 56 mm. There are other measurements which change as a result of this being increased from 51 to 56 mm.
top super final  new disk 4 v.JPG
top super final new disk 4 v.JPG (32.5 KiB) Viewed 2619 times
top super final new disk 4 v.JPG (32.5 KiB) Not viewed yet



The next issue is the height of the working ( friction ) area of the disk proper.

As we are working with a given caliper ( ATE from Porsche RS 911) we are working with some key fixed dimension requirements.

See my primitive drawing showing the dependencies :
show 3.jpg
show 3.jpg (113.21 KiB) Viewed 2619 times
show 3.jpg (113.21 KiB) Viewed 1 time


1/ the pad height for my calipers is 55 mm - so the minimum friction area of the disk must be 56 mm.
2/ the hub height requires the bell depth to be 67 and overall disk height to be 72 mm
3/ the hub face diameter of 117 mm requires the internal bell diameter to be 117.2 mm
4/the disk diameter is determined by the relative caliper position, pad height and hub diameter .

One element that also changed ( after Tom inspired me !) and I measured again the caliper with Ferrodo pads installed is the space for disk thickness. The caliper opening ( with pads installed) is 24 mm . So the disk can easily be 22 mm thick.

This has consequences for possibility of AP rotors (with no bells) . The AP rotor 304 x 20.7mm Bolted - CP4348-626/627 presents one basic problem. The friction area is just a bit to short - see my drawing below.
AP bolted rotor1 .jpg
AP bolted rotor1 .jpg (25.89 KiB) Viewed 2619 times


Will check with AP technical experts, but even if they say yes , I am afraid we would be operating with extremely small margins.

Miro
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TR-Spider
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Re: Brakes for a Fiat 131 rally car

Post by TR-Spider » Wed Mar 16, 2011 11:56 am

Hi Miro
This has consequences for possibility of AP rotors (with no bells) . The AP rotor 304 x 20.7mm Bolted - CP4348-626/627 presents one basic problem. The friction area is just a bit to short - see my drawing below.
As I understand we are talking about the pad beiing 0.5 mm too high here.
I personally would not bother to file (grind) carefully that 0.5mm off on each pad (on the lower flat side) I would use.
I assume that 0.5mm is probably the tolerance of the pad material (mot the carrier) anyhow.
One can easily do it by hand by filing (obviosly executed with care, accuracy and dont breathe the grinded material).
If you are unsure about that take tha pads to a maschine shop, or make yourself a steel "paspartout" (some device where the pad exactly fits in and leaves just the 0.5mm standing off to be grinded...

That will save you so soo much hassle if you can use a stock disk...
The existing disks are too shallow by 5 mm. Instead of measuring 65 it measures only. ( see 60m in red circle).
Can't you put a 5mm distancer between the caliper and the carrier?
That would make the calliper move 5 mm towards the outside and fit the disk, no?


Thomas
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Guy Croft
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Re: Brakes for a Fiat 131 rally car

Post by Guy Croft » Wed Mar 16, 2011 12:49 pm

Sorry but my interim post about bell-less discs from AP Racing got lost during the server change. I guess you saw it Miro before it went off air? If not I will repost.

Sometimes running this site gives me a headache.

G

miro-1980
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Re: Brakes for a Fiat 131 rally car

Post by miro-1980 » Wed Mar 16, 2011 2:03 pm

Tom,

"Can't you put a 5mm distancer between the caliper and the carrier?
That would make the calliper move 5 mm towards the outside and fit the disk, no?"


The problem is it is in reverse , I would need to cut off a total of 5 mm of one or all the below listed elements:

- the caliper mounting lugs,
- the carrier mounting lugs
- the bell inside surface

The problem is the distancer would move it the wrong way increasing the prbolem.

See my drawing ...
WASHER ISSUE .jpg
WASHER ISSUE .jpg (40.25 KiB) Viewed 2631 times
Re: 0.5 mm should be manageable bit awfully close. Nevertheless the guys at BrakesInternational UK said they can work with the AP rotor and make an appropriate bell for it.

Looks like this is a solution. Once done I can replace the stock rotors with AP at little cost , so it looks like a solution.

