Speedo being inaccurate

[Rayray401]

So i was on my way to town today, was keeping up with traffic and my speedo was indicating at 120 kph, but then i wasnt going any faster than any other car.

So im just wondering, is there any way i can test out whether my speedo is accurate or not? and how?

[javawocky]

My bike is the same, site at 120+ at motorway speeds. Most bikes are over clocked on the speedos

Ways to find your real speed - GPS, Those speed trap signs on the side or the road. There are some of these in west harbor.

I have measured my car which is exactly what those speed traps say, but who can know if those speed signs aren't rigged anyway?

[MSTRS:Me]

Borrow a bicycle speedo...set it up in your bike...go ride and compare the two readings. Your bike speedo probably reads about 10% high

[Rayray401]

My bike is the same, site at 120+ at motorway speeds. Most bikes are over clocked on the speedos

Ways to find your real speed - GPS, Those speed trap signs on the side or the road. There are some of these in west harbor.

I have measured my car which is exactly what those speed traps say, but who can know if those speed signs aren't rigged anyway?

I see, west harbor....so far. So any way I can make it accurate? i read something like speed healer, but dont know what it is

[MSTRS:Me]

So any way I can make it accurate? i read something like speed healer, but dont know what it is

I think the speedo healer unit only works on electronic speedos. The ones that work off your final drive. They work much the same as a bicycle unit, and can be recalibrated electronically. If a speedo is cable-driven (usually off the front wheel) I think you're fucked. At least, you are if a mechanical device can't alter the speed at which the cable rotates. Or the magnetic field it generates in the speedo itself can't be altered.

[vifferman]

I think the speedo healer unit only works on electronic speedos. The ones that work off your final drive. They work much the same as a bicycle unit, and can be recalibrated electronically.

True, but not easily. The "Speedohealer" is several hundred dollars, and is very much model-specific, as it has the plugs for your particular bike (or not, if it's not a listed one). However, Jaycar sell a speedo corrector kit, which I used on my VFR when I geared it down. I think the current version is around $56, but "some assembly is required" (i.e., you need a soldering iron and some skills, but if I can do it, surely anyone can?)
Note that in either case, correcting your speedo may mean your odometer is then inaccurate, as the usual case is the odo is pretty much spot on, but the speedo is optimistic. When I corrected mine (-10%), the speedo was accurate, but the odometer under-read by 10%.
Did I care?

If a speedo is cable-driven (usually off the front wheel) I think you're fucked. At least, you are if a mechanical device can't alter the speed at which the cable rotates. Or the magnetic field it generates in the speedo itself can't be altered.

There are a couple of instrument maintenance places that do speedo calibration and resetting - check the Yellow Pages. They were originally set up before electronic instruments were the norm, but I guess they may do both types. However (but!) you may find it's cheaper to buy another speedo from a wrecker, or to fit a bicycle speedo.

[p.dath]

The best way to really verify your speed is to get a GPS. Go for a ride, and then see what it reports as your top speed.

[firefighter]

However, Jaycar sell a speedo corrector kit, which I used on my VFR when I geared it down. I think the current version is around $56, but "some assembly is required" (i.e., you need a soldering iron and some skills, but if I can do it, surely anyone can?)
.

I'm sure you'd be happy to help out for a box of beer for those of us that are soon to be gearing down our bikes?