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Old 05-29-2008, 03:18 PM   #1 (permalink)
cfg83's Avatar
Join Date: Dec 2007
Location: Southern California
Posts: 5,864

1999 Saturn SW2 - '99 Saturn SW2 Wagon
Team Saturn
90 day: 40.49 mpg (US)
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My Continental Contact-Pro Tires

Hello -

I just got these Continental Contact-Pro tires around June 3rd, 2007 :

New tire size : 195/65 R15
Stock tire size : 185/65 R15

Here are some specs on the tire :

Size                  = 195/65HR15
UTQG                  = 400 AA A
Max Speed             = 130 MPH
Max Load              = 1356 lbs.
Max. Inflation Press. = 51 psi
Tread Depth           = 10/32"
Tire Weight           = 18 lbs.
Rim Width Range       = 5.5-7"
Meas. Rim Width       = 6"
Sect. Width           = 7.9"
Tread Width           = Not Available
Overall Diam.         = 25"
Revs Per Mile         = 835
These tires are one size up from stock. Rated up to 51 PSI, currently running at 51 PSI after ~7 miles of city driving.

I used this site to figure out my difference in speedometer readings : Tire Size Calculator

It told me that the speed will read 2.1% too slow.

I don't use my ScanGauge for my mile/distance readings, I use my car odometer with a GPS correction. Here are the two GPS correction tests I have done using my wife's eTrex GPS :

              Car Odometer    GPS       GPS/ODO    % Correction
2007/06/19    19.00           19.6      1.0310     +3.1%
2007/06/19    36.15           37.2      1.0290     +2.9%

Almost 6 months later :

              Car Odometer    GPS       GPS/ODO    % Correction
2007/12/01    30.40           31.2      1.0263     +2.6%
2007/12/05    31.40           32.3      1.0286     +2.9%
I am sticking with a 2% error correction on my gaslog because I don't want to accidently inflate (ha ha) my MPG numbers. Also, tire wear will eventually bring this correction down over time (i.e. always losing tread => always reducing tire circumference => always reducing odometer error over time).

The only problem is that on freeways that are grooved in the direction I am traveling, the car "wiggles", aka the tread tracks into the grooves like a phonograph needle and the car has a noticeable wiggle. I had a feeling this might happen, but no proof until after I bought the tires. Thank goodness my main commute only has this for maybe a mile or two. My wife's new GoodYear Eagle GT's do the same thing to a lesser extent.

Back in the day it was MUCH worse on my motorcycle,



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Last edited by cfg83; 06-19-2010 at 01:50 AM..
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