Can I avoid falling in the rain on a corner?

Question

I was riding in the rain a few months ago and fell turning a 90° corner. Here are the details:

• Riding on a road bike with new 25mm smooth tires inflated to 100 psi (Cannondale Synapse with Continental Gatorskins inflated to 690 kilopascal)
• It had been raining for at least an hour, but was not raining hard at the time of the fall
• There was no obvious oil or other liquids around, no dirt or other substances
• There was no strong wind and the temperature was well above freezing
• I was coasting at about 10 mph (16 km/h) around a corner on smooth asphalt
• I weigh 210 lbs (95 kg)
• I fell to my inside, right side
• The fall was immediate with no dramatic skidding or sliding

Here is a photo of the corner, with a red square where I slipped:

I was surprised to discover that the smooth tires are not particularly the culprit in my fall, as bicycle tires for on-road use have no need of any sort of tread features; in fact, the best road tires are perfectly smooth, with no tread at all.

(Edit: Per multiple comments and answers, the above link is not specific to wet surfaces and the assertion that no tread is optimal does not apply here. It appears treads should help with wet surfaces.)

I live in a desert climate so I haven't had much experience with slippery roads, and none since that accident. Is there anything I could have done to avoid falling, or do I simply need to avoid any wet, asphalt surfaces?

Answer 1

16 km/h is so slow that even the worst tyres should keep you up, unless something like oil spills were involved.

If something is so slippy that you fall without warning at such low speeds there is not much one could do. If you have a hunch this might happen tripodding corners or getting off the bike may help.

The first drizzle after a long dry spell can leave a very slippy mix of wet dirt on the tarmac. It sometimes feels almost like soap. More intense rain washes it off quickly.

Some surfaces (eg metal or road markings) can get slippy when wet. Avoid anything that looks smooth and wet. edit: The smooth tar of the patched cracks visible in your photo are also example for such treacherous surfaces.

If temperatures are closer to zero black ice may form spontaneously. It is nearly impossible to distinguish from wet road and is extremely slippy.

Answer 2

In places where it rains very little or hasn't rained in a while and then a light rain falls, the water is not enough to "wash" the road surface; instead it only wets fine dust and oils that are on the surface. These oils come from cars' engines and exhausts, but are not noticeable at first sight. This mix turns into a fine, paste-like substance that is very thin and difficult to see, but is really slippery, so much that even walking there can be difficult or dangerous. This can cause falls similar to the one you describe.

I've had several near-misses while riding or driving in these conditions, but a particular one that I remember, I was pedalling energetically and tried to make a slight s-curve (imagine changing lanes on 1 metre wide lanes) and on the second part of the manoeuvre, the front tire slipped to the right without warning and I fell on my left side and slid on the pavement a few metres. I was surprised as neither my hand nor my hip was scratched, and I didn't develop road rash. My pants where smeared with a black paint-like paste. I was using semi-slick tires at around 60 psi.

I have observed as both a cyclist and a car driver, that after a slight rain streets are very slippery, but after heavy rain, even if the road is wet, traction is very good.

Answer 3

To fall to the inside of the turn means that the bottom of the wheel has slid to the outside. When that happens, it is really quick.

I would look back at the corner and see if there's a metal plate in the roadway, which are terribly greasy when wet.

Other possibilities include round grit/gravel/dust/sant that acts as a ball bearing, and oils on the roadway.

Answer 4

In addition to the previous answers, your tire pressure was likely too high for the conditions. If you know you're going to be riding in the rain, it's usually a good idea to lower your tire pressure from what you would normally have them at in dry conditions. A lower tire pressure allows the tire contact patch to deform more, thereby increasing the amount of tire in contact with the road and increasing the tire's grip.

According to Challenge (bike tire manufacturer):

A hard (due to materials or pressure), bouncing tire will lose contact, allow water to penetrate under the tread and lose traction quickly and without warning.

How much pressure you take out of the tire depends in large part on your personal comfort level, but dropping the pressure by 10% is a good starting point.

Answer 5

I'm surprised to see that no one else mentioned it, and this isn't a terribly detailed answer, but that road has what motorcyclists refer to as the dreaded "tar snakes".

The tar they use to patch cracks ends up very smooth, and depending on weather conditions can get polished even more by traffic. Especially in wet conditions, that thin line of tar can be enough to break a tire loose in a turn.

So, watch out for Tar Snakes. All motorcyclists know to stay away from the grease spots at stop lights and stop signs as well, but cyclists are usually off to the side of the road far enough to miss those.

Answer 6

First off, it's untrue that smooth tires are best in the rain. In spite of what Sheldon said, a tire with some tread will provide a better grip on a wet surface.

But regardless of that, you can slightly reduce your chance of skidding on a curve by leaning OUT on the turn. Basically, keep your bike as upright as you reasonably can. This isn't as sexy as leaning in, but it helps reduce slightly the centrifugal force tending to cause an outward skid. And, more importantly, it makes you more conscious of your speed.

And that it the most important thing -- SLOW DOWN on curves when the pavement is wet. 10 mph is probably too fast for anything other than a very broad turn.

Answer 7

Perhaps it could be due to the type of asphalt, I know there is Open-graded friction course (OGFC) (very porous asphalt with a lot of air gaps in it) which is much better at draining the water that falls on its surface, perhaps the asphalt you were riding on was not of this porous type causing more water to accumulate on the surface. However I am quite sure that in the Netherlands this porous asphalt is not used on bike lanes and I still have a lot of grip on these in general (when wet). More info : https://en.wikipedia.org/wiki/Pervious_concrete

Were you braking in the corner? if so: rear or front brake, and how hard? How sharp was the corner? Were there many potholes in the road? Was there any sand/gravel/leaves or similar on the road to your knowledge? How old are your tires? When rubber ages it tends to harden (get less grippy).

Going through corners at that speed shouldn't be an issue at all on road tires, even when it's raining. In my experience road tires have a lot of grip on asphalt even when wet (tram tracks, pothole covers etc are a different story). Your tire pressure also sounds right to me..

Answer 8

A few weeks ago I rode into the parking garage of my apartment building. I had just come off wet streets and my tires (25mm near-slicks) were still wet. The concrete of the parking garage is quite smooth–nearly polished (why??)–and even though I was going but a couple of MPH, as I made a leisurely left turn, I went down.

That sort of wipe-out cannot be averted once it starts. I have good reflexes, but you’re almost on the ground by the time you’re registering what’s happening.

To contrast, when I’m riding my nice road racing bike (same one as in the preceding anecdote) on our crappy streets, I’ll often hit debris or road disturbances (potholes and asphalt turds fused to the road are common here) which, when struck, will unseat my rear tire from the road surface. Without exception that sort of thing not only is recoverable, but it always recovers. I hit boatloads of crap like that (pine cones, anyone?) without going down. And these incidents often happen at fairly high speed or output, including in turns.

So a really good, stable, responsive, agile bike that in almost 19,000 miles of hard urban riding has never gone down, but for that super-slow wipe-out in my parking garage!

C’est la vie!