Bigger brakes

Nice job. Those adapter plates you made look exactly like the prototype I made to mount VW rear brakes on my X. I'm sure the actual dimensions differ, but the style is the same. I bet the calipers you are using are very similar to the VW one's I have. ;)
 
By the way Dr Jeff, if you want to see a Regata, go watch the Michael Keaton movie Gung Ho. :) Those "Assan Motors" cars were Fiat Regatas.
 
Fiat 132 discs, 251mm solids. Montecarlo S2 uses....One downside of this style of disc is they weigh 4.5kg compared to 3kg for std 227mm discs, the wheel mounting face flange is 11mm thick and there is a lot of extra metal around the hub od, so I will be doing some machining on these to loose some weight. Those brackets, 4447735 are hard to find.View attachment 40632

interesting, so this means the bg pile of 251mm 132 2000 discs I have actually fit a car that someone may want the parts for and are still on the road..., an S2 Monte with the 251mm discs.

for other readers that don't know, the 124 / 125 / 132 cast iron caliper carrier is very similar to the 128 / X19 / 131 type caliper carrier except the mount blt spacing is wider.

Greg, I'm sure it suits you (and I can sure see the progression / steps in what you're doing), but I find it quite unusual that you have 227 discs up front and 251mm discs in the rear, which will of course move the rear brake bias rear-wards...as you say you can always move it back again by going same / larger discs at the front...but maybe too much?? only testing can tell.

SteveC
 
I agree Steve, it seems unusual, but I think with 60% of the weight on the rear wheels it can use a bit more braking there. 227 to 251 is only about a 10% increase, but the first sprint in 2021 I will find out if it is too much.🙂
 
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yes, but, that's 60% when static... loads of forward and lateral weight transfer later.... that's my thought.

The adaptors you made are pretty much exactly as I did pre 1987/88 (when I got hold of my first 100s brakes from a wrecked 1985 model 100S) and the 251mm 132 discs / bracket was almost exactly the same as the front conversion I did with 251mm discs, I think I used 13mm / 1/2" plate and a thinner spacer and 10.9 grade hardware

the change to the 257's was after trying what you've done at the back (but on the front) a few times, and even with the Beta style caliper carrier and pads up front, but the lighter / larger discs of the 100s, the sliding PIN and not wedge design, the larger (more common by that stage) pad shape / pad material availability and pretty much above all the desire for a 14 inch wheels / tyre combination for gearing / suspension setup / tyre choices led me away from that brake package.

SteveC
 
The Vicks calipers and vented disks come from a Lada. Vick Auto makes an intermediary steel part for the mount differential between what an X is and the Lada mounting bolt center to center dimension.

The calipers are a modular Bosch design (so I have been told) which I have only seen on Lada’s but I am sure they exist for other cars. The caliper piston assemblies can be separated from the sliding pin mount ‘fist’ that encapsulates the pads. I am sure it is a strong enough assembly but it is an odd arrangement that could have its own version of flex.

They sell the piston assemblies as a replaceable element versus the seals which I find odd.

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Wow, my love for a Russian FIAT............. a Lada Niva......... Great car. Lousy quality control. Oh worse than Turin Mirafiori or Lingotto. Still a FIAT though...... Where would Russia be without them......
 
I agree Steve, it seems unusual, but I think with 60% of the weight on the rear wheels it can use a bit more braking there. 227 to 251 is only about a 10% increase, but the first sprint in 2021 I will find out if it is too much.🙂
Update to fitting 251 mm diameter discs on the rear. I did machine the discs to loose some weight, 5mm from the wheel mounting face, 2mm on the 147 OD, and a step at the OD of the wheel mounting face to equal the 227 disc face, to go from 4.5kg to 3.7kg.
With standard front brakes and 251mm rears with 38mm pistons the braking torque is 58% front, 42% rear. Last Sunday I had a sprint meeting at The Bend West circuit and braking balance was good in a straight line, had a front brake lock momentarily once, but no drama. When trail braking into a corner there was a slight tendency for the back end to move a bit more than before, but not too bad.
I am undecided as yet whether to go with larger fronts or not, 239mm maybe, I have Regata calipers if I decide to.
 

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The Vicks calipers and vented disks come from a Lada. Vick Auto makes an intermediary steel part for the mount differential between what an X is and the Lada mounting bolt center to center dimension.

The calipers are a modular Bosch design (so I have been told) which I have only seen on Lada’s but I am sure they exist for other cars. The caliper piston assemblies can be separated from the sliding pin mount ‘fist’ that encapsulates the pads. I am sure it is a strong enough assembly but it is an odd arrangement that could have its own version of flex.

They sell the piston assemblies as a replaceable element versus the seals which I find odd.

View attachment 40639
View attachment 40640
View attachment 40641
I have a set, but not installed yet. I cross referenced the part numbers and came up with Fiat Uno Turbo front brakes. At least that's what the pads are from. I'd like to do something similar for the rear, looking at 2012-19 Abarth 500 rear clalipers, rotors and integrated handbrake. Anyone ever tried that yet?
 
