I was given the honor of reviewing/evaluating one of the prototype S10 style boosters for Rodney. As part of this review, I will be doing an in depth dimensional comparison between this booster and a stock fiero one and will eventually install it in an 88 fiero and verify the change in line pressure at the calipers and overall braking improvement.

As I go through this review, please feel free to share your comments/feedback – especially if you have previously installed an S10 booster into your fiero as there are a few minor differences between the two boosters that may or may not be an issue in service.

Also, keep in mind that the booster I received is a prototype version and some of the items I will discuss could be changed for the final version.

Let’s start with some pictures… First thing I noticed when taking the booster out of the box was the powder coated exterior. This is a very nice looking balancer… so I will try not to scratch it. Here is a picture of it alongside a fiero booster:


Booster Overall Diameter and Area:
This upgrade is all about increasing the surface area of the vacuum diaphragm internal to the booster and bigger is better in this regard. I can’t measure the actual size of the diaphragm w/o taking both boosters apart, but I can get the overall diameter of the housings and compare them.

The stock fiero booster is 8.79” in diameter so the internal area should be around 59.0 in^2 (I assumed 16ga wall thickness).


Rodney’s booster is 10.57” in diameter and its internal area would be about 85.6 in^2 (again 16 ga wall thickness assumed) or about 45% larger in internal area than the stock fiero booster.


Booster Depth:
The fiero booster has the master cylinder flange recessed into the booster body and Rodney’s is flat, but the overall distance from the backside of the booster to the mounting face of the brake master cylinder is essentially the same between the two. Notice I used a hole saw to rest the booster on to get this measurement, so the actual length isn’t important, we are more focused on the relative difference between the two. As you can see there depth is probably within 1/32” of each other, which is close enough to call them the same.

Fiero Booster:




Rodney’s




Booster to Brake Pedal Banjo:
Since both boosters will reuse the same booster to firewall mounting bracket, I measured the length of the booster to pedal pushrod from the backside of the boosters. This dimension needs to be close, or the brake pedal position will be changed, or the booster will not be able to fully retract. Both boosters have the center of the banjo at 9 5/16”, so they are essentially the same.

I also measured the ID of the banjo fitting to compare the sizes of the holes. Rodneys banjo hole is about .004” smaller than the fiero one (the pictures show .009, but it is difficult to get the precise reading while holding the caliper in one hand, the camera in the other, and making sure the caliper display is visible). This .004” difference is most likely due to the fiero one being a used part and slightly worn.

The overall thickness of banjo was also checked and Rodney’s is about .040” thicker. Since the overall length stays the same, keeping the thickness the same as the stock fiero setup would have worked, but the thicker pushrod will be overkill… which is good in my book.

Fiero Banjo





Rodney’s Banjo





Booster to Master Pushrod:
Up to this point everything between the balancers has been very close (aside from the larger diameter). When comparing the pushrod side by side, it is obvious that there is a length difference between them (Rodney’s is the shorter new one).


The overall length of these pushrods isn’t the critical dimension, because there could be some changes to the diaphragm that changed this length. The critical dimension is the depth of the pushrod, from the master cylinder mounting face. To get this measurement, I fabbed up a round washer tool so I could measure the plunge depth with the calipers. Again the actual measurement includes the thickness of my spacer tool, but all we are looking for at this point is the difference between them. As you can see, the pushrod on Rodney’s pushrod is .0625” deeper into the booster – or there would be 1/16” additional gap between his pushrod vs. the fiero one. This is an area we would like some feedback from other S10 booster installers – was this extra gap an issue? Rodney could have this pushrod length changed for the final version, just don’t know if there is any need to do so at this point.

Fiero:



Rodney’s:



Vaccum Check Valve:
The nipple on the vacuum check valve that came with the booster is .120” smaller than the fiero one. This is another area for feedback from previous S10 booster installers. Did you use this smaller nipple with a hose clamp, or did you swap out the check valves? I am going to try swapping out the check valves.

