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cfg83 05-29-2008 03:18 PM

My Continental Contact-Pro Tires
 
Hello -

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

http://ecomodder.com/forum/member-cf...taltirepu7.jpg

http://ecomodder.com/forum/member-cf...altreadkf4.jpg

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=
Code:

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 :

Code:

              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 05-29-2008 03:36 PM

Quote:

Originally Posted by cfg83 (Post 29429)
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 05-29-2008 03:58 PM

RH77 -

Quote:

Originally Posted by RH77 (Post 29447)
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
Code:

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 :

http://ecomodder.com/forum/member-cf...ch95-ci2-l.jpg

My tires are not an exact match, but they have the same "pedigree" (fingers crossed :o ). 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 05-29-2008 04:28 PM

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! :thumbup:

RH77

cfg83 05-29-2008 04:40 PM

RH77 -

Quote:

Originally Posted by RH77 (Post 29463)
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! :thumbup:

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 10-09-2008 04:37 PM

Hello -

I just did another GPS correction test :

Code:

              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 10-09-2008 08:45 PM

Quote:

Originally Posted by cfg83 (Post 66251)
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! :thumbup: I really need to do this :o

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 06-02-2009 02:04 AM

Hello -

I just did another GPS correction test :

Code:

              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 08-01-2009 07:29 PM

Quote:

Originally Posted by cfg83 (Post 29429)
...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 08-02-2009 01:54 AM

Old Tele man -

Quote:

Originally Posted by Old Tele man (Post 119043)
...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 :
http://www.tirerack.com/images/tires...a_bw_ci1_l.jpg

My ContiProContacts :
http://www.tirerack.com/images/tires...tact_ci1_l.jpg

Toyota Prius Goodyear Integrities :
http://www.tirerack.com/images/tires...rity_ci1_l.jpg

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

2win2rbo 04-05-2010 08:24 AM

Quote:

Originally Posted by cfg83 (Post 119089)
Old Tele man -



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

Your Eagle RS-A's :
http://www.tirerack.com/images/tires...a_bw_ci1_l.jpg

My ContiProContacts :
http://www.tirerack.com/images/tires...tact_ci1_l.jpg

Toyota Prius Goodyear Integrities :
http://www.tirerack.com/images/tires...rity_ci1_l.jpg

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

Those tires look very eco but also with less grip probably. They're really fun attack the corners with though. I am to change tires soon I maybe looking at using these LRRs.

AeroModder 04-05-2010 10:41 AM

Word of warning- The Integrities have lousy wet traction.

Here's a video from Tire Rack comparing various LRR tires: When Round and Black Becomes Lean and Green


Here's the ones I'm getting this week (Yokohama Avid Touring-S):
http://www.tirerack.com/images/tires...ings_ci1_l.jpg

cfg83 04-05-2010 02:42 PM

AeroModder -

Yup, that's what I look for in a tread pattern, smooth + wide gaps. It's not scientifically proven on my part, but the LRR tires all seem to share a uniform style of tread pattern.

CarloSW2

Frank Lee 04-05-2010 04:20 PM

Think of treads (ignore slicks because we can't run 'em legally) as a continuum: knobby and blocky = bad, ribby and non-blocky = good; the closer to solid ribs the better. The pro-contact has so many sipes I would think that makes for a squishy tread. I'd think the nearly solid center ribs on the Integritys and Avid Tourings are a good indicator of likely low r.r.. Of course there is an element of armchair aero in this; but in the absence of good data what else is there?

About 3 days after I bought new tires I found Integrities on close out for dirt cheap! :mad: Oh well, the Falkens I bought have the right visual indicators for low r.r. AND are rated to 51 psi so they should be good too.

cfg83 05-07-2010 02:11 PM

Hello -

I just did another GPS correction test :

Code:

              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%
2010/05/07    28.9            29.7      1.0277    +2.7% (35 months later)

I am getting the same results. However, you can see in the above that I am working with 1/10 mile resolution. I watched the GPS click over to 29.7 miles. If the odometer was also about to click over, the result is different :

Code:

              Car Odometer    GPS      GPS/ODO    % Correction
2010/05/07    29.0            29.7      1.0241    +2.4% (35 months later)

This implies to me that the tread depth isn't as important as I thought.

QUESTION: Would it be fair to say that "young/deep tread depth" just compresses? It is a form of (synthetic) "rubber", after all.

In any case, me still happy, :) .

CarloSW2

CapriRacer 05-08-2010 07:18 AM

Quote:

Originally Posted by cfg83 (Post 173635)
..........
I am getting the same results...........

If you look carefully, you've got a very slight downward trend.

Quote:

Originally Posted by cfg83 (Post 173635)
..........

This implies to me that the tread depth isn't as important as I thought.

QUESTION: Would it be fair to say that "young/deep tread depth" just compresses? It is a form of (synthetic) "rubber", after all.

In any case, me still happy, :) .

CarloSW2

Perhaps this will help:

If you go to Tire Rack, you'll notice that in their tire specs,there is both a column for Overall Diameter and one for Revoultions per Mile (RPM). This seems to be redundant, but if you do that math, you'll find that the 2 values are off by 3%. In other words, RPM value is related to 97% of the diameter, not the full diameter. This varies somewhat from tire to tire, but the rolling diameter is not equal to the measured diameter.

Why?

The best explanation I have heard is that the true rolling diameter occurs at the diameter of the steel belts - and that the steel belts act much like a tank track, in that it hardly matters how much rubber is on top of the belt, the length of the belt (or the length of the tank track) determines how far the vehicle moves in one revolution.

So you shouldn't be surprised that the speedometer doesn't vary much over the life of the tire.

cfg83 05-08-2010 01:33 PM

CapriRacer -

Ok. I love tirerack because of all the specs they publish, but I don't always know how to interpret them. It never occurred to me to cross-reference the stats. In the back of my mind I was wondering if the steel belt had something to do with it, but I wouldn't have been able to describe the mechanism.

CarloSW2


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