1973 R107 rear caliper not fitting

[hubby]

1973 450SL. I purchased new rear calipers (1234200683 new) the left one went on great, the right one is hitting on the rotor backing plate where there is a cutout for caliper. the flange on the caliper is thicker. (circled in photos) I had some old calipers from a w123 that are the same as new ones purchased that should go on R107 also, so I know they are correct. I know I have to change out the brake hoses and eliminate some extra parts, that isn't the problem. Anybody else have this problem? Do I bust out the grinder?

[Todd Miller]

Looks like a very different caliper when comparing the left area of each, in our first photo. Maybe there was a serial number break and "early" production cars got one, and "later" production cars got the other? And maybe there's an internal difference, like piston diameter? I know this was done on the W108's because I swapped a 4.5 rear axle into my coupe. I could find the small piston "later" version calipers all day long, but the early, large piston version that my '66 needed, was a challenge.

[Sugar Bear]

Looks notably different, could have been boxed incorrectly. I'd try to find the correct/exact one or have the old ones rebuilt with sleeves if necessary. I'm not comfortable with mismatched brake parts.

Good luck!!!

[hubby]

The later versions are supposed to work, you have to change the brake hose. I tried fitting the caliper from my w123 parts car and it still doesn't fit.