Bike tyres tread direction.

[Mark McM]

Originally Posted by Jan Heine

Even at the very high speeds you tested – few of us can hold 30 mph for very long – rolling resistance differences between different tire models has a much greater effect than the wind resistance you measured. That is why the pros always ride on hand-made tires for the important TTs...

You've probably seen the tests done by Flo Cycling to find the best tires to use with their aerodynamic wheels:

http://flocycling.blogspot.com/2016/...ire-study.html

In this study, they did wind tunnel tests using 20 different tires (some were the same model but in different widths) on one of their aerowheels, and also had rolling resistance tests done on the tires. They combined the aero drag with the rolling drag to come up with the overall best performing tire. If you take a look at their data, you'll see that tire rolling resistance was the biggest factor in wheel performance. The tire at the top of the list placed only 11th out of 20 on aerodrag, but was tied for 1st for rolling drag.

Digging deeper into the data, some interesting things can be seen. The wind tunnel test was performed at a speed of 30 mph. At the yaw angles experienced most frequently by cyclists, the average drag experienced by the different tires varied between about 90 and 125 grams, which results in drag powers of about 12 - 16 Watts. The rolling resistance tests were performed at 35 kph (21.8 mph), and produced drags of between about 12 and 20 Watts. Scaling up the rolling resistance losses to 30 mph yields drag powers of between 16 and 27 Watts. So it can be clearly seen that even at 30 mph rolling resistance is greater than aero drag, and also that variations in rolling resistance between tires is greater than the variations of aero drag between tires. Since very few people spend a lot of time at 30+ mph, and because aerodynamic losses increase with the cube of speed (rolling resistance losses only increase linearly with speed), at the speeds most people ride rolling resistance losses will be proportionately even larger than aero losses than is shown in the test data.

Flo Cycling designed their latest aerowheels around the 23mm Continental GP4000s (a natural choice as they had found that this tire was the most aero in a previous test of several tires). So it is not surprising that this tire had the lowest aerodynamic drag of all the tires in this test. But what they found in this new test is that not only did the GP4000s only place 4th when both aero and rolling losses were combined, but that the wider 25mm version of this tire was overall better, even though the wider version was not as well aerodynamically matched to the wheel.

[Steve in SLO]

Originally Posted by jinbok

Few of my friends are arguing over tyres tread direction of certain tyres.

Is this tyre mounted correct tread direction?

Tread is on the outside, so yes, it is mounted in the correct direction.

[froze]

[QUOTE=oldpotatoe;2296339]

Originally Posted by froze

The wet weather enhancement was due to the Black Chili compound, so what exactly is the Black Chili compound?

Rest snipped..when conti tires got 'color', they got color because of silica, and anecdotally, these tires performed less well in the wet. Conti went back to 'black', which is carbon black..cannot do colors..it's black. BUT it's not as slippery..

-info from Conti lizard when 'black chili' was introduced...

That's interesting I didn't know they had switched, but if carbon black is so good why hasn't it made its way into car tires? apparently car tire manufactures that make winter tires think that silica is the best for traction. I find that odd that car tires work better with silica and bicycle tires work better with carbon black...something is amiss here?

[Louis]

This is how I've always thought about this issue:

If a tire has significant tread, and if you think that tread can help move water away from under the tire to the side, then you want the grooves to be pointed such that as the tire contact patch rotates the grooves allow the water to move outwards. That means that at the contact patch you would see a V as you look down (if you could see through the rim, and the bike is moving toward the top of the screen). If you imagine the tire rotating and the contact patch moving you'll see what I mean. You'll also see that a patch that is oriented such that the grooves look like this: ^ the water would tend to be driven toward the center of the tire, which is not what you want to have.

Caveat: I'm not a tire manufacturer and don't really know if anything I've said above is correct, it just intuitively seems right to me.

[froze]

Originally Posted by Louis

This is how I've always thought about this issue:

If a tire has significant tread, and if you think that tread can help move water away from under the tire to the side, then you want the grooves to be pointed such that as the tire contact patch rotates the grooves allow the water to move outwards. That means that at the contact patch you would see a V as you look down (if you could see through the rim, and the bike is moving toward the top of the screen). If you imagine the tire rotating and the contact patch moving you'll see what I mean. You'll also see that a patch that is oriented such that the grooves look like this: ^ the water would tend to be driven toward the center of the tire, which is not what you want to have.

Caveat: I'm not a tire manufacturer and don't really know if anything I've said above is correct, it just intuitively seems right to me.

Intuitively speaking you are correct because that's how car tires are made, but with narrow road tires it doesn't matter because the tires slice through the water film pushing the water away from the tire, combined with high air pressure to make contact with the road and are impossible to hydroplane. I am not sure if that same thing applies to new fat tire bikes but I doubt it because I think that even with fat tires a human can't pedal the bike fast enough to hydroplane, assuming the combination of a wider tire with low air pressure that effects a car would also effect a fat tire bike.

With any tires, bike or car, the worst time to be on the streets is the during the first 10 minutes of a rain if it hasn't rained in awhile, especially light rain, the oil comes up off the road and layers on top of the water making it very slick. And of course as you all should know that painted and steel surfaces are very slick when wet regardless as to how long it's been raining. But don't get slick confused with hydroplaning. Hydroplaning with cars starts at 35 mph on average, wider tires it happens quicker which is why certain high performance cars suffer from hydroplaning before regular cars do, that and high performance tires are designed for ultimate traction on dry pavement and not wet pavement.