brakes locked up on me

[SILINC3R]

this is the first time this has ever happened. i was getting into a right turning lane at around 35 to 40 when a car that was stopped at the light decided he wanted to get into this lane to make a right as well. luckly he did this before i was to close, i saw him and started on the brakes, not sure if i had downshifted at the same time. now that i recall this has happened before but i had stock brakes and tires. i was coming to fast to somewhere were i needed to turn and downshifted at the same time and next thing i new the car was kind of sideways. i let of the brake and made it into the road i was going. it had been raining slightly. this time however i have WRX brake conversion all the way around (calipers, rotors, pads) also i have steel lines and 2005 Leg GT rims with Kuhmo tires on them 215/45-17s. what i am trying to ask is, is this normal if i put the brake on to hard they will lock up with this new brake system. do i need to fix the bias and move some of it toward the rear. not sure if my car has a proportioning valve or not.
any help or comments would be helpful thanks

Tony

[SLODRIVE]

Assuming your car is non-ABS, yes it's normal for the wheels to lock up if you apply enough pressure on the brakes...in fact, the brakes are SUPPOSED to be strong enough to be able to. Better brakes will lock the wheels even easier. That said, the rear brakes should ideally lock just before the fronts.

[SILINC3R]

yes this is the non-abs. well i figured with the new upgrade that they might do that. so dont worry about it or about messing with the valve

[RJ93SS]

in the brake sticky, josh made a spredsheet that will help tell you how much your bias changed!

[SILINC3R]

my computer sucks and i cant open it how would i change the bias myself

[RJ93SS]

put in a different one

[skid542]

That said, the rear brakes should ideally lock just before the fronts.

I'm not to argue the theory, just going to state that in the real world it is extremely difficult have the rears lock just before the fronts.

If the bias is too far rearwards and the rears lock before the fronts and the braking isn't strong enough to also lock the fronts - you're going to be in for a fun ride. I know - my brake setup used to lock the rears first. If you're not a very capable driver - this will get you in trouble.

But then again this all a moot point since the only way to have that adjustment on a Leggy is with an aftermarket proportioning valve and anyone doing that mod probably knows all this .

Not trying to correct you, just making sure the bypassers of the thread don't get the wrong idea .


Back on topic - the brakes should lock up if you press hard enough on a non ABS car. The only way to change brake bias is with an adjustable proportioning valve (which usually costs you the stock diagonal redunancy system of the car) or by changing rear brake setup, i.e. a larger rotors/calipers with more clamping force. Being a FWD NA, you do have some options here.

[SLODRIVE]

^^^ No, I totally understand and agree with your point...if the rear brakes lock too soon and the fronts aren't doing enough, things won't go well. However, if the fronts lock first, even if it's just before the rears, you will no longer be in control of your car. It's something of a fine line.

There are a few ways to play with brake bias without changing any brake hydraulics...changing F/R ride height, tire pressures, weight balance, different front/rear tire diameters (only on a 2wd of course), and spring/shock rates. Even using different brake pad compounds between the front/rear can get you what you want. Be aware that most of the above changes can change the overall balance of the car though, sometimes for the better, sometimes for worse...but they ALL affect front/rear brake bias!

[SILINC3R]

guys i put what i had installed up top

tires=215/45-17 Kuhmo

rims=2005 Legacy GT 17

rotors= fronts WRX 04
rear WRX 04

calipers=front WRX 2 pot 03
rear WRX 1 pot 03

pads=Subaru pads

brake fluid= super blue racing

steel lines

[ultrasonic]

The brakes didn't "lock up on you." You locked up the brakes.

It's 100% normal for a non-abs equipped car to be able to lock up the tires with enough force applied to the brake pedal. Assuming, of course, that everything is working properly.

Without abs, in a panic stop situation, it is the responsibility of the driver to apply the maximum amount of braking, while still keeping the wheels rolling. This will probably require modulating the pedal. If the wheels are not rolling, you don't have any control.

Maybe you should practice panic stops on surfaces with varying degrees of grip-- gravel/dirt, wet asphalt, dry concrete & pavement, etc. Especially since you've modified the braking system, you've got to get a handle on how it feels under different conditions.

[555BCTurbo]

^ Pretty much dead on...


You ought to practice your threshold braking on a lightly traveled road

[SILINC3R]

sounds good and yea i know it was my fault cause i pressed it to hard. how fast should i try it at like 10-20. i have wanted to test the brakes but am afraid of slaming on the pedal. feel like i might hurt something

[skid542]

You should start slowish and work your way up to speeds that resemble actual daily driving.

You won't hurt anything as long as you don't leave the tires locked - you can flat spot the tires this way. But you won't hurt anything else on the car. Do make sure you have room on the road as you will likely have to do a little counter-steering when you lock them up.