95 Camry LE speedometer accuracy

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Old 11 Oct 2003, 09:42 am   #1 (permalink)
Larry King
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Default 95 Camry LE speedometer accuracy

My wife has sometimes commented about anxious drivers tailgating her and
generally acting like she is going too slow. Now she is a cautious person
(not necessarily a bad thing), and this is New Jersey where people can tend
to be a bit impatient [to say the least] but I don't think it is overly so
in either case. However, I just chalked it up to those two factors
coinciding on occasion.

This morning I had to take her car (95 Camry LE - 4 cyl) in for inspection,
and when I was driving over to the inspection station I went by one of those
little mobile radar speed display trailers which the Township PD had set up
on the shoulder. And it said that I was going a nice steady 29 mph when the
Camry's speedometer indicated approximately a nice steady 35 mph !! On the
way back, I went out of my way to check it again with the exact same
results.

Tires are all inflated properly (30-32 PSI) and checked regularly; they are
P185-70R14 which is "OEM" correct as far as I can determine [well, the
little placard Toyota stuck on the glovebox door says P195-70R14 but I can't
see how the width would affect the speedometer/odometer accuracy].

Never had any work done [e.g., no disassembly/reassembly] on the
transmission, etc. except the usual fluid flush every 30000 mi or so.

Is it possible that the car was mistakenly assembled with an incorrect
speedometer gear which was intended for use with larger tires ??

Thanks very much in advance. Will watch newsgroup for replies.


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Old 11 Oct 2003, 11:40 am   #2 (permalink)
Philip
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Default Re: 95 Camry LE speedometer accuracy

In news:zFUhb.176402$3o3.13084776@bgtnsc05-news.ops.worldnet.att.net,
Larry King <lking@startech.net> being of bellicose mind posted:
> My wife has sometimes commented about anxious drivers tailgating
> her and generally acting like she is going too slow. Now she is a
> cautious person (not necessarily a bad thing), and this is New
> Jersey where people can tend to be a bit impatient [to say the
> least] but I don't think it is overly so in either case. However,
> I just chalked it up to those two factors coinciding on occasion.
>
> This morning I had to take her car (95 Camry LE - 4 cyl) in for
> inspection, and when I was driving over to the inspection station
> I went by one of those little mobile radar speed display trailers
> which the Township PD had set up on the shoulder. And it said
> that I was going a nice steady 29 mph when the Camry's speedometer
> indicated approximately a nice steady 35 mph !! On the way back,
> I went out of my way to check it again with the exact same results.
>
> Tires are all inflated properly (30-32 PSI) and checked regularly;
> they are P185-70R14 which is "OEM" correct as far as I can
> determine [well, the little placard Toyota stuck on the glovebox
> door says P195-70R14 but I can't see how the width would affect
> the speedometer/odometer accuracy].
>
> Never had any work done [e.g., no disassembly/reassembly] on the
> transmission, etc. except the usual fluid flush every 30000 mi or
> so.
>
> Is it possible that the car was mistakenly assembled with an
> incorrect speedometer gear which was intended for use with larger
> tires ??
>
> Thanks very much in advance. Will watch newsgroup for replies.


You might better find a speedometer shop that can check front wheel
drive cars and take it there. If such a shop is not in your area,
placing a call to the Auto Club (even when you're not a member) can
get you a referral to a speedo shop.
--

~~Philip "Never let school interfere
with your education - Mark Twain"




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Old 11 Oct 2003, 01:56 pm   #3 (permalink)
Yoonsoo
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Default Re: 95 Camry LE speedometer accuracy

Tire width matters in this case since you're using the same 70 series tires.
The result I got from tire size calculator is following:

Tire Size Comparison

Specification Sidewall Radius Diameter Circumference Revs/Mile
Difference
185/70-14 5.1in 12.1in 24.2in 76.0in 834
0.0%
195/70-14 5.4in 12.4in 24.7in 77.7in 815
2.3%


According to this result, your should have 29 mph in your speedometer when
driving exactly at 30 mph. But yours is 35 mph.

That means something definitely wrong... Why don't you check all the
connection in instrument panel or ask a professional in your local area.
Thanks.


