Some tires have arrows to indicate which way to mount the tire. What is the intention? If a rear tire grips better during acceleration with the arrow pointing forward, doesn't that mean the front tire would grip better during braking with the arrow pointing backward?

For road tires, no. Dumb theories abound (like hydroplaning). The only thing that I have read that makes any sense is Continental and other manufacturers use arrows to help reduce the number of customer inquires on which way to install their tires.

This is a sore subject for some of us, you know. There's nothing worse than changing a flat, and finding out you got your arrows backwards. I'm pretty sure there are directional police, just waiting to catch me, with my arrows pointing backwards. 😟😉

Too much wheelspin on acceleration?

I always assumed the thread was designed to transport water and mud out of the way so the outer rubber grips the road and not what's on it. Grooves in the thread that work together with the rotation will do that more efficiently. A braked front wheel is still rotating in the same direction, so the answer is no I guess.

The tyre tread on road bike (and I include any city/utility bike under that heading) seems to be largely for aesthetic purposes. As other people have said in the past, bicycles don't aquaplane unless you're rolling at 'terminal velocity' type speeds. You won't see that on the daily commute!
Some road/utility tyres reflect this thinking, with a 'knurled' or fine herringbone pattern, both of which will grip the road better than something which looks at home on a pickup.

Saying that, I would always fit tyres with the arrows going forward. This is not to avoid aquaplaning, but because I think it might help reduce rolling resistance. As the tyre rolls, it will squeeze down onto the tread pattern. If the pattern is the wrong way round, it might not be as compliant as it might when it is fitted correctly.

Anyway, that's just my four-penneth...

I installed a Serfas Vida backwards on a front wheel a few weeks ago. This is a tire with fairly pronounced chevron pattern tread. A few miles into my ride I noticed more road noise (buzzing) coming from the front wheel than from the last time I'd run that tire (on a different bicycle). It wasn't horrible or anything, but it was noticeable. Turned the tire around and the extra noise went away. That being said, the extra buzzing was kind of cool.

-Matt

They could just make their tread symmetrical and eliminate questions, or make them slicks, since tread is worthless anyway.
That would make their molds simpler too.

For tractors, with very prominent lugs, the theory is that the point of the "V" hits first, then any mud gets squeezed out the V, thus improving traction. Installing them backwards, and it would tend to force the mud towards the center of the tire.

In theory, the same would be true on a bike, whether it is pushing mud out of the way, or pushing water out of the way.

For a lay-person, it is hard to make a good 1:1 comparison between tires as several factors change. I've found that Schwalbe Marathon Plus tires with a prominent tread tend to be quite grippy, but they also use a softer tread compound than say a Gator Hardshell, and thus also wear quicker.

My experience with those speeds and road bikes in general isn't worth mentioning, but I do have the experience that slick tyres are more slippery in the wet. I don't believe aquaplaning is the only issue with water and rubber. Race cars don't aquaplane in slow corners either, but on slicks they are all over the place on a damp track. Brake pads don't work as well in the rain too, is that because they aquaplane? I don't think so. I think there's more to it than aquaplaning and not aquaplaning.

Most directional-tread tires I've encountered seem to be so indicated according to the tractor analogy mentioned above. That said, I've had a few MTB tires with arrows indicating one rotation for front mounting, the other for rear. I honestly don't remember what the tread looks like on those. Then I see the occasional tire where the tread looks decidedly directional, but with no arrow on the sidewall.

Yep. This.

I also can't not see the treads if they're going different directions, and it slowly drives me mad.

That didn't help.

Pedal faster, and you won't see the treads.

There are tires on which I know there are arrows, but I can't find them (the arrows).

For some tires, the directional indications are for tread purposes (i.e. moving water or mud to the edge of the tires).
For some tires, it doesn't matter.
For some tires, the weave of the underlying tire casing is woven in such a way as to have a preference for deforming in one direction. For these tires, if you run them the other ('wrong') way, it causes the tire to wear unnaturally and wear out earlier.
Again, it depends on the tire.
The directional arrow on Continental GP4000sII's is located, on the sidewall, right beneath one of the tread wear indicators.

Yes, in theory. And some mountain bike tires are marked as such, with two opposing arrows. Mount the tire to roll in one direction if installing on the front, or the opposite direction if mounting on the rear. This is presumably for best brake and acceleration traction with certain tread "paddle" features. For road-oriented tires, tread paddles aren't nearly as important for traction, and the single directional arrow is likely for aesthetics or sound quality only.

at my performance level I doubt it makes a difference & I find it really annoying how small they make those arrows & often it's black on black embossed. I now have to wear "readers" to find them. & since I sometimes have to do a roadside repair I now have to carry another pair of readers in my trunk, another thing to wrap for protection, ugh. on at least 2 sets of tires, I drew a big freakin arrow with a wax pencil & also the tire pressure on the sidewall. I'm not proud

in this case, looks like I did it twice, first w a sharpie marker, then again with the wax china pencil



& with this tire I reminded myself what size it was & what pressure worked on the frame I usually use it on

Yeah, i feel your pain. now try to do it in the shade of the garage at dusk, or heavens forbid, out on the road after dark!

I've used Vittoria Rubino Pros for as long as I can remember. Originally there was only a label on one side of the tire. So, of course you put that on the right. Then they started to label both sides and put a directional arrow on the tire. The newest ones I've bought no longer have the arrow. Does it matter? I don't know. But, I still mount them with the tread running the same way.

Please read my tag line:

"Don't believe everything you think!" .... Think about it!

Obviously there is no logic for having direction arrows on tires with smooth or ribbed treads.

My line of thinking is that "quality" tire manufacturers would not go to the time and expense of having directional arrows put into the tire molds unless there was good reason. They pay engineers to figure these things out in advance!

Case in point, I bought a lilac 1971 Raleigh Competition last February to use as a beater bike and ride in the partially dirt CA E'roica.

It came with a brand new set of uber cheap Hutchinson NITRO 700c x 28 tires. They were noisy like snow tires on a dry road surface and making slow speed turns caused a noticeable feel in the bike. I inspected the treads carefully and figured that the problem might go away as the tires wore in.



The wheels had the longest Presta valves I'd ever seen so I changed them to Michelin A2 tubes with 40mm stems for aesthetic reasons.




As I was re-mounting the 2nd tire, I noticed a directional arrow molded into the side wall. I removed and remounted the first tire with the arrow pointing in the right direction, installed the 2nd one and took it out for a ride. All the noise and vibrations were gone!

I couldn't see any differences in the tread pattern but I could feel it by rubbing the tread one direction then the other. The pattern is definitely direction oriented.

These tires must have about a 30 tpi casing (see sidewalls in the pictures above).... but they sure ride nicely. I'll ride them into the ground (the ugly suit lasts forever).

I've also felt a slight difference in Pasela tires with the arrow pointing in the wrong direction.

Many car and truck tires have orientation arrows too. Some folks got paid a lot to figure these things out...

Remember the results of "Hey! Watch this!" can qualify you for the Darwin Award!

verktyg retrogrouch

The only thing I do is to make sure the is the brand label is centered on the valve stem. I was taught to "front the product" during my LBS days, but it's also helpful when you have a flat - if you find the leak in the tube, you can figure out where the penetration on the tire happened, and focus your search for the thorn/glass/wire/staple/shiv/etc. there.