Brake proportioning valve location?

[aeronaut]

Has anyone successfully added a brake proportioning valve to an ABS equipped E36, or other similar car?

The big question; install before or after ABS pump/solenoids? After some thought and comments from others, I think installing prior to ABS pump is the best option. I THINK, because most of the ABS modulation occurs between the pump and wheel cylinders, there's less chance of a surprise by mounting the prop valve upstream of the ABS. I'd really like the option to keep ABS; helps save that inside unloaded tire from flat spots. (Easy enough to disable ABS if this all causes problems.)

Just FYI, the ABS system on E36's are purely pass-through when no tire is near lockup, and, both left/right rear are on one hydraulic circuit. So it'd be easy to install the prop valve upstream or downstream of the ABS pump.

[aeronaut]

Wilwood proportioning valved installed, prior to ABS pump on rear circuit. Preliminary results are good! Rainy day, so easy to get to lockup and get into ABS at slow speeds. At about 75% adjustment range (that is, 75% of the maximum rang from 'normal'), fronts/rears are locking at about the same time. This will all change on track and in the dry of course. So some tweeking at the track is expected. But, this is already so much better than prior.

I made a bracket and installed it on top of the ABS pump. Can reach it easily in the engine compartment.

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[theweich]

Sorry to refloat the thread, this worked for you? I want to adjust the brake bias using 4 piston braking front and rear but using abs.

[aeronaut]

Sorry to refloat the thread, this worked for you? I want to adjust the brake bias using 4 piston braking front and rear but using abs.

Yep, I've moved on to a different solution, but these work as advertised. They have a "knee", so for example, the bias will be stock up until some pressure, then the rear pressure will diverge (lower) from stock bias. Which means, you may have to adjust (move the knee lower) in the wet vs dry.

[olemiss540]

Mine is also in line with the rear master outlet before the abs pump.

[theweich]

Yep, I've moved on to a different solution, but these work as advertised. They have a "knee", so for example, the bias will be stock up until some pressure, then the rear pressure will diverge (lower) from stock bias. Which means, you may have to adjust (move the knee lower) in the wet vs dry.

Sounds good, my idea is to reduce the brake bias, I have calculated that it would be something like f62/r38.


What other solution have you worked out? ABS MK60?

Mine is also in line with the rear master outlet before the abs pump.

I imagine that, as the colleague says, you don't have any braking problems, do you?

[aeronaut]

Sounds good, my idea is to reduce the brake bias, I have calculated that it would be something like f62/r38.


What other solution have you worked out? ABS MK60?



I imagine that, as the colleague says, you don't have any braking problems, do you?

If by "reduce the brake bias", you mean you want to move bias rearward, the bias proportioning valve won't work.
(The valve will only reduce pressure, not increase. And while I've heard some folks mounting it on the front brake circuit, most will tell you not to do that.)

I now have dual master cylinders and a mechanical bias bar (and no booster).

[theweich]

So, if I understand correctly, the bias brake will be the same but the pressure could decrease, right?

[olemiss540]

The pressure will decrease to the rear brakes shifting bias to the front. These cars all have a front bias in stock configuration due to weight transfer during braking requiring the front wheels to have more braking ability (since the front end will have more tire friction capacity due to the heavier loading at that axle). Depending on changes to the factory braking system by a driver, that is what requires rear braking to be even further reduced and a bias valve implemented.

Basically, you definately aren't targeting a 50/50 brake bias ever. That would cause rear lockup ASAP which is extremely slow and extremely unstable.

[theweich]

The pressure will decrease to the rear brakes shifting bias to the front. These cars all have a front bias in stock configuration due to weight transfer during braking requiring the front wheels to have more braking ability (since the front end will have more tire friction capacity due to the heavier loading at that axle). Depending on changes to the factory braking system by a driver, that is what requires rear braking to be even further reduced and a bias valve implemented.

Basically, you definately aren't targeting a 50/50 brake bias ever. That would cause rear lockup ASAP which is extremely slow and extremely unstable.

Then, using proportioning valve could change the brake bias?

[olemiss540]

Then, using proportioning valve could change the brake bias?

Yes, except a bias valve can ONLY reduce the pressure. Putting a bias valve on the rear can only increase front brake bias/decrease rear bias. Putting the valve on the front pressure line is required if you wanted to shift brake bias rearward.

[theweich]

Yes, except a bias valve can ONLY reduce the pressure. Putting a bias valve on the rear can only increase front brake bias/decrease rear bias. Putting the valve on the front pressure line is required if you wanted to shift brake bias rearward.

So just to make sure I understand, if I have a 60/40 brake bias and I want to move the brake bias to the rear axle, I install a proportional valve on the front lines and if I have a 60/40 and I want to move brake bias to the front axle I install it on the rear axle and I can leave the braking at 70/30 for example, right?

[olemiss540]

You have it.

[aeronaut]

Yep, you got it. (Although, most recommend not installing this type of valve on the front, because it's very non linear).

[KermitFrog]

Hi.
After read all the comments, i doesn't have a clear idea...

If i correctly understood, the proportioning valve remove pressure in one channel and sends this pressure removed to the other channel.
If the valve is installed in rear channel and i configure it to remove 10% of the pressure in the rear channel, this 10% will be sent to the front? or simply this 10% is lost?
But... if the valve is installed in rear channel, how can send pressure to the front channel?
Or the valve has connection for the 2 channels while only can reduce in one of them sending to the other this pressure?

Thanks in advance.

[olemiss540]

No. The brake fluid reservoir is mounted straight to the brake master cylinder. That splits the fluid pressure into two lines (front and rear). So adding a proportioning valve is done on the brake line going for the rear brake fluid only. All it can do is reduce pressure on ONE circuit. It can not increase pressure on a second circuit.

You are just changing balance front to rear by lowering the fluid pressure going to the rear calipers.

[aeronaut]

No. The brake fluid reservoir is mounted straight to the brake master cylinder. That splits the fluid pressure into two lines (front and rear). So adding a proportioning valve is done on the brake line going for the rear brake fluid only. All it can do is reduce pressure on ONE circuit. It can not increase pressure on a second circuit.

You are just changing balance front to rear by lowering the fluid pressure going to the rear calipers.

Bingo.