I'm used to riding on a MTB, but since I've got a new road bike, I'm quite paranoid about the slick tyres. How good are they in wet weather? I'm scared of braking too hard, or even just turning!!
They're fine. I live outside of Vancouver so I'm already riding in wet a few days a week some weeks. Just this morning I was coming down the backside of a climb at 70km and they were totally secure.
Since the tires are so narrow they don't suffer from hydroplaning. The biggest thing to worry about is painted lines and manhole covers (or other metal covers on the road). Both are very slick when wet. I've always been careful but I know a number of other riders that have gone down cornering hard on both types of surfaces.
You're right to leave yourself extra room to brake. Also don't forget to account for reduced visibility for both you and cars.
3 great answers here already, but I'll just add: ride more cautiously. You can ride safely in the rain, but you have to remember that the road will be a bit slicker and your brakes will likely be much less effective. Don't corner too hard and brake earlier than normal. When I know a stop is coming up, I usually give the brakes a light squeeze early on to dry them off and warm up the rims a bit.
And as curtismchale pointed out, watch out for drivers. They'll have the same reduced braking capacity and dramatically reduced visibility (I can see much better cycling in the rain versus driving, due to water and reflections on the windows). Dress in bright clothing, use plenty of reflective tape and bring some nice bright lights.
It's (almost) completely safe, but you can help yourself:
- Avoid manhole covers, you'll often wheel spin if you're not careful
- be wary of coloured road surfaces and lines, London has just ludicrous amounts of painted tarmac (and the new 'cycle superhighways' are some of the worst)
- take a wee bit of speed off, you'll still get there, but give yourself a little more time to look at the surface coming up
- keep your weight balanced, especially when descending, you'll be more secure if you can maximise the grip on both wheels
- ride a little further out than normal, cars passing you need to give you more space, so make yourself more obvious
- mentally I prefer a tyre with some grip, rather than completely slick, but I know that many people think that there's little effective difference
The other answers covered this quite well, but I can speak from recent personal experience. I got a Bike Friday Tikit with skinny, treadless Kojak tires earlier this year, and I had the same concerns you do -- should I ride in the rain or not?
As you may be able to make out in the picture, I do ride this bike in the rain. The Kojaks grip wet pavement as well as the conventionally treaded tires on my touring bike, possibly better. I would avoid snow and ice, but wet isn't a problem. I would swap out the tires on my touring bike, but I do take that on gravel paths from time to time, and I'd like some tread for that!
Just get ready for the wiseacres who'll kid you about those "worn-out" tires! (I got that almost every day at work in the elevator as I carried my folded bike upstairs.)
From my experience the biggest loss in grip between MTB tires and slicks is on the sand (especially sand on tarmac), mud and snow. On ice there is no grip in either case.
On wet surface the slicks are actually better and this makes the border conditions thinner, you either grip well or skid completely.
In addition to all of the suggestions already, and slightly off-topic, if you're riding your bike in heavy rain and you're on skinny wheels and tyres be very careful when riding through puddles.
Even apparently shallow puddles can conceal fairly deep potholes and a buckled wheel or being thrown off your bike into the path of oncoming traffic could put a serious dampener on your enjoyment of the ride or prevent you making it to work completely (if it's a commute).
As you ride in the wet, try to plan your trip around all of the slippery surfaces already mentioned. When you cannot, try to stop turning and braking until clear of the bad stuff, then get back on it.
I wanted to comment on surfaces others have mentioned, with "that's the worst" or "this is even worse than that!"...but anything besides clean pavement can be a hazard.
Something else you might do if planning to ride: realize that visibility for drivers goes way down; get lotsa lights. I keep a front flasher going throughout the day, as well as a regular tail light and a helmet-mounted tail light. The best bike I saw, the rider had colored light sticks on his spokes, lights on his handlebar ends, saddle, helmet, 2 headlights. It seemed like overkill, but I could see him through a rain-spattered windshield easily. Remember, being hit by a car once is worse than multiple slips and falls.
Note that riding in the wet is generally more risky than riding in the dry since things are indeed slipperier than in the dry. Relatively innocuous things in the dry become hazardous in the wet regardless of your tire type (such as wet leaves). Wet also is accompanied by oil in many cases on the road, especially if rain hasn't washed the oil from the cars off the road yet. Stopping distance goes up, etc.
Many racing bikes tend to have sensitive and twitchy steering/geometries, so they aren't great in the wet since they are not easy to control to begin with (even in the dry). But this is a function of the bike itself, not the tires primarily. Note that some control of speed and riding style will help here (riding like a racer means taking risks like a racer).
1) You can't hydroplane (bicycle tires are too thin and high pressure for this).
