clayne

Well forget the treadwear ratings, I just looked up S-02s in a listing of sizes, all the same TWR.

SleepR1

Having run this tire myself in 225/50-16, I recall 140. Not sure what 245/45-17 and 275/40-17 treadwears are though?

SleepR1

Can we assume treadwear ratings and rubber compounds are related given the size ranges?

DamonB

I have already decided that I will perform the experiment for you guys and document it with pics. Basically anyone who doesn't believe that merely adding a wider tire will increase grip in all directions without changing ANY other variable is flat wrong

I gotta car I have to get ready to race this weekend. Look for the expriment next week

ptrhahn

iTrader: (9)

They don't make that tire anymore, so i'd have trouble finding specs, but i don't see any tires where the tread wear rating asn't the same for all sizes (on tire rack site).

I'm sorry, i don't buy that the manufacturers use a sliding softness compound for each larger size.

And besides, its not the sidewalls or the rubber that are "supporting weight", its the air inside. These ain't runflats. Now, 32 psi amounts to more actual air to fill a larger tire because its "per square inch" and there are more square inches. I can't tell you how that might affect the equation.

All i'm saying is that this "wider tires really won't help you" concept is rubbish. Try it.

ptrhahn

iTrader: (9)

Nope. I've used 245/40 and 275/40.

Someone suggested that the height of the 275 contributed to the added grip. I then surmised that if this were true, then a 245/45 or even 225/50 would have yeilded the same grip because they are the same height as the 275/40. I don't believe that would be true.

DamonB

Your experiment does not represent RUBBER; it represents plywood. Your results do not apply to tires. Your results are true of hard materials which do not deform to grip the surface. Rubber is completely different. Rubber actually generates grip not only due to the mechanical pressing of it against another surface, it also has adhesive properties.


This is complete horseshit. I can find plenty of scientists who feel that aliens have been visiting our planet on a regular basis too

Doesn't that say drag racers get more grip with wider tires?

SleepR1

I went from running 225/50-16s 140 treadwear Pirelli P-Zero on 8 x 16s all around to 255/40-17 140 treadwear Yokohama AVS Intermediates on 9 x 17s all around. One could argue that treadwear comparisons between tire makers can't be made, so cavaet emptor.

The steering feel is more numb with wider tires up front. Lateral grip has increased (surprise surprise). Braking and launching grip didn't increase proportionally with lateral grip.

No scientific numbers. Only seat-of-the pants, so feel free to flame away LOL

I have laptime comparisons between setups, but they're on different days. I'm 1 to 2 seconds faster per lap @ Putnam Park Road Course with the 255s vs 225s. The drop in laptimes is probably attributable to better cornering grip, but not necessarily to better braking and acceleration grip?

Only a true scientific test will tell the real story LOL

clayne

The experiment must be done with pressure taken into account. I do not believe we are flat out wrong here.

The simple assertion of "wider is better, it's gotta be guys, it's just BIGGER" would never fly, and I couldn't see you yourself believing that either.

SleepR1

DamonB, how about going over your study design with us "scientists" eh?

clayne

I wouldn't buy it either. Although I can see tread pattern/width possibly affecting things.

Well we know sidewall support is definitely required, otherwise the tire would just pull out of the bead when you drop the jack.

I don't think anyone is actually saying that, however.

I think that what people are arguing is that it does indeed help laterally (which is to be expected) but for braking and acceleration grip to ALSO go UP at the same time seems to go against standard physics.

clayne

Duh! Of course it isn't about tires. It's about friction vs surface area vs pressure. I'm surprised you thought I was trying to parallel tire performance with dragging an engine through the garage. I was not. I was making an analogue of SURFACE AREA vs PRESSURE vs cF.

Your example of rubber pads of different thicknesses takes into account nothing about pressure OR deformation other than the weight of the rubber itself.

Yes, but does it say they get more grip because they actually have MORE GRIP ALL THE TIME? No. He is saying they try to minimize the situations of reduced grip.

SleepR1

This is the heart of the "controversy"

DamonB

I have done the best I can at explaining the concept. I am going to perform the experiment I described and I will document it with pics to try and prove it to everyone. I will use both rubber and some other substance which is hard to prove that rubber acts completely differently in regards to friction. The naysayers can invent some other variable at that point.

You guys already understand, you just won't let yourselves believe it. How can a wider tire EVER generate more grip than a narrower one if every other variable is the same? Weight transfer and loading is constant for both the narrow and wide tire. It is not a matter of weight, air pressure, rubber compound, force per area etc. It really is just that simple that in the case of RUBBER all you need is more rubber!

You guys honestly and genuinely believe that if I put 5" wide tires on the back of my car and launched down a dragstrip and then repeated with 10" wide tires that my 60' times would be the same??? (same air pressure, same rubber compound, same time of day etc) Do you truly understand how funny that sounds? You're letting your knowledge of other things cloud up your thinking and overcomplicate the problem.

Imagine you're an Olympic sprinter and you're running the 100 yard dash. If I made the rubber soles of your Nike's only 1.5 square inches you think you would be able to explode out of the blocks just as hard as if you had normally sized shoe soles? You honestly think that?

All these other frictional arguments dealing with vertical force and area are true of hard materials but they are not true of materials which deform and "grab" the surface!

DamonB

When the experiment is performed each pad will be under a solid plate of some sort with the same amount of weight on top of it. This ensures that each pad must support the same amount of weight and that each pad is uniformly pressed against the surface.

