Speedo calibration

[hjfisk]

Looking for input from the guys that have done a late model suspension swap for the 17" wheels and how there speedometers were reacting. Mine is very smooth and not bouncy or anything , but I am not sure of accuracy. I went for a ride today on the "Roadkill" bike and the bike feels very good, very solid. But the speedo was reading like 65mph and I felt like I was going 45mph. Kind of reminded me of my old 97 GSXR1100, felt slow but you were flying. The setup I have is a 96 Bandit front wheel and speedo gear, with my 78 1000 speedo. So either this Speedometer is wrong or this bike is faster than I think. I don't believe that speedometers have gearing , aren't they just magnets that spin on the end of a cable?
And the gearing is actually for the diameter of the wheel, and a different speedo drive for each different wheel size?

[posplayr]

Looking for input from the guys that have done a late model suspension swap for the 17" wheels and how there speedometers were reacting. Mine is very smooth and not bouncy or anything , but I am not sure of accuracy. I went for a ride today on the "Roadkill" bike and the bike feels very good, very solid. But the speedo was reading like 65mph and I felt like I was going 45mph. Kind of reminded me of my old 97 GSXR1100, felt slow but you were flying. The setup I have is a 96 Bandit front wheel and speedo gear, with my 78 1000 speedo. So either this Speedometer is wrong or this bike is faster than I think. I don't believe that speedometers have gearing , aren't they just magnets that spin on the end of a cable?
And the gearing is actually for the diameter of the wheel, and a different speedo drive for each different wheel size?

My 18" GSXR 1100 wheel/speedo drive has a 110/80-18 on it and with a stock GS1100ED speedo it is no much more than 1-2 mph off a 60 mph. It tends to read high which is fine by me.

One of the problems with the 17" wheel conversion is you will be going faster than you think because of the riding improvement.

I think I was a little lucky

[chuck hahn]

This may sound totally nuts to you but..if you see a cop sitting on the side street or something, approach him and explain that youve done some repairs and in the interest of respecting speed limits you would like to have him radar you at a few different speeds to see whats happening.

They will usually look at me like Im a nut job but they will say OK..lets go over here and we can do some runs. They usually lead me to some back street or indusrial park with no traffic and we have some fun.

[hjfisk]

I'm thinking that if I see one of those radar signs that the towns set up I'll check it then. But until then I have to be cautious , don't want any tickets.

[MOC]

I went for a ride today on the "Roadkill" bike and the bike feels very good, very solid. But the speedo was reading like 65mph and I felt like I was going 45mph.

GPS app on a cell phone taped to the handlebars is how i checked mine. If you put a smaller wheel on, your speedo is almost certainly off. What size wheel was on there before?

[eil]

I've never found those police radar signs to be accurate. Around here, they read everything from spot-on to 5mph over. I assume there's a calibration or adjustment on them that can be monkeyed with.

GPS is the best way to get an accurate speed reading. If you have a recent smartphone, there are a number of free programs that will work. Even the low-end TomTom and Garmin GPS units will work too.

[AJ]

Put a GPS on your tank bag and compare to your speedo reading.

FWIW, I think the speedo drive is changed down at the wheel to compensate for wheel (tire) diameter, not the speedo itself. So if you changed the drive with the wheel, the speedo should still read correctly.

If you are brave, you can tweak the clockspring in your speedo to make it read more accurately. Open the loop a little to make it read lower. Close the loop a little to make it read higher.

To get started, use an electric drill with a flat-blade screwdriver tip to spin your speedo cable (disconnected at the wheel). Use the fastest drill you have (at least 1000 rpm) and see what your speedo reads. Drill is in reverse direction.

For sake of example, let's say this makes your speedo read 43 mph. Reconnect your speedo cable and ride the bike with a GPS to see your actual speed when your speedo reads 43 mph. The GPS reads 37 mph (6 mph = 14% low), so you will want to open up your clockspring to tighten it and make it read lower.

Pull the speedo, open up the housing, reconnect the cable and hook up your drill. Use a pick to carefully open the clockspring to make the speedo read 37 mph. It's really not that hard to do.

This will not change your odometer readings. Use your gps to measure 10 miles and see what your ODO reads.

[rustybronco]

Distance/time

Find a highway set her at 60mph, drive ten miles and use a stopwatch. (or something with a stop watch function, a watch with a second hand, your grandfathers pocket watch, your own pocket watch, an egg timer, a $9 Blackberry with timer function, a newer'ish smart phone, a metronome so you can count in your head... just trying to cover all the bases for those who like to split hairs)

[posplayr]

Distance/time

Find a highway set her at 60mph, drive ten miles and use a stopwatch. (or something with a stop watch function, a watch with a second hand, your grandfathers pocket watch, your own pocket watch, an egg timer, a $9 Blackberry with timer function, a newer'ish smart phone, a metronome so you can count in your head... just trying to cover all the bases for those who like to split hairs)

egg timer, tape measure ............................

[rustybronco]

Jim, nothing quite like like erroring on the side of accuracy.

tape measure

[hjfisk]

I have the speedo drive that goes with the wheel on the bike so it should be accurate, but next time I take it out ' I'll take my Garmin and compare.

[MOC]

my GPS app is called "GPS essentials" and it's free from the app store/google play

let us know what you learn.