RC45

Can the experts please weigh in on the topic of brake bias.

Is it s a "static" setup value one shoud llearn to drive around, or is there an ideal bias that will be conducive to going faster safer - is it a value one should leave to the braking system to manage?

If one was to "play" with the brake bias, is it better to make thos eadjustments with changes in rotor size/caliper type, swept area changes or just stick with the hydraulic bias changes?

Is an adjustable masyer cylinder the ideal ticket?

I would love to hear what the resident experts have to say.

wallyman424

the c5 has electronic modulation of the brake bias. It works pretty well.

RC45

Is this system clever enough to work around caliper changes? And then there is the rumour that the 01's and earlier have a fixed bias.

RAFTeRACER

I'm no expert but I do know some have had good luck running C-5 calipers front and rear and tuning the bias with pad compounds.

MungoZ06

I'm guessing you want to develop post # 130 here into a separate discussion ...
http://forums.corvetteforum.com/show...2036290&page=7

RC45

Partially yes - as a while ago I was set to buy a manial bias adjustder, btu was informed it was not needed for post 2000 Vettes... besides which, I wondered if major front/back caliper/pad/rotor changes would interfere with the stock systems ability to compensate and manage bias autimatically (assuming the 2001 system is not fixed.)

davidfarmer

The only GOOD bias adjuster is dual master cylinder with a bias bar. Hydraulic pressure valves (lever and dial) are simply spring loaded bypass systems that decrease flow when the pressure reaches a give "break point". In other words, the system is still mis-biased at low pressure (say trail braking, or other light braking), and the pressure adjustment varies depending on load.

I ran a mis-matched system temporarily with the stock ABS, and it actually did some amazing amounts of correction. However, the moment you have a failure (very common in regularly tracked cars) you end up with a car that is basically NOT drivable.

My advice is to either keep the relative piston sizes extremely close the those that came with the master cylinder setup you are running (Like Stoptechs systems, which are matched to each and every car they build for), OR switch entirely to a dual master setup with bias bar (like the pro race cars use).

Manually adjust can be usefull for racing. Higher grip level require more front braking, lower grip levels (rain etc) require less front grip due to less weight being shifted forward under braking. Also handy at tracks where the braking zone is uphill/downhill etc, as this can have a pretty serious effect on bias needs, primarily in cars with no ABS.

RC45

Thanks for weighing in David, I had hoped you might pop by,

Paul

Lichen

I can just speak for a C4 point of view. I upgraded my front brakes to J55 over a year ago. I just replaced the bias spring this week. All I can say is "Wow, what a difference". Best brakes that I have had in 6 years.

Bill Dearborn

The 2001 and up cars have Dynamic Rear Braking. It is adaptable to changes in the braking system since it uses the wheel speed sensors to determine how much braking can be applied to the rear. You can get as much rear brake application as you have traction to handle. However, as David says the electronics can fail and if you have changed major parts of the brake system you may not be able to slow the car properly without the electronics.

I know it is hard enough with the stock system when the EBCM fails. I had that happen at Watkins Glen last year and I had nice surprise when I got rear brake lock up while braking hard into Turn 1. I was able to compensate by changing my brake application on subsequent laps but it does emphasize that a changed base brake system would be even more sensitive to lock up.

Bill

0RAAMaudio

I agree completely with the farmdude (no offense meant, I grew up working on farms and ranches either get matched piston sizes as close to stock as possible or run a true dual master. I happen to be doing both on my Vette

I am running a Wilwood valve on another car but it can only reduce rear pressure, not increase it if needed. I just thought of this, if I put one on the front as well................

Rick

RC45

So, as an example then, running C6 Z06 front and rear calipers on a C5 Z would be a good compromise, instead of trying to rely on the bias compensation of the Dynamic Rear Braking.

Or just go for a manual bias master cylinder - would the Doug Rippie master cylinder be a good fit?

Bill Dearborn

It all depends on what you mean by relying on the dynamic rear braking bias compensation. With the C6Z calipers you will still have the same relative front to rear braking capability and still end up relying on Dynamic Rear Braking just as the C6Z does now.

Bill

RC45

I guess I must have forgotten to type the rest of my thought

What I meant to say was: So, as an example then, running C6 Z06 front and rear calipers on a C5 Z would be a good compromise, instead of trying to rely on the bias compensation of the Dynamic Rear Braking to compensate for a C6 Z06 front caliper/14" rotor and C5 rear caliper/stock C5 rear rotor setup. (the italic is what I forgot to add the first time round).

0Todd TCE

I'd not suggest anyone install a manual bias adjuster in conjunction with any electronic or other factory biasing systems. Compounding a pressure reducing device upon another of the same wouldn't do much good and potentially limit rear brake way too much. *nor should any such valve be installed in the front system (yes I've heard it suggested...yikes!)

Your static 'brake bias' is simply a balanced relationship between the front components and rear components of the brake system. Regardless of who's parts they are or what dimensions they are. Changing some aspect of the part (larger rotor, smaller pistons, high zoot pads) all effects this final number. Say 60/40 for example.

