Dr1v3n

Tl;Dr - Does a gravel bike with 38c treaded tires that are at about 40-50psi handle significantly better than a road bike with slick tires in wet weather?

I began riding last May, avg 75 miles per week. I had been riding solely a road bike (Giant Contend 3) with 700x28c "slick" tires on it (Giant S-R3). A month ago, I picked up a Giant Revolt Advanced gravel bike which has 700x38c Giant Crosscut AT1 tires on it with a tread pattern.

This entire time, I only rode in wet conditions once with the road bike, and had no problems because the day I did it, was on an asphault bike path where I basically just rode straight the entire time.

Today was very wet out - drizzling and it just started so the roads looked pretty slick. I decided to go out for a "technique/handling" ride to get some practice riding in wet conditions in low traffic and at lower speeds. I took out the gravel bike because one of the main reasons I bought it was to use it to ride in inclement weather instead of my road bike due to its larger tire size and the fact that it's tubeless means I can run lower PSI to get more traction.

I've heard (both online and from friends in person) to basically try to avoid white painted lines, drain covers, leaves, etc in wet weather. I was lucky to have virtually zero traffic on the road with me just now, so I experimented and essentially, I noticed very little handling difference. Since my gravel bike has disc brakes, braking didnt seem to be significantly affected. In fact, braking as normal, I had zero skids at all. I then wanted to up the ante a bit, so I purposely rode over the painted white lines to see if I slid. I did this both while going straight and turning, and also seemed to have no noticeable problem. Albeit, I did not do this at speeds higher than probably 10-15mph. I have slid a bit on those yellow braille boards at sidewalk ramps for the blind folks, but only on my road bike with slick tires, not with the gravel bike and not today.

I did get up to 30mph on straight road and come to a pretty hard brake at a stop sign, again didn't notice many issues.

Is this pretty normal for a gravel bike? I'm asking because I was trying to avoid lines and drain covers like the plague, but realized if I have to pick between going in front of a car coming behind me or rolling over a drain cover or line, I'll have to roll over them. Are they that bad, or just during fast corners?

Sy Reene

Drain covers, depends on design, you should always try and avoid, regardless of tire. Painted lines, or even worse if you're in a city.. metal plates put in for road repair -- the key really is you have to ride as straight as possible over them. Try and brake or do a quick turn -- fuggedaboutit. Anyway, "tread" won't help on painted lines or if you sink into a sewer grate.

this is a mountain bike tire/wheel meeting a badly designed sewer grate

PeteHski

The only use a tread pattern has on a relatively smooth road surface is to prevent aquaplaning. But bike tyres are narrow enough not to aquaplane anyway when slick, so the tread pattern on your gravel bike tyres is really there just to give a bit more traction and bite on loose off-road surfaces. It isn't really doing anything useful when riding on a wet smooth road.

grizzly59

Slick tires may seem ok on wet pavement, but with just a hair too much speed / lateral force they will suddenly lose all traction and slide across the pavement as you go down. Tires with some tread will be more predictable. Don't brake in corners, especially with the front brake. If there is any oil on the road, the first bit of rain can make pavement very slippery. Layers of wet leaves are terribly slick with any tire except aggressive MTB knobbies.

jon c. 

Avoid drain covers like the plague. Be cautious with painted lines knowing that once in a while they can be slick. But you can't really avoid them and by and large they aren't an issue.

You'll notice a difference with gravel bike tires if you encounter a bit of sand on the road surface. Otherwise, not so much.

79pmooney

There are several variables to be aware of: 1) Not all wet roads are equally slippery. Oil, mud, leaves and other things can make a huge difference. (Oil isn't always to be seen. After a lot of traffic in the dry, it may take several days of hard rain to wash away the buildup from automobile traffic. The first rain after a long dry spell can be near ice slippery.) Different pavements can be very different. Chip seal with sharp gravel can be quite good. With rounded riverbed stones, they can be quite slippery. Some concrete is very good, some very slippery. 2) Different bicycle tire rubber compounds can be radically better or worse in the wet. Sidewall suppleness also can make a big difference. 3) As mentioned above - tire pressure. 4) Ice! Wet ice can be treacherous. The dry stuff is much easier to ride. 3) Rough pavement can effectively "remove" traction since you spend less time with your tires "planted".

Some of my scariest rides have been late summer on my summer-only good road tires caught in that first rain. Deep winter here in Portland, we have days of excellent traction when all the car oil is long gone, all the debris washed off by the rain and race quality rain tires on my bikes. (Vittoria Open Pave tires.)

DaveReading

Newton was probably thinking of bicycles when he formulated his First Law.

Any time I'm riding on a suspect surface, I try to remind myself that (i) it's acceleration that involves the most interaction between the tyre and the road (i.e. grip) and (ii) that acceleration also includes both braking and turning.

Iride01 

No amount of me describing what will or won't cause you to fall on a bike will help you figure out what you can and can't get away with.

About all I or any other can do is point out potential hazards for you to be alert to. As for how fast can you go when encountering them, well if you bust your butt, then you were going too fast probably. Slow down for it next time.

cheesesandwich

It also depends on the tire material right? Some are grippy on wet surface than others. Gravel tires being meant for off road how do they handle wet road surfaces?

blacknbluebikes 

Couple things. One, my understanding is that bike tires do not hydroplane and for roadbikes, tread patterns aren't relevant. Two, all is well until you lock up a rotating wheel, then it's all-bets-off, tire size moot - thus wet riders love disc brakes for the modulation. Three, it's much more about the surface than about the tires, which is true when it's dry outside, too. Regardless, if you ride in the rain, you're badass, period (R#9).

grizzly59

That is the accepted truth. But through experience I disagree. A slick road tire made from long-wearing compound is the worst. A softer rubber with a little tread like a Panaracer TServ will handle better and be more predictable. I'm not pretending to be the authority, that's just my experience.

