Uno Turbo Front Caliper Install

Nice work, Tony. Sorry to hear of the pedal travel issue. I developed a similar symptom ('mushy' pedal, excessive travel) after installing the larger rear brakes (already had the larger Vicks brakes up front, new master, brake hoses). No matter how I bleed it, I don't get any more air out, and the pedal travel is definitely not the firm short travel pedal of old. The brakes will lock up evenly (no pull) when used aggressively, but for normal driving when you want to gently press the pedal & expect results, they are not there. I've gotten used to it when I drive the X for several days in a row, however when I switch cars back & forth I realize again that I'm not happy. I can't see how to resolve it short of switching back to the regular rear calipers. Interested to see what you find.
 
lookforjoe said:
Nice work, Tony. Sorry to hear of the pedal travel issue. I developed a similar symptom ('mushy' pedal, excessive travel) after installing the larger rear brakes (already had the larger Vicks brakes up front, new master, brake hoses). No matter how I bleed it, I don't get any more air out, and the pedal travel is definitely not the firm short travel pedal of old. The brakes will lock up evenly (no pull) when used aggressively, but for normal driving when you want to gently press the pedal & expect results, they are not there. I've gotten used to it when I drive the X for several days in a row, however when I switch cars back & forth I realize again that I'm not happy. I can't see how to resolve it short of switching back to the regular rear calipers. Interested to see what you find.
Click to expand...


Maybe Bernice will chime in, she is into this more techie than I am. I have gone this far and would hate to have to switch the rears back to stock. I am hoping that as the pads bed that it will be better than it is.

I have ordered the Open Flash Tablet for my Abarth engine and will tune it to 180 HP. What I need is brakes that fit the HP. Bob Martin suggested a brake booster, not sure if there is something that could be used on the X. ( Help Bernice!!!)

Just not what I want at this time.

I want to push the pedal and see the car haul down to a quick stop. The new tires are very nice and feel different, just the brakes are bugging me.

TonyK.

Grimsby Ontario Canada.
 
TonyK said:
I am hoping that as the pads bed that it will be better than it is.
Click to expand...

I have not installed my new system, but in looking at the green pad bedding recommendations, they have a different procedure than I have used before. From their web site:

"Bedding in when the red EBC surface coating (marked on the pads as Brake In) is applied.
Best procedure is to drive gently avoiding harsh braking unless in an emergency for first 100 miles. In the second 100 miles (up to 200) you can use gently increasing brake pressures when using the brakes.

Only after 200 miles urban driving (not 200 miles on a freeway where brakes are almost unused) should you attempt to apply heavy load and heat to the brakes. To do this final bedding on a QUIET ROAD in safe traffic apply the brakes and slow from 60 to 10 MPH five times in a row. Then drive slowly for a few minutes if safe to do so to allow the brakes to cool. Try to avoid coming to a rest whilst the brakes are heated.

A smell may be noticed from the warm brakes, this is normal. Repeat this procedure a second time after the brakes have TOTALLY cooled down. EBC pads get better with miles. Even after this bed in procedure it can take up to 1500 miles before the pads are at their best. In the meantime the pads will be good and safe but true potential not realised. EBC makes performance pads that last, they do not bed in within 5 minutes driving. Noises will be more likely during the first 1000-1500 miles use whilst this chemical bedding takes place."

Good luck with it and keep us posted. I am doing a set up like yours this summer.

Paul
 
PaulD said:
I have not installed my new system, but in looking at the green pad bedding recommendations, they have a different procedure than I have used before. From their web site:

"Bedding in when the red EBC surface coating (marked on the pads as Brake In) is applied.
Best procedure is to drive gently avoiding harsh braking unless in an emergency for first 100 miles. In the second 100 miles (up to 200) you can use gently increasing brake pressures when using the brakes.

Only after 200 miles urban driving (not 200 miles on a freeway where brakes are almost unused) should you attempt to apply heavy load and heat to the brakes. To do this final bedding on a QUIET ROAD in safe traffic apply the brakes and slow from 60 to 10 MPH five times in a row. Then drive slowly for a few minutes if safe to do so to allow the brakes to cool. Try to avoid coming to a rest whilst the brakes are heated.

