Hey Guys

How does the brake compensator on the 4bie work? I'm assuming it can't be based on hight like the normal ones, due the the self levelling of the hydro's.

Is it based on the pressure of the hydraulic fluid? More weight on the rear = more pressure in the system = more rear bias?

I remember that to bleed the hydraulics you have to open a bleed nipple on the brake compensator. I have deduced that this means the hydraulic system and the brake compensator are linked?

As the car is now lighter (I will put up a build thread on why this is at some point) will it not be shifting more of the braking up front? Is there a way to adjust it?

Ta
Cam

This is all I can find.

If you check the Mi16x4 workshop manual there is a decent section in there (did you get a copy of it? If not I can send you a link to download it).

When I was considering keeping the rear suspension standard on my car I had decided to ditch the original brake compensator and fit a fixed bias valve. This way you can tune the braking to conditions etc. Just blank off the hydraulic pipe coming out of the sphere holder and re-plumb the brake lines (I assume you will upgrade to full braided hoses running internally anyway?).

As I found out to my cost one day on the M4 the compensator is a single point failure! The sealing failed between the two halves of the unit and I lost all my brake fluid whilst travelling at 80mph in the outside lane with a car full of people!! Not much fun. Definitely get rid of it!

^ Yeah I have a copy of that thanks.

Woah! I'll look at replacing all of that!. That combined with the ABS units habit of causing total failure also (mine has been removed), It seems the odd's are stacked against 4bie drivers

Thanks Peter. Looks like it is driven from the hydraulic pressure. Looks like the wheels are controlled individually? I assume the incriments are the same though. I.E it won't put more braking force on the L/F wheel than the R/F wheel.

The one that failed on me was useless afterwards as it would never seal again properly. If I remember rightly looking at it inside there were two independent pistons in the smaller half of the unit, one for each rear brake. The hydraulic pressure from the suspension would press these in under load allowing the brake fluid to flow, and when the load lifts off them the reverse would happen. As there was only one feed from the suspension that actuates both pistons I doubt that there is much independent braking force distribution, although there might be a little bit.

Personally I think it would be much safer and more sensible to ditch it if you want to do serious track work. If I can find that old unit (I can't remember if I chucked it or not) I will take some photos of the internal workings!

So you have successfully replaced yours? Would you be able to provide details o what you did?

Ta

Well yeah, I have kinda replaced mine I actually have had turrets welded into the rear of my car so that I can fit coilovers that will attach to the original suspension arms. I was orginally planing to use the standard rear suspension, but for ultimate tunability I decided to fit a more conventional system. I was expecting the original system to be OK on track, but it is far more complicated so I wasn't certain how reliable it would have been.

If you are planning to run it then I would do as I suggested a few posts back about replacing the original valve with a fixed proportioning valve and re-plumb the system accordingly. Alternatively you could fit an aftermarket pedal box (again something I have done - I fitted a OBP Peugeot 205 box that went in quite nicely) then you could have a balance bar adjusting the front/rear brake proportioning. Depends on your budget really

Sticking with standard rear susp at the moment. Need a roll cage before I could even contemplate taking on a job like swapping it out for coilovers (would require massive amounts of certification here to be road legal)

Will look at replacing the valve.