Seattle Forrest

Read this again. Avoid riding over everything Sy mentions if the ground is even damp.

Maelochs

None of the situations mentioned are instant death sentences ... but after years of riding, certain riders formulate certain generalities.

Who am I to suggest against Russian Roulette, when the odds are 84% in your favor?

On all of the abovementioned surfaces, I am exceedingly careful, and I support completely @Sy Reene's advice to go straight. I try not to even pedal, because that moves the bike, and well .... I have been riding for a long time and I feel I have sufficiently investigated road rash. I leave it to others to do breakthrough research in the field.

noisebeam

One of the worst surfaces is 'polished' concrete. It is used often here at corners. It gets very polished and develops a patina that has zero traction when wet.
You can not corner across these when wet, need to make sure you travel straight only and turn before/after when on asphalt.
Example:

Sy Reene

These damn things come close -- especially if wet

Litespud

you’ll notice the difference when you get to the limits of traction on your road slicks. Do this experiment (actually, don’t): go out and push your gravel bike to its wet cornering and braking limit. Now go out and replicate this on your road bike - you’ll be on your arse in short order

rumrunn6

became curious & just read this
Typically, a cycle lane is treated in a distinctive red or green colour surface dressing. Main Roads WA require any surface dressing for cycle lanes to have a friction value, similar to the adjoining pavement. ... This ensures sustained friction values

aside from that, I try not to tempt fate. but I agree, it's useful to know what the break/slip point is. I test it in my car, in the snow, all the time. I've even done similar w/ a bike on ice. only to realize when it does break/slip, I'm on the ground. a bit safer in a cage w/ 4 contact points. used to have fun in a little, light, 2door on highway exit ramps. can't do that w/ a bike. well, maybe a dirt bike around a dirt curve?

the worst is hitting something that stops the front wheel cold. surprising how quickly you can go over the bars & wind up looking at the sky

SoSmellyAir

That is a crappy intersection for any vehicular or pedestrian traffic. Made even more dangerous by a Floridian driver in New York.

Ghazmh

My advice it to avoid puddles at all cost unless you can definitively absolutely see the ground underneath it. There could be a 6” deep by 2’ wide crater lurking under the smooth surface that will bend your rim and possibly cause injury.

Maelochs

All kinds of hidden hazards ... and the worst is that one of them could pitch you into traffic, where cars are passing at 55 mph two feet away and two feet apart as though it weren't raining.

noisebeam

A few years ago we had 5"+ of rain overnight and into the morning with extensive flooding including on some roads. I decided to ride to work and for the several miles of my commute I was in water over my wheel axles while passing many cars that were floating. I had cycled that route many hundreds of times before so knew the (pre-flood) surface well, plus I was moving only fast enough to keep balance.

Gonzo Bob

I agree on both points. But IMHO, tread patterns on MTB tires are relevant. MTB tires have a smaller contact patch with pavement which reduces traction compared to a slick tire. I've ridden in the rain and on wet roads after a rain a lot and the only time I've gone down was on my MTB. Now, I realize that's anecdotal - I didn't go back and try that corner at the same speed on my road bike.

Carbonfiberboy 

I've been doing group rides in the winter in the PNW for 25 years almost every Sunday, rain or not. I once went down while testing a new-to-me tire in the wet parking lot before a ride. I rode anyway and had a rear wheel slide-out in a sharp corner but no fall. Threw those tires away. That said, it is possible for new tires to still have the mold wax on them. They aren't really safe until they've been ridden in the dry a few times.

My other fall was on the tandem when we took an off-camber turn in the wet and blam, down. The pavement there was made of polished stones about the size of marbles, polished by countless sliding car tires over the decades. We went down correctly on the NDS, staying clipped and holding the bars. No damage other than one smashed Sidi buckle. The surface was so slick we had no clothing damage. We almost went down on the tandem once when a rider went down in front of us from a road seam. I accidentally locked up the rear (never lock up the front) and we fishtailed a few times but stayed up. That's just moto experience. It is possible to not go down from a skid.

My experience and the experience of my riding group is that it's mostly about tire compound. There are big differences in sticktion in the wet. Touring magazine did extensive tire testing under controlled conditions a few years ago. They found nothing better than the Conti 4KIIs. I haven't heard about any testing since then, might be worth looking into. For instance we had a rider go down a few years ago on a straight road using Conit 4 Seasons when no one else thought it was slick. They've changed the compound since then.

We all run almost smooth road tires, counting the Conti road offerings as such. That's what works. Tread makes little positive difference on a smooth surface, nor does tire width. Rough surfaces are another story. That's just the simple physics of friction, verified by experience. I'd drop the pressure 10% if it'll be wet all day. You still want the tire to be stiff enough to slide rather than roll off.

Here's all the pros are willing to say about it: https://www.velonews.com/gear/techni...et-conditions/

Note that some feel that a somewhat worn, rough surface on a tire can count as tread. Sand your tires with #80? Note that they like tubies, clinchers, and TL in that order.

I never ride when the winter daytime temperature is below 40°. I used to, but don't anymore.

urbanknight

I'd be very confident placing a large bet on the softer rubber being the key factor there. Maybe tire width and pressure as well, but not tread.