Fiero:


Rodney’s:


After this first round of measurements, it was time to get the bracket off the fiero booster. I started with using an angle grinder to flatten the top sides of the rivets as much as possible (2 of them are difficult to flatten all the way due to the bracket/grinder head interference). Then used a chisel to take the rest of the rivet off and free the bracket from the booster:






During the installation of the bracket to the booster I noticed 2 things
1. The studs on Rodney’s booster are not fully threaded and stop about 1/8” from the backside. The fiero bracket is only about 1/16” so I added some washers. Rodney’s said that these studs will be shorter on the final version and he was going to look into the having the studs fully threaded.


2. The rubber dust seal on the backside of Rodney’s booster ends up pinched under the fiero bracket. Probably not any issue, just something I noticed. We are curious is all the other S10 booster installs have had the same issue.



If there are any other comparisons of checks you are curious about, just let me know.

My next step is to document the fiero booster location in the car with some pictures of the current clearance to the frame before removal. I also want to take some brake line pressure readings in the stock configuration.

[This message has been edited by fieroguru (edited 03-25-2012).]

Absolutely outstanding so far, I cannot wait to see how this finishes up, and also look forward to the product hitting Rodney's store. With the larger tires and GA brakes on the car, I wouldnt mind having a little more stopping power added to the brakes. keep it up!

[This message has been edited by spc15tdime (edited 03-23-2012).]

Unfortunatly.....

https://www.fiero.nl/forum/Forum1/HTML/088656.html



Kevin

I found someone (an engineer) that is willing to do the R&D. I may change my mind and offer them.

------------------
Rodney Dickman

Fiero Parts And Acc's Web Page:
All new web page!:www.rodneydickman.com
Rodney Dickman's Fiero accessories
7604 Treeview Drive
Caledonia, WI 53108
Phone/Fax (262) 835-9575

quote Originally posted by fieroguru: During the installation of the bracket to the booster I noticed 2 things 1. The studs on Rodney’s booster are not fully threaded and stop about 1/8” from the backside. The fiero bracket is only about 1/16” so I added some washers. Rodney’s said that these studs will be shorter on the final version and he was going to look into the having the studs fully threaded. 2. The rubber dust seal on the backside of Rodney’s booster ends up pinched under the fiero bracket. Probably not any issue, just something I noticed. We are curious is all the other S10 booster installs have had the same issue.

Excellent write-up

The first issue can be resolved simply by including a set of washers with the kit. I'd prefer to use washers on those nuts, anyway.

The second issue also holds true for the S10 booster. I've modded several of those for use in Fieros, and they do the same thing. As Rodney mentioned, the booster housing has a recess that the rubber boot fits into. As a result, the boot doesn't see much compression force. I wouldn't worry about it.

As for the check valve, I also noticed the size difference, and simply used the Fiero unit. Works fine.

Based on the feedback that the rubber seal normally is pinched in these booster installations and that there is a recessed area for the seal, I went ahead and removed the bracket this evening and inspected the seal to see if it was damaged any, or just gently squeezed. After removal, there was almost no indication that the bracket was compressing it (for about 24 hrs), just some slight scuff marks on the left and right sides of this picture. Based on this, I do not see any issue with the rubber seal being gently squeezed by the fiero bracket, which is supported by the feedback from other DIY installs.

I also have been evaluating the booster that Rodney supplied to me.

I have to say that the write-up in this thread is just great, good info, great pictures and easy to understand explanations.

Great Job Fieroguru!

Without repeating everything presented so far, I will just add that the measurements I performed fall in line with what guru has documented. The quality of the unit appears to be very good, and the black finish is better than alot of the OEM units I have seen.

Again, Kudos to guru for the write-up, and Rodney for presenting the product to the community.

I installed an S-10 booster but haven't been able to test drive it yet. I just replaced the check valve with the Fiero booster valve and all was good there.

quote Originally posted by fieroguru: I wanted to do one more check to confirm that the booster to master pushrod was about 1/16" too short. ... This 1/16" at the bango will likely be in the 3/16" to 1/4" range at the end of the brake pedal.