All variables will be absolutely constant. The only thing that will change is the amount of rubber in contact with the surface.

clayne

I also think what is going to be found is that the ability for weight transfer, during braking and accelerating, to deform a tire into having actually *more* available grip (increased pressure due to weight transfer) is much easier to do, physically, with a wide tire than it is with a narrower tire. This is due to the fact that, comparitively, a narrower tire would have a hard time "flattening" (increasd pressure on CP) itself out to provide more grip where as any "flattening" of the wider tire results in better gains.

This is assuming tires of the same or very close circumference.

What if we were to use 10 ft diameter tires with 225 width? I bet they would be awesome for braking and acceleration.

clayne

Here you go Damon:

http://www.physicsforums.com/showthr...&threadid=7476



"Think about it. Double the force per area of the mat. I remember doing this experiment and it doesn't change when you reduce the contact area. We used cement blocks on side, edge, and end. NO CHANGE in the force required to get the block to slide, and NO CHANGE in the force required to maintain sliding."

DamonB

I agree that it may be true that the contact patch size is easier to "grow" due to longitudinal weight transfer. But AGAIN the narrow tire and the wide tire will see EXACTLY the SAME weight transfers from the chassis. The wider tire will ALWAYS have more of its rubber in contact with the road than the narrower one. Even though the narrower tire's contact patch grows as it's squashed down, so does the wider tire's! The wider tire will always have a larger contact patch!

DamonB

That experiment if true of cement blocks which are hard. It is not true of rubber. It's results are as I completely expected for a hard substance. When you perform the same experiment with a tire you'll find the results are different.

redrotorR1

Treadwear ratings are tantamount to the 276HP Japanese sportscar power ratings .... they don't mean jack. Unless you truly believe that Falken Azenis do follow some scale with their 220 UTQG? Tire manufacturers can practically make up their treadwear ratings. Any Yokohama ES100 purchasers here? Yeah, those tires live up to their 280 UTQG ..

There is a great series of articles in the last 4 issues of Sportscar on "The Racing Tire". It has great illustrations to the effects of tire deformation .... images that will clearly show you why wider tires are better ... in every aspect. It shows the effects on contact patch during acceleration, cornering, and braking. A real eye-opener for some of you.

Anyways, I've made my peace ... several times now. If you guys still can't figure it out, then be content with your slower lap times/time slips. Peace out .. yo.

clayne

The wheel may be preventing a narrower tire from making full use of it's longtudinal traction "advantage." The rubber can only deform so much between the road and the wheel before the tire begins to skip. Since it cannot make use of it's theoretical better longitudinal shape it ends up jacking up the pressure on the contact patch to a saturation point where the rubber says "stop, no more."

This may be much less of an issue with wider tires as they are able to displace the additional load more effective than narrow tires.

What I'm saying is that the ability for a narrow tire to deform between the wheel and road is much harder than for a wider tire to offer the same level of deformation BUT result in increased area of coverage that the additional pressure will make use of in a weight transfer situation.

Essentially narrow tires get screwed by the shape of a circle.

I still feel the concept of MORE SURFACE AREA = MORE GRIP is definitely not accurate.

clayne

It doesn't matter if we're talking rubber mats or cement mats for comparision of surface area affecting force required to overcome static cF. A rubber mat, unloaded, is hardly dealing with deformation.

rubber mat will of course have a higher cF(s) than a cement mat. But a rubber mat, just because it is made of rubber, is not even near the same sitiuation as a LOADED round rubber tire dealing with vehicle dynamics.

DamonB

I'm still trying to understand you guy's perspective. From your perspective explain to me why a wider tire only generates increased grip in cornering and not acceleration/braking.

Also realize that when a car is transitioning between cornering and braking it is trading one for the other. Explain to me how a wide tire that obeys your "rules" is able to generate a nice friction circle. A wide tire that obeyed your rules would generate a very squashed friction oval that had lots of increased cornering force, and no increased accel/brake force. This means that as the car enters and exits turns it wouldn't have much grip until the contact patch pointed into whatever magic direction you insist it must to provide increased grip.

Also realize that since you insist that a wide tire generates more grip in the lateral direction only than your car with wide tires would in fact be able to stop in a shorter distance if you turned the steering wheel sharply and pointed the contact patch "into" the slide.

rynberg

I don't understand this argument at all.

wider tires = more traction in every direction

Compare a Viper and a 360 Modena for example.

Viper stops from 60mph in 100 ft. Modena requires about 110 ft. The Modena is lighter and actually has better weight distribution for braking (more rear-weight bias). The Viper has much wider tires (and bigger brakes, but that doesn't effect 60mph-0). Both have excellent ABS.

How can you argue that wider tires do not provide more grip under braking?

clayne

rynberg: Go to page 1 and get on board.



Damon,

I'm saying that a narrower tire may be unable to produce superior longitudinal performance due to the characteristics of it's circumfrence, rubber's physical characteristics during compression, and the possible inability of rubber to compress past a certain point.

A wider tire has all of these same issues, but it has the ability to hit that maximum rubber compression state over a wider area of the tire, possibly resulting in better longitudinal as well.

NOT because it has just plain "more area".

Hypothetically picture inside your head an entire rim made of rubber, that has the ability to distort, providing a narrow tire with the needed displacement to approach superior longitudinal contact patch shape.

Since this is not what we have, wider may end up winning in an indirect fashion, and not because of "more" surface area.