Best way to re-plumb brakes minus abs....

[jaistanley]

Hi guys..

The time has come to get the S50 back on the road (my hack MX-5 is getting a little 'tired'). When I parked it it was with the condition that the next time I drive it the brakes would be up to the job of reining it in in a reliable, confidence inspiring manner.

Till now they have had a vauge feel, with a 'damped' feel to the pedal (not bleeding issue). They should be excellent.. The recipie is good. I have MCoupe front and rear disks and calipers, with an Audi coupe 25mm master cylinder. Braided lines all round and ate blue fluid.

I think the trouble is two fold.. The E30 abs hasn't been wired to work with the E36 sensors so is basically just a large reservoir/labirynth for the fluid to pass through. Also, the original car had two lines running to the rear, whilst the E30 setup I am using has a single line that splits at the rear beam. I think that the larger master and slave cylinders are meaning that the fluid is having to squeeze through the narrow bore and creating the damped feel. It is compounded by the performance friction pads that require too much warming to be any good on a road car that is a good 2-300 kilos lighter than the donor.

I am going to fit a new set of disks and road compound pads. I also want to run two lines to the rear of the car and two lines to the front from the four outputs of the master cylinder. This will remove the ancient ABS unit that I dont use anyway.

My question is about the best method for plumbing it in. I have always understood the best way is to split front rear/left right.. Ie the front two outputs of the master cylinder to the right front, left rear and the rear outputs to the left front right rear. Is this so?

Also: The E30 has a proportioning valve/acceleration valve thingy in the line. What do I need to use going forward? The donor car I took the brakes from didn't seem to have one. It did have abs though. The way I see it is I have approx the same weight distribution, same master cylinder and good tyres all round. I imagine the brake bias set by the ratio of the rear slave cylinders to the front should be spot on..

Can anyone assist me?

Many thanks in advance...

Jai

[beer]

If it were me i would start simple.

Double check the system is all bled through correctly and use a pressure bleeder that fits to the reseviour if you can. They make for a much easier and thorough job of it.

[jaistanley]

Done that many times.. Like I said, it's not a bleeding issue. There is plenty of pedal and definitely no air in the system....

[beer]

How many miles has the component system as a whole covered since you fitted it and got it all up and running?

What im aiming at is, has everything had chance to completely bed in over a few hundred miles or so?

[ian332isport]

Jai,

I think the biggest problem with brakes on these conversions is the less than optimal (small) servo that is generally fitted.

I'm still running fully functional E30 ABS on my car and don't have any issues at all. I doubt you will see any improvement from removing it. Ditto for installing an extra line to the rear.

Have you considered fitting the hydraulic servo system like I use ? I appreciate there's a bit of hydraulic work required, but you do get power brakes that work extremely well.

At the end of the day, the E30 brake mechanics were designed to have a particular mechanical ratio that will work with the standard sized servo. If you reduce the size of the servo, you will be forced to push a lot harder to get the same braking force. You could change the mechanical ratio of the pedal to compensate for this though.

I believe a lot of people with M50/52 & S50 conversions are less than happy with their brakes. It's the smaller servo that's the common link.

Ian.

[jaistanley]

I have heard tale many times that the E36 sensors wont work with the E30 ABS, but nearly always in cases where they are using different sensor rings front to rear.. I had originally intended on wiring the E36 sensors to the E30 abs to try it, as I have E36 rings all round (MCoupe rear arms, Mcoupe (M3 Evo) front struts) but never got round to it. I have never had a car with abs, except for company cars and always found it intrusive when I did. I would ideally like to retrofit E36 four channel abs but the ammount fo work I'd have to do over the next month to get the abs working would be prohibitive..

Ian, I agree that the car is under servo'd. The mechanical ratio is two fold: The mechanical ratio of the pedal, and the physical size/area of the disk pads. Since I have increased the size of the brakes from 270 to 315 on the front and 270 to 312 on the rear I had hoped to mitigate the smaller servo to a certain extent. I'm still not convinced that this smaller servo is the source of my issues though. If the pedal was simply very hard to press, I would agree; but in my case there is a soft damped (slow to press in) feel at first that quickly firms up as you press the pedal through its travel. The brakes are certainly there, just not quite consistant enough. The performance friction pads are to blame a bit too.. A friend fitted them to his E36 M3 and says he gets a similar soft/vague feel at first, unless they are hot.

