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  1. #1
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    Default How to improve forward acceleration, cornering, braking and driveability of your car

    You can make major improvements to your car by only two means, either increased power or reduced mass. Reducing mass is better, as it is the only means to improve forward acceleration, conering, and braking. However, your car has different types of mass, and they are not all equal. By far the most effective mass reduction is to reduce the rotating parts of your car's unsprung mass, although reducing sprung mass can also help but is not as dramatic. I am not referring to the clutch or flywheel, but to the combination of tyres/wheels(rims)/disks(rotors), which will yield the most dramatic improvements in your car's performance. Even the tyres/wheels/disks combination, which are the car's rotating unsprung mass having the greatest impact on a car's performance, are not all equal. Pride of place is given to the tyre, then the wheel, followed by the disks. The reason is that the farther away you are from the centre of the rotating mass, the more power needed to accelerate or decelerate, and hence the more mass you save on tyres the more performance improvements you gain.
    The first thing you should find out is your car's tyre and wheel (rim) OE size, load index, speed index, which is given in your car manual or in a sticker on your door jam. Say if your tyre size is 185/55/15 with a load index of 82 and a speed index of V, and your wheel (rim) size is 6J x 15, OS:28, you now have a basis to start doing some calculations. Rule no. 1 is to use the smallest tyre/wheel combination specified by the manufacturer. Now take your tyre/wheel combination and weigh it. If they weigh 15kg (33lbs) or more for the above size tyre/wheel, then you can easily reduce this weight. You can reduce this even more if you change the rolling radius of your tyre slightly lower (-3%), as a smaller rolling radius has improved dynamics in its rotating unsprung mass, but do not overdo it. For the above example, you simply replace the 185/55/15 tyres with 195/50/15 tyres. You look for high performance tyres-they are usually lighter-that are lighter than your existing tyres. If it is lighter by 1kg for each tyre, you have reduced the tyres weight by 4kg for 4 tyres. After the tyres, you now look for lighter wheels, which is one area where the greatest weight reduction can be had. I hope you have not replaced your original wheels (rims) with larger diameter wheels. If you did, then its plain silly and a real disaster to performance. If your wheels are steel wheels, there is an added incentice to replace them, as steel wheels flex too much and are bad for cornering. Look for light alloy wheels, or better still forged wheels (they are very expensive but very light and strong), that will save you at least 3kg (6.6lbs) on each wheel, giving you a total saving of 12kg for 4 wheels. If you add the 4kg saving from the tyres to the 12kg saving from the wheels, you have a weight saving of 16kg. But this 16kg is no ordinary weight of the sprung type like the weight of a passenger. It is dynamically the equivalent of saving 16 x 16kg (256kg or 563lbs) of passenger or baggage weight. You can feel it; the car takes on an entirely different character; and, yes, it squats more and your body is thrown back more when you accelerate. Reducing the most important rotating unsprung mass, namely the tyres, wheels, and disks(rotors), yields the purist's approach to a car's improved performance. The benefits are immense:
    -More precise steering input and improved "turning in" characteristics
    -Improved acceleration and braking because there is less rotating mass which translates into more responsive acceleration and braking
    -Rotating unsprung mass is most susceptible to road shocks and cornering forces, and reducing such mass significantly improves your car's handling and cornering.
    -By reducing such rotating unsprung mass, there is less moving mass for your brakes to handle and less stress on your suspension, resulting in reduce wear and tear of brake disks, brake pads and suspension components.
    -The driveability of the car is improved.

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    Cool I will go and buy new shoes - today

    You can make major improvements to your car by only two means, either increased power or reduced mass.

    You can make major improvements to your footwork by only two means, either increased power or reduced mass.

    Reducing mass is better, as it is the only means to improve forward acceleration, conering, and braking.

    Reducing mass is better, as it is the only means to improve forward acceleration, turning and stopping.

    However, your car has different types of mass, and they are not all equal.

    However, your body has different types of mass, and they are not all equal.

    By far the most effective mass reduction is to reduce the rotating parts of your car's unsprung mass, although reducing sprung mass can also help but is not as dramatic.

    By far the most effective mass reduction is to reduce the swinging parts of your body mass, although reducing torso mass can also help but is not as dramatic.

    I am not referring to the clutch or flywheel, but to the combination of tyres/wheels(rims)/disks(rotors), which will yield the most dramatic improvements in your car's performance.

