Bolt-on Quad Piston Caliper for 88 Fieros - Caliper Q (Page 1/1)
fieroguru AUG 05, 08:40 PM
For close to a decade, people have been asking me for a quad caliper upgrade with the same bolt pattern as the 88 calipers. My answer before today was "it simply did not exist"... and I was wrong.

Let me introduce you all to Caliper Q (Quad Piston):
  • It bolts directly to the 88 knuckle (no adapter plate needed)
  • It will accept an 11 1/2" x 0.85" rotor (maybe a little larger) with a similar offset to the stock 88 rotor
  • It has quad 38mm pistons, so the caliper will provide 25% clamp force gain in addition to the benefit of the larger rotor diameter (~12% increase in brake caliper leverage)
  • It is a mass market caliper in production for over 10 years


There are 4 downsides...
  • It uses quad 38mm pistons, so it will have a 25% gain. This will require some testing to see if it is OK with the stock master or not
  • It isn't the lightest caliper (cast iron construction) weighing in at 8 lbs, 9 oz.(stock 88 caliper is 5 lbs, 9 oz)
  • Connecting the brake line will be a little more work than normal
  • The outboard caliper body hits the spokes on my 16" wheels


So the caliper will need to be spaced further inboard using some washers, which will require a slightly deeper rotor, and even then it still might not clear the 15" wheels, let alone the narrow 88 front wheels. Unfortunately I don't have any stock 15" 88 wheels to test with, but I know a guy...

Some pics:








Interesting times...
fierobear AUG 06, 10:32 PM

quote
It uses quad 38mm pistons, so it will have a 25% gain. This will require some testing to see if it is OK with the stock master or not



Use the S-10 Master conversion?
skywurz AUG 06, 11:02 PM

quote
Originally posted by fierobear:


Use the S-10 Master conversion?



I think you just mixed up booster and master
theogre AUG 07, 12:08 AM
Very Likely won't work w/ OE 88 MC for same reason as "GA upgrade" for older Fiero.
In short, MC is "squeezed dry" on MC's secondary(front) piston because bigger volume needed by the calipers.

Do the math yourself...

Find Volume used by OE Piston to move just 1mm. (Volume of a cylinder.)
That Times 2 to 4.
(Remember both "shells" may move 1mm too, why they have sliders, thus the 4.)

Find Volume used by 1 38mm piston to move just 1mm.
That Times 8.
(Most or all "Shells" won't move w/ 2 side piston setup.)

Pad Clearance can be 1mm or even less If everything is Perfect.
If hubs have play, "warped" Rotors, etc then pads are often push back more and gets a lot more pad clearance and require more fluid volume.
I think like older Fiero, 88 Front and Back hubs have a little play because bearings aren't "preloaded" to protect the bearings.

Note that 88 also uses Quick Take-up MC but smaller size main bore then older Fiero.
QT function will hind front brake pad take-up but only a little. Not like rear brakes famously causing low pedal when have E-brake problems.
Secondary piston have very limited volume because front spring etc stops it moving.

And is ignoring piston main seal design. Many seals (and other parts) are made to make more pad clearance to help MPG and brake wear issues. GM started that before Fiero. Other have done this too.

So 1mm or more piston travel to apply isn't hard to imagine.

------------------
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(Jurassic Park)

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Dennis LaGrua AUG 07, 07:44 AM
While new replacement wheel cylinders will be badly needed on all Fieros now and in the next few years I believe that we will need to be cautious about replacement swaps. As Theogre has indicated the system must be matched . Master to Wheel cylinder capacity must be considered. If its too large pedal pressure can go up and if its too small the MC runs out of capacity. The master cylinder presented by Fieroguru may be good if we match it to the master cylinder that was designed to go with it.
There are literally thousands of cylinder combinations available but how can we determine what fits? Has anyone contacted Wilwood to see if they have anything that will fit?

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
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theogre AUG 07, 09:31 AM
Wilwood et al likely has setups could work but Dual MC etc are no direct replacement.
Duel MC are exactly that... 2 MC in parallel w/ a floating link bar attach to "pedal" in the center that let them work. You can then have 2 different MC to match volume needed or whatever.

Many GM and others including the GA have Cross Feed Brake Systems.
That means the RF and LF to one MC output. LF and RR to the other. (Often those MC's really had 4 outlets and 2 Proportion Valves.)
Plus GA Rear axle has Drum brakes and often they use less fluid volume.
Many FWD cars and others has this setup partly for lower flow volume for each MC piston to move and part so better brakes when 1 circuit leaks.
Example: 70's Chevy Monza had this but is RWD car w/ Front Disk and Rear Drum. (And was a bit odd to bleed them for this reason.)

Now w/ most cars having ABS... Many designers etc can way over design so MC has more flow and power via higher line pressure and let ABS to sort out the "Proportion valve" function. You can have more power and flow but you need to design the whole system... Where MC/Booster connect to the pedal, Booster Size matters too and so on. Also Many vehicles have Hydraulic or Electric boosters that could change booster power for a given speed like many PS does.

And even when a vehicle has 4 wheel Disk Brakes... Front and Rear are Very different for Size of Pistons, Size of pads, Size of Disks and Working area on the disk. Plus Many Still use Solid rotors on the rear too. This was true w/ many "Performance" cars like many Porsche models before ABS. You nearly Never see Front and Rear use same pads like Fiero does. 84-87 are only different PN mainly because front inner clip is attach to the pad plus one or both Front pads are a bit Thicker for longer life.

For this "new" setup, very few look how OE car for this caliper is "wired." Just like most ignore GA Original brake plumbing etc.
Or worse use same setup Front and Rear... While could get away doing that for a Trailer Queen Race Car but Not Legal for Street Use in most places.
fieroguru AUG 07, 10:28 AM

quote
Originally posted by fierobear:
Use the S-10 Master conversion?


