Custom Brake Master Cylinder For Bigger Calipers

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Dan Sarandrea (Phila)

Waitin' On Parts...
Over the past winter I got to 95% on a project that took waaaaaaaaaay to long, a full suspension refurb and rear caliper 38mm upgrade. This week and weekend upcoming nice weather should see the car come out of hibernation and get back on the road at least for a trip to the alignment shop.

Anyway, regarding the 38mm caliper upgrade, I'm not thrilled with the added pedal travel. Stock brakes (to me at least) have a remarkable feel--short travel then Gibraltar-like solidity, none of today's cars' "mushy-mushier-mushiest" feel! In the back of my mind I remembered that Midwest-Bayless used to sell a custom-built brake master cylinder that compensates for the added pedal travel that results from upgrading the rears from stock 34mm to the larger bore 38mm pistons. So I found this via Google:
www.midwest-bayless.com

Brake Master Cylinder - Improved Performance (Fiat Bertone X1/9 All, Lancia Scorpion/Montecarlo) - NEW

Brake Master Cylinder - Improved Performance (Fiat Bertone X1/9 All, Lancia Scorpion/Montecarlo) - NEW
www.midwest-bayless.com www.midwest-bayless.com

I contacted Matt and he says they will be restocking this item shortly, so y'all can get in line behind me for when they come in :p

Now excuse me, I have to call my rescue squad, chiropractor and orthopedic surgeon to make an appt for the day after I install the new master cylinder.
 
I will be very interested to hear how that MC affects the pedal travel. Design wise, if it retains the stock cylinder bore, then the only way it can increase fluid volume is to lengthen the piston stroke. Which, without any other modifications, will also increase pedal stroke. But I do not know exactly how they are achieving the increased output from it so I look forward to hearing your results. :)
 
I am interested as well. I also have 38mm rear calipers/rubber brake lines and thought the brake feel was OK. However, I recently installed a set of the stainless braided lines and WOW what a difference. Nice firm pedal and not a lot of travel.
 
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Dan Sarandrea (Phila) said:
Over the past winter I got to 95% on a project that took waaaaaaaaaay to long, a full suspension refurb and rear caliper 38mm upgrade. This week and weekend upcoming nice weather should see the car come out of hibernation and get back on the road at least for a trip to the alignment shop.

Anyway, regarding the 38mm caliper upgrade, I'm not thrilled with the added pedal travel. Stock brakes (to me at least) have a remarkable feel--short travel then Gibraltar-like solidity, none of today's cars' "mushy-mushier-mushiest" feel! In the back of my mind I remembered that Midwest-Bayless used to sell a custom-built brake master cylinder that compensates for the added pedal travel that results from upgrading the rears from stock 34mm to the larger bore 38mm pistons. So I found this via Google:
www.midwest-bayless.com

Brake Master Cylinder - Improved Performance (Fiat Bertone X1/9 All, Lancia Scorpion/Montecarlo) - NEW

Brake Master Cylinder - Improved Performance (Fiat Bertone X1/9 All, Lancia Scorpion/Montecarlo) - NEW
www.midwest-bayless.com www.midwest-bayless.com

I contacted Matt and he says they will be restocking this item shortly, so y'all can get in line behind me for when they come in :p

Now excuse me, I have to call my rescue squad, chiropractor and orthopedic surgeon to make an appt for the day after I install the new master cylinder.
Click to expand...
Are you sure the self-adjusters for the hand brake are done self-adjusting after you replaced the rear calipers? This does affect pedal travel, and others have reported difficulties with this after replacing rear calipers.
 
There is a more fluid required to run 38mm rear calipers,, but not that much more fluid.. and it is a trade off. For the same force mandates more pedal travel with less force -or- more force with less pedal travel. This is the way of Hydraulics mandated by Nature's way.

If the stock/oem rubber brake hoses are used, replace ALL of the with DOT/TUV approved (very real safety reasons for this) teflon/metal braided hoses. This will significantly reduce mushy brake pedal, but will not address the pedal travel.

~Do this first if firmer/more solid brake pedal is the goal.

Most significant difference with 38mm rear calipers is alteration of the brake balance when the brakes are pushed harder for stopping.

As for modern cars, brakes tend to be way over assisted with zilch pedal feel. This is due to power assisted ABS negating the need for pedal feel/feed back. The exxe has no power assisted brakes. This demands a lot more pedal force to work the brakes, trade off being possible excellent pedal feel and control and feedback.

Pick your trade off,
Bernice
 
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I have heard all the comments from people re brake travel and long pedal with uprated brakes. I can say I have not noticed it on mine, maybe I am just not noticing as each change has a long time between drives.
My UT front brakes, well the car was off the road for the UT engine, so there was a gap.
I have the 38mm rears, but randomly I got them one at a time. The first was the only spare I could find at the time and then years later after parking the car up for a couple of years (blame Tenerife for that) I matched the other side.

