Front 390mm brake upgrade
#27
Senior Member
However, if we introduce other variables such as what @kenneyd has done with the PowerStop pads, the result may be different. For example, if the new ceramic pads have lesser friction relative to the original pads, then the 390mm rotor upgrade will help to offset more pedal force necessary to maintain decent modulation ability.
Last edited by maxusa; 04-10-2023 at 04:07 PM.
#28
Super Member
Yes, because the brake caliper design wraps over the rotor edge, the larger diameter rotor pushes the caliper with pads out by 15 mm ((390 - 360) / 2). A new bracket or spacers are needed. The contact patch does not change, but the increased radius (leverage) provides the relative reduction in force to achieve the same torque.
#29
Senior Member
The W212 brake caliper design wraps around the rotor edge. This means that it follows the outer edge of the rotor. The pads inside the caliper have basically a fixed position with some minimal play to accommodate rotor/caliper alignment and wear issues. This wraparound caliper design dominates the auto industry. There are nuances like the floating vs. fixed calipers, number of pistons, hydraulic vs. electric, etc.
I have driven cars and motorcycles with the barrel drum-style brakes, but these are much older designs without the rotor/caliper.
I have driven cars and motorcycles with the barrel drum-style brakes, but these are much older designs without the rotor/caliper.
Last edited by maxusa; 04-10-2023 at 04:38 PM.
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billvp218 (04-10-2023)
#30
Super Member
The W212 brake caliper design wraps around the rotor edge. This means that it follows the outer edge of the rotor. The pads inside the caliper have basically a fixed position with some minimal play to accommodate rotor/caliper alignment and wear issues. This wraparound caliper design dominates the auto industry. There are nuances like the floating vs. fixed calipers, number of pistons, hydraulic vs. electric, etc.
I have driven cars and motorcycles with the barrel drum-style brakes, but these are much older designs without the rotor/caliper.
I have driven cars and motorcycles with the barrel drum-style brakes, but these are much older designs without the rotor/caliper.
#32
Senior Member
Correct. To be more precise, the caliper/pad assembly moves out (from the wheel center) to match the new rotor radius, exactly by 15mm. You need a new bracket for this. Pads generally move inside the caliper only to clamp the rotor... and a few mm play for alignment and wear. It is impossible to reposition the pads on their own.
![](https://cimg8.ibsrv.net/gimg/www.mbworld.org-vbulletin/736x414/b031d998e8cd8bdbbe95db67790587d1_mercedes_benz_4f8d2afaffb1d6bd273ff605e805016c06be13ea.jpg)
Hope this helps.
Last edited by maxusa; 04-11-2023 at 11:34 AM.