By Ken Beck on Monday, July 02, 2001 - 05:24 am: Edit

Has anyone try to by-pass the factory brake pressure valve to increase brake caliper pressure. LR factory has a brake pressure valve (under the brake master) to reduce line pressure. It us known that brake pressure needs to be reduce for the rear brake: ie (front brakes should always lock up before rear brakes) when brake is apply, weight transfer to front wheel, and weight is reduce from rear wheel; reducing pressure to rear prevent it from locking and loseing control. (this also apply to ABS equipped vehicles)

However, LR reduce pressure to the front brakes too, has anyone alter these setting.

Warning, do not try this at home, messing with brakes might cause serious accident.

Please reply if you actually has done it... no theory please to save bandwidth.

Ken Beck

By Mike J. (Mudd) on Monday, July 02, 2001 - 06:56 am: Edit

If your pads and rotors are replaced or good there should be no need to alter pressure! MJ

By al hang on Monday, July 02, 2001 - 08:29 am: Edit

won't work, have you ever seen the brake pads on a rover? they are just too small(except on new style rangie and d2) increasing pressure won't improve braking cause there is not enough pad there to be effective.

-al

By Milan on Monday, July 02, 2001 - 09:25 am: Edit

I'm not aware of any hydraulic brake system on OEM passenger cars that reduce pressure to the front. That includes LR. The sole purpose of the "pressure reducing valve"/"proportioning valve" is to keep the difference between front pressure and rear pressure in the correct proportion to each other (hence the other term "proportioning valve"). Front is always applied full pressure and the rear is reduced depending on how much you brake.

The only thing that will reduce pressure to the front is the ABS but only when engaging.

By Ken on Monday, July 02, 2001 - 09:40 am: Edit

Check the factory manuel, both the front and rear brake lines pipe into the pressure valve. A reduce pressure to the rear is call Cross-over pressure. Yes I understand what it does, my question is still:

Has anyone by-pass the proportion valve to the front.

Ken

By pjkbrit on Monday, July 02, 2001 - 11:13 am: Edit

Would'nt piss about with it, that's a lot of truck to stop and if you get it all wrong, you will only find out by hitting something or someone.

By Milan on Monday, July 02, 2001 - 02:38 pm: Edit

What year Disco do you have?

I know you're not much interested in this dicussion other than an answer to your question but I think it's a good topic with possible benefit to others.

On my 96 the lines go to the ABS modulator, then to the proportioning valve. The ABS controls the pressure when the wheels spin and the proportioning valve controls the difference between front and rear. Again, as far as I know, under normal conditions (or when the ABS is not engaged) the fornt circuit runs at full pressure all the time, only the rear gets reduced.

By Milan on Monday, July 02, 2001 - 02:51 pm: Edit

I, of course, meant to say "...when the wheels lock up" not spin.

By Ken on Tuesday, July 03, 2001 - 03:37 am: Edit

It is a 95 Disco. Most of the time I find the discussion helpful and somewhat entertaining. I kept the question specific so people don't talk about brake pads, rotors, or air in the brake system.

On my 95, the brake line from the master cylinder (both lines) goes to the proportioning valve first before going to the ABS unit. On a dry day, in a straight line, can you lock (before ABS kick in) the brakes (or feel the pulse of the ABS?)

TIA
Ken

By Kyle Van Tassel (Kyle) on Tuesday, July 03, 2001 - 08:24 am: Edit

Ken , the people on the board are pretty much free to post what they have to say about what ever. You have something against them telling you that it would not be wise to do this? I have never set myself on fire and run around my back yard but I have no doubt it would be painfull. The same gos with your proportioning valve...You are playing around in an area that could get painfull. The addition of ABS to this equation makes it even worse..

Kyle

By Milan on Tuesday, July 03, 2001 - 01:38 pm: Edit

Ken,
I have my ABS disconnected all the time and so I can lock the brakes up. With the ABS connected it would kick in before the wheels would lock up even on dry pavement.

I actually mislead you a bit with my previous statement. I have lines going from the MC to both the ABS modulator and the proportioning valve. I suspect you have the same. The front (secondary) circuit goes to PV first and the rear (primary) goes to ABS modulator first.

I also believe the proportioning valve is the same on all vehicles, ABS or not. That's why I think you'd be able to plumb the ABS modulator right out of the system but I have not done so yet, so I don't know for sure. I posted more details about the plumbing on the LRN board, so you can search there if interested.

Alternatively, you could bypass everything beyond the MC and plumb the front circuit directly from it. Then put in an adjustable proportioning valve between the MC and the rear brakes and you're done. I may actually do this.

Regardless of the above, I still stand by what I said about the pressure reducing/proportioning valve. Where did you get the information that leads you to believe the pressure to the front is reduced? If you want to test this, you could unplug your ABS and test your brake's lock up somewhere safe.

Let me know how it goes or what you think.