Pacing With a Prius

Delta Flyer · 12-02-2004, 12:20 PM

This morning I was driving alongside a Prius just before dawn. I could see the speedodometer and noticed the Prius' readout was about 0.5 mph faster than mine.

Big D Insightman · 12-02-2004, 12:30 PM

Maybe one of you has nonstock size tires on your car?.

Hambone · 12-02-2004, 12:34 PM

Could be that one or the other's speedo just was calibrated differently. Actually, only half a mile an hour difference isn't too much, Car & Driver did an article some time back and some speedo's on cars without modifications showed a deviation of +/- 10 mph at 65 mph, so either both that particular Prius and Insight are pretty close to on or are deviating in a similar fashion. Usually speedo deviation becomes more apparent at higher speeds, where the percentage error is magnified (10% error at 10mph might show 11mph, where the same error would be showing 66mph at a true 60mph).

Delta Flyer · 12-02-2004, 01:59 PM

We were going 61-62 mph.

My tires replaced the OEM ones.

Delta Flyer · 12-02-2004, 03:41 PM

Big D Insightman: This was on eastbound I635 and Josey, just east of I35E.

figgy · 12-02-2004, 04:23 PM

I would say that 0.5 difference reading at that speed is all within the margin for error. You could also argue that the actual difference was only 0.25, in case yours was rounding down and his was rounding up due to system rounding.

I just realized, ours don't read in 1/2 mph increments.

How did you read a 0.5 mph differential?

Does the Prius read in 0.5 mph increments?

Maybe you were going the same 60.4999 and your Insight rounded it to the nearest integer which was 60 and he was going 60.4999 as well and his Prius rounded it to 60.50 and you were going exactly the same speed to the .0001 mph?

Delta Flyer · 12-02-2004, 04:57 PM

It was a guess. Earlier when I was going 51 mph, the Prius read 52.

Big D Insightman · 12-03-2004, 12:48 AM

Delta Flyer: We should get all of the other Dallas area insighters to meet up some time?. Maybe at a restaurant or something. Maybe on a saturday afternoon.Those that are married (like me) could bring they spouses?. We live in the Walnut Hill + Midway area.

Rick Reece · 12-03-2004, 09:27 AM

The Insight display reads less than your actual speed. You can check your car by measuring it against a GPS or the mile markers along the interstate. My car overestimates speed by approximately 1.5%. Have fun, RIck

Resist · 12-03-2004, 01:09 PM

No speedometer is truely accurate and most are off by 1 or 2 mph.