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Old 11 Oct 2003, 02:30 pm   #4 (permalink)
Howard Lester
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Default Re: 95 Camry LE speedometer accuracy


"Larry King" wrote

> Tires are all inflated properly (30-32 PSI) and checked regularly; they

are
> P185-70R14 which is "OEM" correct as far as I can determine [well, the
> little placard Toyota stuck on the glovebox door says P195-70R14 but I

can't
> see how the width would affect the speedometer/odometer accuracy].


A 195 tire is of a larger *diameter* than a 185, not a larger width. What
makes you think the placard is wrong?

If 195 is correct for the car, then 185 is undersized, and what is happening
is correct, although extreme at such low speeds. For every rotation of the
drivetrain, undersized tires will lay down a shorter path than that traveled
by standard or oversized tires, "fooling" the speedometer.

Howard Lester




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Old 11 Oct 2003, 06:00 pm   #5 (permalink)
Larry King
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Default Re: 95 Camry LE speedometer accuracy


"Howard Lester" <heylester@dakotacom.net> wrote in message
news:3f885ae4$1_8@corp.newsgroups.com...
>
> "Larry King" wrote
>
> > Tires are all inflated properly (30-32 PSI) and checked regularly; they

> are
> > P185-70R14 which is "OEM" correct as far as I can determine [well, the
> > little placard Toyota stuck on the glovebox door says P195-70R14 but I

> can't
> > see how the width would affect the speedometer/odometer accuracy].

>
> A 195 tire is of a larger *diameter* than a 185, not a larger width. What
> makes you think the placard is wrong?
>
> If 195 is correct for the car, then 185 is undersized, and what is

happening
> is correct, although extreme at such low speeds. For every rotation of the
> drivetrain, undersized tires will lay down a shorter path than that

traveled
> by standard or oversized tires, "fooling" the speedometer.
>


First of all, I went out and checked the tire sidewalls again and they are
indeed P195-70R14. It was kind of grungy and not very light outside when I
looked the first time so the "9" looked like an "8" on the one I checked.
But they are indeed P195-70R14 as per the glovebox label.

However, your statement confuses me. I used (as an example)

http://www.mistupid.com/automotive/tiresize.htm

as a reference, and it definitely shows that the first set of digits is the
tire width in millimeters. 1 inch = 25.4 mm, so 195/25.4 = 7.67" which is
roughly the width of my tires.

Isn't the "14" = to the wheel size (e.g. diameter) in inches, and **that**
would be what could cause inaccurate speedometer/odometer readings
proportional to the ratio ?

Or am I overlooking something ??



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Old 11 Oct 2003, 08:59 pm   #6 (permalink)
Howard Lester
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Default Re: 95 Camry LE speedometer accuracy


"Larry King"

> First of all, I went out and checked the tire sidewalls again and they

are
> indeed P195-70R14. It was kind of grungy and not very light outside when

I
> looked the first time so the "9" looked like an "8" on the one I checked.
> But they are indeed P195-70R14 as per the glovebox label.
>
> However, your statement confuses me. I used (as an example)
>
> http://www.mistupid.com/automotive/tiresize.htm
>
> as a reference, and it definitely shows that the first set of digits is

the
> tire width in millimeters. 1 inch = 25.4 mm, so 195/25.4 = 7.67" which is
> roughly the width of my tires.
>
> Isn't the "14" = to the wheel size (e.g. diameter) in inches, and **that**
> would be what could cause inaccurate speedometer/odometer readings
> proportional to the ratio ?
>
> Or am I overlooking something ??



Hi Larry,

Yes, you are overlooking something. The site you cite appears to be
incorrect -- or at least misleading. Go to this site instead:

http://www.tirerack.com/tires/tiretech/general/size.htm

It gives an example of a 185/60R14. Study it a bit. The example gives a
result of 22.74" for the tire diameter. Note the formula. If you were to
substitute 195 for 185 you'll wind up with a larger diameter tire (23.21").
The larger diameter tire will roll further (farther?) per axle rotation
(earlier I referred incorrectly as drivetrain rotation). Yes, the 14 refers
to the wheel diameter in inches. I equate the aspect ratio (60, 65, 70,
etc.) as the tire width. A 60 series tire has a wider tread than that of a
65 or a 70.

