Speedometer Reads 6% High

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PianoAl

Well-known member
Joined
May 16, 2016
Messages
239
Every time I've passed one of those "Your Speed" displays

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The speed shown on the LEAF's speedometer is about 6% high. For example, the sign will say I'm going 50 MPH, and the dashboard display will say I'm going 53.

True for you?
 
mine is off a little in 30 zones.. I can be doing 33 on my reading and 30 on the speed display reader.

I've heard, in the past, that car mph reading can be up to 10% off calibration.
 
The size of the tires on the vehicle can affect this. I have not checked my Leaf to see if it is correct, but I see this on my truck. I installed tires that are one size larger than the truck was shipped with. When the speedometer shows 65mph, the GPS display shows I am going 68mph.

If the Leafs are all calibrated for the largest size tire option available for the car, but it ships with a smaller size, I believe that would result in the discrepancy being reported.
 
You can adjust it down 2.5% on the car (might require a SV/SL to have the center screen though), the rest is up to buying different size tires.

(Turn the Audio Power off, then press Map, Map, Map, Audio Power, Audio Power, Map)

The adjustment in the service pages, "Navigation", "Speed Calibration", is only +/- 2.5%.

If you can't get to that screen you might be able to get the dealer to use their scantool to set the -2.5% speedometer setting.

Then when you go to get new tires pick a tire with a RPM nearest to 815 revs per mile or 25.5" diameter. Doesn't have to match the OEM tire sizes just pick the size that matches the RPM/diameter.
 
baustin said:
The size of the tires on the vehicle can affect this. I have not checked my Leaf to see if it is correct, but I see this on my truck. I installed tires that are one size larger than the truck was shipped with. When the speedometer shows 65mph, the GPS display shows I am going 68mph.

If the Leafs are all calibrated for the largest size tire option available for the car, but it ships with a smaller size, I believe that would result in the discrepancy being reported.

The tire size between the OEM 16" and OEM17" is good for 2.x/3.x% depending on which way you do the math (815/837 vs 837/815). The rest is based on that stupid law that says that the car has to be sold with a speedometer that reads 0% to +10% on speed. There is a fine for the manufacturer if the speed is under reported but not if over reported less than 10%. So they make sure it will over report on even the largest tire that will fit.

Then you the consumer can remove the OEM tires and put on tires that correct that error and you as a consumer are allowed to adjust any calibration setting the speedometer might have.
 
Nope, the speedo on my 2017 Volt is dead on... Our 2013 CUV is also dead on... Nissan is simply lazy or playing a game...

bowthom said:
According to mfr specs and DOT regs a speedo error range must be +2.5/-0, so all speedos read fast when delivered.
 
bowthom said:
Hello,
According to mfr specs and DOT regs a speedo error range must be +2.5/-0, so all speedos read fast when delivered.

They all read fast but you need to site a source or I'm going to disagree.

https://www.fmcsa.dot.gov/regulations/title49/section/393.82 says "Each bus, truck, and truck-tractor must be equipped with a speedometer indicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph)." which is +10%/-10%

http://standards.sae.org/j1226_201108/ SAE J1226 "To begin with, manufacturers are afforded the latitude to aim for within plus-or-minus two percent of absolute accuracy or to introduce bias to read high on a sliding scale of from minus-one to plus-three percent at low speeds to zero to plus-four percent above 55 mph. And those percentages are not of actual speed but rather a percentage of the total speed range indicated on the dial. So the four-percent allowable range on an 85-mph speedometer is 3.4 mph, and the acceptable range on a 150-mph speedometer is 6.0 mph."

http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r039r1e.pdf UN ECE Regulation 39 says : "no speedometer can read slower than the actual speed. Ever. On the high side, it’s allowed to read up to 10% above the actual speed plus four or six kilometers per hour, depending on the type of vehicle." So this one can be 0%/+10%.

And since the manufacturers don't like to do much customization per market they often just let them ride in the +3% to +8% zone for so they have plenty of margin for error.

So yeah I'll go with "all speedos read fast when delivered" but I don't agree with your +/-.
 
PianoAl said:
So, no way to calibrate it in my 2016 LEAF Model S?

As I said above. The dealer might be able to adjust it -2.5% using their tools. Past that you'll have to buy different sized tires.

Pck a tire with a RPM nearest to 815 revs per mile or 25.5" diameter. Doesn't have to match the OEM tire sizes just pick the size that matches the RPM/diameter.

Ideally if you care about range you'll also get rid of the steel rims that come with the S and get 15" alloy rims that weigh around 15 pounds per.

196/65/15 is similar to your current inaccuracy but will increase range.
205/65/15 will reduce speedometer by about 2%

205/60/16 is also good for about -2%

I'd avoid going further than a 3% reduction by tire size due to the lack of variety/sizes of narrow tires with high diameters preventing us from getting larger diameters in narrow tires. It's also not a bad idea to just to stop with a mild correction so you don't have to worry about clearance/rub issues.
 
All my vehicles go faster than the speedometer indicates-- my pickup is 10% faster. I just keep a gps going that shows my actual speed. Whatever speed that says is what police radar will show. At least that is what a deputy friend told me.
 
It's the S model with 16" wheels/tires. I was told by the Leaf Specialist group that the odometer is 100% accurate while the speedo is not.

Low speeds under 40, it's usually 2 mph off.
Middle speeds of 50-60 is usually off by 3 mph.
Higher speeds of 60+ are off by 4+ mph.

I've been told there is nothing the dealer can do. With the S model, you cannot adjust +/- 2.5 mph like with the SV and SL.
 
TomT said:
Nope, the speedo on my 2017 Volt is dead on... Our 2013 CUV is also dead on... Nissan is simply lazy or playing a game...

bowthom said:
According to mfr specs and DOT regs a speedo error range must be +2.5/-0, so all speedos read fast when delivered.

I have found that every car I have owned was off at least 1-2 mph, even my 2006 Prius. The worst one was my 1986 Maza 626GT Turbo, which I had checked out by the same speedometer shop that does all the state police near me. The speedometer was high by 7% and the odometer was high by 4%, putting on 104 miles for every 100 I drove! I had them put a 5% gear reduction in, which put the speedo much closer, and started taking off some of the extra miles the odometer had added. I think I would have had to drive 200-300,000 miles to get even though.
 
My 2015 LEAF S is about 4-5% fast on speed. I plan on replacing the tires with a taller-aspect tire when they wear out to help minimize the speedometer error.
 
I think that both the speedometer and the odometer are tied together. So, if one is off, then they both are.

I noticed that a software update mostly corrected for the 16" wheels on our Leaf S vs the 17" on the SV / SL models.
 
NeilBlanchard said:
I think that both the speedometer and the odometer are tied together. So, if one is off, then they both are.

I noticed that a software update mostly corrected for the 16" wheels on our Leaf S vs the 17" on the SV / SL models.
I think the same but was told differently by Nissan. I haven't done any actual mileage tests vs. mapped distance type experiments.

Which software update?
 
aarond12 said:
My 2015 LEAF S is about 4-5% fast on speed. I plan on replacing the tires with a taller-aspect tire when they wear out to help minimize the speedometer error.

I've gotten quite used to just adding 2MPH to the speed at which I set the cruise control, knowing it reads that much high anyway. It seems like I get to go faster. ;-)
 
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