M
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Re: Brakes for a Fiat 131 rally car

Post by TomLouwrier » Wed Mar 16, 2011 2:11 pm

hi Miro,

Hmmmmm, are you talking to Thomas from Switzerland now or Tom/Thomas from Holland? ;-)

Anyway, hang on a couple of hours because I've found a number of OEM discs that could be adapted. It takes a bit of time to list them all with car brands and add the correct part numbers though. Have to check the drawings as well for 55mm pad height.
Probably tomorrow afternoon or evening.

regards
Tom
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Re: Brakes for a Fiat 131 rally car

Post by miro-1980 » Wed Mar 16, 2011 3:15 pm

Thomas , sorry it is so easy to confuse identities when you are dealing with PC screen only ( no face or voice)

Thank you very much for your help.
I do not even have access to the catalogs

Miro
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Re: Brakes for a Fiat 131 rally car

Post by TomLouwrier » Thu Mar 17, 2011 10:09 pm

hi Miro, guys,

Ah nice, those engineering drawings. Me like very much....

So the ideal size you need is 305x22x72 (outer dia x rim thickness x total height).

I've looked up early 911 brakes and they all used 20 or 21mm thick discs of around 290mm dia, that would be with standard Porsche pads in there.
More recent discs in the 300+ range tend to be fatter and have a rim of 28-32mm thick. Main reason is not mechanical strength but thermal capacity, these SUV's are heavy spaceships and stopping them generates a lot of heat.
It is possible to machine these discs, as long as the material between friction surface and ventilation channel does not get thinner than 6mm, maybe 5,5mm but that would be cutting it close. Remember that average solid discs are normally around 12mm new, which is 2x6mm and 0mm ventilation channels.

Assuming you may
- take about 1mm off the lugs on the caliper
- take about 1mm off the lugs on the hub carrier
- take about 1mm off the face of the hub itself
you could get away with a disk of 69 or maybe 68mm total height.
In theory you could take some material out of the bell's face that sits on the hub, but I would certainly not go below 6mm for that. As most discs have that thickness there anyway, I'll ignore that option.

So we are looking for discs in the range of:
- outer rim diameter: 304 or more (may be machined to fit)
- inner rim diameter: 305-(2x55)= 195mm (pad contact face, the actual bell or hub size will be about 20mm smaller)
- rim thickness: up to 24mm (may be machined to fit)
- total height: over 69 to about 82mm (this would mean 10mm of shimming out disc and/or caliper which I take as maximum)

Unfortunately there is only one disc in the Fiat family of 305mm, but that is only 46mm high. That means we're going to look at other brands and since practically nobody uses the Fiat 4x98mm bolt pattern we won't bother to match that. You'll have to re-drill whatever we find if it will fit otherwise. Same goes for the centre hole, if we find that is smaller than we need (drawing says 74mm).

Spending some hours in several OEM catalogues gives us:

BMW
302x20x73; a bit small but maybe with different pads it could work
EBC partno. D367
302x22x76; a bit small but maybe with different pads it could work
Brembo partno. 09.5142.20
310x24x77; 24mm should work, needs 5mm shim, good match
Brembo partno. 09.9173.10
Brembo partno. 09.9173.14
315x28x76; a bit fat, but some could be taken off the rim depending on the size of the ventilation channels
Brembo partno. 09.5929.10
316x28x77; a bit fat, but some could be taken off the rim depending on the size of the ventilation channels
Brembo partno. 09.5875.10
324x30x71; quite fat, but some could be taken off the rim depending on the size of the ventilation channels
EBC partno. D1246
324x30x74; quite fat, but some could be taken off the rim depending on the size of the ventilation channels
Brembo partno. 09.8961.21
324x30x77; quite fat, but some could be taken off the rim depending on the size of the ventilation channels
Brembo partno. 09.5579.21
Brembo partno. 09.9172.14
324x30x81; quite fat, but some could be taken off the rim depending on the size of the ventilation channels
Brembo partno. 09.9166.10

DeTomaso
314x28x83,5; a bit fat, but some could be taken off the rim depending on the size of the ventilation channels
Brembo partno. 09.5191.10

