CR Tests Wet Braking on Worn AS Tires

[SubLGT]

https://www.consumerreports.org/tires/what-happens-to-performance-when-tires-are-worn/

Quote
To quantify how wear changes tire performance, the CR tire team measured the wet stopping performance and hydroplaning resistance of 23 performance all-season tires with full tread, which typically measures between 9â„32" and 11â„32", when new, and compared it against the same model tires shaved to 4â„32".


I found some of the test results (wet braking, but not hydroplaning) posted at another forum:
https://forums.vwvortex.com/showthr...est-new-and-shaved-tires-for-wet-braking

Quote

Note: listings below show new braking distance, shaved braking distance, and tire name.

Best new:

127 143 Michelin CrossClimate+
137 140 Michelin Premier A/S
138 169 Firestone Firehawk AS

Worst new:

168 208 Uniroyal Tiger Paw AWP3
172 195 Maxxis Bravo HP-M3
175 208 Toyo Celsius

Best shaved:

137 140 Michelin Premier A/S
127 143 Michelin CrossClimate+
141 155 Cooper CS5 Ultra Touring

Worst shaved:

156 207 Yokohama Avid Ascend (V)
168 208 Uniroyal Tiger Paw AWP3
175 208 Toyo Celsius

Least degradation when shaved:

137 140 Michelin Premier A/S
141 155 Cooper CS5 Ultra Touring
127 143 Michelin CrossClimate+

Most degradation when shaved:

168 208 Uniroyal Tiger Paw AWP3
160 204 Nokian Entyre 2.0
156 207 Yokohama Avid Ascend (V)



I'm not surprised to see 2 Michelin tires among the top 3 for best wet performance when worn. They have been emphasizing that performance aspect:
https://michelinmedia.com/the-truth-about-worn-tires/

Quote
Currently, the industry standard is to test wet-braking performance of new tires; however, wet-braking can change drastically as tires wear over time. That means consumers make purchase decisions based on a specific factor that becomes less and less relevant the more they drive on the tires.

Michelin is taking steps to close this gap. Though drivers value different aspects of safety, braking distance (especially wet braking) is recognized worldwide as one of the best indicator of safety in the automotive and tire industry.

Results show that braking performances among new tires are not equal—and a demonstration by Michelin revealed that worn tires can be even more unequal in their braking performances.

 

[ctechbob]

Well, that's all fine and dandy, but it is really only comparing the difference in the tread design. That test isn't going to take into account the hardening of the rubber over the life of the tire.

 

[eljefino]

Originally Posted by ctechbob
Well, that's all fine and dandy, but it is really only comparing the difference in the tread design. That test isn't going to take into account the hardening of the rubber over the life of the tire.


Yup this.

It's hard to be scientific and relevant though because after 5-6 years they won't still be making the tire and even if they did the survey results would be nearly useless as other tires come on the market.

 

[Rand]

yea michelin have some good tires but that is not a real world test.. its a tread pattern/compound validation.. but nothing real world.


its more like "this pattern and compound works good at high and low tread depth"
but 5-6 year old tires that are hard and plastic might have far different results.

 

[DuckRyder]

HMMM

Gotta love the ‘Tex.

Interesting the the 3rd best "best new" tire shaved to 4/32 is stopping within 1 foot of the best "worst new" tire at full depth.

3 ft from new to shaved for the Premier A/S is impressive... glad I have some.

(Everyone whines like a mud tire on the highway that shaving tires isn't real world, but tire aging in the real world is so variable al test of it would only be "real world to a very small subset)

 

[SubLGT]

Originally Posted by DuckRyder
...but tire aging in the real world is so variable al test of it would only be "real world to a very small subset)


Exactly! There are thousands of different tire aging scenarios.

 

[dkryan]

Originally Posted by DuckRyder


...........Interesting the the 3rd best "best new" tire shaved to 4/32 is stopping within 1 foot of the best "worst new" tire at full depth.............)


Doh!

The Michelin Defenders on the Highlander just measured out at 4/32 on each corner. And here I am looking for new skins!

 

[mrsilv04]

I'll point out that the Uniroyal Tiger Paw AWP 3, which shows up as a poor performer multiple times... is owned by Michelin.

 

[edyvw]

I always bought Michelin precisely because slowest performance degradation. Finally someone took time to do this test.
It would be interesting to see snow tire comparison when they go down to 4/32. Michelin provided 4/32 Xi3 compare to other at 4/32 during presentation, but it would be good to be done by CR or someone like that.

