Wet Giro Descents--tire question

[Onno]

What a miserable ride it must have been today. Basso looked very sensible on the descent. Would they be using special tires today, knowing how wet it would be, or is same model of tire used every day, regardless of conditions (i.e. so that a race tire is supposed to handle all conditions)?

[BdaGhisallo]

Well most of them seemingly rode their regular rubber, though Cunego appeared to be on Vittoria All Weather Treads. Note that I didn't say tires. I wouldn't be surprised if they were veloflex carcasses under those tell-tale green treads. Most of the teams, except for Continental and the Michelin teams, tend to ride rebadged Veloflexes.

Further, I don't think tires make that much of a difference in the rain on a bike as they do with a car. The contact patch on a bike tire is so small and knife like that it slices through and displaces water. Car tires are treaded so that a film of water can't build up between the tire and road and cause the car to acquaplane, where it slides on a film of water.

The most sensible thing is to lower the pressure in regular tires to increase the size of the contact patch and, hence, traction. Or you can go to a wider tire and achieve the same, though I doubt any Giro teams would consider that.

[lnomalley]

the thing that sucks about racing in the rain isnt your tires.. it's not being able to see because your eyes are being pelted, its having brakes that don't really do much, it's paint stripes in the road and it's mystery oily stuff in the road. rain tires don't do much for you on radom oily wet paint ... also, when it's cold.. just being there is miserable. you can barely use your fingers to brake. i could see running a softer compound but i dont see some poor sob team mechanic regluing a full team's bikes for a 1/2 day of rain. you just deal with it.

for all the rain racing i've done..tire grip was never an issue.... being able to see, not shivering to death, and braking were much more at the forefront. you really can't see sh*t, your glasses are full of drips and drops and when you take them of your eyes get loaded with crap. who cares about tires at that point.

[Erik.Lazdins]

The contact patch is so small that aquaplaning doesn't happen even at racing speeds, but there are still many things to look out for like leaves, painted lane markers, a drop of oil. All of this is complicated by road spray from riders in front of you or the rain itself.

Does tire compound matter?

[Louis]

for all the rain racing i've done..tire grip was never an issue....

I'm in no way a racer, but certainly water (+ oil in some cases) reduces the rubber-asphalt coefficient of friction.

Wouldn't that cause you to back off some on a twisty descent? (I sure do, but then I'm not racing.)

Louis

[BdaGhisallo]

Consider also that after a good rain, ie one sustained enough to wash off the surface oil and grease on the road surface, traction can be almost as good as a dry road. This combined with the small tire contact patch and no fear of aquaplaning, mean that cornering in the wet can be not so bad.

Now the trick is recognising when the oil has and hasn't been washed away.

[11.4]

You have to remember that in Italy, there's a great dependence on diesel fuel for both trucks and cars. When diesel burns, it spews an oil film onto the roads, and European roads in the wet can be far more treacherous than you find pretty much anywhere in the US or Canada. This oil film is a lot more tenacious than the oil film on US roads, so a hard day (or several hard days) of rain won't necessarily get rid of it. And some asphalts in southern Europe are much richer in tar oil which gets exuded both in extreme hot weather (remember Beloki's crash?) and when there's hydrostatic pressure built up under the asphalt from heavy rains. In Europe, you just learn to live with it. A file center tread tends to grip on any underlying texture in the road a bit better than a center rib or a slick tire, so these are more common among experienced European riders, pro or otherwise. That's why Veloflex puts different center treads on their Criterium and their Carbon. The Carbon is targeted to wet, slippery, and cobbly conditions. The tread's not as nice as the Criterium (which has bare fabric sidewalls), but does stick better when you need it.

Plus, American highway crews use a relatively gritty paint for road stripes which gives moderately decent traction, but in Italy these are like a gloss white. The slightest oil film and you slide on them.

Tires like Vittoria Pave's or All-Weathers don't do much better than a Veloflex Carbon in the rain. Their metier is rough roads, or those with heavy build-ups of clay. Riders will especially use them if a course varies in road width and the peloton is squeezed out onto the sides of the road at narrow points. We don't deal often with that here in the US, but it's a fact of life in European races.

Looking at some of the photos of the Stage 17 course, I figure the leading riders won't have any problem because they'll be picking their own lines and even in thick slushy gravel or sand, they can maintain speed and a line. It's the slower riders behind that will have the worst problem, both because speeds will be slower and because they'll be forced to stop behind other riders having problems. But if you've ridden cyclocross on sand dunes, I assure you these roads aren't as bad. This is bike handling that is part of racing in Europe. Not much demand for it in the US, so most US riders don't know how to handle it at first, but everyone learns.