Speedometer accuracy

[relic-rider]

Just how accurate are these GS speedos? My buddy took mine on the freeway and right away said it was reading about 10 MPH faster than he was going. I didn't believe him. But yesterday I rode past one of those large roadside radar speedchecker, and while my speedo said 45 the radar said 36. Soooo, Could the speedo have been damaged if it was pegged out at one time? It is one of those goofy 85 MPH speedos. Does going past the 85 mark damage these? If so, can they be repaired? Or can I put on a 1983 speedo that went up to 140 again. I realize that the angle drive on the wheel hub might have to be changed. What are your experiences?

Dan

[bwringer]

Nope, all old bikes have pretty lousy speedo and tach accuracy. I like to peek over into cars with digital speedos at night to see how far off I am.

New bikes are no better -- they all read 5 to 10mph high at 60mph. 10mph error at 45 is maybe a bit extreme, but not uncommon. Going faster than 85mph with an 85mph speedo doesn't hurt anything.

There are some strange regulations partly responsible for causing this, I think -- speedos don't have to be accurate, but they absolutely cannot read low. So the manufacturers fudge to varying amounts and the speedos all read quite high straight from the factory. Add in 25 years of spring fatigue, and...

You can hook up a cheap electronic bicycle speedo if it bugs you, or mount a GPS to the handlebars as long as you don't play with the GPS while moving.

[jeh7474]

I ride a 1980 Gs850g with an 85mph guage and I know for a fact it reads low. When I'm doing 0-35 on the guage i am really going 5 mph faster. When I get up to the 40-85 range I am actually going 10 mph faster than what the guage is saying.

[thr3shold]

I must have one of those one in a thousand ones that is only 1 or 2 high, if that. I know that there are speedometer shops that will recalibrate your speedometer to anything you want and install new mph gradiations to match for cars, I'm sure they'll do the same for motorcycles.

[rckrzy1]

So the manufacturers fudge to varying amounts and the speedos all read quite high straight from the factory. Add in 25 years of spring fatigue, and...

Actually spring fatigue would cause it to read high as it's the return to 0
spring. I think the grease in the bearing gets solid and cause the problem.

And taking a 85 WAY past 85 does not bother mine. I love seeing how long
till it moves again after rolling out of the throttle. And mine when checked against the radar signs is about 3-5 miles per hour faster so that seems to be true for most.

[jpaul]

My 750 reads about 5-6 mph low at 60, according to my GPS. I suppose it could be that the Avon Venom X I have on the front is a larger diameter than the original stock tire, but I wouldn't expect that big a difference.

[Jethro]

My speedo reads progressively faster than reality as I go faster. Eg., when I'm going 40, my speedo shows 43. When I'm going 80, the speedo shows 85 or so. With my speedo pinned at 140 I am actually going 130, according to my GPS.