speedometer error

I read on one of the forums about the speedometer errors.Very interesting.
I wondered why I was always getting passed on the expressway. It is good to know that it is about ten mph slow.Went for a short ride but the smoke is bad here from the forest fires near hear in southeast georgia.It has burned close to 100,000 acres so far and still burning. Hope it rains soon. But not too much so we can get in some good ride time before it gets so hot.

You should do your best to go with the flow of traffic at all times, even if it means speeding. Only look at the speedometer if you're going faster than others.

Somewhat similar, I subscribe to the belief that as a rider, I want to be going slightly faster than surronding traffic. This allows me to choose the places where I will pass, and allows more control of the lane area around me.

I believe it is just one more thing putting the odds further in my favor to make it home.

I'm with writeme43 on this one, I prefer to always be overtaking traffic. besides if you go fast enough the objects in your mirror no longer matter!!!

I tested the speedo error this morning! I was riding to work on the expressway at 3:30 a.m. normally there is no real traffic. this morning I came up on a pack of cages doing a speedo indicated 68mph. the posted speed limit is 65mph. I began to split the pack, as I got to the lead car that was causing the bottleneck, just as I thought it was a CHP! seeing how lane splitting is legal in CA. and to easily pass the traffic I was going 77mph,I decided to continue my pass and split the cop and the poor sap to scared to go the posted limit just because the cop was sandbagging. as I pulled away from the cop he left the pack of cars and blew past me. apparently I ruined his fun or a new dounut shop just opened, but either way if he was looking to give me a ticket if the speedo was accurate I would have been 12mph over the posted limit. as is he did nothing.:Sport:

i don't look much on the speedo. lol. as long i overtake and enjoy the road thats fine with me. you would know your limit anyway,. :rockon:

I thought splitting lanes were legal in California only if you are going under a certain speed limit like 35mph, or is it any speed, am I wrong?

VEGASRIDER said:

I thought splitting lanes were legal in California only if you are going under a certain speed limit like 35mph, or is it any speed, am I wrong?

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theres no speed limit for splitting lanes, at the DMV they call it lane sharing, its perfectly legal. (thats one good thing about CA.)

:Sport:

theres no speed limit for splitting lanes, at the DMV they call it lane sharing, its perfectly legal. (thats one good thing about CA.)

Cool........can't wait to ride in California!

I GPS'd my speedo a while back, it was 3 MPH fast at a true 65.

I can't quite understand why there'd be any error on a speedometer. There's a straight linear relationship between engine rpm and wheel rpm, and again between wheel rpm and bike velocity.
That should be cake to calibrate. And if the speedometer is accurate below a certain mph threshold, it should remain accurate above that threshold, too.

Botch said:

I can't quite understand why there'd be any error on a speedometer. There's a straight linear relationship between engine rpm and wheel rpm, and again between wheel rpm and bike velocity.
That should be cake to calibrate. And if the speedometer is accurate below a certain mph threshold, it should remain accurate above that threshold, too.

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Yesterday I went through a fixed speed indicator, I knew it was there so I checked my speedo. I was doing 28mph in a 30mph zone. The roadside indicator put me at 29mph. I don't know who's wrong. Do the authorities over calibrate to make us take care. Or is my speedo really that inacurate?

You were doing 29mph and the roadside indicator showed 29mph aswell.

What's wrong with you speedo again ?

strike_force said:

You were doing 29mph and the roadside indicator showed 29mph aswell.

What's wrong with you speedo again ?

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Sorry mate, im typing in the dark, I was doing 28mph (typo)

Yamaha engineered it like that... The speedo is slow but the odometer is dead on... I wish I had an extra guage pannel to rip apart and find what resistor to change to make both correct rather than using a speedo healer to correct and then have the odometer off.

Khyren

Based on my GPS the speedo on my FZ6 is off by a couple of miles (reads low) up to 55 mph and then is basically 10% low above that. I understand that most bikes are this way for liability. My cage is closer but also low (a couple of mph @ 65 mph).

