Speedometer

I went through a Radar sign that gives your speed and what the speed limit is. I had my 2005 Corolla nailed at 35 mph and the radar fluctuated between 32 and 33 mph.Who do I believe? My Corolla is a CE with the smaller tires. Does Toyota use all the same speedometer parts for both cars. This seems like a big discrepancy. Ron

Reply to
n877
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I'd believe my speedo. I've yet to see a radar post (I'm assuming it's one of those billboard ones?) that gives an accurate and stable reading. Best bet is to call your highway troopers and find out where they have a 10mile odo checker and then compare the 10mile reading with 10 miles on your odo. From there you can get an idea how far off you might be. I'm going to do that to my Jeep when I throw bigger tires on it. As an additional note, when I check my '01 Corolla CE on the highway (10km checker) I am consistently

0.1-0.2 KM off after 10km. My '97 Corolla SD is 0.7 km off. My Jeep is probably 30km off ;p
Reply to
griffin

Two miles an hour off at 35 MPH is pretty darned close - you can easily remember that much of a 'fudge factor' correction. I would trust a 10-mile measured calibration route or a GPS unit, radar isn't perfect (especially the cheap units used in the "Your Speed" tattletale signs) but GPS is a lot closer.

And the odometer can be calibrated wrong and the speedometer right (or vice versa) easily - the odometer is a simple mechanical counter and is never perfect. The older mechanical speedometers operate through magnetic reluction, and assembly-line calibration is an inexact science when the factory churns them out by the thousands - they get 60 to indicate right and move on to the next unit...

Tire brand, type, size and wear affects the calibration too - every make is slightly different in circumference, and as the tire wears it gets slightly smaller and turns slightly faster...

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Reply to
Bruce L. Bergman

My wife got another speeding ticket last year in the 97 Camry 4 with 14 inch wheels and as part of the legal manuevers the lawyer had us take it somewhere that would calibrate the speedometer and show that she didn't know she was going that fast. It turned out that the speedometer was showing 3-4 MPH higher than actual speed. I noticed this also in my old 94 Camry some time ago when driving alongside a new (at the time) Cadillac with big digital speedometer readout that you could see from outside the car. Maybe Toyota calibrates speedometers a bit too high to give you a chance when getting clocked by radar.

Reply to
badgolferman

I've heard +0%/-3%, actual vs. indicated speed, tossed around as a speedo accuracy statistic. In other words, it's OK if it reads a little high, but never low. The radar may have been correct.

Smaller tires make a speedometer and odometer read _high_, as they make more rotations per mile than a given standard.

Know anyone with a GPS? Even the cheap ones are quite accurate for speedo checks these days. You could also time yourself over a measured mile.

Barry

Reply to
B a r r y

the speedometer always is on the high side (original wheels+tires). the faster you are driving, the more difference between speeds. this is standard, i'd believe the radar post

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Reply to
Swamigo

Generally, most speedometers record slightly high.

mike hunt

badgolferman wrote:

Reply to
MajorDomo

Wouldn't that make it *less* likely to get a speeding ticket? For example, ff the speed limit is 60km/h and the leeway is +12km/h and you're doing

70km/h, it would show is 73-74km/h and you shouldn't get a ticket even though you appear to be speeding in your car. However, in order to be speeding 12km/h+, you'd have to be doing 72km/h which would read as 75-76km/h in your car.

Then again it's 9:45am and my brain is still mad at me for waking up so dyslexic be could I.

Reply to
griffin

AAA has a machine to test the speed of your car. It is kind of like a smog check machine and your car is running on the big roller.

Reply to
Guy

Believe your speedometer and you will never get a speeding ticket.

Speedometers are typically off by a few percent, and they are off on the high side so when your speedo is telling you that you are doing 35, you are not really doing 38. If the cops get you for doing 45 in a 35, the judge doesn't want to hear stories of woe that the speedo is not accurate. If the speedo is not accurate, the error should benefit you, not harm you.

