Why I don't trust mechanical speedometers.

xlite said:
My brief experience with a couple mechanical speedometers is they are garbage. Way off compared to GPS. Explains a lot of the ridiculous WOT claims. And only good for a few hundred miles. If you need accuracy and go thousands of miles digital is the solution.
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Yes I keep my little digital speedometer running right next to my analog cheepo. However I doubt that either will ever see thousands of miles.
 
I have one of the schwinn 10 dollar ones from wally world. you calibrate the wheel size when you
first put in the battery. I used old tire tubes on the mount to lessen vibration, just like my motor mounts. vibration hasn't killed it (yet), and it is definitely accurate according to the speed trap thingeys on the side of the road as well as my little ladies car.
 
I got one of the Schwinn digital speedometers tonight and what a pita to set up. You have to set the wheel factor, chose MPH or KpH and set the clock all in secession with out mistake or you have to reset the entire unit and start over. This one has a sticky left button causing it to jump 2 selection at a time every once and a while. By the way if you want to rest the unit just hold down both buttons for a second or 2 in stead of removing the battery.
 
tsmra said:
I got one of the Schwinn digital speedometers tonight and what a pita to set up. You have to set the wheel factor, chose MPH or KpH and set the clock all in secession with out mistake or you have to reset the entire unit and start over. This one has a sticky left button causing it to jump 2 selection at a time every once and a while. By the way if you want to rest the unit just hold down both buttons for a second or 2 in stead of removing the battery.
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O.M.G....dance1you didn't build your own bike, did ya.....the speedo takes literally a minute to set up and another if you don't do it right the first time. the wheel factor is right in the little pamphlet in the kit. lmfao
 
tsmra said:
I got one of the Schwinn digital speedometers tonight and what a pita to set up. You have to set the wheel factor, chose MPH or KpH and set the clock all in secession with out mistake or you have to reset the entire unit and start over. This one has a sticky left button causing it to jump 2 selection at a time every once and a while. By the way if you want to rest the unit just hold down both buttons for a second or 2 in stead of removing the battery.
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I have one of those, it's a great product. But if the button is sticking, you should just return it to the store for another one.
 
roxrcool said:
O.M.G....you didn't build your own bike, did ya.....the speedo takes literally a minute to set up and another if you don't do it right the first time. the wheel factor is right in the little pamphlet in the kit. lmfao
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laff Build my own? Not yet, motor is in the mail. It might only take a minute to set up if it worked correctly. The sticking button would make it skip digits or advance to the next screen. Yep they give you a wheel factor chart, handy. Just relating that I got a bad one.
 
tsmra said:
laff Build my own? Not yet, motor is in the mail. It might only take a minute to set up if it worked correctly. The sticking button would make it skip digits or advance to the next screen. Yep they give you a wheel factor chart, handy. Just relating that I got a bad one.
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The digital unit that I have sounds quite similar. I had to put a ferrite bead on the wire coming from the sensor. It was going crazy because of the electrical noise generated from ith ignition system. It seems solid now. When I said that I doubted that My analog and digital units would never see thousands of miles. It was the bike and moter that I doubted not the insturments. I'll be quite satisfied if I can get 800 or so Mi. of this cheap little motor. However with just 200 mi. it is performing well.
 

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does anyone have a correction factor for the analog taiwan speedo that is advertised as suitable with 26"/27" wheels when using the 26 inch wheels? lets say according to the instrument im going 60km/h how fast am i really going?
 
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google has a really cool conversion thing. all you do is type in 60 kph in mph.....and you get

60 kph = 37.2822715 mph
 
the conversion is easy enough and i prefer metric anyway. what i mean is what is correction factor between the speed displayed on the speedometer vs actual speed? if theyre designed to be used with both 26" and 27", then its gotta be calibrated somewhere in the middle. on a 26" tire displayed speed would be a little faster than actual speed, while on a 27" tire displayed speed is a little slower than actual speed. i want to know how much its off
 
I think it is because a 26" is a mountain/cruiser tire and 27 is a skinny road tire...very close in circumference/height

just like a 24x3 is very close to a 26x2.125 in height
 
Finfan said:
OK, I am basing this solely on the cheap Taiwanese speedometer that I got from Spooky Tooth. If you check the picture below you will see that 200 rpm equals 21 mph so I'll start from there:

200 rev/min = (21 mi/hr) / (60 min/hr)

converting hours to minutes gives:

200 rev/min = 0.35 mi/min

Thus:

200 rev = 0.35 mi

Doing some unit conversions:

200 rev = (0.35 mi) * (5280 ft/mi)
= (1848 ft) * (12 in/ft)
= 22,176 in

Now divide both sides by 200 :

1 rev = 110.88 in

One revolution is equal to the circumference of the wheel and the circumference of a circle is equal to pi times the diameter so the diameter is equal to the circumference divided by pi:

diameter = (110.88 in) / (3.14159)
= 35.29 inches

So unless you have a mighty large front wheel these speedometers are useless! Likely they are a kids toy designed to make them think they are going a lot faster than they actually are.
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thats assuming the rotations per minute are accurate.
 
Mike Hunt said:
does anyone have a correction factor for the analog taiwan speedo that is advertised as suitable with 26"/27" wheels when using the 26 inch wheels? lets say according to the instrument im going 60km/h how fast am i really going?
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I use 191 for the digital for both 26" and 27" which are actually same size. Dead on compared with GPS.

These are very reliable once you take care of the reset problem and incredibly easy to set up. Only takes a few seconds. Calibration is also trivial assuming you have a cheap GPS (who doesn't these days?).
 
I won't put my money on it because I only just ordered it, but for those who want a classic look, why not go to the whizzer motorbikes catalog and buy one of their mechanical speedos. As opposed to those really cheap ones on ebay and spooky tooth, this speedo is made for the 26" whizzer wheel and I have never read any complaints about them. I am excited to get mine! After shipping it came to about $33. Just a suggestion
 
I hear the Wizzer speedometers are a viable option, that they're at least designed for these speeds... but I dunno about calibration, accuracy & wheel/tire sizes *shrug*

Good tip LS614 :D
 
A table of circumference I have in a spreadsheet-

Tire Size- mm- ft

16x 1 3/8 1282 4.20602406
20x 1.75 1491 4.89171753
24x 1 1753 5.75129499
26 x 1.0 1913 6.27622779
26x 1.0 1952 6.40418016
26 x 1.75 1985 6.51244755
26 x 1.75 2023 6.63711909
26x 1.9 2050 6.7257015
26x 2.0 2055 6.74210565
26x 2.1 2068 6.78475644
26x 2.125 2070 6.7913181
26x 2.35 2083 6.83396889
700x20c 2086 6.84381138
700x23c 2096 6.87661968
700x25c 2105 6.90614715
700x28c 2136 7.00785288
27 x 1 2145 7.03738035
700x32c 2155 7.07018865
27x 1 1/8 2155 7.07018865
27x 1 1/4 2161 7.08987363
700x35c 2168 7.11283944
27x 1 3/8 2169 7.11612027
700x38c 2180 7.1522094
 
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