 

[slo town]

Originally Posted by mrsilv04
I'll point out that the Uniroyal Tiger Paw AWP 3, which shows up as a poor performer multiple times... is owned by Michelin.

And?

Scott

 

[slo town]

Originally Posted by DuckRyder
HMMM

Gotta love the ‘Tex.

Interesting the the 3rd best "best new" tire shaved to 4/32 is stopping within 1 foot of the best "worst new" tire at full depth.

3 ft from new to shaved for the Premier A/S is impressive... glad I have some.

(Everyone whines like a mud tire on the highway that shaving tires isn't real world, but tire aging in the real world is so variable al test of it would only be "real world to a very small subset)


I have a set of the Premier A/S on our Honda. I'm on track to get 60k plus miles out of them. A great tire.

Scott

 

[JHZR2]

Originally Posted by Rand
yea michelin have some good tires but that is not a real world test.. its a tread pattern/compound validation.. but nothing real world.


its more like "this pattern and compound works good at high and low tread depth"
but 5-6 year old tires that are hard and plastic might have far different results.


And? Think you missed the point.

You're right that this missed soepme attributes that could affect performance.

But open that can of worms up and people will have yet more complaints about the experimental design.

Even if only a tread test, it validates that at least with quality tires, you can reasonably safely run them down nearly to the wear bars with confidence. I'd say that is an objective outcome, regardless of if more factors would be desirable..

 

[edyvw]

Originally Posted by Rand
yea michelin have some good tires but that is not a real world test.. its a tread pattern/compound validation.. but nothing real world.


its more like "this pattern and compound works good at high and low tread depth"
but 5-6 year old tires that are hard and plastic might have far different results.

All tires were subject to SAME conditions!

 

[CharBaby]

Originally Posted by eljefino
Originally Posted by ctechbob
Well, that's all fine and dandy, but it is really only comparing the difference in the tread design. That test isn't going to take into account the hardening of the rubber over the life of the tire.


Yup this.

It's hard to be scientific and relevant though because after 5-6 years they won't still be making the tire and even if they did the survey results would be nearly useless as other tires come on the market.


And I believe CR even mentions this in a "Talking Cars" video, that they can't take into account that tires/rubber hardens as it ages.

 

[krzyss]

People who complain that it is not "real life" test are forgetting about:

• tire aging depends on multitude of factors
• takes time
• shaving allows to control conditions and with scientific method repeatability is paramount
  and my favourite
• shaved tire shows very likely the best scenario without rubber aging, that means that if tires looses 3ft shaved then worn will be higher, probably as a percentage, and if another tire looses 51ft that is bad news that turns even worse with aging added.

It looks like Michelin is not empty worded when they claim to work on prolonging the level of performance and not just wear.

KrzyÅ›

 

[CharBaby]

I believe that Michelin(as with other tire companies), keep tire examples around for prolonged testing. And maybe even know more than some give them credit for in terms of, how do tires wear as they age.

 

[CapriRacer]

It appears to me that the CR test is mostly about the wet grip level of the tread compound and very little about what affect tread pattern has. Notice that the tires with the least amount of change are the same ones that rate high to begin with - where the tires with the most change are the ones that rated poorly to begin with.

This leads me to suspect that not only is the methodology wrong, but the water thickness wasn't enough to generate hydroplaning effects.

So once again I have issues with how CR tests tires. Does anyone have a subscription? (I don't!) Did CR publish details of their methodology? (Or like they have recently done, leave everyone in the dark.)

 

[krzyss]

Here you go:

"How We Tested


These evaluations were based on standard tire tests that CR performs on every model it rates.

In the wet braking comparison, we measured the stopping distance from 60 mph on a surface covered with 1.2 mm of water (about the thickness of a dime). That is like stopping in a heavy rain storm, and it is an evaluation that we perform hundreds of times a year.

We also recorded each car's speed when the tires start to hydroplane (losing contact and control) on 10 mm of water. This challenging test is comparable to driving through standing water on a rutted road."

KrzyÅ›

 

[SubLGT]

Last year, AAA did some wet traction testing of worn tires ( 6 each of passenger and light truck).
A detailed test report can be downloaded from:
https://newsroom.aaa.com/2018/06/tread-lightly-worn-tires-drivers-risk/

Quote
New research from AAA reveals that driving on relatively worn tires at highway speeds in wet conditions can increase average stopping distances by a staggering 43 percent, or an additional 87 feet — more than the length of a semi-trailer truck — when compared to new tires

...Compared to new tires, tires worn to a tread depth of just 4/32" exhibit...an average increased stopping distance of 87 feet for a passenger car and 86 feet for a light truck.