Yes, Toyota will use the same parts for all cars, the difference in the CE and the LX will be the speed sensor in the transmission. When the tire size changes, then the engine output will also change because a small tire will travel, for example, 4.5 ft per revolution, but the larger tire will travel

6 ft. Since there is a difference in the distance travelled because of the tire size, then there will also be a difference in the speed over the same distance. The larger tire will display a slower speed, so it will actually be carrying the car faster at the same speed. Get it?

The speedometer can be calibrated by calculating the stock tire size and the "new" tire size and determining the number of teeth on the speed sensor's gear, then altering the gear (changing the number of teeth) so the speedometer comes back into the proper range. If the small tires take a gear with 27 teeth, the larger tires will take a gear with 28 or 26 teeth to make the speedo accurate again. (I pulled gear counts out of my ass to illustrate the point, the actual gear count can be different.) The number of teeth and the direction (higher or lower) will depend on the amount of change of the tires. I realize you have not changed the tire size, but the way the factory accomodates the base model and the luxury version is the same as I describe. The speedo head itself is the same.

The error you report is 7.14%, this is pretty normal. I wouldn't worry that something is wrong.

Reply to
Jeff Strickland

If the speedo is showing a speed that is HIGHER than the actual speed, you should never get a speeding ticket because when the speedo shows 40, or 70, or whatever, it is showing a speed that you have not attained yet. So, unless the speedo is showing a number that exceeds the number on the sign, you will never be speeding.

It is common that auto makers set the speedo to show a higher than actual speed. They don't want to eat your tickets becaused they told you that you were doing 35 when you were really doing 40. They prefer to tell you that you are doing 40 when you are really doing 35. It's safer for them and for the rest of us.

Reply to
Jeff Strickland

Timex makes a handy device, I think they call it a Stop Watch.

If you set your cruise control and measure a mile from signs alongside the roadway, then divide 3600 by the time it takes to pass the mile marker, the result is the setting of the cruise control.

Reply to
Jeff Strickland

This is not true if you are still going too fast. You are assuming people only speed slightly over the limit when in her case it was nearly 12 MPH over the limit.

Yes, I figured as much.

Reply to
badgolferman

But wouldn't that 'log on more miles' than you actually travelled?...unless they arrange it so that the odo doesn't read high?

Reply to
Gord Beaman

But you said that the speedo shop showed the speedometer to be reading faster (higher) than the actual speed. No matter how much over the speed limit one drives, the speedo always reads a little more. So, if one does what the speedo and the signs say, then they will NEVER be caught speeding.

Reply to
Jeff Strickland

It isn't a big deal. The error rate is a matter of a couple of percent, and if all cars have a similar error rate, then the comparisons will be the same. On 10,000 miles, the error is in the range of a couple of hundred miles.

Reply to
Jeff Strickland

And thus your warranty is used up faster than it should have been.....

You win some and lose some. Tomes

Reply to
Tomes

Posted speed limit = 35 MPH Clocked speed = 47 MPH Over limit = 12 MPH Speedometer = 50 MPH

No matter what you say, she was still speeding. As I said before, the sign was not a factor in her mind. The screaming baby in the rear seat was her entire focus.

Reply to
badgolferman

I actually believe in those radar signs, as I have paid a lot of attention to this lately. I go by about 4-5 of them in different towns and my Jeep TJ's speed is spot-on on each and every one of them. (The wife has the Sienna btw.)

The reason that I have paid alot of mind to this is that I went from baby tires (215s) up to more medium sized tires on the Jeep. Originally it was running as Jeff discussed (good to see you here Jeff), more miles than reality. I was worried that I would be in the trouble zone where I would be now speeding without knowing it, but the 235s put it right on for me. Now my eyes are drawn to these signs every time like moth to the flame. Tomes

Reply to
Tomes

You can be damn sure the sign was a factor in the cop's mind though.

What I am trying to illustrate is that the speedo is wrong in your wife's favor, and she still stood on the pedal hard enough to shatter the sound barrier. The only important numbers in this discussion are SIGN = 35, SPEEDO = 50. It turns out the clocked speed has the same variance as the shop reported.

The original post seem to imply that the speedo error was part of the speeding problem, but it was not. I have been saying all along that your wife was speeding.

Reply to
Jeff Strickland

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