speedometer might not be accurate

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Old 26 Aug 2010, 01:13 pm   #1 (permalink)
Old Geezer
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Default speedometer might not be accurate

Every time my speed shows on a roadside radar speed indicator, the speed
displayed on my speedometer is three MPH less than the radar shows it to
be. Anyone seeing something similar?

99 Toyota Tacoma 4cyl super cab, standard tires & wheels



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Old 26 Aug 2010, 02:53 pm   #2 (permalink)
Old Geezer
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Default Re: speedometer might not be accurate

On 08/26/2010 01:13 PM, Old Geezer wrote:
> Every time my speed shows on a roadside radar speed indicator, the speed
> displayed on my speedometer is three MPH less than the radar shows it to
> be.

I should have said the speed displayed on my speedometer is three MPH
higher than the radar shows it to be.

Anyone seeing something similar?
>
> 99 Toyota Tacoma 4cyl super cab, standard tires & wheels
>
>
>


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Old 26 Aug 2010, 03:56 pm   #3 (permalink)
clare@snyder.on.ca
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Default Re: speedometer might not be accurate

On Thu, 26 Aug 2010 13:13:00 -0500, Old Geezer <old_geezer@dot.com>
wrote:

>Every time my speed shows on a roadside radar speed indicator, the speed
>displayed on my speedometer is three MPH less than the radar shows it to
>be. Anyone seeing something similar?
>
>99 Toyota Tacoma 4cyl super cab, standard tires & wheels
>

It'll be more accurate when the tires are worn out
3mph at what speed? At 50mph that's 6% At 25 it would be 12%.
A smaller tire size would help - and I'll bet your "standard" tires
are not the same size AND brand as original

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Old 26 Aug 2010, 03:58 pm   #4 (permalink)
clare@snyder.on.ca
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Default Re: speedometer might not be accurate

On Thu, 26 Aug 2010 14:53:34 -0500, Old Geezer <old_geezer@dot.com>
wrote:

>On 08/26/2010 01:13 PM, Old Geezer wrote:
>> Every time my speed shows on a roadside radar speed indicator, the speed
>> displayed on my speedometer is three MPH less than the radar shows it to
>> be.

>I should have said the speed displayed on my speedometer is three MPH
>higher than the radar shows it to be.
>
> Anyone seeing something similar?
>>
>> 99 Toyota Tacoma 4cyl super cab, standard tires & wheels
>>
>>
>>

That changes things. Are the tires NEW, or worn?
And it is not uncommon for speedos to read high. Helps keep you from
getting as big a speeding ticket as you would otherwize get.

What you need to do is check the ODOMETER against a "measured mile".
If it is accurate, check the speedo with a GPS.

Otherwize, like a said in the first reply.

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Old 26 Aug 2010, 09:42 pm   #5 (permalink)
Ralph Mowery
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Default Re: speedometer might not be accurate


"Old Geezer" <old_geezer@dot.com> wrote in message
newsp6dnV-HquYxM-vRnZ2dnUVZ_rYAAAAA@giganews.com...
> Every time my speed shows on a roadside radar speed indicator, the speed
> displayed on my speedometer is three MPH less than the radar shows it to
> be. Anyone seeing something similar?
>
> 99 Toyota Tacoma 4cyl super cab, standard tires & wheels
>


I doubt that very few speedometers show the actual speed at all speeds.
Three MPH may not be bad . My 2007 Tacoma 2 wheel drive is close to showing
5 miles faster than I am actually going at 55 MPH. I use my GPS to determin
the speed. Those things are suspose to be accurate to less than 1 mph.


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Old 26 Aug 2010, 09:51 pm   #6 (permalink)
First of One
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Default Re: speedometer might not be accurate

According to various posts in the TacomaWorld forums, it is normal for the
speedo to overstate the true speed. Toyota (and probably other carmakers) do
it to avoid ever understating the true speed due to speedo mfg variations.
If you go to a slightly larger tire size than stock, say from /65 aspect
ratio to /70, the speedo reading is usually brought closer to the true
speed.

"Old Geezer" <old_geezer@dot.com> wrote in message
news:X6Odne9FRu7dW-vRnZ2dnUVZ_uWdnZ2d@giganews.com...
> On 08/26/2010 01:13 PM, Old Geezer wrote:
>> Every time my speed shows on a roadside radar speed indicator, the speed
>> displayed on my speedometer is three MPH less than the radar shows it to
>> be.

> I should have said the speed displayed on my speedometer is three MPH
> higher than the radar shows it to be.
>
> Anyone seeing something similar?
>>
>> 99 Toyota Tacoma 4cyl super cab, standard tires & wheels
>>
>>
>>

>



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Old 27 Aug 2010, 10:07 am   #7 (permalink)
Old Geezer
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Default Re: speedometer might not be accurate

On 08/26/2010 03:58 PM, clare@snyder.on.ca wrote:
> On Thu, 26 Aug 2010 14:53:34 -0500, Old Geezer<old_geezer@dot.com>
> wrote:
>
>> On 08/26/2010 01:13 PM, Old Geezer wrote:
>>> Every time my speed shows on a roadside radar speed indicator, the speed
>>> displayed on my speedometer is three MPH less than the radar shows it to
>>> be.

>> I should have said the speed displayed on my speedometer is three MPH
>> higher than the radar shows it to be.
>>
>> Anyone seeing something similar?
>>>
>>> 99 Toyota Tacoma 4cyl super cab, standard tires& wheels
>>>
>>>
>>>

> That changes things. Are the tires NEW, or worn?

The tires have between 10,000 & 15,000 miles on them.

> And it is not uncommon for speedos to read high. Helps keep you from
> getting as big a speeding ticket as you would otherwize get.
>
> What you need to do is check the ODOMETER against a "measured mile".
> If it is accurate, check the speedo with a GPS.
>
> Otherwize, like a said in the first reply.
>


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Old 27 Aug 2010, 04:32 pm   #8 (permalink)
clare@snyder.on.ca
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Default Re: speedometer might not be accurate

On Thu, 26 Aug 2010 22:42:00 -0400, "Ralph Mowery"
<rmowery28146@earthlink.net> wrote:

>
>"Old Geezer" <old_geezer@dot.com> wrote in message
>newsp6dnV-HquYxM-vRnZ2dnUVZ_rYAAAAA@giganews.com...
>> Every time my speed shows on a roadside radar speed indicator, the speed
>> displayed on my speedometer is three MPH less than the radar shows it to
>> be. Anyone seeing something similar?
>>
>> 99 Toyota Tacoma 4cyl super cab, standard tires & wheels
>>

>
>I doubt that very few speedometers show the actual speed at all speeds.
>Three MPH may not be bad . My 2007 Tacoma 2 wheel drive is close to showing
>5 miles faster than I am actually going at 55 MPH. I use my GPS to determin
>the speed. Those things are suspose to be accurate to less than 1 mph.
>

Just checked my PT Cruiser today against the GPS - reads 3kph high at
100 KPH, and .3km long per 10 km. Tires are half worn standard tires.
With the oversize snows I run in the winter it's out 3 the other way.
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