BMW maintenance

GS Speedo Fix

GS Speedometer Accuracy Fix Thread

I just installed a speedo hub from the R1100R. It has a 2.875 ratio, compared to the 3.0 ratio stock on the Oilhead GS. The changeover is quick, under 15 minutes including cleaning your hands afterwards. Bottom line: it works just fine, and my speedometer is now *much* more accurate.

Here are some data for 6th gear:

Tires: Metzler Tourance
38.5 rear, 35.5 front, cold pressures

With 3.0 speedo hub,
3000 RPM 65 mph indicated, 60.8 actual, 6.9% error
3500 RPM 75 mph indicated, 70.0 actual, 7.1% error
4000 RPM 85 mph indicated, 79.2 actual, 7.3% error

With 2.875 speedo hub,
3000 RPM 62 mph indicated, 61.2 actual, 1.3% error
3500 RPM 71 mph indicated, 70.0 actual, 1.4% error
4000 RPM 80 mph indicated, 79.0 actual, 1.3% error

I used a Magellan 315 GPS on flat straight sections of freeway at steady throttle to allow the GPS time to settle. Obviously, my data collection technique is imperfect, it’s hard to read the analog speedometer and the digital GPS at the same time while avoiding trucks and SUVs. The GPS is only accurate at steady speeds on straight roads.

The part number from BMW is 62 12 2 306 532. Maybe you’ll find it for less than I paid… but it’s worth it for peace of mind.

Now I’m happy, a 1.4% error is much better than a 7% error. If I were buying a new GS, I would demand that the dealer include the speedo hub from the old Roadster in the package, out the door. It’s absurd that BMW gets away with selling bikes with inaccurate speedometers.