Speedometer 4-5 mph under actual speed
 

Around my neighborhood we have speed limit signs with radar guns built into them. They tell you how fast you are going along with the actual speed limit.

The speed indicated on these devices is consistently 4-5 mph lower than what my speedometer shows.

I know that most car speedometers show mph a couple miles below actual, but 4-5 mph seems too much.

Is anyone else's TCH speedometer this far off?

Paul

Re: Speedometer 4-5 mph under actual speed
 

You're so on this. On each of four 200 mile trips the odometer was off, 1 mile under the actual distance on each trip by the mileage posts. But the indicated mph was 5 to 7 mph faster than actual by the car computer, radar checks and hand calculation. That's 7 to 8% error. I do overinflated my tires to 40lbs., but that should make the mph error smaller and explain the under odometer reading. What gives here? Does anyone have an answer?

Re: Speedometer 4-5 mph under actual speed
 

The inaccuracy of the TCH speedometer has been the subject of significant discussion since June when I first pointed this out. A number of forum members have tested their speedos with handheld GPS devices and have verified this. You can search these various threads for more on this topic.

Re: Speedometer 4-5 mph under actual speed
 

Does the tread stretch when you over-inflate? I think not! The sidewalls stand taller, but the circumference of the tread, held in check by steel belts remains virtually unchanged. If the tire circumference is the same at different inflation pressures, then the speedometer/odometer reading will also remain unaffected by inflation changes. The car will ride higher at higher pressure, but the tread with the steel belts do not stretch, and the tires will still turn around exactly the same number of times per mile as before.

-- Alan

Re: Speedometer 4-5 mph under actual speed
 

I searched the threads and found the ones about the speedometer being off. However, other folks seem to see a 5% difference between actual spp=eed and speedometer. I see a 10% difference. If my speedometer shows 40, I am actually going 36. If my speedometer shows 50, I am really going 45.

I'm fine with a 5% difference, but it bugs me that it's 10%.

Re: Speedometer 4-5 mph under actual speed
 

On the bright side, it just might get you out of a reckless driving ticket when you're doing 90 on the interstate! ;)

Seriously, I think any discrepancy greater than 5% should be grounds for a warrantable repair. Contact your dealer, and be sure to post back and let us know what happens. Thanks.

Re: Speedometer 4-5 mph under actual speed
 

The Toyota Camry Hybrid Repair Manual (page ME-40) gives the factory specifications for the speedometer as follows:

Reference: mph (for USA)
Actual speed 20 — Acceptable range 20.0-23.0
Actual speed 40 — Acceptable range 40.0-43.5
Actual speed 60 — Acceptable range 60.0-64.0
Actual speed 80 — Acceptable range 80.0-84.5
Actual speed 100 — Acceptable range 100.0-105.0
Actual speed 120 — Acceptable range 120.0-125.5

Reference: km/h (for Canada)
Actual speed 20 — Acceptable range (17.5-21.5)
Actual speed 40 — Acceptable range 38.0-42.0
Actual speed 60 — Acceptable range 58.0-63.0
Actual speed 80 — Acceptable range 78.0-84.0
Actual speed 100 — Acceptable range 98.5-104.5
Actual speed 120 — Acceptable range 119.0-125.0
Actual speed 140 — Acceptable range 139.0-146.0
Actual speed 160 — Acceptable range 159.0-167.0
Actual speed 180 — Acceptable range 179.0-188.0
Actual speed 200 — Acceptable range 199.0-209.0
Actual speed 220 — Acceptable range 219.0-230.0

You'll note that the speedometer is not allowed to under-read, as per international legislation. The error is supposed to be less than or equal to 5% according to Toyota's specifications. Mine seems to be accurate to within 1-2%.

Stan

Re: Speedometer 4-5 mph under actual speed
 

Maybe it's rigged to slow you down for FE purposes ;). Probably not but it's worth asking once.

Re: Speedometer 4-5 mph under actual speed
 

No. It's to make sure that you're not actually exceeding the speed limit when you follow the indications of your speedometer.


Stan

Re: Speedometer 4-5 mph under actual speed
 

FWIW - I just verified my Speedometer reading this AM via independant GPS (Garmin GPS-V) at a couple of speeds;


30mph indicated - 28mph GPS
40mph indicated - 37mph GPS

I have not yet been on the freeway with the Garmin in in the car. BTW - it was registering 7 satellites most of the time.

So - it would appear that our fuel economy figures would be inflated as well. :(

When I buy my new 17 or 18 inch wheels for summer, I will run a slightly larger (diameter) tire to help make up for the error.