Tire Sipe

[bestclimb]

Originally Posted by poomanchu

Removing material from the tread block reduces the actual material that is contacting the ground at any one point. I don't know if just 'slicing' the tread on the tires without removing material is siping, but I don;t know much about this.

All the sports cars with wide tires to maximize contact patch are doing it wrong. They should be rollin on bike tires for max traction. Same with those offroaders and wide tires. This seems wrong, no?

Sports cars with wide tires are doing it right, but the increase in traction they see is a result of improved cooling of the surface of the tire which allows for a sticker/softer tire with acceptable wear rates. The wider tires cause the heat from friction to be spread over a wider area, improving cooling and increasing the amount of slip it takes to liquify at the contact patch.

The off roaders use a wide tire to have a lower PSI* so that the tire does not dig into the mud or sand as much. In some other situations wider tires are a hinderance. Big wide tires are somewhat of an affectation in some cases.

A sipe does not remove any material.

*pounds per square inch of contact patch not tire pressure, though lower tire pressure allows the tire to form to the rocks and what not)

[poomanchu]

Originally Posted by bestclimb

Sports cars with wide tires are doing it right, but the increase in traction they see is a result of improved cooling of the surface of the tire which allows for a sticker/softer tire with acceptable wear rates. The wider tires cause the heat from friction to be spread over a wider area, improving cooling and increasing the amount of slip it takes to liquify at the contact patch.

The off roaders use a wide tire to have a lower PSI* so that the tire does not dig into the mud or sand as much. In some other situations wider tires are a hinderance. Big wide tires are somewhat of an affectation in some cases.

A sipe does not remove any material.

*pounds per square inch of contact patch not tire pressure, though lower tire pressure allows the tire to form to the rocks and what not)

Lmao!!! Sports cars and drag racers and anyone wanting maximum traction (in the dry, on a paved road at least) are needing the most contact surface. This includes braking, acceleration and cornering. Tires have an operating temp as well, usually the hotter the better to an extent. Watch how dragsters do a burn out before a run, nascar and circle track racers weave. It's to HEAT up the tires, not cool it.

[Gealii]

Originally Posted by poomanchu

Lmao!!! Sports cars and drag racers and anyone wanting maximum traction (in the dry, on a paved road at least) are needing the most contact surface. This includes braking, acceleration and cornering. Tires have an operating temp as well, usually the hotter the better to an extent. Watch how dragsters do a burn out before a run, nascar and circle track racers weave. It's to HEAT up the tires, not cool it.

I laughed when i saw his post to. so many things wrong with just about everything he said

[bestclimb]

Anyone wanting good traction wants the proper compound. Too small of a contact patch and the (typically) softer tire wears too quickly to be useful. (tire wear as I understand is a function of abrasion which is affected by surface temp)

F = Cf *N (n in this case is the weight of the vehicle pushing down)

Note there is nothing there about surface area.

[CapriRacer]

I've been watching this thread to see where it would go. It's obvious I need to clear up some misconceptions.

There are 2 types of siping.

1) The type put in the tire mold by the tire manufacturer. It produces a thin gap.

2) The type put in the tire AFTER it has been manufactured, typically at a local tire shop. It is simply a knife-cut through the rubber and, in theory, doesn't remove any rubber. It does NOT produce a thin gap, nor does it affect any other physical dimension of the tire, such as footprint size or shape. This is commonly referred to a "Aftermarket Siping".

But what does it do for tire performance? Unfortunately, there are lots of false claims about aftermarketing siping.

Advantages: Wet traction, snow traction (both due to the increased edges). These are significantly better than non-siped tires.

Disadvantages: Tread wear, dry traction, rolling resistance (all due to the increased movement of the tread elements). Of these only treadwear is significantly affected. Dry traction and RR are only slightly affected.

Neither better, nor worst: Durability (as in tire integrity), Ride quality (although there may be some loss of directional stability as the tire encounters grooves and ruts), road hazard resistance. That because the tread doesn't really affect those properties.

I honestly can't see doing this to a new tire. First, it will void the manufacturer's warranty. Second, If wet and snow traction are a concern, buy tires that already have good properties in this area.

But I can see doing this to tires that have lost some traction due to wear (deceased tread depth and lack of siping). This is really about extending the life a bit for economic reasons.

[CapriRacer]

Oh and some other misconceptions:

Tires do NOT behave according to classical friction theory: F = µN (Amonton's Laws). That's because the rubber presses into the texture of the pavement and can generate grip that way. Maximum tractive force is generated in the 10% to 15% slippage range.

As a corollary: Larger tire footprints generate more grip. That's why race tires are smooth.

Tire wear? This is more about driving in a straight line (slow wear) vs going around a corner (fast wear). In the cornering mode, tires have to generate a slip angle in order to generate the force needed to move the mass of the vehicle. This slip angle (the difference between where the tire is pointed vs where it is actually going) abrades the rubber off the car. You see this as the "marbles" on race tracks.

Does more rubber on the road help improve treadwear? Yes, but mostly because it grips better and less slip angle is needed.

[bestclimb]

I was hoping you would chime in with some intelligent discussion and information. I am aware that tires don't strictly follow friction theory I'm not really sure why I tapped it, other than contact patch does not directly correlate to traction and there are a several things going on. Perhaps you can correct inform me if my understanding that one of the functions of tire size is temperature control for the contact patch?

[arcosine]

I might Sipe my half worn tires this week end, not sure how to do an A-B comparison. I could do one side and see how the car pulls in the snow.

[CapriRacer]

Originally Posted by bestclimb

I was hoping you would chime in with some intelligent discussion and information. I am aware that tires don't strictly follow friction theory I'm not really sure why I tapped it, other than contact patch does not directly correlate to traction and there are a several things going on. Perhaps you can correct inform me if my understanding that one of the functions of tire size is temperature control for the contact patch?

Strictly speaking, the function of tire size is to have adequate load carrying capacity (where inflation pressure is also part of that equation).

And while it is true that the more load on a tire (all other things being equal) results in higher operating temperatures, the rubber compounds in tires are selected to keep the operating temperature from becoming too high, not the other way around. If the goal was to strictly keep tires cool running, the rubber compounds would be different.

A good example of this is winter tires - which have higher operating temperatures (all other things being equal), but because they operate in cooler weather, their operating temperature is within reasonable limits.

Race tires is another good example. The tread rubber compounds are selected for grip - and while heat generation is a minor consideration, the problem is that it is possible to over heat the rubber compound and the grip goes away. So race tires come in a variety of tread compounds with the idea that there is a range of values that are too high for a given compound. Careful selection of the right tread compound for the conditions results in faster laps times.

If you follow Formula 1, you'll know that Pirelli was asked to develop tires where the fall off in grip is pretty dramatic - putting tire strategy into play.

And, yes, there is a lot going on when it comes to tire grip. Getting an 10% increase in the size of the contact patch doesn't result in a 10% increase in grip.

[Miller88]

I got a set of Goodyear Workhorse tires for my Cherokee. They are a few years old, but still a lot of traction left. The factory siping was gone. Even studded, their performance left a lot to be desired on my Cherokee (still couldn't go anywhere on hard packed snow in 2WD). It was also extremely easy to lock the brakes.

I took a utility knife and siped the center blocks on all of the tread. Definite improvement! Even in slipper / icy conditions, my Cherokee would move in 2WD. Was also quite a bit harder to lock the brakes.