Triumphrat

Ken M1 · 06-19-2009, 01:28 AM

I've always suspected my speedo was WAY inaccurate! I could ride on the same road everyday when I know the common speed yet I'd get blown by doing same (said) speed on my Streety.
Well...this last weekend I went by one of those "radar speed signs", that post the speed limit and display YOUR speed. This was a back road with NO traffic on it. The limit said "25 MPH". I look down at my speedo...it say's "30". I'm ok, I think to myself. Then my ACTUAL speed displays on the sign that says "YOUR speed is: ". It was 24!! What?!

So I double back and do it again...and again. SAME THING! Doesn't this mean that around 60 on the speedo is only about a REAL 50 ?? No wonder I never get pulled over!! Great. Now I'm racking up miles like crazy that I'm not even doing, and the speedo is a JOKE.

Now some will say car speedo's do same. No. I went back to same sign with my Mazda (I was fuming!) with speedo in car saying 30 MPH. Sign said "29". Just as I suspected. Argh!

rsw81 · 06-19-2009, 02:18 AM

This is pretty standard on motorcycles actually. The reason for this is that it is illegal for them to produce a vehicle who's speedo reads lower than actual speed (ie you could be speeding and think you aren't). By default, they err on the side of caution and make the speedo read higher than actual speed to avoid this posibility.

I mounted a GPS on my bike that I know is accurate. My ST3 runs about 5% high (ie gauge says 65 when GPS says 62), whereas my Yamaha FZ6 consistently ran 10% high (ie gauge says 65 when gps says 59).

Ken M1 · 06-19-2009, 10:21 PM

I can understand them wanting them to read higher than actual speeds for safety/legal reasons...but why don't they make them CLOSER as they do with autos? This is frustrating as we are racking up crazy miles on our odometers that we never rode! If cars/trucks read 1-5% over, why can't bikes do same (instead of around 10%+ over)??

BRich · 06-19-2009, 10:55 PM

Did you change any sprockets? Wrong size tire on the wheel? I got pulled over speeding and the police officer said I was doing 66 MPH, my speedo read 69 or 70, so mine is pretty acurate compared to yours. Something is wrong with yours.

Street RRR · 06-20-2009, 12:08 AM

I've been wondering if a gadget like this would do the trick?

http://cgi.ebay.com/ebaymotors/ws/eB...EF:MOTORS:1123

Anybody ever have any experience with one?

Diego · 06-20-2009, 12:54 AM

Actually, Ken, the odometer readings are very close indeed!

Ken M1 · 06-20-2009, 02:34 AM

Yikes! Wouldn't (about) 6 MPH off at 30MPH would be (about) 10-12 MPH off at 60MPH?

My running gear is bone stock (stock gearing/tires/etc), so guess I'd better have it looked at. Hopefully they can do something to dial it in a bit closer than this. Diego, are the odometer readings separate from the speedo readings?

Diego · 06-20-2009, 03:03 AM

The odometer incrementing comes from the same sensor, but it's a separate computation within the ECU.

As for the speedo error, 6 MPH out of 30 is a tad more than most people find. And, the error does not track linearly in most cases. This topic has been widely discussed in other forums at this site, and even early on in this one. The general report of people who compare their reading against GPS is that the speedo reads more or less consistently about 5 high, even at highway speeds.

Ken M1 · 06-20-2009, 10:10 PM

Thanks for the info!

prpbmw · 06-21-2009, 07:25 AM

I zero'd out the top speed on the bike and my GPS

Then I rode the bike and abserved the speeds on both digital readouts.

At lower speeds there was a 2-3 MPH difference.

When the bike was at 60, the GPS read 56.6