I have a set, but not installed yet. I cross referenced the part numbers and came up with Fiat Uno Turbo front brakes. At least that's what the pads are from. I'd like to do something similar for the rear, looking at 2012-19 Abarth 500 rear clalipers, rotors and integrated handbrake. Anyone ever tried that yet?
I have tried my 13 inch wheels on the rear of our 500S (240mm rotors same as Abarth) they just clear ok with 10mm wheel spacers. But the piston size is 34mm, bigger would be better, and I believe the caliper carrier bolt mounting holes are 90mm centres, but I didn't try fitting them. X1/9 and Fiat 500 fronts are 100mm, I don't know if adapter brackets would be possible.
 
Abarth 500 rear clalipers, rotors
It has been determined the new 500 calipers and rotors (front and rear) will directly fit the X (a little mix and match from the Abarth edition and standard edition makes them align correctly). However as Greg said, the new 500 rear calipers are a step backward in terms of piston size (remember that the 500 is FWD). So the rear rotors may make a good starting point but I think the calipers are not the best choice for the rear. Fronts are a different story; the 500 front brakes work but may actually be too big (too heavy for what is needed)? Depending on the application and use naturally.
 
I have a set, but not installed yet. I cross referenced the part numbers and came up with Fiat Uno Turbo front brakes. At least that's what the pads are from. I'd like to do something similar for the rear, looking at 2012-19 Abarth 500 rear clalipers, rotors and integrated handbrake. Anyone ever tried that yet?
You want a larger diameter piston on the rear to move the bias a bit more to the rear. 38mm pistoned modern type calipers are used with some Alfas in the EU, though they will likely need to have a secondary bracket created to fit them. A user with a Lancia Scorpion did a couple of great videos showing how to put late 500 calipers on his Lancia, the technique would be the same for an X (I will post the links below). There is also an early modern 500 front caliper which shares the same 48mm piston (versus 54mm which the US model uses) size in a modern floating caliper and the same mounting as the X, this caliper wasn’t sold on the US market 500 so it isn’t as easily found here.

A bit of background, with 48mm front calipers and 34mm rear calipers the X has a nice safe front bias of locking the front wheels first. This is not ideal from the perspective of maximum braking performance but it does keep the car from rear wheel lock in nearly all occasions regardless of weather. Before ABS systems this is how cars were always set up and was done to reduce the likelihood of one rear wheel locking and making the car spin. There were more than a few recalls for this the most famous being the GM X cars of the early eighties to remediate this.

Other cars have achieved this by other means than just manipulating the caliper piston diameter, the Fiat 124 and early VW Rabbits (Golf) used a pressure limiting device based on rear suspension movement others used a pressure limiting valve at the master cylinder.

There is a difference between those cars and the X which makes this normal equation and approach rather different which is where the weight of the car is from a front to rear perspective, the previously mentioned cars had a 60/40 front to rear weight distribution or close to 50/50. The X is notably different in that its distribution is more nearly 40/60 front to rear, this rear weight bias means there is more traction at the rear of an X even under hard braking when there is some significant weight shift to the front which increases traction to the front tires.

So the logic is that keeping the front caliper piston diameter what it is, but increasing the rear piston diameter will increase the braking force at the rear. The Lancia Scorpion used a version of the existing rear caliper design used on the X with a larger rear piston, several forum members have done this to move the bias rearward. The negative of this is it is still the same caliper design and mounting, the positive is it is the same caliper design and mounting.

Anyway, yes there are some things you can do to improve the braking performance but it is a safety system and there can be significant issues and problems by changing things on a non ABS car as you don’t have all those sensors and software to save your butt.

FYI other cars use a rear caliper configuration like the new 500 which could be used, VWs in particular starting with the MK4 Golf through the Mk7 all have a 38mm rear piston.

Links for the late 500 brake caliper install in the thread 'Recent lurker, new Scorpion owner #1553 restomod'

https://xwebforums.com/forum/index....corpion-owner-1553-restomod.28514/post-279909

 
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You want a larger diameter piston on the rear to move the bias a bit more to the rear. 38mm pistoned modern type calipers are used with some Alfas in the EU, they will likely need a secondary bracket made. A user with a Lancia Scorpion did a great couple of great videos for putting late 500 calipers on his Lancia but the technique would be the same for an X (I will post the links below). There is also an early modern 500 front caliper which shares the same 48mm piston size in a modern floating caliper and the same mounting as the X, this caliper wasn’t sold in the US.
Bernice has a posting on installing 38mm rears from a fiat 125.


I did this as well as adding uno turbo brakes and ventilated discs on the front as well. I am very happy with the outcome. The parts were expensive.
 
Bernice has a posting on installing 38mm rears from a fiat 125.


I did this as well as adding uno turbo brakes and ventilated discs on the front as well. I am very happy with the outcome. The parts were expensive.
I know of an X1/9 and a Montecarlo with Uno Turbo front brakes (240mm /48mm) and 251mm /38mm rear brakes. Both very happy with the setup, and yes, Uno Turbo calipers and carriers very hard to find now. That's why I don't have them.
 
regata / ritmo / strada, all the same platform / mechanicals (basically) they are a Fiat 138 chassis / model designation, available in sohc/dohc/OHC 1600,/diesel variants.