    I am not referring to the swinging hair, but to the combination of legs/feet/socks/shoes, which will yield the most dramatic improvements in your footwork's performance.

    Even the tyres/wheels/disks combination, which are the car's rotating unsprung mass having the greatest impact on a car's performance, are not all equal.

    Even the Shoes/Inlay soles/socks combination, which are the outermost parts of your body's swinging mass having the greatest impact on your footwork performance, are not all equal.

    Pride of place is given to the tyre, then the wheel, followed by the disks. The reason is that the farther away you are from the centre of the rotating mass, the more power needed to accelerate or decelerate, and hence the more mass you save on tyres the more performance improvements you gain.

    Pride of place is given to the shoe, then the socks, followed by the inlay soles. The reason is that the farther away you are from the centre of gravity, the more power needed to accelerate or decelerate, and hence the more mass you save on tyres the more performance improvements you gain.

    The first thing you should find out is your car's tyre and wheel (rim) OE size, load index, speed index, which is given in your car manual or in a sticker on your door jam.

    The first thing you should find out is your shoe and sock size, load index, speed index, which is given on a sticker on the inside of the tongue of your shoe.

    Say if your tyre size is 185/55/15 with a load index of 82 and a speed index of V, and your wheel (rim) size is 6J x 15, OS:28, you now have a basis to start doing some calculations.

    Say if your shoe size is 10 with a load index of 72 kg and a speed index of B (A being standstill), and your sock size is 8-12, you now have a basis to start doing some calculations.

    Rule no. 1 is to use the smallest tyre/wheel combination specified by the manufacturer.

    Rule no. 1 is to use the smallest shoe/sock combination accepted by the foot.

    Now take your tyre/wheel combination and weigh it.

    Now take your shoe/sock combination and weigh it.

    If they weigh 15kg (33lbs) or more for the above size tyre/wheel, then you can easily reduce this weight.

    If they weigh 600g or more for the above size shoes/socks, then you can easily reduce this weight.

    You can reduce this even more if you change the rolling radius of your tyre slightly lower (-3%), as a smaller rolling radius has improved dynamics in its rotating unsprung mass, but do not overdo it.

    You can reduce this even more if you change the size of your shoe lower (-3%), as a smaller shoe has improved dynamics in its swinging mass, but do not overdo it!!

    For the above example, you simply replace the 185/55/15 tyres with 195/50/15 tyres. You look for high performance tyres-they are usually lighter-that are lighter than your existing tyres.

    For the above example, you simply replace the size 10 shoes with 9½ shoes. You look for high performance shoes-they are usually lighter than your old shoes.

    If it is lighter by 1kg for each tyre, you have reduced the tyres weight by 4kg for 4 tyres.

    If it is lighter by 100g for each shoe, you have reduced the shoes weight by 200g for a pair of shoes. (buying more pairs will not improve your footwork)

    After the tyres, you now look for lighter wheels, which is one area where the greatest weight reduction can be had.

    After the shoes, you now look for lighter socks, which is the area where the least weight reduction can be had. However, great wellbeing can be gained.

    I hope you have not replaced your original wheels (rims) with larger diameter wheels.

    I hope you have not replaced your original socks with larger size socks.

    If you did, then its plain silly and a real disaster to performance.

    If you did, then its plain silly and a real disaster to performance.

    If your wheels are steel wheels, there is an added incentive to replace them, as steel wheels flex too much and are bad for cornering.

    If your socks are steel wool, there is an added incentive to replace them, as steel wheels itch too much and are bad for blistering.

    Look for light alloy wheels, or better still forged wheels (they are very expensive but very light and strong), that will save you at least 3kg (6.6lbs) on each wheel, giving you a total saving of 12kg for 4 wheels.

    Look for light cotton socks, or better still coolmax socksw (they are very expensive but very light and comfortable), that will save you at least 3g (.06lbs) on each foot, giving you a total saving of 6g for 2 feet.

    If you add the 4kg saving from the tyres to the 12kg saving from the wheels, you have a weight saving of 16kg.

    If you add the 200g saving from the shoes to the 6g saving from the socks, you have a weight saving of 206g.

    But this 16kg is no ordinary weight of the sprung type like the weight of a passenger.

    But these 206g is no ordinary weight of the torso type like the weight of a beer belly fold.