I don't have an S10 booster handy. But my Fiero has one of the older Rodney Dickman prototype boosters. And sure enough, there's some play in the pedal. I didn't measure the exact amount, but it appears to be around 1/4". I had assumed that was just the take-up in the master cylinder. But I may have been mistaken.

Didn't get much time to play with the booster today (picked up another 88, and changed plug wires on the one this booster will be installed in). I was able to take a couple of pictures of the available clearances:



The S10 booster body is 1.78" larger in diameter, so the body should be .89 closer to the frame rail and the plastic support for the sunroof air deflector. So I fabbed up a little stack of washers that approximate thickness, wrapped them in electrical tape and then test fitted them:


Plenty of room for the body, but the flange on the booster body will interfere:


The booster will also interfere with the plastic piece, but it is quite flexible and will move up the needed amount:



Also, painted the fiero bracket for its final installation:


Waiting on a couple of videos to upload to show the pedal slop in the stock setup...

[This message has been edited by fieroguru (edited 03-24-2012).]

You noted earlier that there was a length difference between the push rod that came out with the old unit and the push rod that was with Rodney's unit.
Would changing to the longer pushrod then be too much extra length to overcome the pedal 'slop'?
Would it have to be shortened to be perfect? If so, by how much?
(Edited for fat fingered spelling)

[This message has been edited by n7vrz (edited 03-24-2012).]

quote Originally posted by n7vrz: You noted earlier that there was a length difference between the push rod that came out with the old unit and the push rod that was with Rodney's unit. Would changing to the longer pushrod then be too much extra length to overcome the pedal 'slop'? Would it have to be shortened to be perfect? If so, by how much? (Edited for fat fingered spelling)

Yes the fiero pushrod is .233" longer, so if you have access to a lathe you could shorten it by .170" to get the right length. This should be a moot point for the final boosters as Rodney will have them built with the right length pushrod.

I will however, be modifying the fiero one to the right size just to satisfy my own curiosity and posting the results here.

quote Originally posted by fieroguru: Here are a couple of pics showing the brake pedal slop in the stock 88 system. I pumped the pedal a couple of time, then shot the video showing how much I could move the pedal with minimal effort

You should consider putting some shims in between the factory OEM booster and the master to see if this amount changes.

------------------
Rodney Dickman

Fiero Parts And Acc's Web Page:
All new web page!:www.rodneydickman.com
Rodney Dickman's Fiero accessories
7604 Treeview Drive
Caledonia, WI 53108
Phone/Fax (262) 835-9575

quote Originally posted by Rodney: You should consider putting some shims in between the factory OEM booster and the master to see if this amount changes.

I figured that the pedal play was coming from internal to the booster - where the slop was between the banjo and booster/master pushrod assembly. To check this, I made this little tool.


It allowed me to put a hard stop at the booster/master pushrod end, then any play left would be internal to the booster.


Here is the stock play internal to the 88 Fiero booster:


Here is the stock play internal to Rodney prototype booster, which appears to be more:


Then I tried to see if I could turn the bolt on the tool and push the pushrod deeper into the prototype booster, and I could.


I have never taken a booster apart to know how the banjo and pushrod end up being connected. I also do not know the purpose of the stepped portion of the pushrod, but assume it keeps the pushrod from going in "too far". For grins, I am going to cut back the stepped lip on the fiero pushrod and see if it allows the pushrod to go in further (without distorting the plastic hub (video 3 in this post) and if it will tighten up the internal clearances. Eliminating this slop, probably isn't a good idea, but I would like to see if reducing it is possible. I am going to use the tool and get an actual pedal measurement of this slop for the stock fiero booster and the prototype as delivered. Then I can experiment with pushrod mods and see what they do.

Did I see made in china on that booster case???????

quote Originally posted by fieroguru: I wanted to do one more check to confirm that the booster to master pushrod was about 1/16" too short. I came up with .294" or .066" deeper, which is very close to the .0625" relative difference in pushrod position between the two boosters.

