I have read how other model caliper/rotars can be installed to upgrade 300E brakes with those from more current models. In reading other forums, it appears that there may be complications due to ball joints being in the way of the upgrade.

Can anyone help with what model and years will fit the std '89 300E brake carriers without resorting to changing the A arms etc. to fit. Part numbers would be especially helpful.

Thanks.

The '93 400E uses 4 piston ATE calipers in the front, with larger ventilated rotors and is a bolt on upgrade for the 300E, which uses dual piston calipers. Making sure that the rotor/calipers clears your rims should be verified first.

400E brakes (at least the late 294x25 versions) won't fit early 124's with the M103 engine (or any diesel 124). The 400E rotor is 6mm deeper, requiring either the late lower control arms, OR using the 400E's R129 knuckle/hub. The rear brakes are a bolt-on, other than needing to cut the splash shield. Full details, with part numbers etc, are in my brake spreadsheet:

http://www.meimann.com/images/mercedes/W124_brakes/124_brakes.pdf

http://www.meimann.com/images/mercedes/W124_brakes/

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Ooops - forgot to answer your question. The only larger FRONT brakes that will fit an 89 300E, using your STOCK control arms, knuckle, and hub, are the early 500E and the SL320 front brakes (300x28). These may require 16" wheels for clearance, though! Part numbers are in the spreadsheet above.

Getting used calipers, new rotors, pads, etc ends up being a lot more expensive than you think - trust me, BT, DT. You may want to consider trying new stock size rotors on your 300E (ATE PowerDiscs, etc) with Porterfield R4-S pads. I did some testing and found there was very little fade after 5 back to back 80-0 stops (about 3-4 minutes between each stop). From 60-0, there was none. For most street driving, just getting the R4-S pads all around might do the trick. If you roadrace, autox, or drive at warp speeds a lot... then the bigger brakes make more sense. Otherwise they'll just get you more fade resistance from ~100mph, where most of us rarely need it, at least in the USA.

gsxr, how is it that the 400E calipers and rotors bolt onto the W201's stock suspension, particularly the 2.3-16 and 2.6L, that uses the same parts as the W124 300E? Is the lower A arm on the W124 designed/manufactured differently? Replacing the dust shields with the larger 400E units goes without saying, as does the need for the rims to clear, although the 400E did come with 15" rims.

Wern't the 500E brake system essentially a Porsche set up using Porsche calipers?