    It is dynamically the equivalent of saving 16 x 16kg (256kg or 563lbs) of passenger or baggage weight.

    It is dynamically the equivalent of loosing 16 x 206g (3296g or 3.296kg) of beer belly weight.

    You can feel it; the car takes on an entirely different character; and, yes, it squats more and your body is thrown back more when you accelerate.

    You can feel it; the footwork takes on an entirely different character; and, yes, you squat more and your body is thrown around court more when you accelerate.

    Reducing the most important rotating unsprung mass, namely the tyres, wheels, and disks(rotors), yields the purist's approach to a car's improved performance.

    Reducing the most important swinging mass, namely the shoes, wheels and inlay soles, yields the lazy bugger's approach to a improving footwork performance.

    The benefits are immense:

    The benefits are immense:

    -More precise steering input and improved "turning in" characteristics

    -More precise steering input and improved "turning" characteristics

    -Improved acceleration and braking because there is less rotating mass which translates into more responsive acceleration and braking

    -Improved acceleration and stopping because there is less swinging mass which translates into more responsive acceleration and stopping

    -Rotating unsprung mass is most susceptible to road shocks and cornering forces, and reducing such mass significantly improves your car's handling and cornering.

    -Swinging mass is most susceptible to uneven and slippery floors, and reducing such mass significantly improves your footwork.

    -By reducing such rotating unsprung mass, there is less moving mass for your brakes to handle and less stress on your suspension, resulting in reduce wear and tear of brake disks, brake pads and suspension components.

    -By reducing such swinging mass, there is less moving mass for your shoe soles to handle and less stress on your knees, resulting in reduced wear and tear of shoe soles, socks and inlay soles and joints and muscles.

    -The driveability of the car is improved.

    -Your game is improved.

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    Quote Originally Posted by taneepak
    You can reduce this even more if you change the rolling radius of your tyre slightly lower (-3%), as a smaller rolling radius has improved dynamics in its rotating unsprung mass, but do not overdo it. For the above example, you simply replace the 185/55/15 tyres with 195/50/15 tyres.

    I hope you have not replaced your original wheels (rims) with larger diameter wheels. If you did, then its plain silly and a real disaster to performance.
    Going from 185/55/15 to 195/50/15 reduces the tyre diameter by about 1.5%
    (and your speedo and tacho will read 1.5% higher than before, as your small wheels have to rotate faster than big wheels at the same road speed, and so your engine will have to rev higher, so you will use more fuel)

    you would normally move to larger wheels if you want to go to much lower-profile tyres - for the improved handling
    e.g. from 195/50/15 to 205/35/17

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    I was going to say the major weight reduction that I could do to my car is to "remove" my GF out of my car (at least 40kg ) and that would surely help my car the most ....HAHA!!


    Downside would be, getting smacks......

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    Quote Originally Posted by Neil Nicholls
    Going from 185/55/15 to 195/50/15 reduces the tyre diameter by about 1.5%
    (and your speedo and tacho will read 1.5% higher than before, as your small wheels have to rotate faster than big wheels at the same road speed, and so your engine will have to rev higher, so you will use more fuel)

    you would normally move to larger wheels if you want to go to much lower-profile tyres - for the improved handling
    e.g. from 195/50/15 to 205/35/17
    Yes, the speedo and tacho will be 1.5% out, but can you really see the difference with your eyes. Your gearing is 1.5% more lively and AOTBE you accelerate 1.5% faster.
    The best is to use the smallest OE tyre size. The "Plus-One", "Plus-Two" concept is rather silly and is more of a "One-Up" gimmick, although there is a sound engineering principle. Tyres with lower profile than OE tyres have shorter sidewalls and tend to ride slghtly more firmly. They also enhance quickness of steering response and the precision of a car's handling feel. These are the pluses. The minuses of "One-Upmanship" are much greater than the pluses. They include much heavier wheels (rims), heavier tyres (mainly from reinforcements of tyre sidewall), adverse impact of mass shift of wheels and tyres to the outer edge (the wheel now extends 8.5" instead of 7.5" from the centre and the mass of the tyre is now compacted on the outer edge because of the thinner sidewall), and messing up your car's springs (need for uprated springs).
    Lets take an example. A 15" OZ Superleggera wheel weighs 10.7lbs; its 17" weighs 15.1lbs. A Toyo tyre T1-S high performance 195/50/15 tyre weighs 17.4lbs; its 205/40/17 weighs 18.5lbs (they don't make 205/35/17 tyres, but should weigh about the same or a bit heavier). We are talking of 5.5lbs heavier mass for each corner, adding up to a total of 22lbs or 10kg. The actual dynamic mass increase is even greater because of the "Plus-One" or "Plus-Two" tendency to push the wheel and tyre mass to the outer edge. Remember these are the most critical part of unsprung mass, because they are rotating. A 10kg difference is significant, wiping off some of the very small advantages of using low profile tyres. However, large diameter wheels and tyres make a car pretty and can transform the looks of a car. This is why it is easy to fall for the trap.
    By the way, do you know what diameter tyres and wheels Formula 1 Racing cars use? You will be surprised.

