Brake Bias

[benz-tech]

My brakes seem to have too much front bias. On a hard stop, the ABS seems to kick in too early backing off the fronts. I have a '91 318i, H&R sports, braided steel lines, fairly sticky street tires and a well-bled system. Brake pads are unknown. The rear rotors are clean like they are doing some work, but I'd guess its not much. The front pads are also understandably wearing more quickly. Those of you that have stiff/lowered cars, have you noticed this? Do I need to add a adj proportioning valve? or should I play with brake pad compound first.

I notice that the normal weight-shift of a stock car is gone with the stiffer suspension, so I figure that the amount of front brake needed would be lower. Just a theory.

[AndrewBird]

Rear calipers may be worn/rusty and aren't functioning correctly. Pull them and take a look at the pistons.

[jlevie]

An E30, like most BMW's, has a distinct front brake bias. Subjectively it seems like about a 75:25 split. So what you are experiencing may be normal. The slight reduction in weight transfer to the from the Sport springs would, if anything, increase rear braking. So your suspension mods aren't the cause.

Possibilities are a bad bias valve, sticky rear calipers, or an obstruction in the fluid path to the rear wheels. The latter could be a crimped line or a problem in the ABS unit.

[benz-tech]

Ya know, when I bled them a while back, the fluid flow was very low in the rear. I know it is always lower but it seemed to be a trickle. I will check the Pvalve and make sure the calipers move freely. THX

[Just Scott]

I have a similar issue with fluid flow to the rear.

Have you fixed this yet?

[Just Scott]

My factory brake pressure regulator had a bit of gunk in it. Pretty easy to remove, disassemble and clean. I used brake cleaner and air to blow it out.

[benz-tech]

Haven't had a chance to fix mine yet. I will prob look at the valve first.

[benz-tech]

An E30, like most BMW's, has a distinct front brake bias. Subjectively it seems like about a 75:25 split. So what you are experiencing may be normal. The slight reduction in weight transfer to the from the Sport springs would, if anything, increase rear braking. So your suspension mods aren't the cause.

I disagree here, or, at least need a better explanation. With stock suspension, the front of the car dives and loads the front wheels, giving them more traction. BMW knows this, so they bias braking toward the front for a stock car. Also they designed-in reduced rear braking force since the rear wheels are unloaded a decent amount.

On a car with stiffer suspension, and, susequently, less weight transfer to the front during heavy braking, the stock-based braking system is unneccessarly (sp) baised toward the front when the rear can now do more of the braking.
My brakes still may have some bugs to work out so the above argument is purely academic.