Rohloff PM Bone
The Rohloff PM Bone (8555) anchors the torque of a SPEEDHUB 500/14 with PM axle plate on frames with a direct Postmount brake mount – a necessary component for every Postmount SPEEDHUB.
Why the PM Bone?
Uses your Postmount brake mount. The PM Bone takes the hub torque through the frame’s Postmount interface, so no extra torque arm is needed on the chainstay. 
Two Postmount sizes. With 160 mm direct Postmount use a 180 mm rotor; with 180 mm direct Postmount use a 203 mm rotor. 
Works with IS frames too. On IS frames with a 160 mm IS/PM adapter use a 180 mm rotor; with a 180 mm adapter use a 203 mm rotor. 
Necessary component. Rohloff lists the PM Bone as a necessary part for Postmount SPEEDHUBs – the hub must not be ridden without its torque support.
Clean look, no long arm
The PM axle plate and PM Bone sit neatly inside the brake area – the classic choice for modern frames with Postmount brake mounts.
The axle plate is fixed with five TX20 screws at 3 Nm.
Who is it for?
- Builders of a Postmount SPEEDHUB. The PM Bone is required with the PM axle plate.
- Riders who lost or damaged the bone. A direct genuine replacement.
- Frame builders. Plan the rotor size together with the Postmount size from the start.
Compatibility
| Rohloff part number | 8555 |
|---|---|
| Axle plate | PM axle plate (e.g. CC PM 8225, A12 PM 8558) |
| Hub spacing | 135, 142, 148, 170 or 177 mm |
| 160 mm direct Postmount | 180 mm rotor required, gap plate–bone at least 0.3 mm |
| 180 mm direct Postmount | 203 mm rotor required, gap at most 7 mm |
| Not compatible | 140 mm and 203 mm direct Postmount, tandem and cargo use |
Frequently asked questions
Can I use the PM Bone with a 160 mm rotor?
No. On a 160 mm direct Postmount frame the PM Bone needs a 180 mm rotor; on a 180 mm Postmount it needs a 203 mm rotor. 140 mm and 203 mm direct Postmount are not compatible.
Is the PM Bone approved for tandems or cargo bikes?
No. Rohloff does not authorise the PM Bone and PM axle plate for tandem or cargo use. Ask us about the OEM2 axle plate options.
What is the difference to the PM Bone 2.0?
Rohloff also lists a PM Bone-2.0 (8555-2.0) for Postmount SPEEDHUBs. Tell us your frame and hub version and we will confirm which one you need.
About Rohloff
Rohloff AG is a German engineering company based in Fuldatal near Kassel. Its SPEEDHUB 500/14 is a sealed 14-speed gear hub with evenly spaced gears, built for riders who want a drivetrain that keeps working for tens of thousands of kilometres with little more than an annual oil change.
BoodaBike in Budapest is an official Rohloff service centre, trained by Rohloff, and an official European distributor of Rohloff hubs and spare parts. Every part we sell is genuine Rohloff, and we are happy to help you find the right part number for your hub.