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    it'll be better to just buy a new car

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    Quote Originally Posted by taneepak
    (they don't make 205/35/17 tyres, but should weigh about the same or a bit heavier)
    I just made those numbers up without checking
    There is a 215 35 17 though. (Dunlop SP SPORT 9000 XL, 8.676 kg)

    Anyway, using you example
    A Goodyear 185 55 15 Eagle F1 weighs 7kg
    A Goodyear 195 50 15 Eagle F1 weighs 8.1kg

    I picked Goodyear tyres because I work for Goodyear.
    the 195 50s may have a fractionally smaller sidewall, but because they have a wider tread, you have added weight at the outermost part of the tyre.

    The 1.5% difference in diameter is also equivalent to the difference between a brand new tyre and one with the tread worn down.

    Either way, it's all about trading 1 thing off for another.
    I don't have any problems doing that as long as you know what is gained and what is lost. Then you can choose according to your personal preference.
    (or for whichever you find more impressive No. I didn't mean it, no flaming please)

    Lower your gearing too much and you might run out of grip. Just gotta find the right balance.

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    Quote Originally Posted by Neil Nicholls
    I just made those numbers up without checking
    There is a 215 35 17 though. (Dunlop SP SPORT 9000 XL, 8.676 kg)

    Anyway, using you example
    A Goodyear 185 55 15 Eagle F1 weighs 7kg
    A Goodyear 195 50 15 Eagle F1 weighs 8.1kg

    I picked Goodyear tyres because I work for Goodyear.
    the 195 50s may have a fractionally smaller sidewall, but because they have a wider tread, you have added weight at the outermost part of the tyre.

    The 1.5% difference in diameter is also equivalent to the difference between a brand new tyre and one with the tread worn down.

    Either way, it's all about trading 1 thing off for another.
    I don't have any problems doing that as long as you know what is gained and what is lost. Then you can choose according to your personal preference.
    (or for whichever you find more impressive No. I didn't mean it, no flaming please)

    Lower your gearing too much and you might run out of grip. Just gotta find the right balance.
    So you work for Goodyear. I used to deal with them many moons ago as a supplier. Also, an old friend of mine who was our company's president at that time, had a father who was Goodyear's vice president at their Akron office. He was a chap who went with the name of Laibe.
    Frankly, I am surprised Goodyear can make tyres as good as the Eagle F1 GS-D3. They must have bought the rights or patents from someone else. I don't mean to be discourteous, but I have never ever used Goodyear tyres despite having worked with them. I will consider the F1 GS-D3 tyres for my future replacement, if they can reduce the weight by 5-10%.

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    Quote Originally Posted by taneepak
    Frankly, I am surprised Goodyear can make tyres as good as the Eagle F1 GS-D3. They must have bought the rights or patents from someone else.
    I am but a lowly computer programmer. Our Research and Development mostly takes place in Luxembourg and the US. I thought we developed the new tyres like F1 and Ventura and Hydragrip ourselves.

