Clutch Master Cylinder Sizing

Post Tue Mar 20, 2012 10:22 am

Hi,

Does anyone have any information on the size of the stock master cylinder for the clutch on an E30 318is? Are all the E30 models the same size?

Running an SR20DET with the stock nissan slave and the E30 master but the pedal feel is very heavy - I'm not too bothered about the weight its more that the seals in the E30 master went as it wasn't up to the job. Am I correct in saying I need a slightly larger master?

After a bit of reading I've seen the E34 M5 cylinder is a direct replacement, and slightly larger - but finding one of those might be a bit of a challenge.

Does anyone know what other clutch master cylinders can be used to solve this issue?

Cheers.

Post Tue Mar 20, 2012 1:27 pm

All E30 clutch masters are the same, AFAIK.
If the pedal is heavy, you need a SMALLER bore master cylinder. This will require less pedal pressure, at the expense of longer stroke.

Post Tue Mar 20, 2012 1:32 pm

Its heavy but seems to be struggling with the nissan slave, already replaced the master once... Its got a standard clutch in at the moment but its shortly getting an uprated item (paddle), so more than likely stiffer. i can cope with the weight, but just need something that can cope with the nissan bits and not start leaking... Would that still mean a smaller one is required?

Cheers.

Post Tue Mar 20, 2012 3:02 pm

ask theo on here i remember his conversion being a bit special-
i bet he has solved it

Post Tue Mar 20, 2012 3:07 pm

Yeah already seen his numerous threads about it - he remade the bulkhead and replaced the pedal box with a triple cylinder setup and used a normal master cylinder for the clutch. Trying to find something to use on the standard pedal before I go that far, even if it means making a custom bracket from the standard pedalbox... Just trying to find out what other options are out there

Post Tue Mar 20, 2012 7:14 pm

You have a better chance of finding differently sized slave cylinders than masters

Post Tue Mar 20, 2012 9:01 pm

You can get the slave rebored to suit to e30 master.

Hope your project is coming along well

Post Tue Mar 20, 2012 9:05 pm

Il have a browse and see what other slaves fit the S14a box, if not thats an option too I guess.

I've been down there this evening measuring up to see if the servo/cylinder can be moved onto the RH side straight behind the pedals - obviously its doable but its how much work is involved when I may as well bin the lot of and start with a pedal box... Hmmm.

Post Tue Mar 20, 2012 10:07 pm

f0xy wrote:Il have a browse and see what other slaves fit the S14a box, if not thats an option too I guess.

I've been down there this evening measuring up to see if the servo/cylinder can be moved onto the RH side straight behind the pedals - obviously its doable but its how much work is involved when I may as well bin the lot of and start with a pedal box... Hmmm.

It would be good if you could get a servo and mc setup to work on the RHD side of the car. I think a pedal box setup is just as hard as it does require bulkhead modifications as well.

I'd love to see if you get the whole brake setup on the rhd side of the car.
Good luck mate.

Post Tue Mar 20, 2012 10:11 pm

Well I kinda have to modify the bulkhead either way - as Il have to move it towards the turret on the LHD to clear the turbo/manifold (again) or put it on the other side, and its going to be the latter lol.

I had a quick measure before and found out the chassis/inner arch is in the way to fit the servo I used last time, as the clevis comes through the bulkhead well to far over for the pedal.

Post Tue Mar 20, 2012 10:13 pm

I thought that the new shell is rhd?

Then you can cut the battery tray out, and fit servo and mc there.

Post Tue Mar 20, 2012 10:21 pm

It is, and thats what I thought....

But it would require a new back plate making for the pedalbox itself, the bulkhead plating up (as there is already a huge hole there in the wrong place) then I would have a blank canvas to play with - BUT, after measuring earlier even with the battery tray removed the inner arch would be in the way for the servo to fit far enough over in the correct position.

If it was slightly offset to clear the inner arch it would be in the way of the clutch, so there are a few things to look at

Post Tue Mar 20, 2012 10:30 pm

It doesn't have to be all the way to the edge, with an sr20, the inlet manifold doesn't get in the way much at all. The servo and mc can be in line or just to the right (looking at bay from front of car) of the suspension turret.

Post Tue Mar 20, 2012 10:38 pm

Yeah, I know it wont be in the way of the manifold, I was more so on about it wont go far enough over to line up with the brake pedal on the inside of the car... To line up with the original brake pedal clevis fitting it would be into the arch by a bit.

The closest you get is around two inches to the side of it (which then is very close to the clutch pedal)... would need to move the pedals over a bit to make it work properly I think

Post Wed Mar 21, 2012 9:15 am

Going back to the OP, if the master that failed was a used one, I expect the failure was caused by the piston moving into an area in the bore that it hadn't been in before and stirring up the crud. Very common for this to happen after replacing the slave cylinder on a standard set up.
I've just looked at a set of E30 pedals, and it looks quite possible to increase the line pressure by slotting/re drilling the two mounting holes for the cylinder and the pivot where the pushrod joins the arm on the pedal, moving it towards the fulcrum a little.