Tires of Wisdom

[activedirt_imp]

While cleaning the CB I noticed a label on the rear tire that read “for rear use only”. Hmmmm. Next step was the habitual web search looking for information. The result of that search was as expected, the good the bad and the ugly.

The purpose of this post is to ask if we have members in this forum that have significant and informed knowledge of this rear tire - front tire only issue? So far I have found that: (1) not all tires are made such that the front is different than the rear, (2) the internal structure is different (but no real technical believable details were listed), (3) the tread design is often different. Like all or our esteemed members I can search and read but with the experience level and depth of motor bike knowledge floating around this forum I recon some real meaty details could come forward (where the rubber meets the road so to speak).

[Lord Popgun]

CA200 is the tire man.

[activedirt_imp]

CA200 is the tire man.

I have PM-d him.

[CA200_imp]

Wow, ok there are many reasons a street motorcycle tire is made
to go in one direction. Tread of course but also the way in which it is built. There are some very good you tubes on how a tire is made.
https://www.youtube.com/watch?v=outx807C7QI
The old way a tire is built on a drum and as the material is laid on
is over lapped somewhat so you want that joint to go facing back
so the power from the motor does not open that joint. I have never seen this happen on a tire mounted "backwards" but I have seen them
chunk apart as they get warn. Front tires are also made in this manner. If you think about it a front radial tire "cups" because you putting a big force on it in the opposite way that it was built. When you brake hard.
Tread design for fronts is whole different subject.
Rear tires of course have a lot more material on them. One thing I always remind people of is the contact patch on a street tire is no
bigger then a credit card. You are putting a lot weight and HP through
that small patch. Think of it as we are riding a balloon all the time.
Pirelli a few years ago came with a new way to build a tire. They built a machine controlled by a computer that put the material
on the drum in a small string and changed it as it went so no people
needed. They still make some of their sport tires this way.
I have some of my track day junkies switch their front Pirelli's around because they ware them out on one side more then the other. I always tell them it's wrong but you won't believe the tires I have seen from the track. Some of these people are real junkies and spend
all their time and money there.
I have tried to keep this simple. There is a lot of technical stuff on the net if you want to know more.
If you have ever seen them make a tire in person you won't feel bad about paying for them .
Keep in mind that tire flexes every rotation at it's contact patch. Now think about how many times it flexes in one spot on the tire after 5000 miles.

[Motogeezer1949_imp]

Noticed recently (think it might have been in Motorcyclist) upcoming soon, tires will be manufactured so they can be mounted in either rotational direction. Pretty cool and about time

[Django]

Noticed recently (think it might have been in Motorcyclist) upcoming soon, tires will be manufactured so they can be mounted in either rotational direction. Pretty cool and about time

Hm, what would be the benefits of that?

[Motogeezer1949_imp]

Not having the shop accidentally mount backwards (seen it done), plus being able to swap sides on track bikes run on tracks with turns more of one direction than another, wearing one side more, like at Jennings GP.

[kmoney_imp]

Wouldn't for rear use only label be somewhat pointless anyway? I guess you have to do it in case, but the smallest commonly available rear I've seen is a 140, while the biggest common front I've seen is a 120 (at least for street bikes). I can't really see someone trying to mount a 140 on a front wheel.

[Toddman_imp]

Here's one that'll blow yer mind....

As a tire rolls, doesn't it have to stop and start up in the opposite direction when it contacts the street? Else you wouldn't get traction, it would just spin.
This might help...

Here's a little more detail. The car's engine turns the wheels. When
the tire turns at a constant rate, the point at the bottom of the tire
is stationary for a moment; the wheel acts like a lever with the
fulcrum at the bottom, because friction of the tire against the road
keeps it from slipping. The axle, at the center of the wheel, moves
at the speed of the car; the point at the top of the wheel moves twice
as fast.

[rboe]

Tire does not stop; it is constant rotation while rolling. But. If you draw a line from rim to rim, imagine that line rolling around with the tire. That line comes into contact with the road within the tire patch area (an elongated ellipse because the tire in flexible so we have a patch contact are instead of a point like you would get with an ideal rigid circle).

While the line is in contact with the road (assuming perfect friction and we're not burning out or slipping around) the line and road remain in static contact as the tire travels over it. As the the bike moves forward, if you had an imaginary camera pointed at the line it would appear that the line slides across the patch - but really the patch is moving.

The line rises up, rotates around and gets another shot at touching the road. In the mean time, the tire keeps spinning around, and, hopefully for your health, the patch remains in contact with the road. It's not unlike interlocking gears, They spin, teeth pushing each other around while momentarily in contact but not stopping.