Ducati Sporting Club UK > General > Idle Chat > Speedo Accuracy

[rockhopper]

We filled both bikes up prior to our trip to Donington on sunday and zero'd the trips. When we got home my bike had done 53.5 miles and Lynns had done 51.3. I didnt expect them to be the same but i'm supprised how far out they are. Both bikes are running standard size front tyres as well.

[HW]

Made me think for a moment until I remembered that the ST has a speedo drive on the front wheel. Can it be that tyre wear could make that difference? Just a thought, but maybe not a very good one.

[JPM]

Could be a whole host of things I guess, tyre pressures, wear on tyre, and I guess to a lesser extent actually riding and one taking a wider/longer line over said distance could add a few feet here and there.

It's about 5% from the figures above which would fall within government regs I guess.

[phil_h]

Hmmm .. I've always meant to work out how different the rolling circumference is when you are leant over.
Sounds like lynn braked a lot and kept the bike upright, and you took the corners faster (more revolutions)

[Edited on 31-5-2005 by phil_h]

[rockhopper]

Well my bikes got a brand new front tyre while lynns M600 has a fairly worn one. Having said that they are running the correct sizes i must check the monster to be sure when i get home. I'll take the GPS out with us next time and try and see which one is closest to being right.

The only thing i have changed on my bike is the speedo drive as i managed to crack it when i changed the tyres. I'm assured the new one came from a 916 so it should be okay. Are they the same across the range? Did some 748's have a differnt profile front tyre as standard?

[rockhopper]

Originally posted by phil_h
Hmmm .. I've always meant to work out how different the rolling circumference is when you are leant over.
Sounds like lynn braked a lot and kept the bike upright, and you took the corners faster (more revolutions)

[Edited on 31-5-2005 by phil_h]

That might be true for most of our riding but from my house to Donington is motorway nearly all the way!

[Jools]

Tyres may be standard sizes, but what are the standard profiles? Could it be a difference between 60's and 70's?

All the speedo drives are the same, Ducati fitted the same thing across the range, but they're is bound to be some difference between bikes.

I'm more concerned about the innacuracies of the speedo to be honest. Although my speedo cable is still broken at the moment, when it does work the ST speedo seems to be wildy out on both my ST and Glyn's. Anything over 100 and it seems to make it's own mind up what to read. On our private test track the most I've ever seen on the clock is about 110-115 when my colleague test riders with 749/999 digital speedos reckon it should've been reading 135+

As I've said, Glyn's is the same.

[rockhopper]

I meant to say profile rather than size. Yes, my concern was speed accuaracy. I do use the gps sometimes but only if i'm going on a route i dont really know and i've never had it on the monster and i havent had it on mine recently.

Sounds like a good excuse for some road testing!

[Shazaam!]

Like most, Ducati speedometers are set-up to read optimistically to avoid law enforcement issues. The speedometer error for a 998 with a 70-section was measured against a GPS standard by one owner to be:

40 998 = 37 GPS
50 998 = 46 GPS
60 998 = 56 GPS
70 998 = 65 GPS
80 998 = 73 GPS
90 998 = 82 GPS
100 998 = 89 GPS

So for example, after a one hour trip at an indicated 80mph he would have traveled only 73 miles but the odometer will read 80 miles. The odometer always records more milage than the actual mileage traveled. The greater the difference, the less accurate the clock.

So if your friend’s odometer reading is lower than yours for the same trip his odometer is more accurate than yours.

[nelly]

Looks like Lynn popped about 2 miles worth of wheelies Paul