Wet Grip Road Tire Data at BRR

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sethjs
Posts: 279
Joined: Fri Feb 04, 2011 4:02 pm
Location: San Francisco, CA

by sethjs

Jarno has developed a wet grip tire test. Really an industry first as far as I'm aware - and really important data for those of us who ride on wet roads.

Super interesting to see the variation - both between tires, and also when looking at center vs edge grip.

A lot of our "seat of the pants" impressions over the years have actually been reasonably on point.

https://www.bicyclerollingresistance.co ... /grip-test

tjvirden
Posts: 540
Joined: Sun Nov 22, 2020 9:21 pm

by tjvirden

It seems like a nice attempt, but I'm not convinced it's useful - for a start it's not measuring lateral force when testing with the wheel inclined.

Michelin's test rig is the only realistic one.

From the explanation given, it's a test of "sliding grip" (significant relative movement between the surfaces) and that's no good for a bicycle - IRL if the tire is sliding because traction has been lost at the maximum lean angle available, then the next thing that happens is that you hit the deck. What happens just before the tire loses traction is the critical part, and that isn't measured here.

What is disappointing is that Jarno talks a lot about casing and tread flexibility as a significant factor, but hasn't measured (quantified) it - measuring on a flat, smooth surface is exactly the circumstance when casing and tread stiffness will make little difference - on the road, perhaps it will make a small difference, but tire pressure/size will dominate that in any case.

I can't agree with his assessment that:

"What we've learned from our test results is that the compound by itself isn't as crucial as we initially expected. The flexibility of the casing is just as important as the tread thickness of bicycle tires is very low compared to most other tires. The thinner the tread, the more critical the casing becomes, as it will make up a more significant portion of the tire's flexibility."

For wet grip on tarmac, compound is the critical bit; that's why the tread of all tires to be used on pavement is black.

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Bb13
Posts: 85
Joined: Fri Nov 16, 2018 11:34 am
Location: Aix en Provence

by Bb13

At which psi was the test done ?
I adapt the pressure according to the weather. I think it plays an important part of the grip

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Mr.Gib
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Joined: Fri Mar 18, 2005 4:12 pm
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by Mr.Gib

tjvirden wrote:
Sun Nov 28, 2021 1:18 pm
I can't agree with his assessment that:

"What we've learned from our test results is that the compound by itself isn't as crucial as we initially expected. The flexibility of the casing is just as important as the tread thickness of bicycle tires is very low compared to most other tires. The thinner the tread, the more critical the casing becomes, as it will make up a more significant portion of the tire's flexibility."

For wet grip on tarmac, compound is the critical bit; that's why the tread of all tires to be used on pavement is black.
When it come to actual use on the road, I believe both compound and casing flexibility may have equally important roles depending on the smoothness of the surface. If the surface is smooth, then compound is key. A rougher surface will favour casing flexibility. I do agree with your basic premise though, nothing can help a slippery tread compound. I recall an earlier generation of Vittoria's, both front and rear, squirting out from underneath me when starting from a track stand at a traffic light in the rain. The whole bike pivoted about 20 degrees before I got it back. Those tires were plenty flexible but that compound was not great on wet roads.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

shimmeD
Posts: 544
Joined: Thu Jun 28, 2012 10:52 pm
Location: eNZed

by shimmeD

Thanks Mr Gib for reminding me about those cursed Vitt tubs I bought a few of some 9yrs ago. I still have one left, carried as a spare. And that's all it's good for. Not quite true, it rides well and feels fast and not bad weight but :roll: remind me to ride slowly and/or in a straight line home if I puncture on moist roads.
Less is more.

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