General musings on 4-piston brake upgrades

I found a couple cool videos on youtube.









You guys might like these.

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Michael LeCompte

Tim,

The PDF file was a Big help. The overlap of the calipers really puts things into perspective.
From what I've learned in manufacturing and product design classes, standardization is the key to any successful product.

I'll have to do the brake force calculations, but I'm thinking that 11x.81's all around would do it, then just size the piston diameters front and rear for bias.

Keep everything standardized and use straight vane rotors, that way, a front left is the same as a right rear, etc... Calipers all the same so you can buy 4 sets of identical pads.

You just make the brackets do the work. Is the distance between the hub face and the mounting tabs the same front to rear?

The question no one at wilwood can answer for me is...How much more an awd car can utilize rear brakes compare to a fwd or rwd?

I would think the kinetic energy would get transfered into the driveline allowing more rear brake torque before locking the wheels.

---

Michael LeCompte

pikespeakgtx Wrote:
-------------------------------------------------------
> Tim,
>
> The PDF file was a Big help. The overlap of the
> calipers really puts things into perspective.

For those of you playing along with the home game this is the drawing mike is referring to:





> From what I've learned in manufacturing and
> product design classes, standardization is the key
> to any successful product.

If we are defining successful as maximum result for minimum effort then I agree with you completely.


>
> I'll have to do the brake force calculations, but
> I'm thinking that 11x.81's all around would do it,
> then just size the piston diameters front and rear
> for bias.

11x0.81 in front and 10.75x0.81 in the rear...they are both stock items from wilwood and and use the same mounting pattern so you only have to make one type or rotor hat.


>
> Keep everything standardized and use straight vane
> rotors, that way, a front left is the same as a
> right rear, etc... Calipers all the same so you
> can buy 4 sets of identical pads.
>
> You just make the brackets do the work. Is the
> distance between the hub face and the mounting
> tabs the same front to rear?

Yup, four identical brake hats, two off the shelf rotor sizes...it's so much easier. Then you only make the custom brackets once. You don't have to modify some oddball rotor every time you wear one out.


>
> The question no one at wilwood can answer for me
> is...How much more an awd car can utilize rear
> brakes compare to a fwd or rwd?
>
> I would think the kinetic energy would get
> transfered into the driveline allowing more rear
> brake torque before locking the wheels.

This is GTX specific. If the center diff is locked then it will share braking duties 50/50 with the front brakes. If the center diff is open the stock bias is about 60% front and you can't use all of the force created by identical rotors on all corners. So use the 10.75" ones in the back because they're lighter.

This is slightly changed if you swap a BPT transmission with the viscous center diff but you still want smaller rotors on the back.






Edited 1 time(s). Last edit at 11/16/2007 05:09PM by Tim Taylor.

PikesPeakGTX,

If you want to get rid of those 'old' 10.5" x 1.150" rotors, let me know. Like I said, my road race car has this setup so I could always use spares.

Bob

---

Opel is a 4-letter word...
http://www.flickr.com/photos/10498579@N07/sets/

I already PMed you. Check your box.

---

Michael LeCompte

I have the BPT tranny in the car. What sort of differences are you talkin'?

I'm still debating changing caliper styles. Mine cost $125, yours are $250. That's an extra $500 in total cost. For only .25 of an inch difference in wheel spacer. How far is your rotor away from the mounting tabs of the hub? 1.5mm? Looks larger to me.

Why not run 160-3305? a 10.75" / .35" solid rotor in the rear. It's 4.2lbs instead of 7.9/7.4 pounds.
Use NM dynapro in the rear. Total cost over $500 dollars less. You could use the same rotor hats front and rear since the bolt circle is the same.

Or you could run a vented rotor with the NM dynapro. The rotor weighs more but you'd have better cooling, less potential for fade.

Whats better the weight savings or the cooling capacity?

---

Michael LeCompte

Tim can you tell me all the spec on readily available master cylinders for the GTX?

I've found the stock GTX is 7/8.

Where's the 1" one your planning to use come from? AWD protege?
Do you switch the brake booster as well?

How does the proportioning valve in the mazda work? You mentioned it changes bais as the pressure increases, can you elaborate?


How much piston travel do the GTX master cylinders have?

I've started the calculations for a bunch of different setups.

What torque values are good to end up with in terms of total brake torque for a front and rear rotor?

---

Michael LeCompte

I'm pretty sure the Mazda 929 is the one with the 1" MC. I think that Mazda actually terms it a "differential valve" rather than a proportioning valve. Front brake pressure is dependent on the pressure applied to the rear brakes, I believe. And i've noticed myself that with proper adjustment of the e-brake, the front brakes work better.