Controlling the reduction (it's never more) to one or more wheels is dynamic biasing and is done either through a proportioning valve or other similar electronic means. Newer cars all taking a spin on something like EBD or Electronic Brake Distribution. This would be your 'dynamic bias' and changes on production cars (not on twin mc) all the time by way of input from EBD and your applied pressure.

Changing components on the car can can alter the static number but the EBD systems can probably save a few butts from doing something terribly bad. Making a change won't require you keep the sizes the same totally so long as you either change both ends a like amount or monitor the changes on rotor torque produced by one of the changes relative to the other. That being said I'd also urge you to keep an eye on front and rear line pressures also and not vary too greatly from that. Since most systems rely in part on monitoring pressures installing too much or too little piston area on one end will effect both ends in the real world due to the single mc. As pointed out; here you'd need a twin mc set up to alter the pressures by way of different size bores.

For some more insight into cause and effect bookmark the brake bias page and plug and play a bit as you look at some options.
http://www.tceperformanceproducts.co...alculator.html

For those with twin mc racing set ups I can run them also in a more complex program offline.

0Randy@DRM

Here is the story with our master. It will work like crap using stock calipers. There is too much piston size which cause almost no feel. It just doesn't work. They work great with a larger piston caliper like our AP setup, which with a stock master is no fun at all.

Why put in a valve when the computer valve is already doing it's job? Well because the computer isn't always right. Our master has a lot of rear brake dialed into it. So we need to take some of that away. So it becomes a prefect time to make it more adjustable.
My garden hoses are very simular. I have a valve on the house and also a valve at the garden. Either way you can adjust the water flow. I had a customer that has been away from the track for years call last week. He told Doug that the rear tires were locking up deep into the corner. A turn and half on the ****, problem gone.

Now why shouldn't you put a valve using the stock master? Well it's not enough already why block it off.


Gotta run
Randy

geerookie

Randy,
Then how does your bias spring for the C5 make a difference. From what I'm reading above it won't change anything (computer controlled brake biasing).....Or am I not understanding what I'm reading.

0Randy@DRM

Before 01 they were still using the spring to do the bias pressures. So you will find on 97-01 cars about 7-9 percent more rear brakes.

Randy

Everett Ogilvie

My car has Tilton pedals, master cylinders and the bias bar with cockpit adjustable ****. In looking at it, I am not entirely clear how it works - as you turn the **** the "bar" (threaded shaft which goes through two clevis setups, one for each master cylinder) appears to move "in or out". Obviously, this changes how much pressure is applied to one or the other master cylinder, but is it simply based on the "fulcrum" position the bar is in relative to the two master cylinder actuators?

If so, is this a course adjustment - meaning it takes several turns of the **** to feel any difference? I have not attempted to adjust it yet, and am curious how it works. The car does not have any electronic systems for braking or traction control.

Edit: I found some pretty good info regarding balance bars and how they work - guess I should have searched the internet before posting. As I surmised, it simply moves the pivot point towards one master cylinder or the other, altering the pressure. I still don't know how much adjustment it will take to "feel" any difference, so it will take some very careful testing. Don't want to swap ends.....

Bill Hetzel

Good, you got the info on how they work. Now, a question first, did you (or whoever installed the system) set everything up evenly? This will give you a good, known starting point. The first thing to do is make sure the bias bar is centered. I use a piece of wire or a straightened paperclip to find out where the pivot bearing is in the bar. Insert the wire on one side bar until it hits the pivot, mark it with a fine tip Sharpe.
Then insert it thru the other side, if the measurements are equal, you're good and the bearing is centered. Then make sure both pushrods are equal in length, from where they screw into the biasbar to their ends. Now you have a neutral starting point.
You can do a rough "bench" setup with the wheels off the ground. You need someone with a steady foot or you can use a pistolgrip clamp that has the spreader option placed between the seat and the brake pedal. Have your helper push the brakes until the fronts just lock up. Check this by rotating the tire in the direction of travel and always use the same method to rotate the front and rear tires ( if you're pulling up on the bottom of the tire, do the same in the rear). When the fronts are just locked and the rears take a lot of force to move them, you're good. Again, this is just a starting point.
It can easily take a half turn on the **** when doing the bench setup to get it from almost right to just there.
The amount of turns for you to feel an adjustment depends mostly on the brake system combination you're running, master & brake cyl. diameters etc. and your feel for the brake lockup.
Now you need to find a straightaway (preferabily at the track on a test day) to set the bias. trying to set this up going into corners isn't very safe. You need to get the pads and rotors warmed up and then do a threshold brake and see how the car feels. The fronts should lock up just before the rears. It helps to have someone watch the fronts to see when they're locking or just starting to jerk a little under hi brake force. I've even used a video camera to do this. The rest is about how the car feels to you. I'm betting that the min. you'll be able to feel with a new system is one full turn.
It's safer to have the fronts lock before the rears.
If it's raining, I run more rear bias.