Homolgated brakes for the x19

D

Djaraceandrally

Daily Driver
Hello all,

Looking to see if anyone can shine some light on this, but Im building group 4/Group B rally car and looking through the homologation forms for the car (225).

In it, it shows a signed off brake upgrade for the car and wondered if anyone would know if it was out of the Fiat parts bin.

It shows a bigger/different caliper and a vented disc.

Any ideas - oh, I cant just go a big brake upgrade, has to be as approved in the day as the car has to get a historic passport to compete.

IMG_2375.jpeg
 
Ritmo 130TC standard parts

scroll down in the .pdf file of the Ritmo 130TC grp A homologation, section 8 is brakes, the first schedule is the standard sizes...same exact dimensions as the X19 homologated part, 702xxxx part numbers are usually Abarth made / supplied items

SteveC
 

Attachments

  • homologation_form_number_5189_ritmo 130 group_a.pdf
    2.4 MB · Views: 66
Last edited:
I think in a pinch you could argue the case for Uno Turbo vented discs... the disc for those is 240mm x 20 size, and Uno T calipers, simply as they are probably easier to find... I would guess the 130TC stuff would be pretty thin on the ground.

But good luck in your search.

SteveC
 
Djaraceandrally said:
Found some used 130 tc calipers, and a new set of discs - £1000! Would they need 14” wheels though?
Click to expand...
you'll also need the cast iron caliper mounting bracket... as the standard item wont clear both the disc width and it's OD.

I think fitment under 13" wheels would depend to some degree on the wheel... I've been able to fit 257mm discs under some 13" wheels but not others... UnoT at 240mm discs uses 13" wheels, so I think 243mm OD disc would be a safe bet.

Ritmo calipers are likely to be a different thread pitch where the flexible rubber lines screw into them... older Fiats use a 3/8 -24 thread... after about 1984 they went m10 x 1.0 ... Ritmo also uses m10 x 1.0 thread pitch at the hard line too, earlier cars are m10 x 1.25

SteveC
 
UT front brakes do fit in the stock 13 wheels, but it is such a close fit you can't fit balancing weights inside the wheel much to the annoyance of the fitter who last replaced my tires.

They are a different type of mechanism on pins/rails rather than slider/wedges which is lower maintenance but would they count it for the homologation?
 
Thats the fun bit - so the Homolgated rim is the stock steel rim shown in an earlier paper when it was goup 3 - but there is a submission/extension that was in prep for group 4, that shows extended arches and much wider alloy wheels. Its been crossed out saying “do not rush, will be in Group 4 submission” but there isnt a group 4 form in the FIA records, but there is a form for group B. Both my local scruit. and the chap who signs off cars as historically correct has noted this - so it goes back to “prove it was in use in the day, and you can use it!”

So the arches are fine, but the brakes - well I guess they could be open to interpretation if no clear records exist as long as they are of the same format (single pot, vented ext.)

Ive been told I can run Kugelfischer, but they would ideally want pictures of them running it with butteryflys, if I wanted to run it rather than a slide throttle. Same with twin webers, not in the forms but if I can prove it ran in period (works or private entries) they would consider it. But I cant run something that is simply too new or not in period.

All good fun
 
Last edited:
Djaraceandrally said:
Thats the fun bit - so the Homolgated rim is the stock steel rim shown in an earlier paper when it was goup 3 - but there is a submission/extension that was in prep for group 4, that shows extended arches and much wider alloy wheels. Its been crossed out saying “do not rush, will be in Group 4 submission” but there isnt a group 4 form in the FIA records, but there is a form for group B. Both my local scruit. and the chap who signs off cars as historically correct has noted this - so it goes back to “prove it was in use in the day, and you can use it!”
Click to expand...
Group 4 (grand turismo speciale) homologation data does exist ... but there's no folio number, as the 500 cars were never built.

grp 4 page on wheels... still 13's, and not a whole lot wider at 5.5inches... light though at only 4kg per wheel
prototipo04.JPG


2.6 turns lock to lock too... pretty sure that's the steering rack out of the Fiat parts bins that I told you about already...

looks like they managed to squeeze a 252mm disc under the 13's, with what looks like a Girling (probably the same as early alfa - same piston and pad size as a girling caliper for an early 105 ) 2 piston fixed caliper

prototipo08.JPG


SteveC
 
Thats interesting Steve, thanks - is that off the FIA site? If not, any chance you could scan and send me a full copy over?
 
Last edited:
Djaraceandrally said:
Im wondering how good I can get the stock brakes with properly serviced calipers, quality discs and decent modern material pads
Click to expand...
Stock exxe brakes are design to have front brake lock up due to the safety and other related requirements from that era. This is why when an exxe is pushed hard for braking the front brakes always cook to beyond well-done and not produce the shortest stopping distances.
If the driver and road conditions allow, the brake balance can be altered by using 38mm piston rear calipers in place of the stock oem 34mm piston rear calipers..