A smell may be noticed from the warm brakes, this is normal. Repeat this procedure a second time after the brakes have TOTALLY cooled down. EBC pads get better with miles. Even after this bed in procedure it can take up to 1500 miles before the pads are at their best. In the meantime the pads will be good and safe but true potential not realised. EBC makes performance pads that last, they do not bed in within 5 minutes driving. Noises will be more likely during the first 1000-1500 miles use whilst this chemical bedding takes place."

Good luck with it and keep us posted. I am doing a set up like yours this summer.

Paul
Click to expand...
I am using the EBC Green Stuff brake pads and although all of this seems nice. The first thing I want to know is whether or not will this car stop. Feeling the pedal have much more travel than what I am used to is a bit un-nerving. Pussy footing around with longer pedal travel than normal does not inspire confidence that the car's brakes are up to the task, so I took the car our again and drove it another 5KM trying to bed the pads. I also brought the car up to about 70 miles an hour and applied full pressure several times along with the hand brake. I need to know what the car is capable of when it comes to stopping. On the third attempt I was able to lock up the front brakes and the tires smoked. A trip down a very steep hill allowed the 2 front tires to lock and the right rear tire also to lock up. This caused the car to lurch to the right a bit in a shallow turn. I am not confident that the car will stop when pushed and that there is still pedal before it hits the floor. I would say about 1.5 to 2" from the floor. I put the car back on the lift and bled the brakes one more time hoping that the steep grade down and the climb up would cause an air bubble to move toward the calipers. In bleeding a bubble was observed from both the right rear and left front calipers on the 2nd bleed of each caliper. I repeated 4 more times on each corner. Since I use a wooden stick to hold the pedal down when bleeding afterward it required both hands to place the stick as the pedal has come up more from the floor. I am gaining here but I still would like a higher pedal, one that I am used to having before the upgrade.

TonyK.

Grimsby Ontario Canada.
 
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Assuming all the air is out, isn't this basic hydraulics, IOW, if you increase the diameter of the pistons at the working end (calipers) but do not increase the diameter of the application end (master), the master has to move more fluid (which can only be done with more pedal travel) to create the same pressure at the working end?

Probably what needs to happen is the original master has to be bored out and wider diameter master cyl pistons and seals will have to be fitted. if so, curious if there is anything from the FIAT parts bin that would work.
 
A larger master cylinder bore will REDUCE line pressure, and require more pedal effort to produce the same line pressure... simple hydraulics...
100lbs of pedal force onto a 1" area piston will produce 100lb/sq inch of line pressure... transfer this to a 2" area caliper piston and you have 200lbs force pushing on the back of the pads.

If you increased the master cylinder bore to 2" square and kept the same 100lbs of pedal force, the line pressure would be just 50lb/sq inch, the same 2" square caliper piston will then only produce 50lb/sq inch of force, so 100lbs pushing on the back of the brake pad.

Sure the 2" area master cylinder will only move half the distance to transfer the same VOLUME of fluid, but the pressure at the caliper will be halved if the master cylinder area is doubled.

The change from a 34mm piston to a 38mm piston will not significantly increase the amount of fluid VOLUME required to move the piston the 0.1mm or so before pad to rotor contact occurs...

pi x r square x distance
3.14285 x (17 x 17) x 0.1 (fluid displacement to move a 34mm piston 0.1mm)
3.14285 x 289 x 0.1
90.82 cubic mm (which is .9082cc)

3.14285 x (19 x 19) x 0.1 (fluid displacement to move a 38mm piston 0.1mm)
3.14285 x 361 x 0.1
113.45 cubic mm (which is 1.1345cc)

extra displacement required by 38mm piston over a 34mm piston
113.45 - 90.82
22.63 (which is 0.2263cc)

3.14285 x (9.525 x 9.525) x 1mm (volume of fluid displaced by the master cylinder in 1mm of pedal stroke)
3.14285 x 90.76525 x 1
285.13 cubic mm (which is 2.8513cc per mm of stroke)

extra stroke required on the rear brake circuit by increasing piston size by 4mm
1 /(285.13 / 22.639)
0.08mm (approx 1/12 of a mm)

the simple fact is the 38mm piston rear calipers were used on other Fiat models and used the same 19.05mm master cylinder bore... so the increase in pedal stroke for that particular change was not considered significant by Fiat engineers.

