speedometer accuracy?

[Mark T-TB]

(Yes, I will have a lot of questions as I am just now getting to the actual driving)

I had #545 out for its maiden drive [for me] yesterday :cool1::burnrubber:
When on the interstate. it seemed as tho everyone was blowing by, as my speedo indicated a steady 70 (65 zone).
Tried to time it today with stopwatch, seems like I might be reading about 5 mph high. stock size tires.
Is this about par for the course? Thanks.

 

[jarredsoon]

Your speedo should be accurate if stock size wheels and factory gears.

 

[Mark T-TB]

Your speedo should be accurate if stock size wheels and factory gears.

Thanks Jarred.
That is what I thought. No way [yet] to be sure about the gearing.
I'll try to check it vs my GPS on my next outing. TIres are brand new all stock size on stock wheels.

 

[Mark T-TB]

Checked the speedo vs my Magellan GPS on Saturday retuning from Kirban's.
Speedometer readings were consistently 5 mph low vs the GPS at highway speeds (55-70 mph range). Wonder why? ... or is simply "within tolerance"?

 

[robert lee]

Checked the speedo vs my Magellan GPS on Saturday retuning from Kirban's.
Speedometer readings were consistently 5 mph low vs the GPS at highway speeds (55-70 mph range). Wonder why? ... or is simply "within tolerance"?

Something was changed, rear gear ratio, TC , ect. Sound's like you have a NLU T/C ...

 

[Mark T-TB]

Something was changed, rear gear ratio, TC , ect. Sound's like you have a NLU T/C ...

Thanks for the input.

I'm waitin' for Jim Dunn (nearby Buick Turbo Performance) to have some time to check the car over and make sure that everything is "good to go" for the longer term... hopefully he'll be able to confirm "what is up" with the inaccuracy(?).

 

[WS6]

I'm thinking your rear gears are 3.70's and not the original 3.27