I did this same check for the fiero master to fiero booster and came up with .011" of clearance vs. the .066 on the fiero master/rodney booster. This would imply that the pushrod is only .055" to short.

quote Originally posted by amflyer: Did I see made in china on that booster case???????

Yes. I went thru a lot to get these made. Time, money and effort. This was no small project to get a brake booster custom made to my specs.

------------------
Rodney Dickman

Fiero Parts And Acc's Web Page:
All new web page!:www.rodneydickman.com
Rodney Dickman's Fiero accessories
7604 Treeview Drive
Caledonia, WI 53108
Phone/Fax (262) 835-9575

Pressure time! - all these readings are for the stock 88 booster setup.

I needed something to push the pedal in a somewhat repeatable manner to check caliper pressure. I found some pipe and a piece of angle that I could use.


Here is the caliper fluid pressure gauge:


My first pressure check was with the car off. I was able to stand on the pedal and install 2 pieces of aluminum between the pipe and the angle. The resulting pressure at the caliper was about 550 psi.



The nest step was to turn the car on to see what the vacuum assist added from a pressure standpoint. The gauge then read 800 psi, or a gain of about 250 psi without changing the pedal position.


With the engine running and the booster assisting, I was able to push the pedal down further. I added a 5/16" shim and got about 1310 psi.



Then I really stood on the thing and slid another 5/16" shim in place, this bumped the pressure to almost 1500 psi (probably 1480 to 1490).



With a 48mm caliper piston, there is 2.80 square inches of surface area that these pressures act on.

I am going to see if I can get a used air cylinder from work that I can install and use a fixed PSI input pressure (maybe 2 or 3) and record the resultant brake line pressure.

[This message has been edited by fieroguru (edited 03-25-2012).]

quote Originally posted by fieroguru: Pressure time!

Is this test with the OEM Fiero factory brake booster?

------------------
Rodney Dickman

Fiero Parts And Acc's Web Page:
All new web page!:www.rodneydickman.com
Rodney Dickman's Fiero accessories
7604 Treeview Drive
Caledonia, WI 53108
Phone/Fax (262) 835-9575

quote Originally posted by Rodney: Is this test with the OEM Fiero factory brake booster?

All pressures so far are from the stock 88 booster. I won't get to checking the pressure on your booster until I document the removal and installation, and I have a couple more things to check on the stock setup before I remove it from the car.

I'm loving the caliper adapter shaped shims.

I can't imagine a better person to evaluate this boster than you Guru. I was quite distraught to learn that this project was stalling out thus I can't thank you enough for spending your valuable time such that the rest of us can benefit.

Devil's advocate:
This doesn't actually increase clamping force. Just fools you into thinking the brakes are stronger because they're boosted more. If anything you'll lose modulation feeling, as it'll be harder to tell exactly how much pressure is applied.
Many race cars don't even have boosted brakes.
/Devil's advocate

quote Originally posted by Austrian Import: Devil's advocate: This doesn't actually increase clamping force. Just fools you into thinking the brakes are stronger because they're boosted more. If anything you'll lose modulation feeling, as it'll be harder to tell exactly how much pressure is applied. Many race cars don't even have boosted brakes. /Devil's advocate

Actually, it will increase clamping force for a given input force due the higher amount of assist the larger booster will provide. As for modulation, to get the pressure this high in the stock system, I had to apply excessive input force - at this level of input force, any modulation is almost impossible - the brakes are either on or off. The key benefit of this booster upgrade is you get a higher line pressure for a lower input force and as you get used to it you can better modulate the braking force.

The actual limitation of the booster upgrade is that is does not change the ability for the brakes to deal with heat. It increases caliper pressure, which will increase the heat the system generates, but you are still left with stock rotors to dissipate the heat. Under heavy use, the stock system will experience brake fade due to it excessive heat, and with just the booster upgrade it will do the same (but possibly sooner). To reduce the opportunity for brake fade, you must focus on changes to the brake pads and rotors (diameter, mass and cooling).

