The Horror!
 

After installing my new Continental GP 4000 on my front wheel I realized my tires are matching!
Installing GP is slightly less painful then my old Gatorskin that was on the rear wheel. When I replaced it with GP4000 couldn't really tell the difference. Maybe I will be able to tell now that I have another one up front. Will see.

Make sure you've got them installed the right way, there directional, I found out after putting both on the wrong way.

The thread direction doesn't matter, unless you're able to tell a sub-fractional wattage difference. But it does ruin the look and feng shui of your bike.

I've always wondered why some bike tires are directional. Are you saying that it's to reduce rolling resistance?

Bob

Well at least on GT4000 middle part is bold, so I don't think direction really matters. The "thread" is on the sides, so maybe it has to do with cornering?

I'm not saying it reduces it, I'm saying that there will be a tiny tiny difference in rolling resistance between running the thread in one direction and another.

Directional tires are usually about expelling water. BTW: I have always liked my GP4000's.

Prove it!

If there would be a difference, than it must be reduced in one direction and not the other. Truth is, directional tires are marketing BS in the road world.

Anybody run the new GP4000S's? I bought them at the HHH but I haven't stuck them on the bike yet. I've run the old GP4000's for a couple years and like them. I've notice if I mount the tires opposite the correct rotational direction, the planet's rotation seems to slow down and wobble just a tad.

The tread shaped things on GP4K tyres are for wet weather grip and expelling water as a previous poster said. As they are non-symmetrical, they must work in a specific direction. As for marketing BS, these tyres are not marketed as directional, and the fact that they are directional is easy to miss as many users have experienced, so I meet your BS and raise you one:)

If you have access to a comparator, try fixturing two small wheels with treads on it, apply some pressure to the axle, and roll it across the screen from either direction, the contact patch is going to look slightly different. You won't be able to measure it with a ruler but with a comparator, I can tell you if one hair is 10% wider than another, that's where you'll be able to see the difference. And two different contact patches, I guarantee you, will have different rolling resistances.

That same wheel, if I were to free roll it from in a room from north to south then south to north, will take two distinctly different paths. Just beacuse you can't see it with your naked eyes doesn't mean there isn't a difference.

To the layperson, you are going to have to accept the fact that the tire is the same in both directions, in terms of rolling resistance and grip in wet weather (especially if it's a narrow tire).

As is so often the answer in modern society:
Marketing.