That's just my 4,872 rubles worth of minor information...


--sarge

---

---** To be in compliance with the Anarchy **---
Jorden R. Kleier
Baraboo, Wisconsin, USA
1990 Mazdog Protege 4WD
1973

pikespeakgtx Wrote:
-------------------------------------------------------
> Tim can you tell me all the spec on readily
> available master cylinders for the GTX?
>
> I've found the stock GTX is 7/8.
>
> Where's the 1" one your planning to use come from?
> AWD protege?
> Do you switch the brake booster as well?

Use the 929 master cylinder...here is how to do it:

http://www.dustdevilsracing.com/how_to/929mc/howto929mc_001.htm


>
> How does the proportioning valve in the mazda
> work? You mentioned it changes bais as the
> pressure increases, can you elaborate?
>

Page 11-47 of the factory manual.





>
> How much piston travel do the GTX master cylinders
> have?

I have no idea and it doesn't really matter either if you keep the caliper piston size within reason.


>
> I've started the calculations for a bunch of
> different setups.
>
> What torque values are good to end up with in
> terms of total brake torque for a front and rear
> rotor?
>

I'm not going to spoon feed this to you any more that I already have. You already have the keys to the kingdom. That graph of the proportioning valve gives you the line pressures, you have a car to measure all of the relevant dimensions, and you have the brake torque formula...you don't need anything else...it's all right there.

As for the decisions on which caliper and rotor why don't you do a decision matrix on the different combinations and pick the best one for your goals. You are not headed for the same end goal that I have. In fact I'm not really sure what you want your end result to be.

Yes, you can use the cheaper non-radial mount calipers but they will not fit 15" wheels without cutting the stock brake ears and tapping the casting. In fact nothing good will fit on the front without modifying the casting.

Yeah, gotta agree with Tim here. I have completely lost treack of the point of whatcher trying to do?

I think as far as we know find out, and accoriding the the collective knowlege of the Intra-web, that I was the first person to come up with a decent 4 piston set up which retained the stock four bolt hubs when I did Derek Bottles set up way back in 02.

It was quite simple and used extremely inexpensive discs, off the shelf Willwood Superite calipers, and involved making a very simple triangular shaped adapter, for the caliper---after of course lopping off those absurd "antlers"---and in the front a simple spacer that the new studs were pressed into and the rotor placed OVER like anything modern.

Simple and within the means of any half clever fool like me to actually pull off.

We used one of the 2 types of 929 masters, the bigger one, and used RX7 calipers and the same discs in the back.

EXCELLENT pedal feel and modulation, relatively low cost, and of course lots of boys talking gotta get this goota have it and zero follow thru.


So is this just a desk-learning exercise or are you trying to make some affordable brake to run a car in the woods?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I agree the stupid antlers have to go. I'm not afraid to cut my spindles.

I'm inquisitive. I'm not asking you to "spoon feed" me. I don't see why you need to use phrases like that towards me. That's some bullshit. I take a little sum sumthin of your advice and now you're spoon feeding me? I don't think so.

I need those "irrelevant" numbers for my school assignment. They're not irrelevant just because you don't care. Maybe someone else on here knows, no harm in asking. This is a learning exercise.

You still never said why not a solid rotor in the rear to save weight?

Also according my calcs... a 10.75 rotor vs. an 11 rotor will give about a .5% difference in bias. Why wouldn't you run the same rotor all the way around to fit your "most gain for minimal effort" saying. Certainly not just for weight savings. Otherwise you'd be running a solid disk in the rear.

So, what is the end goal/main purpose for your car?

---

Michael LeCompte

pikespeakgtx Wrote:
-------------------------------------------------------
> I agree the stupid antlers have to go. I'm not
> afraid to cut my spindles.

Well get on it.
>
> I'm inquisitive. I'm not asking you to "spoon
> feed" me. I don't see why you need to use phrases
> like that towards me. That's some bullshit. I take
> a little sum sumthin of your advice and now you're
> spoon feeding me? I don't think so.

Hey, whatever your name is, keep your shirt on. This isn't some forum for comparing E-Penis size and you won't find any sympathy here saying a respected and helpful guy like Tim giving you "bullshit".
I think he's right, it seems you're asking others for your answers.
>
> I need those "irrelevant" numbers for my school
> assignment. They're not irrelevant just because
> you don't care.

Dood, Tim used spoon feed because you're asking for somebody to supply you for something YOU have right there on your own car.
There's not a lot of GTXs around and most the rally guys aren't modding much so you need some info about your car, why haven't you FIRST established what your basic sizes are for the critical shit like Front Piston, rear piston, master diameter, stroke, pedal ratio?