SteveC
 
Dan Sarandrea (Phila) said:
Assuming all the air is out, isn't this basic hydraulics, IOW, if you increase the diameter of the pistons at the working end (calipers) but do not increase the diameter of the application end (master), the master has to move more fluid (which can only be done with more pedal travel) to create the same pressure at the working end?

Probably what needs to happen is the original master has to be bored out and wider diameter master cyl pistons and seals will have to be fitted. if so, curious if there is anything from the FIAT parts bin that would work.
Click to expand...

Dan you bring up a good point. I have an old master cylinder, a lathe and a milling machine. I am unsure of size of the piston in the old master or if it is the same for both the front and the rear. It would be possible for me to bore out the rear section which is close to the front of the master cylinder then turn a piston to fit. I would have to find a similar size piston seal kit to fit the modification. I wonder what the 76 Lancia Scorpion was using for a Master cylinder that the new 38 MM calipers came off of. How different is it from the stock X1/9 Master. Possibly Bernice will give an opinion on this.

Just looked at Midwest Bayless web site and the Lancia Scorpion Master Cylinder is a different part number but is a direct replacement. This may be the option to correct this issue.



TonyK.

Grimsby Ontario Canada.
 
Last edited:
fiatfactory said:
A larger master cylinder bore will REDUCE line pressure, and require more pedal effort to produce the same line pressure... simple hydraulics...
100lbs of pedal force onto a 1" area piston will produce 100lb/sq inch of line pressure... transfer this to a 2" area caliper piston and you have 200lbs force pushing on the back of the pads.

If you increased the master cylinder bore to 2" square and kept the same 100lbs of pedal force, the line pressure would be just 50lb/sq inch, the same 2" square caliper piston will then only produce 50lb/sq inch of force, so 100lbs pushing on the back of the brake pad.

Sure the 2" area master cylinder will only move half the distance to transfer the same VOLUME of fluid, but the pressure at the caliper will be halved if the master cylinder area is doubled.

The change from a 34mm piston to a 38mm piston will not significantly increase the amount of fluid VOLUME required to move the piston the 0.1mm or so before pad to rotor contact occurs...

pi x r square x distance
3.14285 x (17 x 17) x 0.1 (fluid displacement to move a 34mm piston 0.1mm)
3.14285 x 289 x 0.1
90.82 cubic mm (which is .9082cc)

3.14285 x (19 x 19) x 0.1 (fluid displacement to move a 38mm piston 0.1mm)
3.14285 x 361 x 0.1
113.45 cubic mm (which is 1.1345cc)

extra displacement required by 38mm piston over a 34mm piston
113.45 - 90.82
22.63 (which is 0.2263cc)

3.14285 x (9.525 x 9.525) x 1mm (volume of fluid displaced by the master cylinder in 1mm of pedal stroke)
3.14285 x 90.76525 x 1
285.13 cubic mm (which is 2.8513cc per mm of stroke)

extra stroke required on the rear brake circuit by increasing piston size by 4mm
1 /(285.13 / 22.639)
0.08mm (approx 1/12 of a mm)

the simple fact is the 38mm piston rear calipers were used on other Fiat models and used the same 19.05mm master cylinder bore... so the increase in pedal stroke for that particular change was not considered significant by Fiat engineers.

SteveC
Click to expand...

Hi Steve,

Don't forget to take into account that Tony's car has Uno Turbo calipers fitted to the front as well as the 38mm bore calipers in the rear, so maybe the combination of the two is what is creating the issue. I would have to assume that the piston bore size on the UnoT brake calipers is bigger than X1/9 stock calipers.
 
