I drive a 97 accord ex inline 4

I have a TomTom Go (GPS). It displays the MPH, which is 3 MPH lower than what my car reads. For example when i'm at 75mph the GPS will read 72mph.

Which do you think is more accurate, my car or the GPS?

 

are your tires the stock size and at the right PSI? if not, I'd trust the GPS, they are damn good at telling you your mph.

 

have someone roll next to you at the same speed and compare your speedometers. or try putting the GPS in another car and see if it's still off.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by businessmanph &raquo;</TD></TR><TR><TD CLASS="quote">Which do you think is more accurate, my car or the GPS?</TD></TR></TABLE>Probably the GPS. It's VERY common for speedometers to read high.

 

The GPS hands down. I operate a Trimble AG134 for my job as a drive test engineer, and it's actually successfully argued my way out of a speeding ticket with the systems recall and printout function. The GPS takes waypoint computations every 1/2 second and computes your speed based on time for distance traveled.
As to your variation on your speedo indications. This can change from no more than different tire manufacturers variations in the rolling diameter of the tire


editted for spelling

 

exaclty....remeber the vehicle speed sensor gives out speed only as a function of wheel RPMS....so its VERY easy to throw it off, as its not acutally measuring distance over time, but rotation over time

 

GPS is right. I had a GPS device in my car and it ready exactly 3 miles less than what the speedo would read. So you have no problem. The speedo just isn't completely accurate. Most speedometers are usually off 2-3 MPH either up or down.

 

I've always noticed that my speedo is ~2-3 mph faster than i'm actually going. Tire pressure is one of hte main problems with the difference in speed. I'd stick with the GPS

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by accordselux &raquo;</TD></TR><TR><TD CLASS="quote">I've always noticed that my speedo is ~2-3 mph faster than i'm actually going. Tire pressure is one of hte main problems with the difference in speed. I'd stick with the GPS </TD></TR></TABLE>

maybe if youd up your tire pressure back to stock settings, you wouldnt have that issue.......you and your JDM ultra-gripping low tire pressure

 

It's cheaper than wider tires, d00d!

 

You can find out exactly how accurate they both are by setting your cruise control at 60 mph and then watch the mile markers as you time how long it takes to go a mile. If it takes 55 seconds you're going 65 mph, 65 seconds is 55 mph etc.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Schmitey &raquo;</TD></TR><TR><TD CLASS="quote">You can find out exactly how accurate they both are by setting your cruise control at 60 mph and then watch the mile markers as you time how long it takes to go a mile. If it takes 55 seconds you're going 65 mph, 65 seconds is 55 mph etc.</TD></TR></TABLE>

I would find that kinda hard to do unless if you have cruise control and a stop watch in your hand that is accurate to the second. Just go by the GPS. So much easier.....

 

I put 33 psi in all four tires. I know I should only do this for the front but, I didn't think it would be a big deal for the back tires.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hondaracin24 &raquo;</TD></TR><TR><TD CLASS="quote">I would find that kinda hard to do unless if you have cruise control and a stop watch in your hand that is accurate to the second. Just go by the GPS. So much easier.....</TD></TR></TABLE>

you also cant trust the markers to be exact...

 

they should be accurate to within a few feet, each marker is suposed to be surveyed