(The worn Michelin Premier AS had an increased stopping distance of 29%, or 55ft, a lot more than the 3ft difference CR saw in their testing)

They tested these tires:

Quote
The test sequence for the Toyota Camry was as follows:
1) Nexen Classe Premiere CP671
2) Goodyear Eagle Sport
3) Fuzion Touring
4) Pirelli Cinturato All-Season Plus
5) Kumho Ecsta 4X II
6) Michelin Premier A/S

The test sequence for the Ford F-150 was as follows:
1) Firestone Destination LE II
2) Bridgestone Dueler H/L Alenza Plus (113T)
3) Cooper Evolution H/T (115T)
4) Michelin Defender LTX M/S (115T)
5) Hankook Dyanpro RH12 (113T)
6) Goodyear Wrangler Fortitude HT (115T)

... A test speed of 60 mph was chosen for wet stopping distance tests because this test speed is a recognized industry standard. Additionally, Gegenback et al. [6] have found that while traction level is mostly independent of water depth at low speeds (
To conduct new and worn tire testing, two sets of each randomly selected tire model were procured from a major tire retailer. One set was tested as-is (new) and an identical second set was artificially worn to a uniform tread depth of 4/32" prior to testing. Artificial wearing of all test tires was performed in a manner consistent with ASTM3 International standard F1046-01 [4].

Wet stopping distance measurements were conducted on all new and artificially worn test tires for each vehicle. At the beginning of the day, track personnel checked the water system for proper operation, measured water depths in various parts of the testing lane to determine the average water depth and burnished the surface by conducting multiple ABS stops in the testing lane. Once the testing lane was prepared by track personnel, AAA researchers conducted all track-testing activities.
Before test tires were measured, the stopping distance of a new set of OE reference tires was measured nine consecutive times; all measurements were averaged. After six test tires were run, the OE reference set was rerun six consecutive times and all six stopping distances were averaged. The average stopping distances before and after the test tires served as a reference to account for environmental variations that occurred throughout the day.
To ensure the brakes were applied in a consistent manner for all stops, including the reference stops, pedal force measurements were compared between all tires. The data acquisition system was configured to measure the brake pedal force (N) and the brake pedal force rate (N/s). The data acquisition rate for brake pedal force and brake pedal force rate was set at 2000 Hz.

To measure the stopping distance from 60-0 mph, the testing lane was entered at 65 mph. Full braking was applied at this speed to allow the braking system to reach a steady state before the target speed of 60 mph was reached. The data acquisition system was programmed to begin measuring the stopping distance once the instantaneous vehicle velocity reached 60 mph. To enhance data quality, stops were initiated within a consistent location; the lateral tolerance was ±4 in and the longitudinal tolerance was +6 ft (longitudinal tolerance was unilateral because stops must be initiated in an area of consistent water depth). Each test tire set underwent nine stops; each stop was averaged to determine the average stopping distance. The average time to stop (s) is also reported for each tire. To identify outlying runs for each test tire, the Shapiro-Wilk test was first used to determine normality of the stopping distance dataset. If the Ï-value from the Shapiro-Wilk test was greater than 0.05, the Extreme Studentized Deviate test was utilized to identify a maximum of two outliers per dataset. Any identified outliers were excluded from averaging.
The reference stopping distances were utilized to apply a linear correction factor to the stopping distance of each test tire. All stopping distances were corrected with respect to the reference measurement with the shorter stopping distance. Specifically, a portion of the difference between the reference set stopping distance at the beginning and end of the test tire runs was subtracted from the stopping distance of each test tire. The value subtracted from a specific test tire was linearly dependent on the time at which a test tire was run relative to the reference sets.

 

[nthach]

Originally Posted by mrsilv04
I'll point out that the Uniroyal Tiger Paw AWP 3, which shows up as a poor performer multiple times... is owned by Michelin.

Michelin doesn't really pay that much attention to most of the Uniroyal line or even make most of them in house - it seems like that's outsourced to Hankook or some obscure Indonesian tire maker last time I fondled a Uniroyal on display.

They managed to pull of an engineering stunt with the Premier A/S, but I won't be recommending them for cars that see the snow.