Dan Sarandrea (Phila) said:
Hi Steve,

Don't forget to take into account that Tony's car has Uno Turbo calipers fitted to the front as well as the 38mm bore calipers in the rear, so maybe the combination of the two is what is creating the issue. I would have to assume that the piston bore size on the UnoT brake calipers is bigger than X1/9 stock calipers.
Click to expand...

Since my issue with this did not arise until after I added the 38mm rears, I would have to agree that it is the combination of front and rear oversize calipers that creates the symptom. I didn't consider the MC bore an issue, as I put much larger brakes on my Volvo without any issues at all. That does have a brake booster though, so perhaps that offsets the change in mechanical advantage lost in MC pressure?
 
TonyK,

Just a thought, is it possible for the rear brake pistons to be to far from the discs and need ajustment?

DaveR
 
My experiences with modified brakes...

The rally X had Uno Turbo front brakes and the bigger rear calipers.

The current X has 4 piston Wilwood front calipers with 500 disks and front calipers moved to the rear.

In both cases the standard master cylinder worked perfectly. The pedal would travel further than standard to displace a suitable amount of fluid, but not significantly so, and certainly would not hit the floor. I find I get much better brake modulation with these set ups.

Tony, to be fair to the EBC Green brake pads, a 5k drive to bed them in isn't really going to achieve much, but I understand your reticence to drive further if you are uneasy with your brakes performance.

Cheers,

Rob

p.s. the hydraulic handbrake (e-brake) system is working great.
 
rjplenter said:
My experiences with modified brakes...

The rally X had Uno Turbo front brakes and the bigger rear calipers.

The current X has 4 piston Wilwood front calipers with 500 disks and front calipers moved to the rear.

In both cases the standard master cylinder worked perfectly. The pedal would travel further than standard to displace a suitable amount of fluid, but not significantly so, and certainly would not hit the floor. I find I get much better brake modulation with these set ups.

Tony, to be fair to the EBC Green brake pads, a 5k drive to bed them in isn't really going to achieve much, but I understand your reticence to drive further if you are uneasy with your brakes performance.

Cheers,

Rob

p.s. the hydraulic handbrake (e-brake) system is working great.
Click to expand...

Well as usual I am flying by the seat of my pants and I found a Scorpion Master Cylinder in the UK for $85CND delivery included. When I get it here I will take it apart and see what is different from the X Master Cylinder. The Scorpion used the same front calipers as the X does 48 MM but the rears are 38MM instead of 34MM. This master should be a good fit as it was used with the same piston diameters on the Scorpion. It appears to be a direct replacement as well.

Just a note here I changed the master cylinder and bled the front brakes first, I was surprised how low the pedal was with the rears not bled. The rears brought the pedal up a lot.
Today I took the car down the road after more bleeding yesterday and found the pedal a bit firmer than yesterday's drive. The travel is certainly still longer.

TonyK.

Grimsby Ontario Canada
 
I can't remember where I read this, but I think it is advisable to bleed the caliper furthest from the master cylinder first.
 
TonyK said:
Well as usual I am flying by the seat of my pants and I found a Scorpion Master Cylinder in the UK for $85CND delivery included. When I get it here I will take it apart and see what is different from the X Master Cylinder. The Scorpion used the same front calipers as the X does 48 MM but the rears are 38MM instead of 34MM. This master should be a good fit as it was used with the same piston diameters on the Scorpion. It appears to be a direct replacement as well.

Just a note here I changed the master cylinder and bled the front brakes first, I was surprised how low the pedal was with the rears not bled. The rears brought the pedal up a lot.
Today I took the car down the road after more bleeding yesterday and found the pedal a bit firmer than yesterday's drive. The travel is certainly still longer.

TonyK.

Grimsby Ontario Canada
Click to expand...