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    Quote Originally Posted by taneepak
    Yes, the speedo and tacho will be 1.5% out, but can you really see the difference with your eyes. Your gearing is 1.5% more lively and AOTBE you accelerate 1.5% faster.
    The best is to use the smallest OE tyre size. The "Plus-One", "Plus-Two" concept is rather silly and is more of a "One-Up" gimmick, although there is a sound engineering principle. Tyres with lower profile than OE tyres have shorter sidewalls and tend to ride slghtly more firmly. They also enhance quickness of steering response and the precision of a car's handling feel. These are the pluses. The minuses of "One-Upmanship" are much greater than the pluses. They include much heavier wheels (rims), heavier tyres (mainly from reinforcements of tyre sidewall), adverse impact of mass shift of wheels and tyres to the outer edge (the wheel now extends 8.5" instead of 7.5" from the centre and the mass of the tyre is now compacted on the outer edge because of the thinner sidewall), and messing up your car's springs (need for uprated springs).
    Lets take an example. A 15" OZ Superleggera wheel weighs 10.7lbs; its 17" weighs 15.1lbs. A Toyo tyre T1-S high performance 195/50/15 tyre weighs 17.4lbs; its 205/40/17 weighs 18.5lbs (they don't make 205/35/17 tyres, but should weigh about the same or a bit heavier). We are talking of 5.5lbs heavier mass for each corner, adding up to a total of 22lbs or 10kg. The actual dynamic mass increase is even greater because of the "Plus-One" or "Plus-Two" tendency to push the wheel and tyre mass to the outer edge. Remember these are the most critical part of unsprung mass, because they are rotating. A 10kg difference is significant, wiping off some of the very small advantages of using low profile tyres. However, large diameter wheels and tyres make a car pretty and can transform the looks of a car. This is why it is easy to fall for the trap.
    By the way, do you know what diameter tyres and wheels Formula 1 Racing cars use? You will be surprised.
    LOL, car subject, I'm here

    taneepak: " Look for light alloy wheels, or better still forged wheels (they are very expensive but very light and strong), that will save you at least 3kg (6.6lbs) on each wheel"

    Yes, alloy wheels are lighter BUT forged wheel is heavier, not lighter, than its casted or stamped cousins. LOL

    Neil Nicholls had made a valid point about lowering tire profile (aspect ratio) to improve handling (hey, he works at GY, what he had observed can't be that wrong ) although Neil (and taneepak) didn't list out all the low profile advantages and allowing taneepak's countering points to sound one sided. These unmentioned advantages are:

    1. wider tire may weigh slightly more but has more contact area to provide more grip.
    2, A lower aspect ratio tire of the same brand and model will increase how quickly your car responds to steering input (and, thus, handling feel), but it probably won't improve extreme grip
    3. third and not least important, is that low profile tire LOWER THE CAR CENTER OF GRAVITY, providing more even griping on all 4 tires.


    example: sidewall height:

    185/55R15 = 101.8 mm
    195/50R15 = 97.5 mm

    195/50R15 lowers a car COG by 4.3mm It may not sound much but on a say 3500lb car turning at high speed, the extra leaning make the difference between gripping and slipping.

    ------------------------------------------------------------
    here are the tire and wheel specs of the 2005 corvette and 2005 porsche 911 (american and european design so there are no doubts)

    Corvette
    Wheel size:
    front: 18 x 8.5; rear: 19 x 10
    front: 18 x 8.5; rear: 19 x 10

    Tires:

    Standard
    Goodyear Eagle F1 GS
    Extended Mobility
    front: P245/40ZR-18
    rear: P285/35ZR-19

    Z51 sport package
    Goodyear Eagle F1 SC
    Extended Mobility
    Asymmetric Tread
    front: P245/40ZR-18
    rear: P285/35ZR-19

    Porsche 911 Carrera

    Performance upgrades for the 2005 Porsche 911 Carrera S include 19-inch wheels with 235/35 tires in front and 295/30 treads in back.

    -----------------------------

    Hmm, they all use very very wide tires and biggy wheels Is someone here smarter than GM, Porsche and tire maker engineers and their supercomputers?? LOL
    Last edited by cooler; 08-09-2004 at 03:39 AM.

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    [QUOTE=cooler]LOL, car subject, I'm here

    taneepak: " Look for light alloy wheels, or better still forged wheels (they are very expensive but very light and strong), that will save you at least 3kg (6.6lbs) on each wheel"

    Yes, alloy wheels are lighter BUT forged wheel is heavier, not lighter, than its casted or stamped cousins. LOL

    Forging changes the shape and alignment of the metal's grain-like crsytal structure. In a cast alloy wheel, when its molten metal solidifies, its grain structure is non-directional, amorphous, grains in the sense of "grains" in the sand. As metal is forged, these grains are stretched in the direction of deformation, making them more like the "grain" of wood. Cast alloy wheels are cheap, heavy and easily formed into a variety of shapes. The other one, forging, is strong and light. The vast pressures used in forging also compact the metal, eliminating porosity and voids that can be the source of cracks or corrosion. This also results in less metal being used to achieve a given strength, meaning lighter and stronger wheels can be made with forged wheels.