So, after all this, it seems your speedometer is way the hell off! ;^)

Howard Lester




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Old 11 Oct 2003, 11:45 pm   #7 (permalink)
Ibrahim
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Default Re: 95 Camry LE speedometer accuracy

Just an oberservation:

But I noticed radar/speedometer discrepancy on my '02 Camry as well as
my '91 Stanza. However, it's not as extreme as yours. Different
police radars read between 2 and 3 mph *above* my speedometer reading
in both cars.

Intersting.

--Ibrahim
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Old 12 Oct 2003, 01:45 am   #8 (permalink)
mark Ransley
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Default Re: 95 Camry LE speedometer accuracy

Speeding cases have been in favor of people that Prove tire
size altered readings. Basicly PUT. You should be able to BEAT
any 9mile over tickett.

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Old 12 Oct 2003, 07:41 am   #9 (permalink)
Ibrahim
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Default Re: 95 Camry LE speedometer accuracy

Correction;

It should have been:
Different police radars read between 2 and 3 mph **below** my
speedometer reading in both cars.

p_man101@hotmail.com (Ibrahim) wrote in message news:<8f573a5e.0310112045.ffb4fb0@posting.google.c om>...
> Just an oberservation:
>
> But I noticed radar/speedometer discrepancy on my '02 Camry as well as
> my '91 Stanza. However, it's not as extreme as yours. Different
> police radars read between 2 and 3 mph *above* my speedometer reading
> in both cars.
>
> Intersting.
>
> --Ibrahim

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Old 12 Oct 2003, 09:36 am   #10 (permalink)
Larry King
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Default Re: 95 Camry LE speedometer accuracy


"Howard Lester" <heylester@dakotacom.net> wrote in message
news:3f88b634_2@corp.newsgroups.com...
>
> "Larry King"
>
> > First of all, I went out and checked the tire sidewalls again and they

> are
> > indeed P195-70R14. It was kind of grungy and not very light outside

when
> I
> > looked the first time so the "9" looked like an "8" on the one I

checked.
> > But they are indeed P195-70R14 as per the glovebox label.
> >
> > However, your statement confuses me. I used (as an example)
> >
> > http://www.mistupid.com/automotive/tiresize.htm
> >
> > as a reference, and it definitely shows that the first set of digits is

> the
> > tire width in millimeters. 1 inch = 25.4 mm, so 195/25.4 = 7.67" which

is
> > roughly the width of my tires.
> >
> > Isn't the "14" = to the wheel size (e.g. diameter) in inches, and

**that**
> > would be what could cause inaccurate speedometer/odometer readings
> > proportional to the ratio ?
> >
> > Or am I overlooking something ??

>
>
> Hi Larry,
>
> Yes, you are overlooking something. The site you cite appears to be
> incorrect -- or at least misleading. Go to this site instead:
>
> http://www.tirerack.com/tires/tiretech/general/size.htm
>
> It gives an example of a 185/60R14. Study it a bit. The example gives a
> result of 22.74" for the tire diameter. Note the formula. If you were to
> substitute 195 for 185 you'll wind up with a larger diameter tire

(23.21").
> The larger diameter tire will roll further (farther?) per axle rotation
> (earlier I referred incorrectly as drivetrain rotation). Yes, the 14

refers
> to the wheel diameter in inches. I equate the aspect ratio (60, 65, 70,
> etc.) as the tire width. A 60 series tire has a wider tread than that of a
> 65 or a 70.
>
> So, after all this, it seems your speedometer is way the hell off! ;^)
>
> Howard Lester
>
>


Thanks for reply & reference to the tirerack.com URL. You are right, it is
a much clearer explanation.

I think I understand it ... the 14 is just the diameter of the metallic
wheel on which the rubber tire is mounted.

Then there is the width of the rubber tire which is indicated by the first
set of digits (in my case P195).

Next, you compute the height of the tire's rubber sidewall by multiplying
the width by the aspect ratio (.60 for my tires).

Finally, the overall "rolling" (for lack of a better word) diameter of the
tire is 2 times the sidewall height plus the wheel's diameter.

Now I see how a P195 can have a larger "rolling" circumference than a P185,
all other factors being equal.

Did I get it right this time ??


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