Cars - Tires Fall 2018
Tights	..

Soft and Hot wheels - 13th Sep + 4th October 2018

Slipping wheel can have two practical explanations. The friction between road and tire can be too small. The force system is under-loaded. In this case narrow tire is better than wide. Narrow tire increases G force at the area in between road and tire.

Then the force, which rotates the wheel can be too big. The momentary friction in between road and tire is too small, wheel starts to slip. When so, horizontal force takes too much from the available friction force. The force system is overloaded and wide tire is better. Wide tire decreases G force in the contact area.

The friction force comes from the mass, which pushes wheel towards road. Another is the friction factor of tire-road system ( there are lists from friction factors ). 

Soft compounds better grip comes from internal lengthwise tilt of the tire. Internal tilt increases max possible X-vector force. Tire's internal tilt, tilts also the force vector in between road and tire.

Hot tire can improve both friction factor and tilt. Explanation fits well to the practice ... the way things are known to work. The picture on the right  shows how it goes. Blue arrow is force, which comes from engine and transmission. The horizontal force, which born from internal tilt, is the green line at the bottom. When you accelerate the tilt and horizontal, forwarding force grow. The black G-force shrinks. The green tilt line begins from the rim, it ends to road. 

The system is an application from Pythagoras and Sin clause. Tilt can be measured and it can presented with graph. In graph X axis is force and Y-axis tilt. The blue force comes from engine-transmission. The black G-force has already formulas for calculating friction forces. With graphs you can match engine-transmission and tires. Build sport, everyday and heavy duty tires. Tires have currently standards for size, fuel economy, payload-weight and maximum speed. Grip graph has direct connection to safety of the tires. With new theory you can build safe tires, with relatively good durability and fuel economy. You can make part from the tilt for safety & grip in air-space. With sides of the tire. Use harder compound, transfer the lost grip to sides and belt system.

System is exactly the same in sideways. When you accelerate in curve, you create 2 dimensional force system. The end point moves also in sideways. In common acceleration end point moves only in lengthways.

In rubber tire road-side is ahead of the car-side all the time. In braking road side is left behind car side. Iron-steel wheel misses rubbers tilt, friction, friction factor and grip are smaller than with rubber-air system. From the picture you can figure out, why race cars - like cart / formula 1 - never uses low profile tires. Trendy low profile tire cannot tilt as much traditional 0.8 tire and race tire. It improves fuel economy. Then it downgrades grip and comfort.

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First current rubber-air tires were invented-made by French Michelin an awful long time ago. Steel belts came in late 1960's and tubeless tires in 1970's. When Italian mid-engine dream cars came, they all had Pirelli P8 tires. Pirelli P8 is the best known and most appreciated tire ever. In the beginning P8  was the only tire, which last enormous speeds and engine powers.

Good Year and Dunlop are rather well known tire makes. Dunlop built tires for race, sport and GT cars. Good tires for driving fast on narrow, curved asphalt road ( talking also from own experience ).  Michelin was famous from durable tires, not from tires with excellent steering capabilities. Before speed limits and four lane highways, tires' qualities were tested and evaluated in practice. Not only in magazines.

Free roll, friction factors - 4th + 10th October 2018

When wheel or ball rolls freely without external power, the movement must come from the weight center. It must be ahead of the attachment point. Powered wheel obviously moves the weight center so that it goes before the attachment point.  The back shrinks and front stretches so, that the weight center moves forwards. The weigh center must have some kind of connection to the green x vector. 

Not saying it is impossible, but I couldn't find a way, how powered wheel could create an attachment point tilt, which would be reversed from the picture. Power point X in the rim moves faster than the attachment point to the road.

Books say that old fabric tire has 0.16-0.22 friction factor, steel belt tires friction factor is 0.14 - 0.15. The values in the table are tire's nominal friction factors. It is the another component for the overall friction factor. Another component is road's nominal friction factor.  As you can see, cross-belt tire needs a table for speeds. In common speeds factor changes already 25%.

Could mention that the reason for the mysterious accidents and deaths ... dangerous aquaplaning ( raise and slide over water ) ... was discovered in late 1960's, at the same time steel belt tires came to cars. Steel belt tire has poorer grip than older cross-belt tire. Especially at high speeds.

Tires higher friction factor shortens braking distance, increases maximum steering angle at speed X. When you have speed limits, higher friction factor increases safety and fuel consumption. The part from the better grip, which goes to increased speeds, is marginal. Speed limits were taken to use soon after steel belts came. Speed limits came slightly before oil crisis, reason was increased number of road accidents.

From the table old tire has 0.016 and steel belt 0.014 factors at city speeds ( 30-50 km/h). Friction factors are simple multiplicands : old tire has 14% bigger grip forces at city speeds. The difference is so big, that it is visible in practice. Difference to modern EU-US rooted eco tires is bigger than in the diagram. Possible to say that EU-US politics, civil servants and co-operative midgets are not trying to increase road-safety, when they downgrade speed limits. They obviously try to hide something from the public, with nicely formed words, goals and excuses ... as usual.

