I keep reading about or seeing racers talking about adjusting brake bias forward or backwards, but I was wondering how it was done? Google isnt' yeild too much, just discussing techniques while doing it, and a lot of them are focusing on adjusting it for games or something.

Has anyone here ever adjusted theirs? I'd love to get a bit more forward bias for this upcoming autocross season. How do I do it on the FC?

Thanks!

 

I think it's something called Line Lock. Using hydraulics to switch the balance between rear and front. i can't be 100% sure. I think you have to ask RXTASY of teamFC3S.org, he has one.

 

http://www.wilwood.org/ds129.pdf


you can use a line locker but then you have no rear braking what so ever.

the wildwood one is for american cars but i'm sure other companies like HKS or Greddy make them too.

 

Is that how people do burnouts for like 10 minutes without moving?

 

yep.


as for cars like ours...brake bias is controlled by a proportioning valve which divides up the pressure for the front/back. only way i can see to change bias would be to get a different valve.

 

Awesome, this is exactly what I'm looking for.. . I'll have to pick one up after I get the 7 running. Thanks

I really think this will help me out, as I always lock the rear brakes before the first going into a tight turn, and it's bloody annoying.

 

Uhhh, you should be happy its that way and not the other way around... you dont wanna understeer and slide off the road. on extremely tight roads I'll pull the e-brake going into corners and just drag the rear end. Much more controllable then not knowing if your front end is gonna stick

 

Racing cars do it by using two master cylinders for the brakes - One for the front, one for the rear. The bias is adjusted by means of a "balance bar." The bar is connected to the brake pedal and it's just a matter of adjusting the angle of contact between the bar and the two masters. For example, if the bar contacts the rear master first, the rear brakes get more braking effect, dependent upon how long the rear master is operating unitl the bar contacts the front master. Regarding a line-lock, if I remember correctly, it's basically an on/off type of affair. That is, the front brakes will be fully locked on, with no control beyond that. That's not something you would use while driving the car, obviously. It's great for burnouts, but you can guess what would happen if you lock the fronts at 50mph going into a turn.

 

I know I appreciate it on the roads, but what I'm looking for is something to help with the bias for autocrossing. That's why the link that Karack is so useful, maybe I'll be able to get the car to actually turn while braking, without using the e-brake.


nopistons - That's a pretty good idea. Not that practical for a car I still want to street, though.. and it sound expensive Damn college.. I'm glad I'm done this semester! Definatly check out that link that Karack posted, though, it's good because n00b tuners like me can't completely disable the rear brakes, it will only restrict up to 55% or so of the braking ability, so I likely won't kill myself out on the autocross course, and it seems rather quick to switch back to normal mode for driving away.

 

Put brake pads with a little more bite in the front.

 

How is your suspension set up? You might be getting too much weight transfer, i.e. unloading the rear, and allowing them too lock early. If you have adjustable shocks, you might try changing the settings and see if that helps.

If the suspension is still stock and origional, sort that out first.

 

Any preference on which ones to use? I just put on 4 new disks and pads less than 3000 miles ago. This was a great increase in braking, but still cause a straight line lockup when I jammed the brakes going around some hairpin on the course.

I'm running Eibach Pro springs with Tokico Blues both with less than 5000 miles on them. I think I need to get a urethane bushing set, but I dont' think that's a major problem. I know my stock stuff was more than shot, and although it seems better now, it just feels like the front is grabbing too much.. I really can't break the rear free on tarmac, and the hairpins suck when you have to come to nearly a complete stop.

 

Put better or wider tires in the rear.

Getting into brake proportioning valves is something over your head right now (looking at your current set-up).
As someone else mentioned, you can play with the brake pads front-to-rear to deal with this also.

Although the BPV is relatively cheap, ensuring a proper job is a royal pain in the ***, especially if you're going to run it inside the cockpit.
Messing with brake lines is something better left to the professionals.



-Ted

 

do u hae any links that talk about the BPV?? i have been thinking about this in the back of my miond ever sence i got into motorsports and i think i have an understanding of whats up but its very basic(is it really that basic??) but dont have any idea about install and such and i would like to learn more so when the time comes i can act accordingly!

 

I hope it's not too bad to leave to unprofessionals like me, Ted I've swapped out every part of brake systems on more than the 7.. Why I think that would be helpful is that it never fully shuts off, unlike the line lock.. I would be installing it in the engine bay anyway, and playing with it only on the autocross track or abandoned parking lots or the like... it's back to normal for everyday driving.

Do you seriously think it would be better to go with different thickness pads on the back? I mean, that sorta locks you into a set bias, and I just want to dial it in so the front locks up slightly before the rear...

I think I'm going to wait until I burn through these tires to get another set, too.. the ones I have on only have about 4 or 5 thousand on them...

 

Line lock does not work as a proportioning valve.
It keeps brakes locked on for lauches and burnouts.

 

Honestly, you don't want your fronts locking up first, that is if you want to make the corner.

It may be as simple as braking a little earlier coming into the corner, and or playing with your tire pressures a little more.

Are both rears locking up, straight line, or only one side consistantly? My right rear has a tendency to lock up first, dodging deer and things like that.

There are a lot of little things you can do before you need to to start changing brake bias.

 

I'm confused here, even in autocrossing, why woudl you want the front to lock up first? All its going to do is massively understeer the car, if not just slide it right off the course?

 

No, the point I was making is that if the brake system has even a minute leak, the brakes fail.
Brakes failing at the wrong time can KILL you.
Now do you understand?


They are not the "best" option, but it's the cheaper option considering one set of brake pads usually does not cost more than over $100 per axle or tires that cost maybe $200 (for expensive ones) per tire.


-Ted

 

You, sir, should not be commenting in this thread with such myths.


-Ted

 

My knowledge expands, I think I'm going to look into this a bit more

 

Loud and clear on that one, commander


How do you order brake pads to a specific size? All I've ever done is go "I want some of the good pads for an 86 Mazda Rx-7"...

 

The problem that I'm having is that the rear brakes grab so much that it's impossible to make the car do anything other than a safe (for roads and highways), low-speed turn. This works great out in the public, however, the fastest way through a corner on the track is rarely to come to nearly a complete stop before you can get the car to turn at all...

An idea autcross setup (from what I understand), is that if you were to press down on the brakes normally, all the way down to the point of locking the wheels, the front would lock just slightly before the rear does, allowing you to have that slight bit of drifting/sliding/whatever you want to call it to get the rear to swing around, while not losing all of your velocity.

 

It's simple really. Locking up the fronts first means you'll brake more or less in a straight line, since the rears still have grip and are dragging the car. Lock up the rears when there is even a hint of lateral force on the car and you're looking at a spin, as the fronts still have grip, keeping it planted, and the rear tries to rotate sideways around it. You don't really need even the hint of lateral force to get a good spin going, since the rear is trying to get past the front anyway in such conditions.

To the original poster: I agree with Ted on the brake pads. Try a grippier pad up front. EBC green worked very well for me as a street/autox pad, because even cold it bites pretty hard. I ran a set of them at all corners and didn't have issues with the rears locking up first. The BPV might bump you out of whatever class you're in for autox, which is something else to consider.

Don't take EBC greens to a circuit course though, you'll be spending a bunch of money you didn't plan on when the pads wear down to the backing plates and eat your rotors.

 

Thanks for the info Gene, I'll look into a set of them...

The part about sliding is true too, once you get to that low speed that I have to be at to corner properly, it's really easy to put it into a spin coming out of the corner...