I worked at a GM dealership, 16 years ago. It was not uncommon to have the same part listed for two different cars under two different part #'s. The cadillac part would cost twice what the other would. It would be the same part but back then they would use two different #'s.Using the same part # for the two different vehicles that is different, from 16 years ago.
honda and acura do this - an example would be their shifter lever assembly - 40$ for the civic and 75 for the rsx - for all intensive purposes they are identical
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10:27 AM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
should be picking up my project car next weekend - I going to order the brake parts so they will be here in time and and work on altering the rear bracket to shift the caddy caliper for ebrake clearance
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07:48 AM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
Bill Strong and I were conjecturing that the same Caddy calipers used in this upgrade might be readily adaptible to the A-body knuckle used on 5x115 bolt circle conversions... Dunno if you were thinking of that, so FYI...
oh yeah the front calipers have a 2.5" bore and the rear have a 2.125" bore.. (along with the 1.125" blazer master cyl we can calc pressure ratios)
just to keep this out of the trash and since i'm ordering my parts i did some quick math and with ni brake bias the front and rear bore difference =
58% braking front and 42% braking rear this is the pressure distribution at the brake pads due to piston sizing. with the fieros weight distribution being more to the rear this sounds like a pretty good distribution of braking to me.
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11:09 AM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
I think this was alluded to earlier but I recall that if you are going to use new calipers and want a master cylinder to match you would need to consider cars with the similar seperate front/rear circuit rather than the cross bias of most modern cars, like using the earlier corvette MC. I wonder if a custom built MC is in order (KA-ching!!) and of course the combination valve limits the pressure to the rear brakesd anyway. I don't know why, but I seem to recall the figure of it limiting the pressure to 450 lbs on 84-87's before diverting the rest of the pressure to the front circuit. Russel makes DOT-approved Stainless lines in a variety of lengths. see, you're not so lonely after all... and this, for a discount from rockauto!
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[This message has been edited by USFiero (edited 02-24-2005).]
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12:00 PM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
Originally posted by Kohburn: 8- wheel studs (610-323)
? not 10?
thanks for the list - was pretty sure what I wanted, but wasnt sure of the years. I'm planning this also - lemme know how it works out. didnt think about longer line for the rear. my existing one is tight as-is
thanks for the list - was pretty sure what I wanted, but wasnt sure of the years. I'm planning this also - lemme know how it works out. didnt think about longer line for the rear. my existing one is tight as-is
doh - good catch - I ordered 10 just typed wrong
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12:29 PM
thismanyfieros Member
Posts: 3468 From: Red Deer, alberta,canada Registered: Dec 2002
ok all the confusion aside with what to use and whats the best, break it all down for a poor schlub who is planningon this brake upgrade...i have an 86se 4 spd so i need to have a functioning park brake...which is the more better suited rear caliper choice??? as for rotors and pads too...and from what i have read the blazer s10 master cylinder is used too..so please can someone just post a final list of parts used....the more i read the more ****ed up i get..lol thanks tim...
I think this was alluded to earlier but I recall that if you are going to use new calipers and want a master cylinder to match you would need to consider cars with the similar seperate front/rear circuit rather than the cross bias of most modern cars, like using the earlier corvette MC. I wonder if a custom built MC is in order (KA-ching!!) and of course the combination valve limits the pressure to the rear brakesd anyway. I don't know why, but I seem to recall the figure of it limiting the pressure to 450 lbs on 84-87's before diverting the rest of the pressure to the front circuit. Russel makes DOT-approved Stainless lines in a variety of lengths. see, you're not so lonely after all... and this, for a discount from rockauto!
I seem to remembar an analysis of the proportioning valve showd that it was only to slow the flow to the rear brakes to aboid a rear lockup during a panic stop and that under maintained pressure the rears receaved the same fluid pressure as the fronts after a delay
as for the master cylinder as long as if mounts up properly the only thing to it is the bore - thats what determins the pressure ratio from master to slave. the blazer master cyl is a tried and true effective replacement
My rotors are supposed to arrive today but we'll see if this snowstorm holds em up getting anxious to modify the rear adaptor design to make the stock cable setup work better.. I may do some in aluminum just to testfit. (and since i have aluminum scrap by my mill)
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08:43 AM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
The prop valve isn't about flow, it's about pressure. When there's upwards of 1,000 psi of line pressure, even the small hole in the prop valve will pass enough fluid to apply the rear brakes without slowing it down. The needle on the spring acts as a plunger to limit the pressure the rear brakes see to a certain fraction of what the front brakes see.