I removed the ABS unit last night, and drained the system ready for more work. I think I will continue to plumb it up as a simple cross split system, running two lines to the rear. This will also allow me to later fit a four channel system if I think it is neccessary.

I currently have the smaller MK2 golf servo in there. Can anyone remember which servo was later recommended to M50/S50 installers? I seem to remember Clio (plastic winged) ones were a tiny bit bigger and offered a bit more assistance. For now, fitting the hydraulic system from the 7 series is a little too rich for my blood! A lot of effort and parts required to get sorted in the month(ish) that my Mazda still has MOT for...

Many thanks for your help guys...

Jai

[DanThe]

Golf servo is pants Jai, ive only ever had good results from fitting clio servo's

Cross split systems are a thing of the past

[daimlerman]

Plastic wing Clio servo is what I am using,pedal 'feel' is slightly different to the standard system in my other E30,but it stops just as well.

[jaistanley]

I had a feeling Noah used one on the ark... How best to plumb them then? Two to the front, two to the rear from common outputs on the master cylinder? I suppose it would offer more consistancy across the car (in-case the pressure front to rear of the master cylinder isn't the same).

I'm definitely loosing the E30 abs; for now at least. I either want more modern four channel or nothing really. Not because the E30 stuff is the work of the devil, but because all of the effort to get it to work, and I'd still only have abs from the mid 80's!

Which Clio servo shall I hunt and gather then? Is there a specific one?

Jai

[DanThe]

Some E90 race cars are using E30 ABS systems

Just pipe it up as per standard E30, airbox FTW though

[Taxin]

In my opinion your brake system is completely unbalanced you have a extremely large pad surface and nothing to push them with and the Golf and Clio servos in my opinion are just a way to get the engine to fit and are a downgrade to the original setup. Have you considered fitting the E34 V8 servo.

[jaistanley]

I guess your oppinion is based on gut feeling?

Anyway.

An update on this. I stripped the Clio servo down to components and measured the rod/stroke. Compared this to the Audi master cylinder I had and had to modify the push rod inside and the master cylinder itself slightly. I dont recommend this AT ALL if you dont know what you are doing, but in my case (I am a smart arse) it was all gravy. The key to this operation is allowing enough clearance between the servo push-rod and master cylinder so the internal valve is open, but leaving it close enough that it operates almost instantly when the brakes are pushed. I guess about 0.3-0.5mm.

Gave it a paint in my favourite hammered black finish (basically textured metallic) and re-assembled with PTFE grease and some tire soap on the diaphragm seal and refitted. You have to pre-load the servo, get it in the right orientation and hammer the tabs in all round. NOT easy on your own!

The brakes were plumbed minus the ABS and new road pads and disks fitted all round. Bleeding was very simple and with a common or garden easy bleed. I then adjusted the E34 pull rod so there was zero play and no pre-load to the cylinder before the pedal was pressed.

Results:

WOW!

The brakes are 100% much much much better. Instant response, HUGE power, excellent balance and bias, and very good modulation. They feel extremely modern, not like the tat setup I had before.

I think the biggest difference is the Clio servo and the adjust thereof. I think the Golf servo simply didn't have enough pneumatic force, and that the internal rod was too short. This meant that the 'damped feeling' I was talking about was the initial stroke of the piston without servo assistance, followed by the normal (but heavy) feeling of the servo assistaed braking. I could have possibly perservered with the E30 ABS and tried to get it talking to the E36 senders (has been done before, I am lucky that mine are E36 all round, not just the front). I might look into fitting later E36 M3 Evo ABS. Dual channel rear and switchable ast (if its possible). It'd be a lot of wiring and fecking about though, and I am VERY VERY happy with the brakes at the moment. They are the best E30 brakes I have experienced so far...