Certain models used 257mm solid discs up front, 100s regata (1600 dohc engine) ritmo 105 (a ritmo is basically a regata hatch if you like) ritmo 125 all used this same setup, pad is larger than the regualr "DB29 - which is the Bendix reference - seeing as they ae Bendix made brakes.... shape the usual Fiat uses.

Rear of the race car is 257 solid, willwoods (but much smaller piston) and uses the exact same adaptor bracket, just without the spacer under the disc hat. Brakes on the race car are like ths as it's being built to go lemons racing, and has to last 24 hours of abuse...

Greg, Hot setup for your road registered street car would be (and given the reduced weight of your car I would be hesitant to laod the car with very heavy discs that are unsprung weight)

257 x 12 discs up front, regata 100 calipers / carriers and pads of a decent compount, if you look around I think you'll find you can get right up to the equivalent of DS11 compound material

227 x 11 on the back, using 38mm piston rear calipers from 132/125, use a front caliper carrier (the cast iron bracket) from a regata 85s (manual), as this lets you use a larger pad shape (it's the same as lancia beta rear will work on the back)

much more consistant brakes, slightly more rear bias than stock.... cheap enough for the discs to replace them often if they ever get too hot, and very little increase in sprung weight mass

If you really wanted 257 solids on the back and you MUST have a hand brake, then you could use the 100s front calper CARRIERS that will bolt to the rear hub, and then use rear calipers from alfa 164 / fiat croma / lancia thema like one of these, they are 36mm piston (like a lancia beta rear, whuich will also fit an x19)

(https://www.ebay.it/itm/PINZA-FRENO...572419?hash=item35eadc4b43:g:lX8AAMXQsoNRhfu~)

240mm discs don't give much increase in the way of brake torque, the differnce in the radius centreline of the pads when mounted is so minimal... and if you're not complaining about fading and cooking the fronts, then going to vented discs is simply adding mass for no good reason. The 257mm discs howver ... well thats enough of a %age difference in the radius of the pad centreline , plus with the bigger pad....

wilwoods will have a bigger pad, but also more piston area, which equates to pedal travel issues with the stock master cylinder setup... I also run a willwood pedal box / and seperate circuit master cylinders which is bias adjustable on the fly.... but I don't have to pass any road legality engineering requirements, your car is road registered and it does.... every component would need to have engineering approval / certification.

Jeff, they fit virtually everything Fiat made 1985 - 1999 when fitted with engines over about 80hp, they kept the "usual" one piece sliding wedge design caliper for many smaller engined models ... but the larger cars got Girling brakes (most made under licence) for 48mm size the caliper is 791365 and 791366 , they also come as 52mm and 54mm and look pretty much the same.

View attachment 36385

the reason that this is technically a far superior brake setup lies in the fact, and it is fact, that if you have the caliper fixed (in high performance situations) then usually you would set the disc up to be "floating" or self centering. The reason is "knock off" of the pads due to float / movement of the hub on it's bearings. Toodling around at pedestrian road speeds is hardly a test for brakes, and in that use, a fixed disc / fixed caliper could work perfectly adequately...but when pushed hard, the system will find it's limit

If the disc is fixed (i.e. bolted firm to the hub) then the calper is floating, i.e. able to self centre on the disc.

Look at almost every modern braking system and that's how it is.

Now the sliding wedge that Fiat used does a good job for it's cost, but it is right down at the economy end of the scale of what's available as production parts off the shelf, Fiat saved that for the low perfomance end of their range... the system would have been adequate, and in ways was ground breaking when introduced on the 1100 range back in 1966 on the 1100R, slightly upgraded and used on the Fiat 125 and Fiat 124 sedans in 1967/68... but again the biggest problem is actualy just simple deflection that makes the pedal feel soft / inadequate/ travel. To prove my point take a wheel off the car, have someone else press the brake pedal as hard as they can and watch how much the caliper "bends" in it's holder.

The Girling system with the sliding pins, simply has far less delection. The mount / pins / caliper body are all much later design, probably with a ton of CFA testing on computer, it works better and is simple to service, and has kind of become the industry standard as most "mid sized" cars are like this.

SteveC
Hi Steve, Are you sure about the rear Thema calipers fitting the front Regata carriers? (so that 257mm solids can be installed on the rear)
I have the front Regata 100s carrier, and the rear Thema caliper, but the mounting points on the caliper are not far enough apart to match the carrier. Is an adapter required perhaps?
 
Hi Steve, Are you sure about the rear Thema calipers fitting the front Regata carriers? (so that 257mm solids can be installed on the rear)
I have the front Regata 100s carrier, and the rear Thema caliper, but the mounting points on the caliper are not far enough apart to match the carrier. Is an adapter required perhaps?
there's more than one model of Thema / Croma /164 rear caliper.... some of the lucas/girling type calipers use a 90mm bolt spacing, some use 100mm

SteveC
 
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