Don't think of it as the fluid pushing on the needle. Think of it as the needle pushing on the fluid.
Effectively, the prop valve adds some expansion room to the rear brake system. That's how it reduces rear line pressure.
When the driver stands on the brakes, the front master cylinder bore pushes fluid to the calipers and develops a certain pressure. Say for the sake of argument that once that pressure is developed, the master cylinder piston no longer moves. So in the rear brake circuit, a certain pressure would be developed, except that the pressure is now limited by how hard the needle in the prop valve is pushing on the fluid, rather than how hard the master cylinder piston is pushing on the fluid. The harder the driver pushes, the higher the rear pressure goes because of the fact that displacement is proportional to force when compressing a spring. It is not that the prop valve limits pressure to the rear circuit... it causes pressure in the rear circuit to rise at a slower rate relative to pressure in the front circuit as the driver applies the brakes. Since it's virtually impossible to maintain EXACTLY stock brake bias in the basic system, it becomes necessary to recalibrate the prop valve when changing brakes.
The prop valve isn't about flow, it's about pressure. When there's upwards of 1,000 psi of line pressure, even the small hole in the prop valve will pass enough fluid to apply the rear brakes without slowing it down. The needle on the spring acts as a plunger to limit the pressure the rear brakes see to a certain fraction of what the front brakes see.
Don't think of it as the fluid pushing on the needle. Think of it as the needle pushing on the fluid.
Effectively, the prop valve adds some expansion room to the rear brake system. That's how it reduces rear line pressure.
When the driver stands on the brakes, the front master cylinder bore pushes fluid to the calipers and develops a certain pressure. Say for the sake of argument that once that pressure is developed, the master cylinder piston no longer moves. So in the rear brake circuit, a certain pressure would be developed, except that the pressure is now limited by how hard the needle in the prop valve is pushing on the fluid, rather than how hard the master cylinder piston is pushing on the fluid. The harder the driver pushes, the higher the rear pressure goes because of the fact that displacement is proportional to force when compressing a spring. It is not that the prop valve limits pressure to the rear circuit... it causes pressure in the rear circuit to rise at a slower rate relative to pressure in the front circuit as the driver applies the brakes. Since it's virtually impossible to maintain EXACTLY stock brake bias in the basic system, it becomes necessary to recalibrate the prop valve when changing brakes.
would be interesting to have someone test the front and rear line pressure simultaniously as you increase pedal pressure.. all I know for sure is the stock bias is horrible. when i did the GA brake upgrade to the rear only of one fiero the brakes were suddenly perfectly balanced - the nose didn't dive as much - the increase in piston size of the rear required less pressure compared to the front to do its job - and was perfect for my taste..
Going to the cadillac setup it has a smaller piston in the rear than front (fiero is same size front and rear right?) so it's going to need bias adjusted for sure.. I'm curious to see what the 85 cadillac seville used for brake bias. or if it was just based on piston size.
this is the test peice of rotating the rear caliper down 10* to make the stock e-brake cable line up and not interfere with the CV boot..
Some things I noticed on the zetner write up .. I calls out the need for an 12Mx1.50 tap (I assume to tap your mounting holes in the new adaptors) the caliper bolts that came with my Cadillac calipers were 12Mx1.25 He calls out 1/2" holes for mounting to the stock location but these need to be 7/16 for a closer fit as well as 7/16" lockwashers not 1/2" - however the bolts that thread into the stock fiero knuckles do seem to be 7/16" thread -
nowhere in his write up could I find mention of any grinding to the stock knuckle - however atleast on the 86 there is a tab that sits just past the stock rotor edge that has to be removed for the lebaron rotors
[This message has been edited by Kohburn (edited 03-07-2005).]
question on the blazer mc. it was designed for rear drum use, so there is a quick take up valve for the front or rear circuit (cant remember which). i dont remember why now, but when i looked at how the valving was set up, i had ruled out using a drum equiped mc for my stuff. there are so many choices now for 4 disc, and in aluminum . . .
but i do like the tried and true part.