Ferrari
310x24x76,8; good match, but inner rim dia maybe too big for 55mm pads
Brembo partno. 09.4966.10
EBC partno. D514
310x28x80,5; a bit fat, but some could be taken off the rim depending on the size of the ventilation channels.
Brembo partno. 09.5519.10
Brembo partno. 09.5519.30

Hyundai
315x20x87, a bit high but may work
EBD partno. D1264

Jaguar (many)
305x20x68; quite low at -4mm, but a could be good match if you can take enough off the lugs and/or hub flange. check inner rim diameter.
Brembo partno. 09.7217.20

Mercedes (many)
310x28x82; a bit fat, but some could be taken off the rim depending on the size of the ventilation channels.
Brembo partno. 09.5726.10
312x28x76; a bit fat, but some could be taken off the rim depending on the size of the ventilation channels.
Brembo partno. 09.8127.10
320x30x82; quite fat, but some could be taken off the rim depending on the size of the ventilation channels.
Brembo partno. 09.5704.20

Opel Monterey / Isuzu Trooper
313x18x80; looks good, a bit thin maybe. inner rim dia too big for 55mm pads?
Brembo partno. 09.7377.10
Opel Movano / Renault Master / Nissan Interstar
305x27x80; a bit fat, but some could be taken off the rim depending on the size of the ventilation channels. check hub centre hole diameter
Brembo partno. 09.8904.10
305x28x78; a bit fat, but some could be taken off the rim depending on the size of the ventilation channels. check hub centre hole diameter
Brembo partno. 09.9080.10

Porsche (would have listed them under VW.... ;-) )
304x32x72; just under 305 but may work. very fat, some could be taken off the rim but probably not enough
Brembo partno. 09.8420.10
Brembo partno. 09.8421.10
309x28x83; quite fat, but some could be taken off the rim depending on the size of the ventilation channels
EBC partno. D1164L / D1164R
330x28x73; both big and quite fat. some could be taken off the rim depending on the size of the ventilation channels. check inner rim dia. check hub centre hole. not a very good choice.
Brembo partno. 09.A056.11
EBC partno. D1327

Subaru (many)
316x20x68; quite low at -4mm, but a pretty good match if you can take enough off the lugs and/or hub flange. check inner rim dia.
Brembo partno. 09.7217.20

Toyota / Lexus (many)
307x16x67; quite thin and too low really, many holes in the bell already, so not a very good choice.
Brembo partno. 09.A138.10A
322x21x69; a bit big and some 3mm low, but a pretty good match if you can take some off the lugs and/or hub flange. check inner rim dia.
EBC partno. D1039

VAG (Volkswagen, Audi, Seat, Skoda)
VW Tuareg
314x22x76; could be quite good
EBC partno. D1328
Audi A8 RS2
304x32x77; just under 305 but may work. quite fat, some could be taken off the rim but probably not enough. check number of bolt holes.
EBC partno. D995L / D995R


So it seems like you have some options here to explore :-)

I would first look into the following:
BMW
310x24x77; 24mm should work, needs 5mm shim, pretty good match
Brembo partno. 09.9173.10
Brembo partno. 09.9173.14
Ferrari (you won't find that in a breakers' yard for a trial fit...)
310x24x76,8; good match, but inner rim dia maybe too big for 55mm pads. don't have the drawing right now.
Brembo partno. 09.4966.10

Then maybe the Jaguar or Subaru discs, then the rest.

There are undoubtedly more possibilities available, but for now I guess we have enough to get started.
The Brembo Aftermarket section of their website gives you very good drawings with all dimensions you need. It also includes OEM part numbers which help you find the car model and part numbers from other suppliers (cross references). There is a pdf version of that catalogue as well, a 75MB pdf that I probably can't mail you. I'll send you the link.
EBC have a similar catalogue, the 2005 I used so far version is a 1.8MB pdf file. On their website you can download their current catalogue, both in pdf and -tada tada!- in Excel-format. That should make sorting and selecting much easier and faster.

Can I post those links here directly, Guy?

regards
Tom
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Re: Brakes for a Fiat 131 rally car

Post by Guy Croft » Fri Mar 18, 2011 9:57 am

Tom, hi

always impressed by the scope and detail of your posts, thank you very much for your regular and significant contributions on the site. That last must have taken hours to write. Readers - be impressed and inspired!

Yes, post the links, thanks for asking,

G

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