I was recently PM’ed asking if there was any way that this setup could enable a larger rotor to be placed under a 15 inch wheel. I replied that I wasn’t sure, while Mercedes did offer a caliper configured for a 312mm disc - not far from the OE 300mm diameter – there might be a problem finding a rotor that would slip over a modified factory or Kore3 hub and in the right thickness to mate properly with the caliper.
The more I thought about it though; I began to wonder if there just might be a way to make it work. As mentioned before, M-B uses a 5 on 112mm (4.4 inch) bolt circle, which if you’ve reworked a B-body rotor to fit inside the Corvette rotor, you know there is very little extra room to play with. It seemed unlikely that 5 on 5 inch hub could be placed into a rotor designed for a 4.4 inch bolt circle when it has all it can do to fit into a rotor intended for the 4.75 inch pattern. Nevertheless, I suppose that I should at least check.
Some time ago I had tucked away a couple pairs of rotors retrieved from a Mercedes dealer’s discard bin. Find rotor, find spare hub, place rotor upside down on workbench, try to set hub into rotor. Now that wasn’t what I expected… Fitting the hub to the rotors revealed that if the center bore was enlarged, they should fit.
Time to do some machine work. I collected up the various bits & pieces and headed to the shop. I began by opening up the center to the B-body hub diameter and set the hub into the reworked rotor. It dropped in as hoped, and fit at least as well as it does in the GM stuff, perhaps even a bit better. I followed up by drilling them for the 5 on 5 inch bolt pattern. As both operations are required to fit a Corvette rotor anyway, no additional cost would be incurred by choosing to start with the M-B units. This opens up more options to choose an appropriate rotor for conversions, in both diameter and offset, and presents some possibilities that would be otherwise cost prohibitive.
Looking quickly at a 15 inch solution, a good place to start would be a 2003 - 2006 E500 / W124 chassis as they used a 312 mm x 28 mm rotor and corresponding 4 piston caliper.
Modified 345mm Rotor:
Modified 330mm rotor with B-body hub:
Caliper for use with the 312mm rotor - Note the "312" cast into the frame:
Comparing them to the ML calipers posted earlier, one can see that the bridge frames are shaped differently to accommodate the smaller wheel.
OK, that was neat, but admittedly there is limited interest in a 15 inch setup. Does anyone else care that they could use M-B spec rotors? Is a point to all this? Yes, there is. Hang on, we are getting there.
If you recall, this thread started when OP asked if it was possible to use the 8-piston 4-pad calipers from a 05 CLS55. Awhile back, while searching for rear calipers, I had come across a wrecking yard offering a pair, and although I didn’t know what to do with them just yet, perhaps they might be useful someday. Once they arrived, I began looking to see what it would take to make them work.
Sliding the caliper over the Z51 rotor showed they were so mismatched that I didn’t even try locating a Z06 front to test fit, as it wouldn’t tell me anything I didn’t already know. Finding a rotor large enough in diameter to accept the caliper and in the necessary 36 mm width that didn’t require applying for a gold card was proving to be difficult. I even considered trying to find something in a narrower - say 34 mm - width and fabricating a set of titanium heat shields to make up the difference. No obvious solutions presented themselves, so progress had pretty much stalled as the rotor situation was looking pretty bleak and the need to complete the current upgrade was taking precedence.
But the recent discovery that the M-B rotors might also be used renewed my determination to see if the calipers could be made to work. More internet searching ensued. The ’05 CLS55 uses a 360mm one-piece style looked like it might work. The ’06 CLS55 uses a 380mm two-piece design. The larger diameter would be preferable, as experience showed such a large caliper will be very close to the spindle. Unfortunately, they list for $985.00. Each. 360mm it is. A trip to eBay yielded a pair of NOS Mercedes rotors advertised for an E55, accessing the online M-B parts system verified they are the same PN as the ‘05 CLS55. Incidentally, even on these assemblies M-B still lists the same rotor for left & right, which contradicts the popular thought that left & right directional vanes are a necessary feature.
Once the rotors were modified to fit the B-body hubs, things began shaping up. The spindle, although already modified for the 340mm conversion, required further trimming to accept the caliper. I started on a set of mounting brackets, but didn’t have a 12mm x 1.5 tap needed for the caliper-to-adapter bolts on hand, not wishing to wait until one could be located, I just re-drilled the Mercedes radial-to-axial adapter bracket as a temporary solution to check with. The parts were then assembled, using shim washers to move things to where they wanted to be.
As you can see things are pretty tight, and I haven’t installed it to verify that everything is going to clear the suspension, but the potential is there. Using a Z06 assembly as a benchmark, it looks to be least in the ballpark.
Previously posted photo of a B-Body spindle with the Z06 caliper:
I did verify that this combination easily cleared an 18 inch wheel I had on hand. The alternate rotors are available in both 380mm & 390mm diameters, I suspect using either of them will require a 19 inch wheel at a minimum.