Converted from Drums to Discs

[Driftit 1948]

My E30 series car has been converted from drums to discs. Now I was just wondering about the valve that controls the rear brakes. Is this valve (can't remember the bloody name of it) any different on the models with Drums?

I spoke to another driver over the weekend who had done the same conversion and was also looking into this.

Now as for my peddle not returning. It is actually a little more than this. My brakes are actually staying on. To the point where I lost a few positions coming onto the back straight. Until I pulled the peddle up with my foot. Didn't worry me too much over the weekend as there is only two braking points for us really. But was another thing to try and remember.

Is this the booster playing up? I have tried adjusting the linkages. I drove the car home from the track and pretty much had to hold the peddle up the whole way home. So was getting worse over the two days. A light on my dash was flicking on and off occasionally.

: o : sort of looks like that.

Edited January 25, 2009 by driftit

[smokenbaby 0]

I can only suggest that you have done something wrong with the conversion and that is why the pedal is not returning (linkages don't need adjusting and the booster/master cylinder doesn't need changing unless it has 2 pipes for the front brakes). All you need to do when doing the conversion is to MAKE SURE you put the Bias/Proportioning valve from the donor car in. I did this conversion on my old E30 road car without putting the valve in and it gave it to much rear brake bias. Tended to lock the rears before the front and it was not to fun in the wet when needing to stop in a hurry.

The other thing come to think of it in respect of the brakes staying on, is there may be a fracture in the diaphram inside the booster and this is allowing the vacuum from the motor to apply the brakes and retain pressure. But for this symptom I would have to say that every time you applied the brake it would compound the problem to the point that your brake were locked on and you would stop.

Hope this gives you some insight and you will be able to diagnose the problem.

[Forrest 35]

When my car is road legal in about a month I will be keen to come back to this thread as I have too swapped to discs in the rear so once I had trialed can give back some comments too.

[Driftit 1948]

The brakes only started playing up on Saturday morning. And I did the conversion quite a while ago. I have a feeling it is the booster causing the probs. Will get it rebuilt. The brakes stay on. But I can hold them off by pulling the peddle back. Could be only a small split.

And I never installed the proportioning valve from the other car. I will get one to put in. I never changed this over as the guide I followed for the conversion never mentioned it. Easy fix though.

Cheers mate.

[smokenbaby 0]

When you go and get a valve, I would suggest you buy the master cylinder and booster at the same time. The valve is bolted on where the cylinder bolts to the booster. By buying the whole lot you will then only have to change the shaping of the front brake lines to fit the valve. If your car is currently running a cylinder with 2 front line plumbed into it you will need to make a new section up between the cylinder and valve with a 'T' in it as the valve only has 1 port for the cylinder to valve front input.

Is a bit of a pain and I am reserved about doing it. Hence why I didn't fit the valve to my car once I had worked out why the back was locking up first.

Picture attached is not indicative of the actual look of the valve but shows what I mean about the input and output for the front brake lines.

[Driftit 1948]

Hmmm I see. I am going to drop the car at my mates Pitt Stop tomorrow morn and will look at my other 320's setup and see what needs to be done. I may run out of time to sort out the valve this week. But will get into it next week.

Needs to be sorted. Will keep you updated.