brakes conversion. need advice please

[koons]

how do guys,
i have just converted my 316i to a 318is and now i have just put disc brakes on the back. i have also put black diamond drilled, grooved and ventalated on the front the drilled and grooved on the back. my problem is my brakes are crap. the are very spongy and if you press the pedal hard enough it nearly hits the floor. wheels won't lock up either. now i have bleed the system acording to the haynes manual but still no joy. i even tried changing the master cylinders around with another e30 i have and still no good. can anybody shed some light on this for me please. some one was saying that there is a dampner/presasure regulator on the line to the back brakes witch doesn't give enough force to the back brakes. but still the front should lock up? could it be that both master cylinders are crap or is there a different master cylinder for 4 wheel disk brakes?

[Bimmer8604]

That sounds right about the regulator being in the line.

Drum brakes dont require as much fluid to operate than disk brakes. Therefore, the mastercylinder is perportioned differently.

I did a bit of looking at www.pelicanparts.com and noticed the early 318's have different master cylinders than the other cars with Disk brakes. That might be enough info to justify switching the MC.

Also, did you just bleed the system or are you doing a complete flush?

Kyle

[Templ8e30]

My 2.7 was originally a 320i with drum brakes, I upgraded to discs and didn't touch the regulator or master cylinder. My brakes are superb and have never had any problems.

The drum brakes require more fluid pressure for the same braking effect than discs as they aren't as efficient so theoretically a drum equipped master cylinder and pressure regulator should give more rear braking power than disc master cylinder/pressure reg.

Cheers,

Iain T

[jonbuoy]

My 2.7 was originally a 320i with drum brakes, I upgraded to discs and didn't touch the regulator or master cylinder. My brakes are superb and have never had any problems.

The drum brakes require more fluid pressure for the same braking effect than discs as they aren't as efficient so theoretically a drum equipped master cylinder and pressure regulator should give more rear braking power than disc master cylinder/pressure reg.

Cheers,

Iain T

Completely right!!!

You have'nt bleed it out right or you need to go over the rear line's for air leak's as you must of had to change the brake line's to fit the disc brake's. This is'nt something to play with or go by the Hayne's Manual, you need a professional to sort this for you!

[koons]

i just disconnected the joint on the arm for the brake line and the disk brake one matched up perfectly. i'm just after flushing out the system again and bleeding them properly and they seem a little better. still though it takes alot of preasure to get them to lock up on a raod with a few small stones on it. the old man is a carburator and fuel injection specialist so i know a little bit about cars from him but he did it this time. maybe it because of all the weight in the car that its hard to stop?