True MPH and reading the speedometer

One of the answers is why do you need to look at the speedo the whole time - why not look at the road !

Don't GPS gizmos (tom tom etc) have speed read-out ?

 

Sounds like the original poster would benefit from some form of visible speedo. The portable GPS is a great idea as it serves may more purposes than speed measurement. For those of us who can see the dash, if just barely, one great improvement is to upgrade the gauge lighting. I know there are brighter lamps but that usually means hotter lamps. I need to pull my dash out to reinstall a gauge. When I do, I will experiment with bright LED replacements - and report back.

 

Yes they do. I've got a Garmin Quest 2 and it works great.

 

10% error is what I measured.
Start your chrono at the mile post while traveling at constant speed.
Stop the chrono ant the next mile post and read it. Some watches can tell you the actual speed.
At 70 MPH indicated my chrono measured 63 MPH.

 

my 328 speedo is about 5mph high, as checked against those portable flashing speed signs set up by the cops.

 

Get a GPS for a more accurate measure. I think the DOT says that manufacturers can't have the speedo read slower than you're actually at. Since there's always some error, they usually set it below so that it reads more than you're doing. I guess if yours is of 10%, wouldn't that mean your car has 10% more miles than it really does?

 

Bmw usually has a 7 percent error. Im not 100 percent positive but i have read many times that is more for safety reasons. That doesnt make much sence though because if you crash at a 100 or 93 i cant see that 7 percent saving your life.

 

Color me lucky, with Mich Pilot Sport PS2 255/4? R17 she is perfect according to GPS.

 

My first 77 read dead nuts, at least up to 120. My current one reads about 2% optimistic.
When you say you can't read the speedo, do you mean the steering wheel blocks it? If so, you can adjust the angle of the wheel by removing the cover on the underside of the steering column and loosening the 2 bolts that set the angle. Not by a huge amount, but it can be significant in terms of seeing the speedo. I'm sure there's a thread on here on the subject.

 

At 85 my speedo is bang on for a 78 308. Confirmed by Tennesee state troopers!

Regards,
JP

 

there was one of those side of the road lighted speed detectors the other day went through it three times. my 308qv speedo is spot on.

 

not sure which gps you are refering to, but what is the difference between a gps speed and a ferrari speedometer relative to focusing on the road?

 

my 348 is roughly 5% optimistic at "normal speeds" and seems to climb to 10% optimistic at more theoretical speeds, with gps (Garmin Nuvi). gps seems to be a 2-dimension speed, that is - it doesn't seem to take into consideration the 10% grade up or downhill as additional speed - anyone know?

I find the gps mounted on the windshield easier to read than the speedometer that's tough to see from 60km/h up to 220 or so.

 

that's a great question. I don't have the answer, but as a GPS is aware of the elevation, I would expect that it is 3 dim speed.

 

My Mondial's speedo is the other way around. It reads 75, but the gps says I'm actually going 84.5. I got my first ticket in 10 years because it read too low, so watch out.
Thor
www.JavelinArt.com