Speedo inaccuracy stats

[quickbuck]

Having done quite a lot of riding with a GPS on my Shiver, I can report that the onboard speedo has a 6% error engineered into it, while the odometer's measurement is perfect.

Reminds me of a 2 stroke 250 triple of 1984 vintage I used to own (Won't mention the name but becoming popular around these parts of late....)

Anyway, the Odo was perfect IAW the 5 km markers just south of the Blue Gum Motel just south of Hornby, a shame the speedo was 40% optimistic!
Nope, that isn't a typo!
Truly, it did 100 in first indicated, and went off the clock (180) in 3rd....
My mates used to take it out the back of town and think they were Eddie Lawson! No traffic to reference against, and in reality only doing 130k.

Were amazed, and used to say things like, I can't believe how fast it is going...., It is so smooth.
Of course they were used to XR200's and the ilk....

Oh, memories.

[F5 Dave]

Of course for pure-bread racing speedos the Italian Velga (sp) were the raciest. Back in the day a friend on her Guzzi V50 put her head flat on the tank & sped up, rather bemused I pull alongside sitting bolt upright with one hand on the bar on my GS550, -just to rub in a point as you see.

Anyway later she says all full of enthusiasm "Sometimes I just like to do the 'ton'"
"That's odd" sez I , "I was only doing 140"
What a bastard, clearly I wasn't trying to sleep with her & what I wasn't letting on was, that with my slightly over geared GS, that was pretty much my practical top speed sitting upright. But it did tell me not to trust instruments, especially not Italian ones.

[imdying]

True. I have checked the odo out against the measured test sections on motorway - it is accurate to within a couple of metres over 5km...

Having done quite a lot of riding with a GPS on my Shiver, I can report that the onboard speedo has a 6% error engineered into it, while the odometer's measurement is perfect.

Yep, thus why you shouldn't fit a speedo healer to fix the speedo inaccuracy, only to correct for a gearing change, and even then you only want to correct it back to it's existing inaccuracy

[imdying]

Oh, and interesting that this is under electrical system....

Not at all, the description for this subforum reads:

battery, wiring loom, lights, ignition system, ECU, dash, charging system, starter motor & other electrical devices

[quickbuck]

Fair enough then....... Will blame electrics next time my speedo fails then

Always electronic stuff more likely to fail than good quality mechanical stuff....
First rule of my job is: Always blame Avionics first....

[pete376403]

Old Brit bikes (ie 1950s, 1960s old) used Chronometric speedos (and in some cases rev counters) made by (IIRC) Smiths under licence from Jaeger. Very accurate indeed. The later Brit bikes used common old magnetic cup type speedos as standard, but when they were converted to MoT use, the speedos were replaced with the old chronometrics
http://velobanjogent.blogspot.com/20...er-and_21.html

[hmmmnz]

my van at 100 was doing 91kmh (gps speed) now with 275/75/16's at 100km/h she's doing 99kmh
all my bikes read between 93 and 95 at an indicated 100, except the xz400 which at an indicated 100 she's actually doing 107kmh :O

[merv]

Interesting! I recently checked the Striple against my GPS and at an indicated 100, the GPS was reading 95.

Yep about right, the bike speedos (and car ones too) are typically fast compared to reality.

[AllanB]

So when my Hornet was reading 300 I was actually only doing 290?



Bummer ..........

[kwaka_crasher]

So when my Hornet was reading 300 I was actually only doing 290?

Bummer ..........

Nah - dream kms are considerably shorter than real kms...