Inaccurate speedo

huyvu90 · #1 07-27-2002, 10:03 PM

Why are speedo inaccurate at high speed? I heard that the maker did it intentionally. I don't know why or if it is true. Can somebody fill me in?

Polygon · #2 07-27-2002, 11:09 PM

Well, what kind of car are you talking about?

ivymike1031 · #3 07-28-2002, 10:46 AM

The simplest error to introduce into a speedometer, using the wrong size tires, will result in speed error that grows proportionally to speed. This is true regardless of what kind of car you have.

Some manufacturing defects (depending on kind of speedo) can have a similar effect.

huyvu90 · #4 07-28-2002, 01:38 PM

I'm talking about Honda accord 1995. My friend didn't do anything to his car (change tires etc.) and it showed that 135 mph is his top speed on the freeway which confirmed that his speedo is wrong. I heard honda did it intentionally. I can't confirm it but if you can plz do.

911GT2 · #5 07-28-2002, 02:00 PM

All speedos get innaccurate at high speeds. Equations and wheel sizes are fine in ideal situations, but the real world isn't ideal at all. There's too many variables to accurately tell speed over such a broad range.

And i know for a fact that Honda is electronically limited to 112 mph by gearing and rev limiters.

ivymike1031 · #6 07-28-2002, 02:08 PM

Quote:

And i know for a fact that Honda is electronically limited to 112 mph by gearing and rev limiters

oh yeah? which honda?

huyvu90 · #7 07-28-2002, 02:19 PM

elaborate plz. Limit to 112? you mean accord can only go 112 mph?

enginerd · #8 07-31-2002, 08:38 AM

do you have those retarded dayton gold spoke wheels on your car?

454Casull · #9 07-31-2002, 10:51 AM

Quote:

do you have those retarded dayton gold spoke wheels on your car?

???

enginerd · #10 07-31-2002, 05:14 PM

Quote:

Originally posted by 454Casull

???

These wheels kill wheel bearings and totally fry the accuracy of speedometers.

454Casull · #11 07-31-2002, 08:28 PM

No, actually, there was a section in a popular car mag (C&D or R&T or something like that) about speedo inaccuracy, with BMW as the one with screwiest speedo, and GM with the least.

Jay! · #12 07-31-2002, 08:49 PM

Quote:

Originally posted by ivymike1031

Quote:

Originally posted by 911GT2
And i know for a fact that Honda is electronically limited to 112 mph by gearing and rev limiters.

oh yeah? which honda?

And which is it? Gearing or Rev Limiters? (Or drag?)

That seems to be an interesting fact you have there...

huyvu90 · #13 07-31-2002, 11:49 PM

Know anything about honda accord and the inaccuracy of its speedo?

ivymike1031 · #14 08-01-2002, 12:14 AM

nope, I know nothing about the accord

my 97 civic consistently read about 8% too high after I installed indiglo gauge faces (checked w/ gps, estimated gps error 0.8%). I never noticed the problem before buying the faces (didn't have the gps then) and I never took the faces back off to compare.

My '88 civic with the factory gauge faces reads spot-on with the gps.

Quote:

(enginerd)These wheels kill wheel bearings and totally fry the accuracy of speedometers.

I'll take your word for it on the wheel bearings (large offset wheels, I guess?). I'd like you to go into a bit more detail on how you expect the wheels to affect the speedo accuracy, if possible (were you assuming a smaller OD tire to accompany the clown wheels?).

enginerd · #15 08-02-2002, 08:59 AM

Quote:

Originally posted by ivymike1031
nope, I know nothing about the accord

my 97 civic consistently read about 8% too high after I installed indiglo gauge faces (checked w/ gps, estimated gps error 0.8%). I never noticed the problem before buying the faces (didn't have the gps then) and I never took the faces back off to compare.

My '88 civic with the factory gauge faces reads spot-on with the gps.

I'll take your word for it on the wheel bearings (large offset wheels, I guess?). I'd like you to go into a bit more detail on how you expect the wheels to affect the speedo accuracy, if possible (were you assuming a smaller OD tire to accompany the clown wheels?).

It's been my experience that the od of these wheels (wheels are smaller in diameter than stock; even with tires) is smaller vs. stock sizes. They are offset about 3-4", thus greatly leveraging the weight of the vehicle against the wheel bearings. I've made a fair amount of income from replacing wheel bearings/ hubs on cars equipped with these wheels. I'm am sour about them because one such car had an owner who drove off after having new beaings installed and crashed into another car. Keep in mind these wheels skew caster and camber angles and the steering wheel will not self-center when released. The owner of the car decided to sue my boss and I had to go testify in court. The car owner lost the case, but after that, any employee touching a car equipped with those wheels was immediatly terminated. The smaller diameter wheels indicated a higher speed than actual.

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