I don't know (didn't do the calculation) if these bring the balance back getting bigger front and rear brakes, but all I know is the brakes work very well thank you.
 
Alex(Tenerife) said:
I have heard all the comments from people re brake travel and long pedal with uprated brakes. I can say I have not noticed it on mine, maybe I am just not noticing as each change has a long time between drives.

I don't know (didn't do the calculation) if these bring the balance back getting bigger front and rear brakes, but all I know is the brakes work very well thank you.
Click to expand...
The goal and rational for 38mm rear brake calipers is to alter the brake balance, move more braking force to the rear away from the front. As delivered the front brakes on the exxe have a tendency to lock up and roast the brake pads if the brakes are pushed hard. This is the norm for all production road cars from that era, rear brake lock up was an absolute no-no due to the potential for rear end out spin, specially in wet conditions. This set up will not and does not produce optimum braking performance, but it tends to be safe under most real world road conditions.

Moving the brake bias towards the rear makes the rear brakes do more work and the front brakes less work, The front brakes will produce less heat and less braking force with the rear brakes doing more producing more uniform braking resulting in better stopping. Trade off being there will be more of a tendency for rear brake lock up, but not that much more.

The exxe with a stock size master cylinder, 48mm Uno Turbo brakes front & 38mm rear calipers stops remarkably good with very little fade using stock/road brake pads. Trade off being slightly increased brake pedal travel..which is not that much given the improvement in brake performance.

Bernice
 
Hi Dan,
I have one of the MWB master cylinders on my X with 38mm rear calipers and Uno T front calipers. The pedal is rock solid. I also have braided hoses. I don't remember the pedal travel being much, if any shorter than with the std master cylinder.
However, when I rebuilt the pedal assembly I lengthened the push rod slightly so there was no slack with the brake pedal adjusted to the same height as the accelerator pedal.
Is you pedal initially soft (pushing against the return spring only ) then stiffens as the rod contacts the master cylinder piston?

I also found this a while ago. 22mm bore master cylinder.
No connection to the seller . This looks slightly dodgy to me. The mounting lobes look welded on.

www.ebay.co.uk

LANCIA - 037/beta montecarlo master cylinder 22mm Alluminium - pompa freno | eBay

Cylinder 22mm Alluminium - pompa freno. LANCIA - 037/beta montecarlo master. CODICE UNIVOCO E PARTITA IVA. NORMALE RICEVUTA. PER LA FATTURA ABBIAMO BISOGNO DEL TUO.
www.ebay.co.uk

Andy
 
ng_randolph said:
Are you sure the self-adjusters for the hand brake are done self-adjusting after you replaced the rear calipers? This does affect pedal travel, and others have reported difficulties with this after replacing rear calipers.
Click to expand...
VERY good question! Wow, never thought of that. I guess working the handbrake thru some cycles is worth a try.
 
lidox19 said:
Hi Dan,
I have one of the MWB master cylinders on my X with 38mm rear calipers and Uno T front calipers. The pedal is rock solid. I also have braided hoses. I don't remember the pedal travel being much, if any shorter than with the std master cylinder.
However, when I rebuilt the pedal assembly I lengthened the push rod slightly so there was no slack with the brake pedal adjusted to the same height as the accelerator pedal.
Is you pedal initially soft (pushing against the return spring only ) then stiffens as the rod contacts the master cylinder piston?

I also found this a while ago. 22mm bore master cylinder.
No connection to the seller . This looks slightly dodgy to me. The mounting lobes look welded on.

www.ebay.co.uk

LANCIA - 037/beta montecarlo master cylinder 22mm Alluminium - pompa freno | eBay

Cylinder 22mm Alluminium - pompa freno. LANCIA - 037/beta montecarlo master. CODICE UNIVOCO E PARTITA IVA. NORMALE RICEVUTA. PER LA FATTURA ABBIAMO BISOGNO DEL TUO.
www.ebay.co.uk

Andy
Click to expand...
Andy, I certainly agree that MC you linked from eBay definitely looks dodgy. The original mounting tabs (ears) have been sawed off and new mounts (tubes) welded onto the body. Among other possible issues, the heat from welding it could easily distort the inner bore. Personally I would not trust it at any price....and ABSOLUTELY not at the ridiculous price it is listed for. ;)
 
Dan Sarandrea (Phila) said:
VERY good question! Wow, never thought of that. I guess working the handbrake thru some cycles is worth a try.
Click to expand...
Previous discussion on 38mm calipers.. Tony had brake pedal travel issues due to the Meh "quality" of aftermarket 38mm rear brake calipers.
Turns out, the "self adjusters" did not adjust.. causing excessive brake pedal travel.

