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Manual brake conversion


Maxzillian
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Just a teaser of a project I've been working on. Ultimately I will be making a more formal post in the brake forum, but not until I complete some testing at an autocross this weekend. In the meantime, here's something to gauge a little interest. :)

 

http://maxzillian.com/starion/mastercylinders1.jpg

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Interesting. Im looking into converting back to a single willwood master and running manual thata way. How would this be mounted?

 

It bolts up to the firewall using the existing holes for the factory brake booster. A short tie-rod connects the balance bar assembly to the brake pedal.

 

why would any one want to do this ?

 

It's definitely not for your daily driver. Manual brakes offer up a small number of advantages:

 

1. Firmer brake pedal feel. Without the internal valving of the brake booster, the brake pedal has a direct connect to the master cylinder, reducing the travel before the brakes engage.

 

2. Better modulation. With the increased pedal effort (calculated to be about 50-70% more with my setup) it is easier to modulate the brakes with more precision, handy for performance driving.

 

3. Applies only to dual master cylinder arrangements: The use of a balance bar allows for price adjustment of brake balance between the front and rear of the car. While a proportioning valve offers similar adjustments, a proportioning valve only adjusts the brake balance after a certain pressure is reached. A balance bar offers an initial balance adjustment. I'm attempting something a little unconventional with my setup where I'll be using a balance bar with the factory proportioning valve.

 

4. More consistent brake pedal feel. The amount of braking effort required does not vary with engine vacuum. Under heavy engine braking, the pedal force required for a certain braking power becomes less than when the engine is not under heavy braking.

 

5. Less weight. 3-5 lbs at best, but it is a benefit. ;)

 

6. Better serviceability of the engine bay. Yet another small benefit, but now the starter and heater hoses are much easier to reach.

 

Disadvantages:

 

1. More complexity. To use a balance bar without modifying the factory brake pedal, a lever assembly must be used. This increase the potential failure points of the assembly.

 

2. Increased pedal effort. While it should not be excessive, it is an undersirable effect for most people when it comes to street cars.

 

It's not for everyone by any means and I don't advise that the vast majority of people use such a setup, but there are some who would benefit or be interested in it.

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I was wondering why also, thanks for the clarification. Unfortunately I'd have to classify this along with "manual steering". There may be a few benefits, but I'm a creature of comfort. For what little power they rob, and the other minor inconvieniences, I'll keep my power stuff. My old Nova had manual steering and manual brakes when i bought it. Drove it like that for months, until I found a parts car. Then we got power steering and power disc brakes. SOOOO much nicer. Never looked back.

That said, if your mod serves the desired purpose, have at it...and good luck.

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Power steering is much different as it is an expensive system to fix and replace...the brakes...power brake boosters don't die often.

 

 

I will admit though...manual brakes are nice as you have less tendency to over brake.

 

 

I still think its funny how people think their brakes don't work unless the car is running...by god if they ever drove a car with drum brakes...lol

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I've driven manual brake cars and love it. I actually like non power steering too. I like the feel it gives and feedback. Also love simple the less to break the less in the way etc. A stock starion engine bay is one of the most cluttered things out there. Makes me really notice when working on my dads 68 Camaro. You can do handstands in that engine bay. Or if you drop a bolt it hits the ground unlike on our cars where it gets lost in the black abyss of our lines and hoses etc.
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Well, the truth is that the major motivation for me was to correct a brake balance issue I had. I built a 12.75" wilwood setup on the front of my car with the intention of upgrading the rear later. Once I determined that upgrading the rears while maintaining a parking brake was going to be difficult, I decided to leave the rear alone. Needless to say, I had way too much front braking capacity over the rear and this was actually hurting my braking distance.

 

With the dual master cylinder setup, I have a .75" bore master cylinder for the front and a .625" bore cylinder for the rear. Along with the balance bar, this allows me to dial in more pressure to the rear brakes to account for this imbalance.

 

Buying smaller bore front calipers would have worked, but this was cheaper at about $120 for master cylinders, balance bar, and fittings. ;)

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well you do have one advantge over most cars the Couquest petal is a good bit longer then most petals this would give you a little extra leverage over a shorter lever , but you'l need to position the activateing rod position in a position to got enought travel and still give plenty force to use ,, could be a bit complicate'd to get every thing set up properly
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Race cars just have to go dont have to stop! Lol. Im actually planning on doing mine this witer so please keep us up dated

 

 

realy humm guess you haven't had to cross thew 1/4 marker @ over 120 and had only 1/4 mile to stop in or less ,

and why are guys doing big brake up grades

 

old man once told me , make sure the car will stop before it's move'd or the first time may be it's last move

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old man once told me , make sure the car will stop before it's move'd or the first time may be it's last move

 

Ha I though about the same thing when I first got my quest and dumped it off the slant car carrie. Figured I could just dump it in gear since the motor was locked up as worst case.

