OK, I know this topic has been visited here before, but I have a few more questions. Yesterday I was riding with a friend on the interstate. I was leading and he was about 50 yards behind. I scooted up to 90 mph (at least that's what the speedo read). When we got off down the road I asked him how fast he was going and he said his GPS recorded 78 mph. I know he may not have kept up with me but it got me thinking... How fast was I really going? Is the GPS more accurate that a speedometer? Has anyone here read a ride report or review that states the speedometer error on a Stryker. It sure felt like 90 mph on my bike and I didn't notice any Harleys passing me.
speedo error
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That is correct sir
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How can we fix this? I put on the 240 and I have no idea how fast I'm going. Lol
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What about if someone wants to keep the stock tire how can it be fix without changing tires size??
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I put the Avon 240 on and the speedo is much more accurate....still just a smidge off at 70. GPS reading 70, speedo shows about 68-69
It's reading dead on at 60. To answer the op's question on GPS, it is my understanding that a GPS is about as close to being 100 percent accurate as you can get.
It's reading dead on at 60. To answer the op's question on GPS, it is my understanding that a GPS is about as close to being 100 percent accurate as you can get.
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Thanks dreadly. Wonder why the stock setup is off so much?
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Good to know. Doesn't make sense that they didn't stick with the 240. Thanks
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Although this seems like a logical answer it's not correct.Ronin said:
This subject was discussed in another topic. And I posted a article on the subject but I can't remember what topic it's under.
All auto and motorcycle companies have 5% to 10% error margin they use intentional.
Most speedometers have tolerances of some ±10%, mainly due to variations in tire diameter.[citation needed] Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size. Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error, to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle, to ensure they are not liable for drivers violating speed limits.
Excessive speedometer error after manufacture can come from several causes but most commonly is due to nonstandard tire diameter, in which case the error is
\mbox {Percentage error} = 100\times(1-\mbox{new diameter} / \mbox{standard diameter})
Nearly all tires now have their size shown as "T/A_W" on the side of the tire (See: Tire code), and the tire's
\mbox {Diameter in millimetres} = 2 \times T \times A / 100 + W \times 25.4
\mbox {Diameter in inches} = T \times A / 1270 + W
For example, a standard tire is "185/70R14" with diameter = 2*185*(70/100)+(14*25.4) = 614.6 mm (185x70/1270 + 14 = 24.20 in). Another is "195/50R15" with 2*195*(50/100)+(15*25.4) = 576.0 mm (195x50/1270 + 15 = 22.68 in). Replacing the first tire (and wheels) with the second (on 15" = 381 mm wheels), a speedometer reads 100 * (1-(576/614.6)) = 100 * (1 - 22.68/24.20) = 6.28% higher than the actual speed. At an actual speed of 100 km/h (60 mph), the speedometer will indicate 100 x 1.0628 = 106.28 km/h (60 * 1.0628 = 63.77 mph), approximately.
In the case of wear, a new "185/70R14" tyre of 620 mm (24.4 inch) diameter will have ~8mm tread depth, at legal limit this reduces to 1.6mm, the difference being 12.8mm in diameter or 0.5 inches which is 2% in 620 mm (24.4 inches).
http://en.wikipedia.org/wiki/Speedometer
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A little late at night for that much math but it makes sense. It's all about the liabilities. Thanks for the info Toby
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I can't find the article I read but I remember it saying that international regulatory laws differ country to country. The 10% margin allows for maximum size tires to be installed ( without modding the frame or enlarging wheel well etc.) without exceeding the 10%. That's why when you put the largest tire possible ( without mods) on the Stryker the speedo is actually reading closer to correct.snowman68 said:
I think this is something that should be brought up when you resell a vehicle because the amount of miles would be 10% less than the actual odometer readings thus the value would be different? Food for thought. Here comes the math, this ones a little simpler, 10% of 200,000 miles 20,000 less miles thus the value being more. Ok you guys can stop me any time now. I'm getting a head ache
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So the error is on the high side of the speedo? If my speedo says 80 im probably closer to 75? If so saweeeeet. Means I can now drive a little faster than normal.
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