38mm Piston Rear brake Caliper install

So does it take the same rear pads as an X or are they the pads used on a Scorpion/125? Or? Takes regular X1/9 pads. I had a brain fart & thought I was using calipers that accomodated the wider front pads.... EDIT - I didn't check to see if there is enough meat on the ears to machine for wider...
xwebforums.com


Bernice
 
Rupunzell said:
Previous discussion on 38mm calipers.. Tony had brake pedal travel issues due to the Meh "quality" of aftermarket 38mm rear brake calipers.
Turns out, the "self adjusters" did not adjust.. causing excessive brake pedal travel.

38mm Piston Rear brake Caliper install

So does it take the same rear pads as an X or are they the pads used on a Scorpion/125? Or? Takes regular X1/9 pads. I had a brain fart & thought I was using calipers that accomodated the wider front pads.... EDIT - I didn't check to see if there is enough meat on the ears to machine for wider...
xwebforums.com


Bernice
Click to expand...
I "purchased" a set of those third-rate calipers from "Mr FIAT", but sent them back because despite the listing saying they were the part number that would correspond to 38mm, they were in fact standard 34mm.

The calipers I have now I got from FiatPlus, with refreshed internals including OEM adjusting innards. IIRC one is a FIAT OEM, and the other is an older aftermarket from a recognized manufacturer, for example TRW. Also running stainless braided lines.
 
Dan Sarandrea (Phila) said:
I "purchased" a set of those third-rate calipers from "Mr FIAT", but sent them back because despite the listing saying they were the part number that would correspond to 38mm, they were in fact standard 34mm.

The calipers I have now I got from FiatPlus, with refreshed internals including OEM adjusting innards. IIRC one is a FIAT OEM, and the other is an older aftermarket from a recognized manufacturer, for example TRW. Also running stainless braided lines.
Click to expand...
If the excessive free travel of the brake pedal is not due to wonky brake caliper "self adjusters", expanding brake hoses, flaky master cylinder, the excessive pedal travel could be due to worn pivot/bearing area between the brake pedal to master cylinder push rod. This is a common problem that is not often considered. This alteration to Monte# 209 was done to improve the design and reduce the wear problem with that joint. The redesigned push rod is length adjustable to allow placement of the brake/clutch pedal's resting position.

Monte# 209, Clutch pedal mod & push rod mod.

Noted from a member on MonteCarlo Consortium regarding the brake and pedal problems with the design in the ScorpiaCarlo, decided to modify the clutch pedal first while waiting for a second brake pedal to arrive. Make an adjustable length clutch master push rod using a M8 grade 12.9 socket head...
xwebforums.com

The plastic bearing both clutch/brake pedals run on can also contribute to excessive brake pedal travel/feel.

Brake caliper problems can be tested by disconnecting each brake calipers, then capping off the brake hose with a dead end bleeder fitting in place of the suspect brake caliper, then testing the brake pedal for travel/feel. Repeat on all four brake calipers. If no problem is found, look for the problem else where.

Bernice
 
Thanks to all who responded with advice and counsel. Per Bjorn's suggestion, I went back and gave the handbrake lever in the car a bit of a workout and that seemed to trim out a bit of the slack. I also re-bled the entire system, and managed to coax a couple of small bubbles out of the rear circuit as well, an added bonus!

A little trick that a longtime mechanic suggested to me for when you are dealing with brake systems that are fussy about bleeding. To free up sticky little bubbles of trapped air, use a hammer to tap the calipers and master cylinder. Of course you're not beating them like you're drop-forging a battleship anchor, just tap-tap-tap-tap to vibrate the master or calipers to encourage the bubbles to break loose.

BTW, I highly recommend the use of "speed bleeder" style bleed nipples. I've used them on my X and on other cars and can't say enough good things about them. Same part number (SB8125L) fits all four calipers and the clutch slave. Available in plated steel or stainless steel. Support a small business and buy them from the original manufacturer:

To keep you from devolving into one of THOSE GUYS who just opens the bleeder screw and lets the fluid get all over, they also have an inexpensive handy hose and bag kit on their accessories page.
 
Steve Thomas said:
With stock callipers front and larger rear, which end locks up first?
Click to expand...
With Uno Turbo vented front disc, calipers and Ferodo "street" pads, 38mm rear calipers on stock sold disc, the fronts still lock up first, but not as soon as oem as delivered braking system. Difference being, the exxe tends to "squat" under hard braking with more heat capacity due to the vented front disc and improved stopping distance due to the shifted brake bias.

Front brake lock up begins to be a problem when front calipers (48mm) are used on the rear. On for a track car, not recommended for a road/street driven car.

Bernice
 
Rupunzell said:
the exxe tends to "squat" under hard braking with more heat capacity due to the vented front disc and improved stopping distance due to the shifted brake bias.
Click to expand...

Bernice, I'm confused. Squat usually means the rear end gets lower. Did you mean "dive", meaning the front end gets lower? Or did you really mean "squat"? If so, I don't understand how that is happening.
 
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