F1 tire and rim contact points look smooth – like standard clincher type wire/Kevlar bead tires on my car or on my bicycle.

That just can’t be.

Low pressure; a ga-zillion G’s braking; accelerations – you’d think they would have to have some crenel-like extrusions connecting the tire to the rim. I don’t see anything like that.

Where are the tires mounted? Possibly at Bridgestone? Some secret bake-on process? Like professional bicycle tires that are sewn on.

Well… wait – looking at this picture of an 05 Williams rim, it looks like maybe some kind of embedded rubber gasket in the rim. Obviously rubber on rubber would be pretty sticky. Is that all that is used?

Since we’re here, anyone have any idea what the answers might be to these questions?

1.) How much does a single F1 tire cost to produce?
2.) Is there any natural rubber, or is it 100% synthetic?

Key F1 tire info here.

”From the 220 different materials used in a tire, more than 100 are mixed to create an optimal compound. The compound is based on four main elements: rubber, carbon, oil and sulphur.

The carcass is composed of a nylon and polyester framework, in a complex weave. This is the skeleton of the tyre. It provides rigidity against high aerodynamic load (more than one ton of downforce at 250 km/h), strong longitudinal forces (4 Gs) and lateral forces (5 Gs).”

”Although low pressure (around 16 psi) allows the envelope to grip the track better and provides a greater contact area, a variation of just 2 psi will greatly alter the performance of the car.”

So maybe the operating air pressure range for an F1 tire is somewhere around 16 to 22 psi?

A total wins perspective.

The biggest thing is that you have to rethink the 700+ hp coming from the engines of F1.

18k rpm happens to equate to approximately 200 ft-lbs of torque which means that there is only 50 ft lbs of torque per bead on the rims. The rims are 13" rims so the beads only have to resist only about 1.2 psi in shear force. Now to most people that doesn't mean much but given that the coefficient of friction between polished aluminum and rubber is at a minimum of .6 (it can be much MUCH higher) and the beads also have a bit of an interference fit to them and the holding force, the tire pressure, is from 13 to 22 psi. The total holding force on the tires are much much larger than the force that would cause the tires to spin on the rim.

The "gasket" can help even more.

I don’t know ANYTHING about this subject, but your “200ft-lbs” value seems a mite puny – no? And since it’s not 4x4, the div should be /2 not /4? And even then – the acceleration power is a fraction of the load endured by the X g-force brake power. Dirt bikes have tire/rim locks. I find it impossible to believe F1 cars do not.

I don't think "rim spin" has ever been a problem for Formula One tyres. Certainly, the treads are very sticky when heated, but as Impatient Inventor pointed out, so are the bead rubber and the finish of the rims.

A much bigger problem, 30 years ago, was tyre-rim separation. If a car went around a corner and hit a curb, or worse, if the tyre went flat, there was a chance the bead could be pulled over the rim. There were some nasty accidents caused by this.

One solution, years ago, was so simply drive short sheet metal screws through the rim and into the bead. A later, more elegant one was to install a series of clamps inside the rim to hold the bead on. If you look carefully, you can sometimes see those small set screws in the rims of tyres in the 70s.

Now, a simpler solution is to simply glue the tyres on the rims. That's why a tyre can tear itself to shreds, but the sidewall still holds on. It's more difficult to change the tyres, but that's a small price to pay for safety.

By the way, the "sewn-up" tyres on some racing bicycles aren't sewn on to the rims, they're glued on to the inner surface of what is, essentially, a hollow, tubular rim. Bicycle racers call them "tubular" tyres because they do have inner tubes, but they are literally sewn inside the tyre casing, which is very, very light.



Fig.1 A typical "sewn-up" tyre, showing layers.



Fig.2 A "sewn-up" tyre, glued on a wheel rim.

Figure 1 shows what "sewn-up" tyres look like today -- two very light plies with a little rubber and a "tread rib" in the middle of the outer edge. The purple part is the inner tube, itself.