Yes the front brakes to a significant amount of the braking, due to the static weight distribution of the exxe, the rear brakes play an important part of overall brake balance and brake performance.. Essentially, both front & rear brakes must be altered to achieve ideal braking performance for a given set of driver/road conditions..

The other serious fixed limitations is 13" wheels. this puts a hard limit on brake size which limits stopping power and brake heat capacity..

Bernice
 
Ive just bought a set of Uno Turbo calipers and brackets to take a look and seen if I can get them agreed. Ultimately they are the same basic spec as the homolgated one - vented disc/single pot. But will have a look for rear upgrades too - I read that the 132 had the 38mm rear calipers - a poss even rarer beast over here than a 130tc!! So will see what I can find out.

But as always, thank you for all your help. This really is a great forum.
 
And... why FWD chassis motos have Huge diameter front caliper pistons relative to their rear brake caliper pistons..

Depending on driver ability and road/race needs, the ideal solution would be to apply any number of current high quality aftemarket brake calipers/pads/rotors/hats as needed with larger than 13" wheels. Then size the brake master cylinders and needed coupled with a driver adjustable brake bias bar and plenty of testing..


Bernice
 
Djaraceandrally said:
Ive just bought a set of Uno Turbo calipers and brackets to take a look and seen if I can get them agreed. Ultimately they are the same basic spec as the homolgated one - vented disc/single pot. But will have a look for rear upgrades too - I read that the 132 had the 38mm rear calipers - a poss even rarer beast over here than a 130tc!! So will see what I can find out.

But as always, thank you for all your help. This really is a great forum.
Click to expand...
Previous post on Uno Turbo front brakes on the exxe..

Uno Turbo Front Caliper Install

These Uno Turbo calipers have been ready for years to be installed. Finally decided to spend about 1.5 hours to get this done. Inside of the Uno Turbo caliper. Powder coated, new seals and all. UT calipers open, pads, M12x1.25, 20mm long, grade 12.9 cap screws, SAE hardened washers...
xwebforums.com

13" wheels `might fit" best to go up to 14" or 15" wheels if this alteration is done.

Previous post on 38mm rear caliper install.

38mm Piston Rear brake Caliper install

These started out as a pair of rear calipers from a 76' Lancia Scorpion. Quite icky directly from the Lancia. They were washed in an industrial hot water & soap washer then abrasive particle blast cleaned. This is what the brackets look like after being primed with Tempo zinc phosphate primer...
xwebforums.com
For a track course car, the 46mm piston front calipers can be installed (essentially direct on the oem stock hoses. brackets and pads) on the rears as a "quickiee" fix to the front brake lock up and over cooking of the brake pads problem. Sorta ok solution.


Bernice
 
Rupunzell said:
are design to have front brake lock up due to the safety
Click to expand...
All cars. The assumption is that front lock up produces understeer which is stable and a minor lift of the pedal regains control. While rear lock up produces oversteer which most punters cannot handle at all. In the case of an X, that huge front luggage compartment adds to the problem. The worst case scenario has 2 people of luggage in there, nothing in the real boot and minimal fuel - and the fronts are supposed to lock first in that case. So, we pretty much never use the car like that so front lock up even more likely. Lockup and fade are two different issues. As we see lockup with the stock setup - there is plenty of brake power available so the brakes do not need to be bigger with respect to stopping power. But - we also see fade. The stock brakes can't get rid of generated heat so pad and fluid suffer. Bigger brakes can help. Bigger disc has bigger area to radiate and if ventilated, will run cooler. Bigger/better pad no brainer. But there are downsides. Unsprung weight goes up. Ventilated disc alone will be about double the mass of the stock disc. And we need to be careful or the front lock up problem will be worse. Bigger brakes = higher brake torque for a given pedal pressure. Even if the caliper piston dia is the same, its effective radius goes up.
 
I have a pal who races one of these, even with a small race size tank mounted in the front he says the difference in understeer between full and empty is noticeable.

In lemons cars, it must be considerable if you are running a large tank (or do you run small tanks up front and fill/swap drivers regularly?)

I can and will be running a front tank in this car.

In my other past rally cars, Ive spent plenty of time working on suspension set ups - after all, the best brakes in the world are useless if you have no control over the suspension.

That said the other cars have been FWD, front engines (Classic Cooper S and Golfs) and RWD front engined (Mk 2 Escorts and MGB’s) - this is the first time I will be push in a mid engined setup, apart from some trackdays I did in a MGF (90’s thing) I had for fun. And despite some slating they got, it was a great car once sorted!! And cheap as chips over here. The K series in it is a peach of an engine - once you have sorted out the headgasket/stud issues!!
 
Last edited:
You must log in or register to reply here.
Back
Top