In my opinion the overall benefit of any brake upgrade really depends on the wheels/tires that are on the fiero that it is installed on. Many people say the stock system is OK because it will lock the wheels (which doesn't take much on stock wheels/tires), but start adding tires with a larger/stickier contact patch and the stock system really starts to show its limitations.

quote Originally posted by Austrian Import: This doesn't actually increase clamping force. Just fools you into thinking the brakes are stronger because they're boosted more. If anything you'll lose modulation feeling, as it'll be harder to tell exactly how much pressure is applied. Many race cars don't even have boosted brakes.

Many here have already done this upgrade. I have yet to see anyone say anything negative about this upgrade. I would be curious to know if you have an advanced degree in this field or extensive experience. Or is this this just your personal opinion? Please let us know. Please offer us some substance to this opinion you offer. You are certainly welcome to start a new topic to discuss this opinion if you like but please do not come here and offer unsupported opinions.

------------------
Rodney Dickman

Fiero Parts And Acc's Web Page:
All new web page!:www.rodneydickman.com
Rodney Dickman's Fiero accessories
7604 Treeview Drive
Caledonia, WI 53108
Phone/Fax (262) 835-9575

The booster applies additional clamping force by using vacuum to apply force in the same direction that your foot is applying pressure. (Or, more correctly, the ambient air applies the pressure because the vacuum removes the air from one side of the diaphragm.) If you have a bigger booster, then you have a larger surface on which the air can push, so you get even more clamping force.
The only thing that worries me about this is, if you lose vacuum, you're back to just your foot applying pressure. Which is why I personally like a brake upgrade that makes the system more efficient with or without boosting. But that's just me.

I would like to know if anyone that has added an S-10 booster on a other-wise stock 84-87 brake system had problems snapping the aluminum caliper in half or problems with overheating the solid rotors. Fieroguru mentioned this in other brake upgrade thread of his.

[This message has been edited by mattwa (edited 03-26-2012).]

Another awesome and well-documented Fieroguru thread. I'm looking forward to the test results with the new booster (And I don't even have a Fiero anymore).

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'04 Mazda RX8 Build Thread
'88 GT- 3800 Turbo 11.367@121.03mph (Sold and gone now)
GM Tuners

From the above reading, adding larger vented rotors to the setup should be able to help address additional heat due to the increased surface area of the rotor, allowing it to cool quicker. Correct?

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-Chris
'85 V6 SE 4sp (SOLD)
'88 GT Auto (fun car)
'99 Kawasaki Vulcan 500, owned since new
'03 Sentra SE-R Spec V (Daily driver)
'09 G37x w/ Premium & Nav (wife's car)

quote Originally posted by mattwa: I would like to know if anyone that has added an S-10 booster on a other-wise stock 84-87 brake system had problems snapping the aluminum caliper in half or problems with overheating the solid rotors. Fieroguru mentioned this in other brake upgrade thread of his.

quote Originally posted by fieroguru: The aluminum caliper needed to be clearanced in the bridge area to clear the larger rotors, and this removes material from the most highly stressed area of the aluminum caliper. Aluminum is prone to fatiguige failure, so this mod would make the caliper weaker. Then add in the current trend to install the S10 brake booster and increase caliper pressure beyond what GM designed the calipers for originally. Given all these concerns, I am not willing to develop or market a kit under these conditions.

As I clearly stated above, my concern stemmed from the needed caliper modification to the aluminum caliper to clear the 12 3/4" rotors (trying to run larger diameter/solid rotors and retain the stock calipers). Added to this was the chance for people to do both my brake upgrade (which required a caliper mod) and then subject it to higher pressure with the S10 booster... and that is just a bad idea. The only way I had to ensure that bad combination didn't happen was to not sell the kit - which is exactly the path I took.

I have not heard of anyone having any parts breakage or caliper failures related to any of the S10 booster upgrades, but this upgrade will increase clamping pressure at the calipers. If you do anything to weaken the calipers, your chance of breaking them is now higher with a larger booster upgrade.

I know what you said, I thought it was still a concern even with stock unmodified aluminum calipers, regardless of what rotor was used. Guess I was mistaken.

[This message has been edited by mattwa (edited 03-26-2012).]