Speedo fix that works (borrowed from another site)

Paul G (BHT)

Mod Squad
Jan 30, 2001
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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.
Nope, the speedo is driven off the front wheel, so it makes no difference:)
Just done my 1100 with this fix, similar accuracy except I have to use 5000 rpm to get near to a real 80 mph.

Is this the longest time between posts :augie
you will find most manufacturers make their speedo,s with up to 10 per cent error, erring on the fast side so that you never get falsely done for speeding, and cant sue them,
a sat nav is (should be ) much more accurate, around 5mph on average as you have seen:thumb
so bmw arnt really any worse than most others
All American hire cars that I've used have been within 1% errors, all European hire and owned cars have been around 10% errors.

Why can the Merkins make accurate speedos :confused:
i thought grossly overeading speedos were a thing of the past?

the speedo in our 04 passat is pretty much bang on. my 1200 speedo is a little fast, but not much.
The point is that the Merkins seem to require accurate speedos and we don't, and given they seem to have invented litigation, I'd have expected their speedos to be as inaccurate as ours.

Then the Spams would sue the speedo manufacturers for faulty products.
For 20 Euros + some shipping bought this:

SIGMA Digitaltacho MC 8 bis 300km/h
Bestellnummer: SIG-000100
Menge: 1
Einzelpreis / Gesamtpreis 19,50 EUR / 19,50 EUR


Looks like it's gone up to 23.50 Euros + shipping.
Pretty sure you can find it in the UK, but shipping's not bad anyway.

Made for a bicycle but works fine on a motorcycle. You attach one sensor magnet on the fork and the other on the disk near the centre. Input the diameter of your tire and Bob's your uncle. Rund the wires up the fork to the base at the handlebar. Gives you vmax, avg speed, trip distance, trip time, time of day. I tested speed vs. my GPS and the difference was 1 km/h. Attaches easily to handlebar.

Note - I did this on my Aprilia Futura, not my GS1150.

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