Which Wildwood Master Cylinder Model Number for Fiero (Page 1/3)
Signupacct SEP 24, 12:39 AM
I am considering a Wilwood Master Cylinder instead of an OEM

there is no other master cylinder make that is new and made in the usa guaranteed. The AC Delco may arrive with the usa stamp or may not and the listings at summit and amazon say mexico. Shipping date is October and Summit said they may push that date further out or back order. Centric is China. A Premium also China. Raybestos is made in mexico and has the the best shipping date of just a few days. Same with front calipers.

Wilwood's are new and made in the USA.


Just got off the tech phone support line and they say they do not have a list of master cylinders for different makes and models

and therefore don't have a specific model intended for fiero and that there units are universal

They offer the following check list of questions to help determine the best unit:

Piston size and number of pistons in calipers

Master Cylinder bore size OEM

Brake Booster with Dual Diaphram

8 inch diameter diaphram

and Minimum 18 inches of vacuum at idle

And finally:

the pedal ratio (calculated using a pdf from Wilwood)

https://shop.wilwood.com/bl...and-how-to-find-them

Has anyone determined the best Wilwood unit for fiero's

They suggested the 260-8555 fwiw


Joe k

[This message has been edited by Signupacct (edited 09-24-2024).]

cartercarbaficionado SEP 24, 02:40 AM

quote
Originally posted by Signupacct:

I am considering a Wildwood Master Cylinder instead of an OEM

there is no other master cylinder make that is new and made in the usa guaranteed. The AC Delco may arrive with the usa stamp or may not and the listings at summit and amazon say mexico. Shipping date is October and Summit said they may push that date further out or back order. Centric is China. A Premium also China. Raybestos is made in mexico and has the the best shipping date of just a few days. Same with front calipers.

Wildwood's are new and made in the USA.


Just got off the tech phone support line and they say they do not have a list of master cylinders for different makes and models

and therefore don't have a specific model intended for fiero and that there units are universal

They offer the following check list of questions to help determine the best unit:

Piston size and number of pistons in calipers

Master Cylinder bore size OEM

Brake Booster with Dual Diaphram

8 inch diameter diaphram

and Minimum 18 inches of vacuum at idle

And finally:

the pedal ratio (calculated using a pdf from Wildwood)

https://shop.wilwood.com/bl...and-how-to-find-them

Has anyone determined the best Wildwood unit for fiero's

They suggested the 260-8555 fwiw


Joe k



their suggestions are usually pretty good. do tell them the bolt holes size needs to fit an s10 blazer since a few gm cars do use a different bolt hole pattern. just so happens the fiero and most of the late 80s-early 90s gms share until they got abs
Dennis LaGrua SEP 24, 03:40 AM
I will measure it later today but from memory the bore size of the Fiero master cylinder is either 1 1/8" or 1 1/4".

------------------
" 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
" ON THE LOOSE WITHOUT THE JUICE "

cartercarbaficionado SEP 24, 04:40 AM

quote
Originally posted by Dennis LaGrua:

I will measure it later today but from memory the bore size of the Fiero master cylinder is either 1 1/8" or 1 1/4".



it should just be 1 inch. that's what I'm measuring off of a few junked ones and one that was slated to go Into a car soon
fieroguru SEP 24, 07:18 AM
You should share the year of the Fiero, as 84-87 are different than the 88s.
All the Fiero brake masters have quick take up features, which I doubt Wilwood has. This will likely mean more dead pedal travel.

84-87 is 25.4mm or 1":


88 is 23.8mm or 15/16"


If you go larger than stock, the pedal will be harder to press, have less travel, less clamp force at the calipers, and less overall braking force for a given pedal input force.
If you go smaller than stock, then pedal will be easier to press, have more travel, higher clamp force at the calipers, and more overall braking force for a given pedal input force.

For 99.9% of people, it would be best to stick with the stock diameter.
Signupacct SEP 24, 11:15 AM


Sorry about not mentioning the year


It is a 1987 Pontiac Fiero GT with a V6

I hope that helps


I am interested in as close to oem on bore size as is possible unless the community thinks that a slightly smaller diameter might enhance brake pressure at the calipers etc.


