Best Master Cylinder - M635CSI

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Boggie
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Best Master Cylinder - M635CSI

Post by Boggie »

Hi All,

So, today I plan to raise the car up high and remove the braking system completely. I am restoring/refinishing the calipers myself with original BMW parts and will be fitting them with EBC RedStuff pads wrapped around new EBC G3000 discs. Assuming I can get them off the car in time, I will send all 6 flexi pipes to BF Goodridge this week to make me a set of matching custom stainless hoses and fittings (sleeved in black so they don't look to MaxPower). It seems all the fixed pipes and connectors are available from BMW so I have placed an order.

I plan to fit a new master cylinder whilst I am at it but after some research on the forum I see there are some who have converted to the E32 MC. Is this an upgrade worth doing? I like to retain originality as much as possible when restoring cars but if this is a sensible upgrade and looks close to original I might consider it. Any thoughts please?

Oh, and one last thing; what was the colour of the original calipers please? Looking around the internet I have seen black, silver and red (the latter would look rather nice behind those BBS wheels)...

Thanks,
Ian
1985 M635CSI
Classic Car and Bike Collector & Restorer.
GazM3
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Re: Best Master Cylinder - M635CSI

Post by GazM3 »

I’ve done the e32 750i MC conversion on both the e24 m635csi and the e23 735i. Both had locking brake issues both were resolved and both had improved pedal feel. It looks very oem and unless someone goes over the MC with a set of vernier calipers they wouldn’t know it’s not oem.

Braided brake lines are good also. I use ferodo ds2500 pads and martini rf700 brake fluid. The fluid is as expensive as hell but if you give your brakes a hard time it’s the stuff to get. Better than Castrol SRF or motul rbf600 and doesn’t absorb water so easy as the other 2. U can hammer the brakes to the disks glow without fade. Only prob is the ds2500 are a little dusty, but good on cold stops for a modestly hardcore pad.
BMW’s
84 E24 M635csi
90 E34 M5 3.6
94 E34 540i/6 SC E85
97 E36 M3 euro SC U/C
97 Z3 2.8 widebody

OTHERS
11 Audi S5 3.0 SC
19 VW Amarok V6
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Soperman
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Re: Best Master Cylinder - M635CSI

Post by Soperman »

Original caliper colour was a passivated zinc plate effect, pale gold in colour. Have a look at this photo of an original....
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E24 M635CSi
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Boggie
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Re: Best Master Cylinder - M635CSI

Post by Boggie »

Thanks Gaz,
Is it a straight swap,like for like? I.E. the same mountings and pipe fittings, no need to mod anything?
I don't suppose you have a part number to hand do you? Rummaging about the internet suggests different BMW part numbers for the 750IL but 34311156643 seems to be the right one.
Ian
1985 M635CSI
Classic Car and Bike Collector & Restorer.
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Brucey
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Re: Best Master Cylinder - M635CSI

Post by Brucey »

there are two main differences when you change the old OEM MC to a new (larger bore) E32 one.

1) your new MC is new, i.e. no longer knackered; so if it is causing binding brakes (not uncommon) then that will go away. But then it would if you fitted a new OEM MC too. So no real difference there, then.

2) your pedal pressure (for any given level of retardation) will have to go up. IIRC it is something like 15 or 20% more pedal pressure. You may or may not want this.


IMHO a larger bore MC is a very sensible idea if you fit different front calipers (with larger pistons). But if you have standard brake calipers and don't want to have to push harder on the pedal to stop, stick with the standard MC.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
wattsmonkey
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Re: Best Master Cylinder - M635CSI

Post by wattsmonkey »

I’m not sure the pipes enter the mc in the same place.
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
GazM3
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Re: Best Master Cylinder - M635CSI

Post by GazM3 »

Some people like a firmer feeling pedal. The difference in firmness from oem is not massive. Yes it just bolts straight in with no pipe modification whatsoever.
BMW’s
84 E24 M635csi
90 E34 M5 3.6
94 E34 540i/6 SC E85
97 E36 M3 euro SC U/C
97 Z3 2.8 widebody

OTHERS
11 Audi S5 3.0 SC
19 VW Amarok V6
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Boggie
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Location: Buckinghamshire UK

Re: Best Master Cylinder - M635CSI

Post by Boggie »

Thanks Chaps, will chew that over a while....
1985 M635CSI
Classic Car and Bike Collector & Restorer.
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Brucey
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Re: Best Master Cylinder - M635CSI

Post by Brucey »

wattsmonkey wrote: Wed Aug 01, 2018 7:44 pm I’m not sure the pipes enter the mc in the same place.
I agree; it depends on the car you start with. In RHD E24 the MC varies with the build date; post 9/86 models have a RH mounted MC and it is usually iron bodied, with the connections on one side. Prior to that you have a LH MC which is more likely to be aluminium and has the connections differently arranged. I think there are variations in the larger MC too.

If you are prepared to make up new hardlines, you can make any of these MCs work in any car, but the connections don't look pretty in some cases.

BTW braided hoses give a firmer pedal too; perhaps a slightly larger effect than the larger MC. Both together is a very different pedal feel indeed (if you have standard calipers).

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GazM3
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Re: Best Master Cylinder - M635CSI

Post by GazM3 »

I may have been lucky twice then.

Bmw always have a habit of changing stuff around which is annoying
BMW’s
84 E24 M635csi
90 E34 M5 3.6
94 E34 540i/6 SC E85
97 E36 M3 euro SC U/C
97 Z3 2.8 widebody

OTHERS
11 Audi S5 3.0 SC
19 VW Amarok V6
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