95 Camry LE speedometer accuracy

In news:zFUhb.176402$ snipped-for-privacy@bgtnsc05-news.ops.worldnet.att.net, Larry King being of bellicose mind posted:

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.

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.

"Larry King" wrote

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

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)

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 ??

"Larry King"

Hi Larry,

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

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

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

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.

Correction;

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

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 ??

In news: snipped-for-privacy@storefull-2172.public.lawson.webtv.net, mark Ransley being of bellicose mind posted:

Oregon state police hand out 58 mph in a 55 mph zone all the time and .... they stick.

"Larry King" wrote

YES!!! We have a winner! No more calls!! ;^) (Standby, as an operator will take your complete name and address to ship your prize.)

58 in a 55 tough state, I know some cars are 1 mile off on the speedo. Makes it hard to drive the limit.

"Yoonsoo" wrote

Yes, and the confusion has to do with the term "width." It appears you're substituting "width" for "diameter." It's the diameter that matters in this case. Nowhere on your chart is the term "width" used.

In news:3f8b43f4$1 snipped-for-privacy@corp.newsgroups.com, Howard Lester being of bellicose mind posted:

Aspect ratios affect diameter. For instance, a 195/70 tire has a sidewall height that is 70% of its 195mm width. Now, 70% of a narrower width would result in a slightly lower sidewall .... meaning also a smaller circumference.

ANd if you decide you just want a wider tire, then go to a 215/70, not only did you go wider, but taller, as 70% of 215 is greater (taller) that 70% of 195. This apect ratio is something that is always overlooked. Technically, you'd want to find a 215/50 or so, same circumference, but wider.

ANd if you decide you just want a wider tire, then go to a 215/70, not only did you go wider, but taller, as 70% of 215 is greater (taller) that 70% of 195. This apect ratio is something that is always overlooked. Technically, you'd want to find a 215/50 or so, same circumference, but wider.