Figure 2 is what the sewn-up tyre looks like in place. Note the patent date: March 10, 1896. This is not new technology. The separate tyre and tube system that holds the tyre on the rim with a wire bead and rim ridge, with a separate tube -- Called a "clincher" tyre in bicycle terms" was well in the future. The tubeless, sealed-rim tyres we know now were even further in the future.

Vive le Technologie!
(or something...)

Ipso - 29 September 2009 11:52 PM

I don’t know ANYTHING about this subject, but your “200ft-lbs” value seems a mite puny – no? And since it’s not 4x4, the div should be /2 not /4? And even then – the acceleration power is a fraction of the load endured by the X g-force brake power. Dirt bikes have tire/rim locks. I find it impossible to believe F1 cars do not.

2 Rear tires

4 Beads

and I thought I sucked at math!

f-1 engins do not have alot of torque--h/p and torque two different animals ,but that can be another can of worms!

200 IS ABOUT RIGHT

impatientinventor - 29 September 2009 11:03 PM

The biggest thing is that you have to rethink the 700+ hp coming from the engines of F1.

18k rpm happens to equate to approximately 200 ft-lbs of torque which means that there is only 50 ft lbs of torque per bead on the rims. The rims are 13" rims so the beads only have to resist only about 1.2 psi in shear force. Now to most people that doesn't mean much but given that the coefficient of friction between polished aluminum and rubber is at a minimum of .6 (it can be much MUCH higher) and the beads also have a bit of an interference fit to them and the holding force, the tire pressure, is from 13 to 22 psi. The total holding force on the tires are much much larger than the force that would cause the tires to spin on the rim.

The "gasket" can help even more.

Your torque figure sounds about right, although peak horsepower is probably obtained at something less then full revs. Regardless, by the time you figure the transmission and differential gearing into the equation, the torque being delivered to the rear wheels is considerably higher. Wouldn't surprise me if some type of adhesive is applied to the bead before it is seated. Now, go have another cup of coffee! Always works for me, sometimes, maybe.

(4 - Doh!)

Just doing some recon on drag race tires, to see how it’s done in the extreme.
http://www.competitionplus.com/05_20_2004/beadlock_wheels.html

They claim 200mph is key, where tires deform and pull the bead inward as the tires expand. They give the number as 1300hp+ where bead-lock rims start to become “mandatory” for rim spin. (Or maybe that’s the point after you’ve already used sheet metal screws.)

Obviously F1 tires are completely alien to drag race tire design – but it’s an interesting perspective.



1300 just seems completely ridiculoso to me. I spin my mountain bike tires all the time.

I found this patent abstract, but have no idea what it means (or how it might relate to F1 for that matter).
http://www.freepatentsonline.com/5137069.html

I suspect it has to do with tires expanding after takeoff – so kind of like a built in gear – quicker off the line with a smaller radius, but then as you speed up the tire grows acting effectively as a compounding larger gear.

I wonder how much F1 tires expand at top speed. This obviously affects ride height, and is countered by corresponding downforce.

Man - bring back the tire wars!

http://www.competitionplus.com/05_20_2004/beadlock_wheels.html





There are several things to remember when discussing drag racing tyres.

First, they run very soft compounds.

Second, they run at very low pressure (I'm guessing 5 - 6 psi), which is one of the reasons they wrinkle so easily and expand (the technical term is "grow") so much when turned at high rpm. That way, you have a very broad contact patch at the start of the run, then a much taller sidewall when the tyres connect and run at high speed.

Third, they are constructed specifically to grow: The side walls and the tread are both made to expand when subject to high centrifugal force. I suspect they use nylon, which will stretch a third of its length before snapping.

200 mph is probably the speed at which the sidewalls grow so much, they unseat the bead. I think wheel RPM is also important. I mention this because you can see the tyres grow as soon as the driver puts his foot down and the engine revs up. That can happen while the car is still in the "bleach box" doing burn-outs, and within a few yards of the starting line during the run. Although it may well get worse as speed increases.

Fourth, the belts under the tread must also be very stretchy.

The over all reason for this is to change the gearing as the car goes faster. If the tyre "grows" by 20%, from say 30" to 36", you've effectively increased the final drive by that much. It's the equivalent of changing from a 4:1 differential to a 3:1. The higher numerical ratio multiplies torque, the lower one allows for higher top speed.