To the best of my knowledge, the only difference between the X1/9 and Scorpion brake master is the Scorpion has one front outlet and the X1/9 has two. Common practice was to use the X1/9 on the Scorpion by blocking off one of the outlets. I think the 124, X1/9, Scorpion and 850 all use the same internal pistons and seals.
 
Dan Sarandrea (Phila) said:
Hi Steve,

Don't forget to take into account that Tony's car has Uno Turbo calipers fitted to the front as well as the 38mm bore calipers in the rear, so maybe the combination of the two is what is creating the issue. I would have to assume that the piston bore size on the UnoT brake calipers is bigger than X1/9 stock calipers.
Click to expand...

Stock X19 (and all Fiat single piston sliding calipers on 128, 124, 131 etc) are 48mm piston size, UnoT calipers are also 48mm diameter, so the one and only area change to the system is the rear calipers.

Montecarlo master cylinder is identical inside to the X19 master cylinder at 19.05mm or both circuits, they use the same master cylinder overhaul kit ... Fiat 132/125 that the 38mm piston calipers come from originally uses the same 19.05mm diameter master cylinder as the 124 etc which use a 34mm rear piston, again the only circuit difference is the increase in rear piston area... so the master cylinder size is not the problem here.

SteveC
 
Brake master used in the Lancia Sccorpion-MonteCarlo is 3/4" or just over 19mm. The current sleeved brake master came out of a Scorpion it is 3/4" bore. Reason for using this instead of the stock 3/4" brake master was the single front brake outlet. This was easier to deal with when installing an adjustable pressure limiter valve for the front.

Difference in brake pedal height with the Uno Turbo front calipers and 38mm dia rear calipers is not significant, maybe 0.3" to 0,5" at the very most.

The Uno Turbo front calipers with 38mm rear calipers has been on the 74' for a few months now. Braking performance is excellent, brake balance is MUCH better, stopping power is greater, heat capacity is significantly increased.

If the brake pedal is lower than without the 38mm rear calipers, it could be due to the brake master cylinder or air in the system or parking brake not adjusted properly.


Bernice
 
Several have mentioned this already, my vote goes to verifying the rear calipers are working as expected. It seems like you have excessive motion before hitting the pads thus lots of pedal travel.

  • I would check to see if there is any space between the pad and the piston, it should be very small approaching zero.
  • Is the e-brake properly adjusted? Is the ratcheting internal adjuster working on both calipers? Are the rear calipers actually sliding and keeping the pistons in close proximity to the pad?
  • From your description, one of the rear calipers isn't doing its full share as it wouldn't lock up when the other did, was this the one that you eked out a bit of air from?
 
kmead said:
Several have mentioned this already, my vote goes to verifying the rear calipers are working as expected. It seems like you have excessive motion before hitting the pads thus lots of pedal travel.

  • I would check to see if there is any space between the pad and the piston, it should be very small approaching zero.
  • Is the e-brake properly adjusted? Is the ratcheting internal adjuster working on both calipers? Are the rear calipers actually sliding and keeping the pistons in close proximity to the pad?
  • From your description, one of the rear calipers isn't doing its full share as it wouldn't lock up when the other did, was this the one that you eked out a bit of air from?
Click to expand...
I have few busy days in front of my before I can get back to this.
Just remember all of the pads are new and I know it takes a bit of time for them to bed. I have only driven about 15 miles so far. The rear calipers are new along with the pads. Brake cables are also new. I expect the reason for the right rear to lock up is because that corner is lighter as I am the only person in the car sitting on the left hand side. Wheel spin when driving alone normally happens on that side as well. Yesterday I drove the car about a mile to return a vacuum brake bleeder. The brake bleeder really doesn't work that well as it draws air in from around the threads of the bleeder screw and does not give indication of air in the system due to the constant stream of bubbles when bleeding.

I reverted back to the long stick wedged between the brake pedal and seat rail method so that I could see if any bubbles of air were passing through the tygon tubing when the bleed screw was opened.

Thanks for all of the comments.

TonyK.

