Tire rack wet stopping tests

JHZR2

Staff member
Joined
Dec 14, 2002
Messages
49,514
Location
New Jersey
I’m looking at replacement tires for my latest 1991 350SD. I like to find US made tires, but because this car is still somewhat a wildcard, and I don’t know how many miles I’ll put on it over time, I was looking for a better option for US made tires than the Michelin defender.

I saw on tire rack that the Cooper Endeavor is a new release tire with hood steering, and needs somewhat better wet stopping. The results show that:

B2A9533E-7F23-4489-BDD3-5C07086158DC.jpg


I thought wow. That’s a long stop, especially since they tested it on a Subaru BRZ which should have good brakes (albeit probably fat tires).

So I went back to look at the Michelin Energy Saver test (on my accord) from like 2009, done on a Prius, which surely has “worse” brakes…

B2C4A52B-D765-4664-810A-44B0CA0422C6.jpg


Huh?? 107 ft vs 155 feet for the energy saver on a Prius vs the new Cooper endeavor on a BRZ?!? What gives?

Are these test worth even reading? Is this test just so sensitive to vehicle weight and tire width?

I’d be using the endeavor on a 1991 350SD in 205/65-15 94H sizing. Obviously the contact patch/weight per tire will be higher.

But what gives? Even if one would argue they don’t like the Cooper (I’ve had good luck with Cooper cs4/5 on my old MB cars), look at any of the others too…

Thoughts?
 
Joined
Feb 27, 2009
Messages
8,092
Location
down in the park
Temperature and water depth make a huge difference, vehicle weight not if the tyres are properly sized, and neither does tyre width if the water depth is shallow enough. If the water is deep it's more an aquaplaning test.

Look at some real performance tyre results aswell, they tend to suffer with deep water.

I'd only compare within a certain group, most likely tested in the same conditions
 
Joined
Nov 24, 2003
Messages
3,415
Location
Middle of Iowa
Somewhere on the tire rack website it states you cannot compare results from different tests. Only the tires in that test can be compared with each other.

Temperature, water depth, vehicle weight, inflation pressure, vehicle ABS capability, tire size, rim size...all come into play.

I would be ok comparing within a test, but not test to test, especially if differing vehicles.
 
Joined
Feb 22, 2003
Messages
4,295
Location
Somewhere in the US
I just uploaded new webpages - and one of them is about wet traction testing: Barry's Tire Tech: Wet Traction Testing

What pertains to this discussion is:

1) Real traction testing involves a traction trailer or an instrumented vehicle. This is so the test results are repeatable, accurate and precise.

2) Real traction testing involves the SRTT (Standard Reference Test Tire) This is so different tests can be compared, but it is always a good idea to conduct the test so that what you want to compare is tested at the same time. There is a lot of variability.

3) Comparing different tire sizes is problematic. In this case it's a 225/45R17 vs 185/65R15. I am sure hydroplaning was a factor between the 2 tests cited.
 
Joined
Feb 18, 2012
Messages
890
Location
MA, USA
I think most, if not all. vehicles sold in the USA have "good brakes". They are at least good for one single stop from highways speeds.
Repeated brakings would overwhelm all of them, some quicker than others.
From TR results it looks like Vredestein is very good in the wet and Cooper should be avoided if wet performance is important to you.
10 ft is a car length from 50mph. That is not fender bender, it is a nice crash.

If CR has similar wet ratings of said tires I would use them in the desert.

Krzyś
 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,514
Location
New Jersey
Somewhere on the tire rack website it states you cannot compare results from different tests. Only the tires in that test can be compared with each other.

That makes obvious sense in terms of setting up an experiment to evaluate some criteria. It is the appropriate approach, otherwise you need to perform an experimental design to try to look at cross factors and it becomes very complex.

Still what struck me is the relative differences. Like a lot. Nearly 50 feet from the best on the Prius to the worst on the BRZ. And obviously something else is up. While it may be true that all cars have working brakes that are sufficient, I don’t believe for a second that the Prius is actually a better braking vehicle as compared to the BRZ. And 50MPH isn’t fast (relatively, for a braking test).

So then assuming (and that’s a big assumption) that the tests were performed the same in terms of parameters… then it has to come back to the contact patch and weight of the car per patch area. I don’t see how it’s anything else.

The other thing is I don’t know how much it matters to me. I’m driving big slow cars pretty gingerly. I’m not an aggressive driver or tailgater. But 50ft is 50ft. And - huge percentage of the overall test stopping length. I don’t know how this translates to real word use, especially when they’re so divergent.
 
Last edited:
Joined
Aug 20, 2003
Messages
18,993
Location
NE,Ohio
you cant compare the 50ft number.
you can compare it to the rt-45 a highly respected tire that stopped 10 ft shorter

The 155ft number is not that scary taken in context.. wouldnt let it steer me away.
 
Joined
Apr 15, 2010
Messages
8,765
Location
Atlanta,GA
I’m looking at replacement tires for my latest 1991 350SD. I like to find US made tires, but because this car is still somewhat a wildcard, and I don’t know how many miles I’ll put on it over time, I was looking for a better option for US made tires than the Michelin defender.