You had some really nice drawings which means you can do things at a desk/keyboard but why haven't you done the basics and noted AND POSTED the data you're starting from?

And while you may be inquisitive, (which is good), you have shown you don't read well:
A) you haven't read our whopping 2 rules, and as such you haven't put your name and home town in the side bar thing

you haven't answered what end use of the car will be.



>Maybe someone else on here knows,
> no harm in asking.

Why haven't YOU gone and measured anything?

>This is a learning exercise.

Well many of us are of the school that you learn best by doing things yourself and practicality, durability, and cost are intertwined together.
Since we really don't know what you're really trying to do, for all we know you're a 14 y.o. without even a car, living in Sverdlotsk, Siberien and really aren't building a car.

Do you understand asking others for info which should be right there in front of you seems odd?

Anyway, go fill out the name thing and location, and then tell us if you're building a rally car or if you're just doing some school assignment or what.
>
.
>
>

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.



Edited 1 time(s). Last edit at 11/18/2007 03:15PM by john vanlandingham.

Fair enough.
I fixed the stuff you talked about.
I'm building a rally car.
I have a BPT Swapped GTX.
I'll get my project done. I have access to everything I need to do so. I don't feel like I need to prove to anyone that I'm ACTUALLY doing this. Take me serious or don't.
I thought a forum was a place to ask questions.
If I have to censor and tip toe around which questions are ok to ask and which aren't , it seems a little counterintuitive to the mission of an forum like this. If I ask questions and I get comments like spoon feeding, what good is this? I thought it was about sharing information and completing projects. Not showing disrespect.

I have done all the critical measurements, I have sized caliper choices and rotor choice many different ways. Just trying to weight out all the options. There's more than one way to skin a cat.

---

Michael LeCompte

pikespeakgtx Wrote:
-------------------------------------------------------
> Fair enough.
> I fixed the stuff you talked about.
> I'm building a rally car.
> I have a BPT Swapped GTX.
> I'll get my project done. I have access to
> everything I need to do so. I don't feel like I
> need to prove to anyone that I'm ACTUALLY doing
> this. Take me serious or don't.
> I thought a forum was a place to ask questions.
> If I have to censor and tip toe around which
> questions are ok to ask and which aren't , it
> seems a little counterintuitive to the mission of
> an forum like this. If I ask questions and I get
> comments like spoon feeding, what good is this? I
> thought it was about sharing information and
> completing projects. Not showing disrespect.

Nobody is showing disrespect, I already suggested you should mellow out.
Now it sounds like you're sounding awfully butt-hurt about something that Tim said that I didn't think was engough to justify all your hurt feelings.

You don't have to tiptoe but if you're going to sound all whiney and petulant then you better grow some thicker e-skin.
>
> I have done all the critical measurements, I have
> sized caliper choices and rotor choice many
> different ways. Just trying to weight out all the
> options.

Why don't you post the fuckin measurements here, doesn't do anybody else any good to say "I have done all the critical measurements"
That way the next person with a similar problem can benefit.



>There's more than one way to skin a cat.

Really? Odd that virtually every real rally car I have been able to dig up specs for have had front calipers with either 4 x 1.5", or 2 x 1.5 and 2 x 1.625 on front.
This includes old Escort MkII
Sierra 2wd
Golf
Opel
Sierra 4x4
Escort Cossie
Subaru WRX
etc etc etc

And it seems like everything has has either 2 x 1.5, or 2 x 2.0 rear.

>
>
>

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

pikespeakgtx Wrote:
-------------------------------------------------------
> I have done all the critical measurements, I have
> sized caliper choices and rotor choice many
> different ways. Just trying to weight out all the
> options. There's more than one way to skin a cat.

If you are trying to decide which combination to use why don't you just do a decision matrix like I told you. Here's a link in case you have never seen one before:

http://www.asq.org/learn-about-quality/decision-making-tools/overview/decision-matrix.html

This is one way engineers and other professionals make informed decisions about complicated multi variable problems (this being a learning exercise and all). I still don't have the faintest idea what your end goal is. Define your criteria do a matrix and post it.

I'm still willing to help you out (and I'm sure John is too) but I'll stand by my spoon fed statement. Where was the up front research on your part? Hell, if you google "323 gtx master cylinder upgrade" the third or fourth link is the step by step instructions I linked above. The proportioning valve graph is in the damn factory manual along with every other dimension on the car. The difference between how a solid and vented rotor cool is fundamental to an understanding of how brakes work. You're just not giving us a lot to work with other than "I can not be STOPPED!!!I'm way too hard headed." which not a very good way to go about what you are trying.