Otherwise yes I would like OEM as close as possible

the calipers and pads are OEM no modification or conversions here.

So far the only deviations in this brake job are the SS brake lines and the wildwood proportion valve replacing the OEM proportion valve and went with the

https://www.wilwood.com/mas...rod?itemno=260-11179

only mildly irritated that wildwood won't say which unit is best fit to replace OEM

any help here is appreciated

Joe k
Signupacct SEP 24, 01:00 PM


Using the pdf document from Wilwood I measure the different points on figure 1 in the document.

Pivot point at the top of pedal to the mid point of the brake pedal foot pad:

P to A is 10 1/4 inch

the point at the top of the pedal to the point where the rod to the booster is attached:

P to B is 2 1/2 inch

the pivot point at the top to the top of the brake pedal foot pad:

P to F is 9 1/2 inch


If anyone else has measured these points please double check my work

I hope I understood their document enough to make all the necessary measurements


Joe k
Dennis LaGrua SEP 24, 04:30 PM
Here is the measurement from a Fiero MC rebuilding kit.



------------------
" 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
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 09-24-2024).]

Signupacct SEP 26, 02:24 AM
Dennis


thank you for posting. Is that a MC rebuild kit by GM or genuine gm parts and it was the size for your OEM master cylinder ?

The diameter is not only key to making a selection of a unit from wilwood but also making sure that the correct diameter is obtained when buying a oem replacement.

Centric's are made in China so why would I want to trust their diameter in the centric graphic that was shared in a post, well intended as it may have been.

Does anyone have documentation from factory technical materials indicating what the diameter is ?

I have checked all of mine and I have not found anything in the manuals and other documentation that I have

Does anyone have WHAT THEY KNOW IS a oem master cylinder that they know was put on at the factory?

My Duralast reman (which I'm returning and trying to go with a new oem unit) measures 1.4350 inches and that is 36.45 mm. Very close to your measurement. Mine is a Duralast part # NM1988.

Duralast being autozone isn't any more reliable a source for accuracy then Centric.

In other posts it is noted that you DO NOT WANT TO GO WITH A LARGER DIAMETER PISTON SIZE as it will result in less breaking power.

And other posts say, be sure you don't inadvertently get the larger diameter bore

I wish I still had the unit that was on my car before I started this brake job from h _ _ _ ! but I turned it in for the core already.

I have a New OEM Raybestos MC39572 on the way that they say is made in Mexico and looked up the specs and it doesnt say the piston diamter

Anyone ?


Joe k

[This message has been edited by Signupacct (edited 09-26-2024).]

Signupacct SEP 26, 02:41 AM

Here is an example of a post seeking the same information and similar dilemma


quote
Originally posted by 2002z28ssconv:

As much as I hate to start a new thread, I have been searching for hours now... I figured it would have been covered before but I sure can't find it.

Car - 88 Fiero 2.5 Auto - 100% factory stock.
Problem - Leaking rear seal on brake master cylinder.

I purchased a reman from AZ (P/N - M2357)
A knowledgeable Fiero friend told me to watch for them selling me one with the wrong bore size.
So I am verifying... maybe...

From the little I was able to find here on PFF in threads about the differences between the Fiero and S-10 masters, the Fiero master has a 0.944" bore diameter. That equates to 24mm.

The spec sheet AZ printed out for me says that their master has a 1.414" bore. So right off the bat, I think I have the wrong master.

However, I went to Advance as well as O'Reilly's and any master they brought up said 24mm/36mm.

So I'm on a hunt for what the correct bore size should be.

I suspect that the chamber for the front brakes is 24mm and the rear is 36mm. Dose anyone have the no longer available shop manual? Perhaps it would say in there. I lost my downloaded version with my last hard drive failure.

Either way I figure I'll be taking the old one apart and comparing it to the new one. I just want to try to make sure I get the right part before I tear the car apart again.





His thread ended without anyone sharing an answer

Joe k