My Continental Contact-Pro Tires

[cfg83]

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 :

ContiProContact
http://www.tirerack.com/tires/Spec.j...irePageLocQty=

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 :

Miata.net Tire Size Calculator
http://www.miata.net/garage/tirecalc.html

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,

CarloSW2

[RH77]

Originally Posted by cfg83

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.

Do you know the Rolling Resistance on the new treads?

I used to have the Eagle GT's on a '90 Beretta. Brand new, they hyroplaned like crazy (stuck to the road pretty well, though). With the higher pressures on my Michelins, the biggest difference is cross-wind stability. It takes a bit more steering feedback to keep it straight.

Yeah, Kansas City has a higher wind speed average than Chicago (the "Windy City").

RH77

[cfg83]

RH77 -

Originally Posted by RH77

Do you know the Rolling Resistance on the new treads?

I used to have the Eagle GT's on a '90 Beretta. Brand new, they hyroplaned like crazy (stuck to the road pretty well, though). With the higher pressures on my Michelins, the biggest difference is cross-wind stability. It takes a bit more steering feedback to keep it straight.

Yeah, Kansas City has a higher wind speed average than Chicago (the "Windy City").

RH77

I started from this document :

LOW ROLLING RESISTANCE TIRES - March 2003 - Page 5
http://www.greenseal.org/resources/r...resistance.pdf

BRAND                        = Continental ContiTouring Contact 
MODEL                        = CH95
SIZE                         = 205/55R16
RRC AVERAGE                  = 0.0083
PRICE                        = $64.00
TRACTION COMPOSITE           = 7.46
WOULD BUY AGAIN              = 6.10
COMPOSITE TREAD WEAR         = 7.29
COMPOSITE PERFORMANDCE SCORE = 6.95

Here's a picture of the Continental ContiTouring Contact from tirerack :



My tires are not an exact match, but they have the same "pedigree" (fingers crossed ). I didn't get the tires from the GreenSeal document because I could not get the size I wanted that was also rated at 51 PSI, .

CarloSW2

[RH77]

That's a good value vs. RR. I think you'll find the treads a fine addtion to the Sat. Plus, the 51 psi certified max PSI is an added assurance.

As for the circumference, an adjustment to the SG may be necessary -- not a big deal. I usually have mine set to the most pessimistic settings so I try harder. The displayed FE prompts additional effort if it's perceived as low. The trick is to disregard the setting and shoot for that higher goal. Hopefully, I'll have 2 record tanks through this and lower cruise speed.

Let us know how the new tires work out!

RH77

[cfg83]

RH77 -

Originally Posted by RH77

That's a good value vs. RR. I think you'll find the treads a fine addtion to the Sat. Plus, the 51 psi certified max PSI is an added assurance.

As for the circumference, an adjustment to the SG may be necessary -- not a big deal. I usually have mine set to the most pessimistic settings so I try harder. The displayed FE prompts additional effort if it's perceived as low. The trick is to disregard the setting and shoot for that higher goal. Hopefully, I'll have 2 record tanks through this and lower cruise speed.

Let us know how the new tires work out!

RH77

Thanks for reminding me. I have adjusted the SG to show a +2% speed increase on the MPH, so it is accurate for these tires.

I will be doing a GPS adjustment in the next few weeks, so I will add the results to the thread.

CarloSW2

[cfg83]

Hello -

I just did another GPS correction test :

              Car Odometer    GPS       GPS/ODO    % Correction
2007/06/19    19.00           19.6      1.0310     +3.1% (after purchased)
2007/06/19    36.15           37.2      1.0290     +2.9%
2007/12/01    30.40           31.2      1.0263     +2.6% (6 months later)
2007/12/05    31.40           32.3      1.0286     +2.9%
2008/10/08    34.1            35.1      1.0293     +2.9% (16 months later)
2008/10/09    35.6            36.5      1.0253     +2.5%

In the 2008/10/08 test, I wasn't being smart and did some strategic EOC, so I am sure that it contributed to the higher % (when you turn the key to the off position, the car odometer stops, but the GPS keeps right on chugging).

In the 2008/10/09 test, I was much more careful. I *like* that the % is going down over time. This is consistent with tread wear.

As stated before, I am sticking with a 2% error correction on my gaslog because I don't want to accidentally 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).

Me happy, .

CarloSW2

[RH77]

Originally Posted by cfg83

In the 2008/10/08 test, I wasn't being smart and did some strategic EOC, so I am sure that it contributed to the higher % (when you turn the key to the off position, the car odometer stops, but the GPS keeps right on chugging).

Kudos on your accuracy! I really need to do this

So the Odometer quits when the key is out? Weird -- I didn't know that some cars did this. It makes sense if the intention is to tow the car behind a motorhome as many Saturns are designed to do.

RH77

[cfg83]

Hello -

I just did another GPS correction test :

              Car Odometer    GPS       GPS/ODO    % Correction
2007/06/19    19.00           19.6      1.0310     +3.1% (after purchased)
2007/06/19    36.15           37.2      1.0290     +2.9%
2007/12/01    30.40           31.2      1.0263     +2.6% (6 months later)
2007/12/05    31.40           32.3      1.0286     +2.9%
2008/10/08    34.1            35.1      1.0293     +2.9% (16 months later)
2008/10/09    35.6            36.5      1.0253     +2.5%
2009/06/01    29.2            30.0      1.0273     +2.7% (24 months later)
2009/06/01    44.0            45.2      1.0272     +2.7%

It's still pretty much dead-on. My intuition was predicting it to decrease, but maybe that will happen in due course.

I just got the tires rotated and they didn't say there were any wear problems. When I get the rotation I drop the PSI to 42 to avoid lectures, and fill 'em back up to 50 PSI afterwards.

Me still happy, .

CarloSW2

[gone-ot]

Originally Posted by cfg83

...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.

...My wife's new GoodYear Eagle GT's do the same thing to a lesser extent.

...samething occurs with the OEM Goodyear Eagle RS-A's on our '09 Vibe.

[cfg83]

Old Tele man -

Originally Posted by Old Tele man

...samething occurs with the OEM Goodyear Eagle RS-A's on our '09 Vibe.

Yeah, at first glance the RS-A's look similar to mine and a Prius OEM :

Your Eagle RS-A's :


My ContiProContacts :


Toyota Prius Goodyear Integrities :


And, I think my friends' Prius also has road wiggle. Your OEM tire is usually picked for upping MPG to increase the EPA MPG score. Maybe that's a clue that we have a tread pattern that is conducive to LRR.

Hrmmmmm, this makes me wonder. If it fits, should I try Prius OEM tires next time?

CarloSW2