Saying yes or no to a master cylinder swap is a little premature as it depends on what I do in the rear to pair with the front. Using a larger master cylinder when just 1 end of the car has larger piston diameters, causes a clamp force loss on the other end for the sample pedal force. That is a bad idea and should never be done. Any change to the size of any hydraulic component within the brake system needs to be done based on impact to the rest.


quote
Originally posted by skywurz:
I think you just mixed up booster and master


He had the right part. Master cylinder swap (when done properly) is to balance out the hydraulic forces and movements in the system. The booster upgrade just adds more input force to the brake master.


quote
Originally posted by theogre:
Very Likely won't work w/ OE 88 MC for same reason as "GA upgrade" for older Fiero.

Do the math yourself...




quote
Originally posted by Dennis LaGrua:
As Theogre has indicated the system must be matched .



I covered that here...

quote
Originally posted by fieroguru:
There are 4 downsides...
[list]
  • It uses quad 38mm pistons, so it will have a 25% gain. This will require some testing to see if it is OK with the stock master or not



    • I have spend the better part of a decade focused on brake system research with testing involving actual measurements as well as lots of calculations, so nothing either of of you has typed is new to me. Your concerns are simply already part of my R&D process. I have a large stack of calipers, rotors, and other parts sitting on the shelf from past efforts because they didn't work or they worked but the results simply didn't meet my standards.

    I do what I do with Fiero parts for the challenge and enjoyment derived from finding elegant solutions that work and look great. The list of things I simply won't do or sell on principle is quite long, and also includes being dissuaded by just anyone.

    The people I listen the most to have demonstrated through their posts several of these:
    * Expansive technical knowledge = they have taught me something, or I suspect they could
    * Highly skilled craftsman - create highly functional and/or aesthetically pleasing stuff
    * Motivated to find new out of the box solutions and ambitious with their goals
    * Commitment to their tasks - nothing it too hard, complicated, difficult etc.
    * Accepting that failure is part of the process and belief that there is more to learn from failure vs. success
    * Being able to impress me with something they have done or figured out
    Mark A. Klein AUG 07, 10:30 AM

    quote
    Originally posted by fieroguru:

    For close to a decade, people have been asking me for a quad caliper upgrade with the same bolt pattern as the 88 calipers. My answer before today was "it simply did not exist"... and I was wrong.

    Let me introduce you all to Caliper Q (Quad Piston):
    • It bolts directly to the 88 knuckle (no adapter plate needed)
    • It will accept an 11 1/2" x 0.85" rotor (maybe a little larger) with a similar offset to the stock 88 rotor
    • It has quad 38mm pistons, so the caliper will provide 25% clamp force gain in addition to the benefit of the larger rotor diameter (~12% increase in brake caliper leverage)
    • It is a mass market caliper in production for over 10 years


    There are 4 downsides...
    • It uses quad 38mm pistons, so it will have a 25% gain. This will require some testing to see if it is OK with the stock master or not
    • It isn't the lightest caliper (cast iron construction) weighing in at 8 lbs, 9 oz.(stock 88 caliper is 5 lbs, 9 oz)
    • Connecting the brake line will be a little more work than normal
    • The outboard caliper body hits the spokes on my 16" wheels


    So the caliper will need to be spaced further inboard using some washers, which will require a slightly deeper rotor, and even then it still might not clear the 15" wheels, let alone the narrow 88 front wheels. Unfortunately I don't have any stock 15" 88 wheels to test with, but I know a guy...

    Some pics:








    Interesting times...


    If we can get a Master cyl figured out - see my write up on LeBaron rotors This might eliminate the need for the adapters!
    qwikgta AUG 07, 07:54 PM
    So then if you have a "kit" to use 12" or 13" rotors w/ stock 88 calipers these should also work right? Those kits have adapters to move the calipers out away from the stock location and in theory, one could swap the stock 88 caliper w/ these new 4 pot calipers? Awesome.

    [This message has been edited by qwikgta (edited 08-07-2021).]

    fieroguru AUG 08, 09:56 AM

    quote
    Originally posted by qwikgta:

    So then if you have a "kit" to use 12" or 13" rotors w/ stock 88 calipers these should also work right? Those kits have adapters to move the calipers out away from the stock location and in theory, one could swap the stock 88 caliper w/ these new 4 pot calipers? Awesome.




    In theory: yes - this caliper could bolt to any bracket a stock 88 caliper attaches to.
    In practices: no - you can't use this caliper on any of the 12 and 13" brake kits. There are two reasons for this.
    1. This caliper moves the caliper piston about .4" further outboard than the stock 88. So if you try to use this on any existing brake kit, the 12" rotors would then need to be 12.4" in diameter to keep the pad on the rotor surface.

    2. This caliper was designed to fit around a 10.3" rotor and has a long caliper body with the bridge support off to the side. This means the structure in the caliper body is on a curvature to support a 10.3" rotor. When bolted to the stock 88 knuckle, I found one of my failure rotors that is 11 1/4" that barely fits, I still need to buy a set of pads to make sure that the 11 1/4" rotor edge is still past the edge of the pad. What this means is that 11 1/4 is likely the practical rotor limit for this caliper. This means use on a 12" of larger rotor is a no-go.


    To better show point #2, when I did the first test measurement off the stock 88 rotor, it was on the inside of the caliper. There was about 5/8" of clearance from the edge of a 10.43" rotor, so around 11.68" of room.


    Here is a 11 1/4" rotor installed and clearance to the outer edges, clearly coming up short from being able to fit a rotor 0.30" larger.