Grimsby Ontario Canada.
 
fiatfactory said:
A larger master cylinder bore will REDUCE line pressure, and require more pedal effort to produce the same line pressure... simple hydraulics...
100lbs of pedal force onto a 1" area piston will produce 100lb/sq inch of line pressure... transfer this to a 2" area caliper piston and you have 200lbs force pushing on the back of the pads.

If you increased the master cylinder bore to 2" square and kept the same 100lbs of pedal force, the line pressure would be just 50lb/sq inch, the same 2" square caliper piston will then only produce 50lb/sq inch of force, so 100lbs pushing on the back of the brake pad.

Sure the 2" area master cylinder will only move half the distance to transfer the same VOLUME of fluid, but the pressure at the caliper will be halved if the master cylinder area is doubled.

The change from a 34mm piston to a 38mm piston will not significantly increase the amount of fluid VOLUME required to move the piston the 0.1mm or so before pad to rotor contact occurs...

pi x r square x distance
3.14285 x (17 x 17) x 0.1 (fluid displacement to move a 34mm piston 0.1mm)
3.14285 x 289 x 0.1
90.82 cubic mm (which is .9082cc)

3.14285 x (19 x 19) x 0.1 (fluid displacement to move a 38mm piston 0.1mm)
3.14285 x 361 x 0.1
113.45 cubic mm (which is 1.1345cc)

extra displacement required by 38mm piston over a 34mm piston
113.45 - 90.82
22.63 (which is 0.2263cc)

3.14285 x (9.525 x 9.525) x 1mm (volume of fluid displaced by the master cylinder in 1mm of pedal stroke)
3.14285 x 90.76525 x 1
285.13 cubic mm (which is 2.8513cc per mm of stroke)

extra stroke required on the rear brake circuit by increasing piston size by 4mm
1 /(285.13 / 22.639)
0.08mm (approx 1/12 of a mm)

the simple fact is the 38mm piston rear calipers were used on other Fiat models and used the same 19.05mm master cylinder bore... so the increase in pedal stroke for that particular change was not considered significant by Fiat engineers.

SteveC
Click to expand...

Steve thanks for all of the numbers but I hate to tell you that the pedal moves more than 1/12th of a mm more, it is like an inch more. I am thinking of doing 1 of 2 things and that is I why I will throw this out there. Option 1 is to ream the master cylinder to 20MM at the rear brake end of it and make a new master cylinder piston to match. I can order 20MM cylinder seals. Option 2 is to bore the entire master cylinder to 20MM and make new piston to match. The increase in diameter is only .035" or about .018" from the wall size all around the bore. The captivating nut is larger than this and the reamer will not affect the threads at all. This would now push more fluid to the rear piston on Option 1 while leaving the front brake side alone. Yes there will be more pressure required but the pedal will be higher. Option 2 would be pretty much the same bias front and rear but the pedal would be higher with more pedal pressure to accomplish the same amount of work.

Give me your thoughts on this one, pro, con or plainly stupid.

Thanks.

TonyK.

Grimsby Ontario Canada
 
Increasing the master cylinder bore for the only the rear circuit from 19.05 mm to 20 mm would negate half the change accomplished by increasing the rear caliper bore from 34 to 38 mm, so you probably don't want to do that.

Boring the entire master to 20 mm gives only a 10% change in fluid volume for a given master cylinder piston travel. It seems your problem is far from a 10% problem, so I suspect something else is going on here. It is easy to suspect that you still have air in the system. I am also inclined to be suspicious of the parking brake self-adjusters. For the fronts, a single application of the brakes would get the pistons in the calipers pretty much where they need to be, but the rears are more tricky. Here you will be fighting parking brake belleville springs. Until the self-adjusters are done self-adjusting, the pistons in the rear calipers will retract more than normal, and you'd need more pedal travel to bring them out enough to get the pads in contact with the rotor. The self-adjusters work when you operate the brakes (not when operating he parking brake!), so if you are confident all th air is out of the system, I'd try stomping on the brakes repeatedly and see if exercising the self-adjusters will give you a firmer pedal.
 
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