I saw on tire rack that the Cooper Endeavor is a new release tire with hood steering, and needs somewhat better wet stopping. The results show that:

View attachment 118827

I thought wow. That’s a long stop, especially since they tested it on a Subaru BRZ which should have good brakes (albeit probably fat tires).

So I went back to look at the Michelin Energy Saver test (on my accord) from like 2009, done on a Prius, which surely has “worse” brakes…

View attachment 118829

Huh?? 107 ft vs 155 feet for the energy saver on a Prius vs the new Cooper endeavor on a BRZ?!? What gives?

Are these test worth even reading? Is this test just so sensitive to vehicle weight and tire width?

I’d be using the endeavor on a 1991 350SD in 205/65-15 94H sizing. Obviously the contact patch/weight per tire will be higher.

But what gives? Even if one would argue they don’t like the Cooper (I’ve had good luck with Cooper cs4/5 on my old MB cars), look at any of the others too…

Thoughts?
I'd ask Tirerack. I bet if you use their chat feature you'll get an answer in a min or so.
 
Joined
Sep 23, 2008
Messages
10,945
Location
Ontario, Canada
That makes obvious sense in terms of setting up an experiment to evaluate some criteria. It is the appropriate approach, otherwise you need to perform an experimental design to try to look at cross factors and it becomes very complex.

Still what struck me is the relative differences. Like a lot. Nearly 50 feet from the best on the Prius to the worst on the BRZ. And obviously something else is up. While it may be true that all cars have working brakes that are sufficient, I don’t believe for a second that the Prius is actually a better braking vehicle as compared to the BRZ. And 50MPH isn’t fast (relatively, for a braking test).

So then assuming (and that’s a big assumption) that the tests were performed the same in terms of parameters… then it has to come back to the contact patch and weight of the car per patch area. I don’t see how it’s anything else.

The other thing is I don’t know how much it matters to me. I’m driving big slow cars pretty gingerly. I’m not an aggressive driver or tailgater. But 50ft is 50ft. And - huge percentage of the overall test stopping length. I don’t know how this translates to real word use, especially when they’re so divergent.
Yeah, I do find it a bit odd that that tire rack test results vary so widely? Maybe they don't use the same patch of pavement with the same amount of water on it? And why use so much water that hydroplaning is a factor at 50mph? Wet grip is a separate measurement from hydroplaning resistance anyways...

Consumer reports seems to run all their tests so they can be compared, and perhaps their raw numbers vary widely too, but they use correction factors to come to each tire's ratings, so the ratings can be compared for say wet grip, between winter and 3 season tires, and summer as well.
 
Joined
Feb 27, 2009
Messages
8,092
Location
down in the park
hydroplaning is directly linked to tyre pressure. For a car with low pressure in the tyres 50 mph is unsafe. low = 30 psi or so.

Before you get full hydroplaning, the weight of the car is partially carried by the water and grip is already reduced.
 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,514
Location
New Jersey
you cant compare the 50ft number.
you can compare it to the rt-45 a highly respected tire that stopped 10 ft shorter

The 155ft number is not that scary taken in context.. wouldnt let it steer me away.
You can draw some conclusions, if the test conditions (water level, road surface) is consistent - it’s telling me that a Prius would stop better with narrow energy saver tires. That 50 feet is non trivial in that context.
 
Joined
Aug 20, 2003
Messages
18,993
Location
NE,Ohio
You can draw some conclusions, if the test conditions (water level, road surface) is consistent - it’s telling me that a Prius would stop better with narrow energy saver tires. That 50 feet is non trivial in that context.
but how much better would it stop than with the coopers? 5ft? 10ft? 20ft? unknown.
 
Joined
Feb 27, 2009
Messages
8,092
Location
down in the park
You can draw some conclusions, if the test conditions (water level, road surface) is consistent - it’s telling me that a Prius would stop better with narrow energy saver tires. That 50 feet is non trivial in that context.

There's other tests out there and they say it won't
 
Joined
Apr 26, 2005
Messages
1,131
Location
Under the hood
Yeah, I do find it a bit odd that that tire rack test results vary so widely? Maybe they don't use the same patch of pavement with the same amount of water on it? And why use so much water that hydroplaning is a factor at 50mph? Wet grip is a separate measurement from hydroplaning resistance anyways...

Consumer reports seems to run all their tests so they can be compared, and perhaps their raw numbers vary widely too, but they use correction factors to come to each tire's ratings, so the ratings can be compared for say wet grip, between winter and 3 season tires, and summer as well.

Tire Rack has its own track, where they're been performing tests since 1995.

They may not follow industry procedure, as outlined above, but consistency and repeatability should not be an issue for the tests they do perform.

Tire testing is a PITA, and hard enough so that the car rags don't really do them any longer. And when they did do them, they didn't have the facilities, consistency, or regular cadence that TR has when doing them.
 
Top