92 Civic speedometer

I have owned my 92 Civic DX 4dr sedan for a little over a year and it
seems that the speedometer reads high, e.g. when it says 65 the car is
going about 60. I say "about" because it is hard to get exact clock
readings when you are busy and living in an area with a lot of traffic
(few measured miles & chances to drive steady speeds). The car has the
same 13-inch tire size specified in its manual. Is this a
characteristic of Civics? Do I have a speedometer designed for 14-inch
wheels?

Dail Singleton

"F. Dail Singleton, Jr." wrote:
>
> I have owned my 92 Civic DX 4dr sedan for a little over a year and it
> seems that the speedometer reads high, e.g. when it says 65 the car is
> going about 60. I say "about" because it is hard to get exact clock
> readings when you are busy and living in an area with a lot of traffic
> (few measured miles & chances to drive steady speeds). The car has the
> same 13-inch tire size specified in its manual. Is this a
> characteristic of Civics? Do I have a speedometer designed for 14-inch
> wheels?
>
> Dail Singleton

Speedometers usually read a bit high and the factory usually gives
generous tolerances on the speedometer spec. BMW specs say that if the
speedometer does not show more than actual speed +10% +2.4 mph, it is
fine. So at 60 mph, BMW says 68.4 on the speedo is just fine.

The '94 DX in the US came with 175/70-13 tires for a diameter of 575.2
mm. The largest wheel that year was 175/65-14 on the 4 door EX and LX.
That comes out to 583.1 mm, or less than 1.4% bigger than what the DX
had. The smallest wheel was on the CX with 165/70-13 or 561.2 mm
diameter. Less than a 4% difference between smallest and largest
available. The speedometers are probably the same for all trim levels.

Randolph wrote:
> Speedometers usually read a bit high and the factory usually gives
> generous tolerances on the speedometer spec.

Thanks for the discussion, Randolph. I've noticed similar apparently
higher-then-actual speedo readings in my 94 Civic EX MT, and I have the
standard 175/65-14 tires. I'd think the reading should be a bit more
accurate to reduce the inaccuracy of odometer readings. Curious.

Abeness wrote:
>
> Randolph wrote:
> > Speedometers usually read a bit high and the factory usually gives
> > generous tolerances on the speedometer spec.
>
> Thanks for the discussion, Randolph. I've noticed similar apparently
> higher-then-actual speedo readings in my 94 Civic EX MT, and I have the
> standard 175/65-14 tires. I'd think the reading should be a bit more
> accurate to reduce the inaccuracy of odometer readings. Curious.

Actually, odometer readings ARE more accurate than speedometer readings.
The odometer is calibrated to be as accurate as possible, speedometers
are calibrated to read a little high. Some countries even require that
the speedometer show no less than actual speed.

Randolph wrote:
> Actually, odometer readings ARE more accurate than speedometer readings.
> The odometer is calibrated to be as accurate as possible, speedometers
> are calibrated to read a little high. Some countries even require that
> the speedometer show no less than actual speed.

Good to know that the odo is more accurate than the inaccurate speedo
would lead one to believe. It does make sense that the speedo would be
required to show no *less* than actual, particularly in countries that
ticket for speeding.

F. Dail Singleton, Jr. wrote:
> (few measured miles & chances to drive steady speeds). The car has the
> same 13-inch tire size specified in its manual. Is this a
> characteristic of Civics? Do I have a speedometer designed for 14-inch
> wheels?

up to a 10% error is normal and acceptable. adding larger wheels might
help a small bit. 14" wasnt standard on the civics til 98, IIRC.

Abeness wrote:

> Randolph wrote:
>
>> Actually, odometer readings ARE more accurate than speedometer readings.
>> The odometer is calibrated to be as accurate as possible, speedometers
>> are calibrated to read a little high. Some countries even require that
>> the speedometer show no less than actual speed.
>
>
> Good to know that the odo is more accurate than the inaccurate speedo
> would lead one to believe. It does make sense that the speedo would be
> required to show no *less* than actual, particularly in countries that
> ticket for speeding.

friend of mine jacked up his ram an put them monster mud tires on it.
before, his speedo likely read slow. now? 70mph is actually around
79mph. not good for avoiding tickets, but it looks bitchen

SoCalMike wrote:
>
> F. Dail Singleton, Jr. wrote:
> > (few measured miles & chances to drive steady speeds). The car has the
> > same 13-inch tire size specified in its manual. Is this a
> > characteristic of Civics? Do I have a speedometer designed for 14-inch
> > wheels?
>
> up to a 10% error is normal and acceptable. adding larger wheels might
> help a small bit. 14" wasnt standard on the civics til 98, IIRC.

In '94 14" was stock on the Si and on the 4-door EX and LX. Don't
remember what the coupes had.

SoCalMike wrote:
> friend of mine jacked up his ram an put them monster mud tires on it.
> before, his speedo likely read slow. now? 70mph is actually around
> 79mph. not good for avoiding tickets, but it looks bitchen

<chuckle>