Hello folks!!
n t
Several weeks ago I bought a set of rebuilt calipers and new drilled/slotted rotors for a 560SL to mount on my W123.

Yesterday I tried to fit the parts in my car and they are not even to close match. The rotors do not fit the W123 hub, as the internal diameter is smaller than the hub. Also, the rotors are meant to be mounted on the outer part of the hub, so they only have the wheel lug holes. This can all be solved with some machining, but that's not part of a drop in swap...

The big problem comes with the caliper. The mounting points are wider the the mounting points in the W123 spindle. To make it worse, the spindles have threads were the original calipers are bolted to, but the R107 calipers also have threads were the spindle is bolted to the calipers.

As a side note, the R107 rotors are about the same diameter as the early W126 rotors, so I doubt there would be much gain in braking power.

I have attached some dimension charts of the rotors for your comparison.

So far, I would say this has been a BIG FAIL! I'm still going to try to figure a way of fitting them in my car, but if the required mods are too complicated, I'll just sell the parts I bought to any W124 or W201 owner that is looking for a brakes upgrade. Yes, the R107 parts fit the W124 and W201 models.

I hope this info is useful for you.

Attached Thumbnails

     

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1982 W123 300D NA Euro, 300K Miles, 4-speed manual, 3.46 rear diff, early W126 front brakes, Penta rims with 205/60R15 FH900's, custom fitted (by me) audio system, more to come into the money pit... Soon to be installed: Bilstein HD, R107 front discs and 4-piston calipers, HD Suspension springs, wagon front swaybar.

if they are the same as the early 126 rotors, then the late 126 rotor is far better than dealing with the R107. how many pistons do the calipers have in the 107? perhaps the improved stopping power comes from the caliper, not the rotor diameter>?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

The calipers have 4 pistons each. There might be better performance because of this, but I just don't know if it will justify the required modding to make them fit...

If I had checked the rotors measures beforehand, I could have saved some $$ and time...

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1982 W123 300D NA Euro, 300K Miles, 4-speed manual, 3.46 rear diff, early W126 front brakes, Penta rims with 205/60R15 FH900's, custom fitted (by me) audio system, more to come into the money pit... Soon to be installed: Bilstein HD, R107 front discs and 4-piston calipers, HD Suspension springs, wagon front swaybar.

Yesterday I did some brainstorming about how to make the calipers and discs fit the W123 spindle and hub. Unfortunately, there is no "easy" way. All the alternatives I could think of required major modding and machining time, which I might have access to, but was not part of the project plan.

The worst part is that some cutting and welding in the spindle area might be required and I really don't have the nerve to go down that road.

I have not given up on this, but I can now confirm that this retrofit is quite more than the weekend mechanic can bite.

I'll report back if I can make this work.

In the meantime, the conclusion is that the myth that the 4-piston calipers/discs from a late R107 can be retrofitted in a W123 is not true.

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1982 W123 300D NA Euro, 300K Miles, 4-speed manual, 3.46 rear diff, early W126 front brakes, Penta rims with 205/60R15 FH900's, custom fitted (by me) audio system, more to come into the money pit... Soon to be installed: Bilstein HD, R107 front discs and 4-piston calipers, HD Suspension springs, wagon front swaybar.