I am commuting in rainy Seattle, and the rain has started. Right now I have Continental Gatorskin tires on my commuter, but yesterday I noticed I was braking to stop the wheels and skidding quite a bit on wet roads. I know I can gradually adjust braking on front and back to come out of the skid, but I was wondering if i should replace my tires to get a little more grip. My LBS seems to think thin slicks are fine however. Is there a study or data on tire types on wet pavement?
- Anybody can ask a question
- Anybody can answer
- The best answers are voted up and rise to the top
If you are riding on the road, slicks are fine in the wet. If you need to go over any mud, etc. then you'll need something else.
From Sheldon Brown:
Also worthy of note is:
Bicycles can NOT hydroplane because:
First you need to analyze the pavement a bit -- smooth pavement or rough, is it generally pretty clean or is there a light coating of sand or dust, or perhaps a heavy coating?
Narrow, high-pressure bike tires do not "hydroplane" at non-supersonic speeds, so you don't need to worry about that. But there is still a thin layer of water between tire and road surface, sufficient to impact the coefficient of friction, and some sort of "tread" or "siping" helps significantly. Any dust or sand exacerbates the problem, and a smooth surface (especially worn-smooth asphalt) can get treacherous. I don't know of any hard numbers (though I would suspect they're out there somewhere), but Wikipedia has this to say (about auto tires):
The conti's really are just fine.
There's just less friction on wet roads and so your rear wheel is going to skid at a lower deceleration. A wider tire will be a little more helpful because your contact patch is larger.
But then you have to balance that with puncture resistance. In addition to reduced traction, you also have a greater probability of getting a flat in the rain. Which one is worse? It's up to you. The michelin's and avocet's are nowhere near as durable as the conti-gatorskins (there's a reason they're highly popular as high mileage urban tires). But if you're doing office-park crits in the rain you're better off with the michelin/avocet's.
Just to add on to what Wilka said about hydroplaning, people involved with the physics of planes landing are particularly interested in hydroplaning. Sheldon Brown of course talks about this.
I've found a chart here which on page 9 includes this plot:
You can see that at the pressures we operate at ones risk of hydroplaning is negligible.
Regarding your concerns about flipping, Sheldon Brown has a very informative page, "Won't I Go Over The Bars?", which details why you should not be concerned with flipping over the handlebars if you are using your front brake appropriately, and shows that when traction is not an issue using just your front brake is the fastest way you can stop. He also speaks about braking in the conditions your asking about (traction impaired).
As long as I am not braking on a manhole cover I have never had issues stopping in the rain on 23C slick tires using just my front brake.