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Driveshaft

Airhead GS Paralever driveshaft

Curious about how the Paralever works?  Try reading this.

Geometry

Ride height was measured from the center of the shock bolt on the rear drive to the top of the rear subframe.

Shock length was measured eye-to-eye, centers. Full shock extension was taken from the free length of my Fox Twin-Clicker, and full compression was estimated based on the apparent travel of the shaft.

Swingarm (driveshaft) angle was measured at the transmission (proximal) and at the rear drive (distal). These measurements aren't very precise; I'll try to repeat them with better instrumentation.

Charts

Raw data

Height Shock length Proximal angle Distal angle
16.1 19.4 -14 18
16.2 19.2 -13 13
15.6 18.8 -11 8
14.9 18.5 -8 7
14.2 18.2 -5 5
13.6 17.9 -3 2
13.0 17.6 -1 0
12.3 17.3 1 -1
12.1 17.15 4 -4

U-joints

Some of them fail. Some don't. Here's what a rebuildable driveshaft from Bruno looks like:

You can also get rebuilds from HPM and Erich Demant (in Germany).

R1150GS driveshaft

Rod Neff made the following observations about his bike:

Position Proximal Distal
full ext -17.2 3.5
  -4 0
  0 -2.5
full comp 7.5 -10

Driveshaft inspection

I replaced my driveshaft at 64,000 miles. I had no real indication that anything was wrong but I didn't want to be stranded on some upcoming rides. I had removed it at 48,000 miles and felt a very slight bit of play when the ends were turned against each other. A local rider checked it and said, "that's the beginning of the end" but I didn't see how much tighter they could really be.

Well, when I got the new one, I tried twisting that thing and there was NO movement no matter how hard I tried. It's clear to see that "no play" really means NONE. But I also noticed that the bearing end caps didn't seem to be evenly recessed in the yokes, so I got out the calipers and took some numbers. The measurements are listed in inches with the following identifiers:

STAKES: the recess distance from the machined flat of the yoke down to the bearing cap where it is staked in position

FLATS: distance across the two machined surfaces of the yoke

CENTER: on the center (floating) part of the shaft

FIXED: on the end pieces of the U-joints

DAMPER and SOLID: the shaft end; damper is the front and solid is the rear

New Old Data point
    DAMPER END
1.880 1.881 Center flats
.059, .089 .064, .064 Center stakes
1.732 1.753 Spacing
    Cross-check
1.881 1.887 Fixed flats
.065, .089 .054, .051 Fixed stakes
1.727 1.782 Spacing  (this one had about 1mm play in the joint)
    Cross-check
    SOLID END
1.881 1.884 Center flats
.069, .077 .055, .070 Center stakes
1.735 1.759 Spacing
    Cross-check
1.887 1.882 Fixed flats
.068, .086 .077, .074 Fixed stakes
1.733 1.731 Cross-check
    Spacing