Triumphrat

ggRAT · 06-26-2008, 10:26 PM

I took a 100 mile trip and did my best to determine the accuracy of these gauges...

BEST GUESS RESULTS
Speedometer: 5% optimistic, i.e. 60mph indicated is actually 57mph
Odometer: 1% exaggeration, i.e. 101 miles indicated is actually 100 miles

(Note: I've got a 19" front wheel and a 17" rear.)

CAPTDON · 06-26-2008, 10:53 PM

Id say you are about rite on!! I dont look @ the speedo much any way./ Prefer to keep my eyes on the road & CARS/TRUCKS!! Stay w/ the flow & you will be OK. ODO diff- Does it matter that much?? Aerostich makes a travel computer that will do anything you want I think?? Might be nice?

tspapa · 06-26-2008, 10:57 PM

+1 on looking at the speedo too many goofy cagers out there these days!

djmakm · 06-26-2008, 10:58 PM

On an earlier post, someone was saying the error was about 10%. There's definitely some error. I guess if you mess with the sprockets you're gauges would be off even more...

For me it seems like the flow of traffic is about 5 mph faster on the bike as opposed to in the cage.

Pauljo · 06-26-2008, 11:23 PM

Quote:

Originally Posted by djmakm

On an earlier post, someone was saying the error was about 10%. There's definitely some error. I guess if you mess with the sprockets you're gauges would be off even more...

For me it seems like the flow of traffic is about 5 mph faster on the bike as opposed to in the cage.

Many of the Japanese motorcycles and scooters read 10% fast on the speedometers. My last three were all 10% optimistic. My Bonneville seems to be off less, but I haven't really nailed it down. I've heard 8% optimistic, and now 5% - it is somewhere in that range. Usually though, the odometers are accurate. I think that a GPS cannot account for changes in elevation (ie hills), so that might account for the 1% difference mentioned in the opening post.

But in any event, changing sprocket sizes on a Bonneville will have no effect on these readings. The speedometer & odometer are driven off of the FRONT wheel.

bendavanza · 06-27-2008, 02:22 PM

3% is about right. I have checked vs my GPS and that's the most off I have seen it. Mine has 20k on the clock so it may be more "broken in". I have not checked against the odometer, but like Pauljo said, elevation can be a factor. Not really here in Dallas, though.
The preferred error would be optimistic, you wouldn't want to be 10% under reading and get a speeding ticket.
-Ben

bendavanza · 06-29-2008, 01:43 PM

Further checking today shows my speedo to be within 1%.
Front tire choice and inflation will have a big impact on the speedo accuracy. Maybe my lasertech is underinflated a bit.
-Ben

Daveski UK · 06-29-2008, 08:53 PM

Quote:

Originally Posted by djmakm

On an earlier post, someone was saying the error was about 10%. There's definitely some error. I guess if you mess with the sprockets you're gauges would be off even more...

For me it seems like the flow of traffic is about 5 mph faster on the bike as opposed to in the cage.

I cannot see how changing sprockets will alter the speedo reading, the speedo reading comes from the front wheel, not the gearbox.