The Truth what is it?

cqyqte

Grumpy retired oldtimer... "eat a Snickers bar"
As most of us here I like to go fast and tinker with whatever is in the stable to make it go faster and look sweeter. Most of the bikes and cars I've owned I have modified and in my opinion are faster and safer at the posted speed limit than what came from the factory.

Here comes my point. Several times in creating a custom bike I have searched for the right gauges and opted for a new piece of technology that requires calibration before the job is completed. There are equations, proceedures and rechecks to be done to make sure you get it right. Yes there's the mark off a mile and ride and set method, there's the measure the tire select the right numerical key method, then there's the drive along side a vehicle and calibrate the gauge to accurately reflect the factory setting of that vehicle method, and last but not least there is the GPS calibration method. All of these means to establish accuracy in a new gauge for a custom build gives you results.

I have done them all, but no matter which one I have chosen I have found that when I ride with friends, albeit for coffee, a trip, or just out for a rip, I get "Man you are going to get caught for speeding one of these days!" Now I do run hot on any road no matter what the posted speed limit, but normally only 10 over. In my neck of the woods most cops on radar duty don't ticket you unless you are 16 over or running hot through a school zone.

So why the comments from the righteous friends? Well, and I am sorry for the long wind, but I have found that most of the factory bikes that my friends ride read faster than they are actually going. Now, I can here the doubters rustling as I type. I have experiment with this idea to see if it is Mythbuster "Busted" or "Confirmed". I have affixed GPS units to their bikes individually, we have found a construction site with one of those radar signs and run multiple bikes at it a speedo held speeds, and have driven with friends in expensive cars on the highway where they have set the cruise at 60. In every instance the factory bike has indicated the wrong speed. In the case of GPS the factory bikes indicated higher speeds than the GPS, the radar sign read lower numbers than those on the factory dial. Now lastly on the highway with a car held to 60 by cruise control each bike had to run faster than 60 to keep up. The last test to attempt to validate our results we ran the same construction site with the car held again at 60 and the radar sign confirmed 60.

For the record, the factory bikes we played with in this less than perfect experiment were, Yamaha VMax, Honda Goldwing Aspencade, Triumph SpeedTriple, Kawaski Concours. So what's up? Are the factories looking out for our best interests because they know we like to run hot when we ride. Is Big Brother controlling us more than we think :eek:
 
I dunno.
My cb350 reads high.
I had it up around 90 and was pretty proud of her. Then I switched to a gps speedo and found out that 90 was only about 75 :/
 
I rest my case, maybe in some magical test facility that CB actually runs the speed that the speedo indicates but not in the real world.
 
From my experience most of the Japanese bikes are about 10% over. Add that into any change in tire diameter and a gauge that cannot be calibrated, at least the vintage cable drive ones.
 
I read somewhere that the bike manufacturers erred on the side of reading high because the fines for reading too low were astoundingly high per bike. Every Honda I've had has read at least 10% too high, if not 20% too high.

Do the 3/4Ton? ;D

Ah, here we go:
http://www.popularmechanics.com/cars/how-to/4260708
 
I have found very consistently that factory speedometers on motorcycles AND cars read at least 5 mph faster than the GPS indicates when at highway speed. That's around a 10% error. On one ride I was on with two other riders, they complained about how fast I was going. I was doing 10 mph over, according to my GPS. They thought I was doing 15+ mph over.

It also blows my long-held belief that troopers will only pull you over if you are doing 15 mph or more over the limit. Now I realize that many of them will stop you for 10 over. Best to keep to 9 mph over the limit as indicated on the GPS.

I also sometimes wonder if MPG calculations are subject to the same error.

It is my belief that the MOST accurate way to calibrate a speedometer is by GPS on level ground. I assume that changes in elevation can affect the speed indicated slightly due to your path being a vector from level.
 
I agree you have to consider the accuracy of the GPS before you completely trust it to govern your speed. I normally check to see that it is at least reading my location to within 3 feet of accuracy before I trust it for my speed. Things like global current events can reduce GPS accuracy significantly, like before the start of the war in Iraq GPS accuracy was around the 3 foot mark, however several days before the war GPS accuracy dropped in North America and remain low during the conflict. Guess the satellites were busy elsewhere... ;D.

Either way I guess it is for the better that the factory speedo read high, saves lives probably just deflates ones' ego to know that you weren't really doing the Ton, unless you used some other means to determine your speed other than the factory gauges.
 
You're only working that out now? Since Jap bikes have been imported their speedos have lied. No point in making a 90 mph bike and telling the public your product is a 100 mph bike if the speedo can't back up that claim,
 
Automotive speedo's most certainly indicate an optimistic reading in most cases. I have one friend that owned a 2004 or 5 Toyota Matrix that read 10 kph lower than it actually ran! :eek: He was regularly flying past people when he drove it!! We put the car on my "low speed dyno" and checked it to be certain and verified his suspicion.

The dealer had no explanation and claimed he couldn't fix it. ???

As well, I find that automotive factory tach's are off too. Usually at least a few hundred rpm higher than actual. :)
 
The Ducati definitely reads over; as much as five mph at city speeds and more than 10 at highway speeds. This was tested and verified after I began to wonder why other people drove really fast, but only when I was on the bike.
 
I've found every bike I've tested to be off - there's several handy smartphone apps that will display the speed in screen filling numbers as to not distract you too badly (other than the problem of riding one handed, right? ;D ). On top of the built in inaccuracies, I have a feeling that a wheel driving a gear driving a cable driving a gear driving a needle might be somewhat of a lossy system after 20-30-40 years. Tolerance stack up and all that.

I have found my car to be dead nuts on with GPS, or at least as accurate as a needle on a gauge can be. It pulls the speedometer reading off the ABS wheel speed sensors, however, and I imagine those have to be pretty accurate. Like the way drive by wire throttle eliminated cruise control amplifiers and idle air valves / controllers, I think vehicle speed senders are going the way of the dodo as manufacturers can consolidate functionality into fewer parts. Most motorcycles are available with ABS as at least an option, so there's your accurate wheel speed sensor right there!
 
No idea what speed mine is "actually" moving at but my speedo was reading a hair over 80 a few days back.

Tell you what........... On my little 350, it felt like 150! ;D hahaha

Like I say; I have no idea of the actual speed but, it felt fast as hell. 8)
 
If its like my 350 you're probably doing about 67 :D

funny isn't it.
 
I thought I was close to doing the ton, until I switched to my iphone as a speedo. Then i quickly realized its unachievable without some more power and different gearing.
 
SONICJK said:
I thought I was close to doing the ton, until I switched to my iphone as a speedo. Then i quickly realized its unachievable without some more power and different gearing.

Yep. :)

I've seen/heard a few claims of it but, to myself, I think not.
 
Another good reason to have a cop as a friend. I just cruise by at the posted limit, he hits me with the radar, and I return to see what I was really doing. All of the bikes I've tried are 10% optimistic.
Interestingly all my cars/trucks have been close.
 
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