R100RS top speed.

[Boertjie]

Interesting reads...I have pushed my R100S 77 to 165km/h, but my R60/6 to 170km/h both on the speedos of course. I did the top end now on the 1000cc and is still in the break-in phase, but would definitely push the sucker once all are settled in. BTW my colleague who has 3 x R100RS bikes all of them 80 models have pushed them all to 200km/h.

Regards
Johan

[Deleted User 62]

I did 100mph on my R75/5 recently, 107mph on the speedometer. My friends two Japanese bikes were my "control". This was at high altitude on a bike tuned for 2000' elevation, straight line, maybe a bit of a tailwind. Oh dang, I just realized, I probably wasn't going 125mph when I pegged the speedometer on my first R75/5 while riding on the German Autobahn. It may have been on a downhill section tho'.

[Rapid Dog]

...well...we all gots our stories Top speed I ever did on an airhead was an indicated 137mph.
1978 R100/7 S fairing with a 77RS topend/40mm pipes/33-11 rearend, loaded down with camping hear and bags.
A slight tail wind, ever-so-slight grade, and a prayer. Indicated 137mph.
Now that's a bike I never should have sold.

[guy]

To get back to the original question, I feel the newer motor fuels do not appear to produce the horse power gasoline did.
Guy

[vanzen]

... In reality, very few speedos are accurate over about 70mph.

In reality, BMW airhead speedos are only accurate at 0 mph.
From that point on – the amount of inaccuracy will become progressively greater.
My experience with the typical airhead will be @ 5 mph of pure optimism at an indicated 70 mph ...
Assuming a rear tire with a measured diameter consistent with
the measured diameter of a stock spec tire –
as any difference will also affect the amount of error.

"Most speedometers have tolerances of some ±10%, mainly due to variations in tire diameter.
Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size.
Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error,
to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle,
to ensure they are not liable for drivers violating speed limits."
~ Wiki

European Union member standards:
. The indicated speed must never be less than the actual speed,
i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
. The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds.
For example, at 80 km/h, the indicated speed must be no more than 92 km/h.

[Kurt in S.A.]

What vanzen posts is what is repeated in a 1996 service bulletin by BMW. The stated reason is to compensate for bad tolerances in tires, the inaccuracies in the speedo, and "other factors."

But still, speedos can be whack all on their own, bulletin or not!

Kurt in S.A.

[Chuey]

My '89 with some performance modifications will pull just under redline on a flat surface, no downhill cheating.

Downhill is cheating?

Chuey

[Deleted User 62]

My '89 with some performance modifications will pull just under redline on a flat surface, no downhill cheating.

Downhill is cheating?

Chuey

Not at Laguna Seca and elsewhere.....

[dougie]

Downhill is cheating?

Spoken like a true bicyclist Chuey.

[Rob Frankham]

All BMW speedos are at least 5% optimistic, some are 10%

It's a bit dangerous to assume that all BMW speedos are innacurate. The one on my R80RT turned out to be about 2% over when measured against a Sat Nav... until it got over 80mph.

Yes, their accuracy is questionable, yes they are more likely to read over than under but anywhere between dead on and 20% over is possible in my experience.

They also don't stay the same... the one on the 'RS used to be about 8% over. Now it's on a different planet, especially at the top of it's range. Fortunately my Sat Nav has a speedo function so it's easy to do a jackleg calibration check every so often.

The point is, when dealing with speed cameras, that 10% assumed over read can turn out to be quite expensive...

Rob