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well you do have one advantge over most cars the Couquest petal is a good bit longer then most petals this would give you a little extra leverage over a shorter lever , but you'l need to position the activateing rod position in a position to got enought travel and still give plenty force to use ,, could be a bit complicate'd to get every thing set up properly

 

Yeah, the stock pedal is pretty good, but does need a little boost. It's difficult to see in the rendering, but there is a red lever arm that not only holds the balance bar, but also serves to multiply the pedal ratio by a factor of 1.2. Between that and the smaller bore cylinders, the pedal effort shouldn't be too terrible.

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Well, after some in city driving, I found that the initial bracket design was too light. While it "looked" ok assuming even load was placed on both master cylinders, the reality is that when one master cylinder requires more force than the other, the bracket was twisting. Not only was it adding travel to the pedal, but it also prevented me from doing a full lock test for fear that the bracket would yield.

 

After removing the bracket and adding some additional gussets and material, it was noticeably better and deflection measured at the end of the cylinder went from 1/4-3/8" to well within 1/16"... pretty darn acceptable.

 

Running an autocross today, the brakes worked great. I initially had the brake bias set too heavy on the rear and attempting to late brake a corner on my first run instantly had the car trying to swap ends. After dialing more bias into the front the car was much more settled, but it's apparent that I either need to remove the proportioning valve or replace it with an adjustable unit... I'm leaning towards the former.

 

The problem is that the car initially has too much rear bias under light braking, but has too little under heavy braking. With the brakes adjusted correctly for full lock conditions, the car can only be stopped in a straight line when braking under light to moderate power. Once the brakes are dialed in to keep the rear end settled, the fronts lock up a hair too early under heavy braking conditions. It's a very minor detail and the brakes are currently comparable to stock in terms of balance, but for autocross I'll take every last bit of braking power I can get.

 

Ultimately I'm not happy with how the bracket is now that it is braced properly and wish to redesign it, largely to increase the serviceability. As it is, trying to remove the bracket without cracking any of the brake lines is far too tedious for my preference. All in all it took me about an hour and a half to get the bracket in and back out.

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  • 11 months later...

Well over-due for a little update on this. I finally got around to gutting the proportioning valve before starting the autocross season this year. This was easier than trying to make new lines or find a coupler for the existing lines, not to mention it's reversible. :)

 

Braking wasn't changed too much at the first autocross, but I neglected to make any adjustments to the bias bar. At a recent autocross (placed 2nd overall amongst production cars, by the way!) I got around to dialing in more rear bias and found that the brakes felt very good and controllable. Now the car is less prone to locking up the front tires and I can even manage a little bit of controllable trail braking which actually works pretty well at getting the car to flick around tight corners without losing too much speed or traction to sliding.

 

The only downside to this setup is that the braking force is higher than I care for. It is very controllable and even my girlfriend found it manageable when I was teaching her to drive a manual (with a stage 4 clutch, no less), but I do have concerns with being able to get adequate braking when the pads are cold. That said, the front of the car currently has street/track pads and they do require some heat before they start to work. Once they're good and warm, they're great, but that takes some time and is difficult to maintain in an autocross. Typically I keep my foot on the brakes during my parade lap just to get some heat in them so they work during the first run.

 

Chances are I will likely move to more of a street pad for general and autocross use, but keep a set of track pads should I ever decide I want to do some sessions.

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Nice update. I use a porterfield r4-s compound, which only needs one brake at first and rapidly gets up to temp. Depending on the track they'd hold up, but would be pretty good on a cone dodger I believe.

 

They've been working great for me, regularly smashing through canyon drives. So good I even had a full set on the wife's car for when I take it for a spin. I'm thinking about getting a set for my van lol.

 

-Robert

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Manual brakes and Steering are Win! The only difficult steering (at first) is a non-powered power rack :). Takes some time getting used to and definitely deters anyone from trying to borrow your car.

 

Leaky 4WS lines on GVR4? no problem! Delete my powersteering pump.

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