The maximum grip force comes from the weight and friction. At high speeds old tires friction force system is a lot safer than new. When you increase speed, tilt grows. More and more from the available friction force goes to x-axis and speed maintenance. On the other hand steering and braking needs more force. Old cross-belt tire compensated the increased grip consumption-demand with upgraded friction factor.

Steel belt tire with steady friction factor loses steering and braking capabilities with increased speed. When you take a tighter curve with over 160 km/h ( 100 mph ), car slips into a soft 4 tire slide rather easily. At high speeds air resistance force keeps the direction. Air resistance also ends the slides quickly. When tires slip at high speed, air resistance brakes the car, until the tires get the grip back. In theory high speed slide is a match to ABS system, which locks the wheels.

? First steel belt tire systems had tubes. The steel wires in the first tires went broke quite often. When a piece of wire came out from the rubber, it punched a hole to the tube. Mysteriously broken, flat tires were common then. When you examined the the tire from the inside, you found a small steel wire, which had punched the hole. The wire seemed to come from nothing. Steel does not last bending as well as fabric.

When steel belt tire came, the maximum engine powers were much more limited, than nowadays. Top speeds were so modest, that steel belts upgraded top speeds Upgraded top speed was commonly used as sales argument  for the new tire type. Air resistance starts to dominate force consumption at highway speeds. After air resistance starts to dominate the force consumption, weight and friction becomes insignificant very quickly.

Soon after steel belts came oil-crisis. Fuel consumption - consumption of the essential, limited natural resource - started to dominate car-tire manufacturing. Sugar oil and pressure sensors makes it possible to waste oil into improved grip and safety of the tires.

Tires efficiency ratio - 13th October 2018

My guess for the fabric belt tires friction system is, that softer tire increases the area, which touches the road. Friction per square millimeter cannot change much. 

The overall friction factor of tire can raise without improved grip. When so, the increase comes from the internal creation of tilt, such warms up the sides of the tire. The division in between internal friction and grip friction is the efficiency ratio of the tire. Tire with poor efficiency ratio consumes lots of fuel, although the grip is poor. The efficiency ratio would need standards for making comparisons easy. Car manufacturers for example, would need efficiency ratios and others for selecting recommended tires for their best selling models.

With breaking you can measure, the friction which is used for grip. You can check the braking force, which locks the tire with known speed and known underlying surface. Also possible to check the acceleration and side forces, which makes the wheel slip at certain speed.

Tilt has a connection to belts' angle and other qualities. When you have a tire with designed rolling direction, you got to check both acceleration and braking grip forces. When you have a tire with free rolling direction, braking and acceleration forces are almost equal. In principle, a tire for common usage should have symmetric belt system. Braking reverses tilt angles. Surface can have dedicated shape and rolling direction. Reverse gear is the only thing, which reverses surface's rolling direction.

For surface grip test you got to build a special tire, which misses sides ( or eliminates tilt ). Surface test results have lots of usage in later tire-tilt development calculations and tests.

ABS Brakes - Aug 2nd 2018

Idea of electric brakes is impossible. Each wheel would need a heavy generator and wrist sized wiring for braking. Instead you can build a smaller generator into transmission. You active the generator, when driver pushes the brake pedal.

First ABS systems used impulse sensors. They released the pressure, when rotation speed was near zero. Modern ABS systems uses also on-off sensors. The wheel is locked before the pressure is released. Impulse sensor system is more powerful and better than on-off system. On-off system locks wheels all the time. Momentary locking downgrades overall breaking power and also the steering capability. 

Good ABS system has 4 pipelines and pressure controllers. It is the only way to independently adjust braking power for each wheel.  Without 4 pipes ABS always adjusts the braking power for axles or wheels with the poorest grip / friction. With foot you can adjust the braking power with the best grip. On uneven surface ABS loses to foot. On-off system loses to foot also on very slippery ( wet-icy ) road-tire systems. The continuous locking of the wheels drops braking pressures to marginal levels. Breaking distances are unpredictable, much longer than you estimated.

During wintertime one wheel on snow / ice and another on dry situations are common in cities : Warm wheels create dry tacks to the snowy and icy streets. Very slippery conditions are common in areas, where there is snow ( occasional snowfalls and storms ), but you do not yet need winter tires / spiked winter tires. Global warming has disturbed climate so much, that there are nowadays more areas, which are hit by occasional snowfalls every winter.

Ideal ABS controller is analog. After ABS is activated it adjusts the break pressure all the time. So that the steering wheel does not hit your hands. Nothing prevents you from adding a manually controlled system, which maximizes breaking power when steering angle is near zero. And also on uneven surface.