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08:14 AM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
question on the blazer mc. it was designed for rear drum use, so there is a quick take up valve for the front or rear circuit (cant remember which). i dont remember why now, but when i looked at how the valving was set up, i had ruled out using a drum equiped mc for my stuff. there are so many choices now for 4 disc, and in aluminum . . .
Originally posted by Kohburn: this is the test peice of rotating the rear caliper down 10* to make the stock e-brake cable line up and not interfere with the CV boot..
Very nice, any chance you are going to make those available to others? I could even do some product testing for you
i've tested the fit now and it solved the e-brake issue beautifully.. you can see that the cable has plenty of clearance.. the calipers are also now right side up instead of ztners upsidedown routing - so you can use the stock brake hoses. or stock length braided lines.
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08:11 AM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
yep - that would be the stock e-brake cable as it sits plugged into the cadillac caliper (it looks like it goes into nothingness because the caliper is gloss black)
[This message has been edited by Kohburn (edited 03-07-2005).]
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08:40 AM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
Will, I don't know if you understood fully what I posted before or not but I was able to mount my rear brakes in the same manner as Kohburn has with brackets made from the Zettner prints. This made it such that you could use the stock hoses and E-Brake cables. The only two problems I found doing so was that the E-Brake cable was extremely close to the CV Boot and the Bleeder screw was now on the bottom which would obviously make it hard to bleed the brakes. I got around the bleeding problem by unmounting the calipers and holding them with the bleeder screw facing up while bleeding and remounted them when done.
With the E-Brake cable that close to the CV Boot I almost changed my mind about mounting them like that but I figured to take a chance and if it rubbed to much I figured that I would design a new bracket to create some more clearance between the cable and boot. Well it did in fact rub but only enough notice and not enough to damage the boot. I have been daily driving the car for 1 1/2 years and always thought many times about redesigning the brackets but never found the time.
Considering all of that I just can't imagine why Zettner didn't change the design of the rear brackets like Kohburn has and ditch the hockey stick brackets. It would have been a much cleaner design with fewer custom parts.
something else I've noticed that I couldn't find anywhere in zetners write up but have now assumed to be true - maybe you can shed some light on what you did.. the stock fiero caliper bolts are an odd size thread - somewhere around a 7/16x16 or an 11Mx1.50 -- So I assume the tap he called out was to be used not only in threading the caliper adaptors but also the stock knuckles for the mounting bolts..
My cadillac caliper bolts are 12Mx1.25 not 12Mx1.50(less common size) So I bought a tap to match and most likely will buy some 12mm fine thread bolts to mount the calipers.. can you shed some light on that?
[This message has been edited by Kohburn (edited 03-08-2005).]
To tell you the truth I can't remember the exact details of what I ended up doing but you are on the right track. Below is what Walt Zettner wrote on the subject.
quote
Pontiac Fiero Connection magazine, 4Q97 issue The tapped caliper bolt holes in the Fiero knuckles and front spindles must be drilled out to 27/64 inches and tapped with a 12M1.50 metric tap. If you are not compulsive, you are free to drill and tap a 7/16 inch English thread. Adjust the tap drill size accordingly.
For some reason I don't think that I bought any Metric hardware so I probably went the 7/16" route. Since you already have the 12M1.25 tap I would probably go that route also.
Thank you for the CAD files I will let you know if I am able to get them made and how they work out.
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09:55 PM
Mar 9th, 2005
spearce Member
Posts: 257 From: Delaware, Ontario,Canada Registered: Nov 2002
The brakets I have were made from the Zettner drawings. It says that the calliper bolts are 7/16 NF. They must be cause they fit perfectly. I'm at work right now but I will check this evening and post back here.
I do have an emergency brake as I am using the Cadillac rear callipers. I'm thinking of changing to your rear brakets. They look real good. I haven't made my mind up yet. The car is a fair weather car and won't be back on the road untill April so I ve got some time yet.
WARNING, anyone who is going to use the Wilwood GM Metric callipers beware that you can NOT use the standard brake hoses with banjo bolts. Thje Wilwood callipers use 1/8 NPT fittings. I am having my hoses made by a friend who works at a plant that makes OEM brake lines. He has the equipment fabricate then and test them to OEM industry standards
