What helps with wet traction?

[y_p_w]

I remember a heated discussion on this very forum with someone who according to his username consumed German Castrol. But the think he was most adamant about was that better wet traction came from tires that would shed water rather than absorb it. That kind of ran counter to the industry literature I found that said that holding onto water improved wet traction through the static properties of water (imagine a wet piece of piece sticking to the side of a cold glass).

I remember when I got some rather dramatic looking tires - the Dunlop SP Sport 9000 summer tires. They claimed that it had a carbon black ring down the center for better static dissipation. I tended to get shocked quite a bit, but didn't notice it was any better or worse. But the look was dramatic. Apparently still on the market in some form, although I'd think after two decades the rubber compound would have been improved.

So is there any better understanding about how all this works? I certainly get that tread design makes a huge difference. But do you want water to stick to the tire or not?

 

[SubLGT]

https://www.tirereview.com/wet-traction-relies-on-where-the-rubber-meets-the-road/


Do a search here for technical papers on wet traction:
https://tiresciencetechnology.org

 

[Eddie]

More weight on the driving wheels.

 

[bullwinkle]

The biggest issue is hydroplaning-that's what those Dunlops & the GY Aquatred/Assurance Tripletred tires are meant to counteract, to stop water from literally lifting the vehicle off the road in standing water. I have these on the Grand Marquis in my sig, and with the periodic ridiculous rainfall events we've had here in the last couple years, they get the job done-I've actually put off rooster tails of water when driving through standing water with them. Otherwise, it seems that the silica-infused studless winter tires do a good job in rain, until things start getting pretty deep. Also, the wider the tire & lighter the vehicle, the worse wet (& winter) performance becomes.
http://thecarguy.com/articles/aquatred.htm

 

[CapriRacer]

I divide wet traction into 2 regimes: Hydroplaning and Grip.

As bullwinkle said in a post above: "I gotta get a new ….." No, that's not right!

What he said was the tire literally is pushed off the road surface. What he didn't say was that this is definitely speed related, although water depth, tread depth, inflation pressure, and ambient temperature are in there.

But tread pattern is a major factor and the some tread patterns will pump water away from the footprint to help delay when hydroplaning starts.

I think the terms y_p_w was looking for is hydrophobic and hydroscopic - and I have only seen this referred to in advertising, not scientific papers.. I wonder if there is any scientific correlation there.

And it is my understanding that tread compound is the single biggest factor in wet grip.

Disclaimer: I am not a rubber chemist, but I have worked along side some very talented ones and have picked up a few things - and since I am not aware of any rubber chemists posting on the internet, you guys are going to have to put up with me.

For tread compounds, there is a technology triangle involving rolling resistance, traction (especially wet traction), and treadwear. In order to get an improvement in one area one or both of the others has to be sacrificed - with an exception I will talk about below.

Each tread compound is actually a member of a family of tread compounds, each with a slight variation in percentage of ingredients - sort of like the difference between bread flour and cake flour. Those differences affect the RR/traction/wear equation.

Now here is the exception mentioned above: Replacing some of the carbon black with silica improves wet grip and rolling resistance without affecting treadwear - so a silica family of tread compounds results in a slight shifting of the RR/traction/wear equation. Please note I said "slight". Compared to the overall picture, such a change is small, and less that the extreme that can be achieved without using silica.

Further, hardness (durometer) is sometimes used to characterize tread compounds - and contrary to what one might thick, tread compounds with good RR are soft, as are grippy compounds, where good wearing compounds are hard. Why? Because compared to the stiffness of the inflated tire, rubber is much more flexible and therefore doesn't impact the deflection much.

Side Note: Inflation pressure has a major affect on a tire's stiffness - much more than the stiffness of the sidewall, For practical purposes, you can ignore differences in different casing's stiffness and use inflation pressure to calculate spring rate - ergo, the spring rate of any given tire is very close to others in the same size regardless of brand.

AND - Because there is such a wide range of pavements, the differences in pavement has a much greater affect on grip than the tread compound. There are some pavements where the wet coefficient is close to ice.

PLUS - the macro texture of the pavement interacts with the tread compound is funny ways - such that you can get reversals. That is, some tread compounds will perform better on some pavements where other tread compounds perform better on other pavements.

And one last thought: New tires have both a waxy build up and mold release compounds, so they can be slippery until those are worn off. Be careful with new tires for the first couple of hundred miles.

 

[y_p_w]

I think the exact word I remember was "hydrophilic", but that's neither here nor there. Those were interesting arguments. I also remember some college project where we were dealing with "hydroscopic" material - one that would swell after contact with water.

I've been up close and personal with pavement before. It was always remarkable to me how little asphalt surface would seem to be in contact with tires given that it was more like a lot of tiny little rocks.

 

[marine65]

What helps with wet traction?

Slow down.

 

[litesong]

Originally Posted by marine65
What helps with wet traction?
Slow down.
.......Simon & Garfunkel said it best AND gave good reasons:
"Slow down, you move too fast
You got to make the morning last......
Ba da-da da-da da-da, feeling groovy"