And the sheet metal screws? Look at that picture again, you'll see eleven of them in the rim keeping the tyre from spinning on the wheel. Or rather, keeping the wheel from spinning inside the tyre.

Formula one tyres are completely different.

For one thing, they have to withstand enormous cornering loads that dragsters never have. Thus, the sidewalls are much, much stiffer to keep from shredding, tucking under and possibly popping the bead off the rim entirely.

Second, consistant handling requires consistant tyres; consistant everything, really. Tyre growth would affect this, partly by raising the car up as the tyre expanded, and partly by narrowing the contact patch and crowning it like a motorcycle tyre. To keep the tread flat on the road, the manufacturers use materials like kevlar and steel mesh, which stretch very little, under the tread.

That, incidentally is why "steel belted radials" were invented -- Radial tyres have their cords angled perpendicular to the thread, or along the radius extending from the wheel centre, or close to it. The maximum cord angle (away from parallel to that radial line) may be no more then fifteen degrees. Or an 75° angle to the tread; usually that cord angle is closer to 80° - 85°. Bias ply tyres typically zig-zag the belts at 30° to 45° away from radial.

The advantage of bias ply tyres is that the cords alternated from one layer to the next, forming a series of X's or V's, making the tyre harder to stretch in "growth." The disadvantage was high rolling resistance, which hurt fuel economy. Radials, on the other hand, can flex their sidewalls more easily, making for lower rolling resistance and a better ride, at the expense of crowning and sidewall growth. The unstretchable materials like steel prevent that.

But forget those commercials of cars running over sharp-edge-up meat cleavers; a few bands of steel don't armour plate your tyres...

One final note about wheels spinning inside the beads of a mountain bike:

The three things that determine whether a wheel will spin inside the bead are: Weight, the coefficient of friction between the tyre and the road, the bead and the torque involved.

First, bicycle tyres don't always have high bead-to-rim friction between the bead and a polished aluminium or chromed wheel.

Second, there is considerable torque mulitplication between your foot and the road, by way of crank length, gearing, and the ratio of the rim radius and tyre profile height.

Let's say you are riding a bike with 27" wheels (13.5" radius) and a 1.5" profile height (distance from the rim to the road). This gives a torque ratio of about 9:1 at the bead.

In contrast, a Formula One tyre is has a 660mm diameter (about 26"), or a 13" radius on a 13 inch wheel, which has a radius of 6.5 inches. (See FIA Technical Regulations 12.4.2 and 12.4.4 Thus, the tyre profile is about 6.5 inches, as well. That means the rim to tread ratio is only about 1:1, so the torque between the axel and the road is a good deal less.

I do have a question, though. You say this happens often, but are you sure? The inner tube and tyre would probably turn together, which would mean that after a rim-spin, the valve stem would be cocked at an angle instead of perpendicular to the rim. Does this actually happen? And if so, by how much?

Also, they are not using compressed air for filling these tires, most, if not all teams these days are using some form of Nitrogen, or a combo containing Nitrogen, which is lighter than the compressed air, and also withstands the temp changes better than Air. Not that its going to keep you straight, but I would imagine it does have more than just a negligible impact on the tires.

GreyWolf74 - 30 September 2009 09:54 AM

…”I do have a question, though. You say this happens often, but are you sure? The inner tube and tyre would probably turn together, which would mean that after a rim-spin, the valve stem would be cocked at an angle instead of perpendicular to the rim. Does this actually happen? And if so, by how much?”...

Yep. Have torqued/snapped valves under braking. (Note: smaller Presta valves tho. Fix problem by running downhill Schrader tubes instead.) I am an odd case though. I won’t bore you with the extreme manliness of my mtb riding.

It will happen on a road bike as well – when you get a flat and are slowing down quickly it can spin the tire/tube, and occasionally snap off. But that is because of low/no air pressure.

We’ve seen F1 tires completely without tread and the sidewalls are still attached. I’ll bet they are glued onto the rim.