2) Slick is best in the dry.
3) Tread is effectively aesthetic on road tires (Specialized argues for a tread pattern of < 0.2 mm, but the pattern doesn't matter according to them, Challenge argues for a particular pattern, Continental says they are effectively aesthetic, Vittoria wants you to have tread [ but remember, they all want to sell you a new tire! ]). The road is rough providing the grip.
4) Things that matter: Softness of the tire/compound, reduced tire pressure, higher tire width, rider weight to get a nice big contact patch.
Painted lines aren't always the biggest problem in the wet. The part of the road the cars drive over the most will be all shiny and smooth and filled with smeared otu rubber. These areas will have the least grip in the wet. If you can ride on the rough looking bit you will have a little more grip. Obviously it's a no brainer to avoid man hole covers and metal grids
I ride daily on whatever tyres are fitted to my bike. Rather than worrying whether it's a slick or not your should worry how hard the tyre is especially in the wet. A knackered old (age wise not wear wise) tyre that hasn't been used for ages will be rock had and won't work well in the wet. Some tyres are just a lot softer rubber than others when new.
I've driven racing cars on slicks, race karts on slicks and race bikes on 'slicks' if you can ever call a bike tyre a slick. The main difference with a wet race car tyre is the compound and obviously they have grooves to stop aquaplaning at high speed. At low speed, if you take a wet line, it's the soft compound giving you the grip, not so much the water displacement from the tread.
What it really comes down to is how happy you are with letting the bike slide around under you and that takes years of experience to learn this. If you can't handle a slide you're likely to find out in the wet. Read on... If you have tyres with hard low grip rubber the bike slides at lower speeds. Softer grippier compounds will make the speed it slides at higher. Obvious right? However there is another factor that isn't as binary as this. It's how easy a tyre is to handle when it's approaching this limit. This is what is really important about a wet tyre. If you have another rider alongside you and you're racing him on different tyres you may find out that one tyre type has more grip than the other as he corners faster on that particular road surface. Without another bike doing exactly the same thing you won't really be able to say one tyre is grippier than the other particularly in the wet as if one tyre handles better you'll think it has more grip.
Here is what it comes down to. The better wet tyre is one which has a greater slip angle before the limit is reached and the coefficient of friction starts decreasing. In the wet there is a dramatic change in grip after you go over the limit. The better tyre is one which has less of a step change as the limit is reached. A soft structure will allow the carcass of the tyre to warp increasingly so up until all of the tyre is sliding and the limit is reached. At low side loads the trailing edge of the tyre contact patch slides and this moves progressively forward as the load increases to the point where the whole contact patch is sliding and the tyre cannot provide any more grip. This is maximum slip angle when no part of the contact patch is not slipping. It is how you feel the tyre reaching the limit. If the tyre is soft you'll feel the slip angle at a lower load and you will be able to keep pushing the tyre with some confidence it wont go over the edge. If the carcass is rock hard you'll not notice the tyre slipping until the bike disappears from under you.
So anyway to summarise. Slick vs tread is a red herring. It's about how soft the compound is and how much the carcass can flex. You'll find any bike tyre handles better in the wet if you drastically lower the pressures. Although in the dry the same thing applies a soft tyre will be completely unresponsive and will feel awful with low pressures. Also if it's too soft the contact patch may start working against itself and provide forces in different directions because it's folding over which reduces grip. Some tyres work better than others but it is not about the tread pattern unless you're doing over 100mph or something! And by the way his is all before we start worrying about vibration and bump damping... there is a lot more to it than just slick = bad/tread = good.
Slicks are unsafe period. Urban environments throw up too many variables, manhole covers, white lines (made from small beads of glass for Pete's sake) copper commemoration plaques, drains, silky smooth concrete ramps/flats that a ground worker has forgotten to etch into and of course tarmac itself. The list probably goes on because it doesn't even have to rain to make tarmac damp, condensation does the same trick. Having come off a racer fitted with slicks and broken my collar bone I advise a tyre with knobbly bits that engage with tarmac's pitted surface. Oh and wear a helmet, I hit my head hard and probably have my collar bone to thank for taking most of the impact first.
Slick Road tires are NOT safe in the wet. Bicycles do not go fast to enough to even consider the hydroplaning argument. As the road get wet the imperfections in the asphalt, that actually provide grip, fill up with water, oil, road gunk making the road and the tire very slick. If the tire now cannot channel any water away you are glass on glass. If you add cooler temperatures to this you now have harder rubber and severely reduced traction. Watch a motorcycle road race on tv. Their rain race tires have very aggressive tread patterns and soft rubber. Slick are only used in the dry and that is the only time you should trust them.