Rear Brake Cylinders

1961-1968: a.k.a "Finnie" or "Heckflosse" models
190, 190D, 200, 200D, 220b, 220Sb, 220SEb, 230, 230S, 250SE coupe, 280SE coupe, 280SE 3.5 coupe, 220SEb cabrio., 250SE conv., 280SE cabrio., 280SE 3.5 Cabrio., 300SE, 300SE coupe, 300SE conv., 300SEL
Post Reply
User avatar
Bartman4800
300 SLR
Posts: 1937
Joined: Fri 10 Oct, 2008 12:10 am
Model you own: w111
Location: Perth WA

Rear Brake Cylinders

Post by Bartman4800 » Tue 03 Mar, 2015 8:21 pm

While taking parts from my 60 finnie (drum brakes all around and booster)
And putting them on my 63 finnie (front disk brakes and booster)

I noticed that the older finnie has 1" rear brake cylinders, while the later one has 3/4" rear brake cylinders.

Both have a booster, and I noticed that the Disk brake car has a tendency to lock up its front wheel quite easily.
Would it be a good idea to mount the larger rear brake cylinders on the 63 car?


Regards, Bart
1963 220 Sb Sedan "Kermit" (Australian Assembly)
1960 220 Sb Sedan "Zum Schlachten" (Early German Assembly, with a torsion bar spring for the bonnet) - Stored in Country WA
1981 Subaru Brumby 1.8 with Weber and 5-speed box "little utie" - Sold to another enthusiast!
2006 Ford Focus "daily driver"
2002 VW Passat V6 30V Station Wagon (SOLD - This car into a money pit)
2011 Kia Sportage "Missus commuter Bus"
2002 Mitsubishi Rosa Bus (converting it to a motor home)

User avatar
Jeremy
E Class
Posts: 72
Joined: Fri 24 Jan, 2014 11:00 am
Model you own: w111
Location: Sydney

Re: Rear Brake Cylinders

Post by Jeremy » Tue 03 Mar, 2015 9:27 pm

I think if the front disks are locking up easily that might indicate a problem with them (or your right foot :blackeye: ) rather than a deficiency in the rear drums. If you changed those to larger units it might not work so well with the standard master cylinder and brake bias settings :dontknow:.
1965 220Sb

CraigB
OZBENZ Admin
Posts: 5004
Joined: Thu 23 Jun, 2005 1:18 pm
Model you own: I own multiple different models
Location: Hawthorndene (Adelaide)

Re: Rear Brake Cylinders

Post by CraigB » Tue 03 Mar, 2015 11:10 pm

I agree re locking of wheel, that sounds like a problem, and just one wheel locking? New brake hoses so internals of both of them good and same flow to the front? Not drums, but as an indication of role of rear brakes, the rear calipers and pads on a big 560sel is the same as a W108 from the 60s, but the fronts got substantially larger.
Craig Baulderstone
Lurch
280s's
280SE3.5
280SL
350SL
500SEC's
560SEL's

User avatar
John Green
OZBENZ Admin
Posts: 6611
Joined: Mon 20 Jun, 2005 3:49 am
Model you own: w112
Region: Australian Capital Territory
Location: Canberra-center of the known universe
Contact:

Re: Rear Brake Cylinders

Post by John Green » Wed 04 Mar, 2015 10:00 am

There are multiple versions of the brakes on these Finnies. The trick is to get everything to match. There is a ratio that I could look up that determines what size wheel cylinder you need for a certain size master cylinder and then you need to take the booster into account. And then there are systems (I think on the 230S) where there was a limiting valve between the master cylinder and the rear drums.

If it feels odd when trying to stop and you are sure that all of the various components are operating correctly the usual cause is that someone has swapped in some parts that do not match the rest of the car.
Inaugural OZBENZ national meet this September, all welcome to attend. https://ozbenz.net/viewtopic.php?f=46&t=25165

M.B Spares & Service 14-16 Lyell St, Fyshwick ACT. Ph 02 6239 1099

http://mbspares.com.au - Supporting Australia's Mercedes-Benz Enthusiasts.

User avatar
Bartman4800
300 SLR
Posts: 1937
Joined: Fri 10 Oct, 2008 12:10 am
Model you own: w111
Location: Perth WA

Re: Rear Brake Cylinders

Post by Bartman4800 » Wed 04 Mar, 2015 10:49 am

Thanks guys.

The locking up was at a test drive before I tackled the front calipers issue. And also with very old and rock hard tyres. Locking up was under hard braking only.

John, you are probably spot on with the volumes of the combined brakes. The master cylinder is the same on both, but I think the front calipers have a larger displacement than the front drum cylinders.
That might be why the rears are smaller.

It was worth a question and I think I got the answer. Leave as is and make sure all components are good :dance:

Craig: for your peace of mind: I replaced all the brake hoses this weekend.
I think the rear ones were still original.

I also replaced the oil sender hose. Now this one was cracked! :think:


Bart
1963 220 Sb Sedan "Kermit" (Australian Assembly)
1960 220 Sb Sedan "Zum Schlachten" (Early German Assembly, with a torsion bar spring for the bonnet) - Stored in Country WA
1981 Subaru Brumby 1.8 with Weber and 5-speed box "little utie" - Sold to another enthusiast!
2006 Ford Focus "daily driver"
2002 VW Passat V6 30V Station Wagon (SOLD - This car into a money pit)
2011 Kia Sportage "Missus commuter Bus"
2002 Mitsubishi Rosa Bus (converting it to a motor home)

User avatar
Bartman4800
300 SLR
Posts: 1937
Joined: Fri 10 Oct, 2008 12:10 am
Model you own: w111
Location: Perth WA

Re: Rear Brake Cylinders

Post by Bartman4800 » Thu 05 Mar, 2015 4:16 pm

Oh, and both sets (the 3/4" ones on Kermit as I found out) and the 1" ones from the donor (4 years ago done by Power Brakes) have been resleeved with Stainless Steel.

So if anyone is looking for a set of refurbished very early rear brake cylinders (1" diameter), I have a reconditioned set for sale.


Bart
1963 220 Sb Sedan "Kermit" (Australian Assembly)
1960 220 Sb Sedan "Zum Schlachten" (Early German Assembly, with a torsion bar spring for the bonnet) - Stored in Country WA
1981 Subaru Brumby 1.8 with Weber and 5-speed box "little utie" - Sold to another enthusiast!
2006 Ford Focus "daily driver"
2002 VW Passat V6 30V Station Wagon (SOLD - This car into a money pit)
2011 Kia Sportage "Missus commuter Bus"
2002 Mitsubishi Rosa Bus (converting it to a motor home)

Post Reply

Return to “W110, W111, W112 Sedans, Coupes and Cabriolets.”