Since I'm a geek engineer I presume that at best they figure out how accurate the reading is and than place the tolerance all on the low side - like not 65 +/- 5% but 65 - 10%. This would make sure you never, ever were going faster than the speedo said. Worst case they do this and then pad it even more 'cuz the lawyers said to.

Botch said:

I can't quite understand why there'd be any error on a speedometer. There's a straight linear relationship between engine rpm and wheel rpm, and again between wheel rpm and bike velocity.
That should be cake to calibrate. And if the speedometer is accurate below a certain mph threshold, it should remain accurate above that threshold, too.

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Your forgetting about the fact that tires get bigger around the faster you go. Resulting in effect, a reduction in gear ratio, meaning the speedo will read slower for a higher velocity. Because not all tires are the same the engineers could be over compensating for this effect. Otherwise I agree with the guys who said it was engineered in as a liability limiter, though you won't see the reduction on Euro bikes as much as Jap bikes.

trailblazer87 said:

Your forgetting about the fact that tires get bigger around the faster you go. Resulting in effect, a reduction in gear ratio, meaning the speedo will read slower for a higher velocity. Because not all tires are the same the engineers could be over compensating for this effect. Otherwise I agree with the guys who said it was engineered in as a liability limiter, though you won't see the reduction on Euro bikes as much as Jap bikes.

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Ah-ha, that makes sense! So does the liability issue, to be sure, but the expanding tires explains why (I thought I had read this somewhere here) the speedo is consistent but starts to behave non-linearly at north-of-legal speeds.

Khyren said:

Yamaha engineered it like that... The speedo is slow but the odometer is dead on... I wish I had an extra guage pannel to rip apart and find what resistor to change to make both correct rather than using a speedo healer to correct and then have the odometer off.

Khyren

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After the new sprockets, kinda had to install a speedohealer. You guys think yours is bad by being off 10%... I was doing around 69mph and i was getting an indicated 90mph.

That's off.

Anyway, these marvelous little devices DO correct your odo. at least, it corrected mine...pretty much completely.

sportrider_fz6 said:

theres no speed limit for splitting lanes, at the DMV they call it lane sharing, its perfectly legal. (thats one good thing about CA.)

:Sport:

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"Lane splitting by motorcycles is permissible under California law but must done in a safe and prudent manner."

It's open to interpretation - it's apparently challenging to find a cop that thinks it's "safe and prudent" at speeds 35+

In other words - the faster traffic / you are going - the more likely you are to get a ticket. The "rule of thumb" is to go no more than 10 MPH than surrounding traffic. Again - very subjective. The courts tend to side with the siting officer as to what "safe and prudent" for the conditions are.

Jeremiah said:

"Lane splitting by motorcycles is permissible under California law but must done in a safe and prudent manner."

It's open to interpretation - it's apparently challenging to find a cop that thinks it's "safe and prudent" at speeds 35+

In other words - the faster traffic / you are going - the more likely you are to get a ticket. The "rule of thumb" is to go no more than 10 MPH than surrounding traffic. Again - very subjective. The courts tend to side with the siting officer as to what "safe and prudent" for the conditions are.

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I might be incorrect, but I thought California lane splitting was legal up to speeds no faster than 35mph, and no faster than 15mph than the flow of traffic. However, probably most Cali riders don't adhere to those rules. Ironically, when I took a trip to LA last December on my bike, the only opportunity I had to split lanes were the last 5 miles of California entering back into Nevada. It was bumper to bumper and traffic puttering at a putt putt pace. I had all kinds of cagers and even truckers honking and trying to sqeeze me, at times I sqeezed by with less than an inch to spare on both sides. I even had some guy open his car door. And there were times where I just couldn't get thru. I was still in California so it was perfectly legal, however, If I did get into a wreck with someone, not sure how much the law would be on my side. At times, I split traffic here in Vegas on the surface streets along or near the strip where the traffic is real bad, even though it's illegal. I just don't have the patience to wait it out, and I figure it's one of the advantages of riding a bike.