    Neil Nicholls had made a valid point about lowering tire profile (aspect ratio) to improve handling (hey, he works at GY, what he had observed can't be that wrong ) although Neil (and taneepak) didn't list out all the low profile advantages and allowing taneepak's countering points to sound one sided. These unmentioned advantages are:

    1. wider tire may weigh slightly more but has more contact area to provide more grip.
    2, A lower aspect ratio tire of the same brand and model will increase how quickly your car responds to steering input (and, thus, handling feel), but it probably won't improve extreme grip
    3. third and not least important, is that low profile tire LOWER THE CAR CENTER OF GRAVITY, providing more even griping on all 4 tires.


    example: sidewall height:

    185/55R15 = 101.8 mm
    195/50R15 = 97.5 mm

    195/50R15 lowers a car COG by 4.3mm It may not sound much but on a say 3500lb car turning at high speed, the extra leaning make the difference between gripping and slipping.

    ------------------------------------------------------------
    here are the tire and wheel specs of the 2005 corvette and 2005 porsche 911 (american and european design so there are no doubts)

    Corvette
    Wheel size:
    front: 18 x 8.5; rear: 19 x 10
    front: 18 x 8.5; rear: 19 x 10

    Tires:

    Standard
    Goodyear Eagle F1 GS
    Extended Mobility
    front: P245/40ZR-18
    rear: P285/35ZR-19

    Z51 sport package
    Goodyear Eagle F1 SC
    Extended Mobility
    Asymmetric Tread
    front: P245/40ZR-18
    rear: P285/35ZR-19

    Porsche 911 Carrera

    Performance upgrades for the 2005 Porsche 911 Carrera S include 19-inch wheels with 235/35 tires in front and 295/30 treads in back.

    -----------------------------

    Hmm, they all use very very wide tires and biggy wheels Is someone here smarter than GM, Porsche and tire maker engineers and their supercomputers??

    I have earlier mentioned the advantages of shorter sidewalls or low aspect ratio tires, provided the rolling radius has not been changed by plus/minus 3%.
    However, the added weight of changing to larger wheels and tyres, more than offsets the advantages.
    Changing to a larger and fatter wheel/tyre does not lower the COG if the rolling radius of the new wheels/tyres are the same. Any difference in rolling radius could mean they either sit higher or lower than the replaced sets, depending on whether your replacements' rolling radius is larger or smaller than the originals, and has nothing to do with lowering of COG because the tyres are fatter or have a lower aspect ratio.
    Formula 1 Racing cars use 13" diameter wheels, nowhere near the 18" to 20" wheels /tyres you are talking about.

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    I don't know if there are F1 rules to limit wheel/tyre size. They introduced many rules to try to slow the cars down.

    The range of tyre diameters that a car can practically use would depend mostly on the engine I would have thought. Torque and how fast it can rev.

    F1 engines can rev very high so they are able to make small wheels spin very fast.

    Mass market consumer engines in day to day use rarely have to go above 4000rpm. If you want to get a reasonable speed at 4000 rpm you need tyres of a certain size. If you use longer gearing you need more torque.

    I don't actually know a lot about tyres. Like I said, I am but a lowly computer programmer

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    Quote Originally Posted by Neil Nicholls
    I don't know if there are F1 rules to limit wheel/tyre size. They introduced many rules to try to slow the cars down.

    The range of tyre diameters that a car can practically use would depend mostly on the engine I would have thought. Torque and how fast it can rev.

    F1 engines can rev very high so they are able to make small wheels spin very fast.

    Mass market consumer engines in day to day use rarely have to go above 4000rpm. If you want to get a reasonable speed at 4000 rpm you need tyres of a certain size. If you use longer gearing you need more torque.

    I don't actually know a lot about tyres. Like I said, I am but a lowly computer programmer
    Neil, your hutch is right. There ARE RULES. One of it is:

    “The first thing that needs to be understood about a Formula 1 wheel is that there are dimensional requirement,” explains Head of Race Engineering Steve Hallam. “All wheels have to be 13 inches in diameter. A front wheel and tyre assembly has to lie between 305mm and 355mm. A rear wheel and tyre is 365 to 380mm. The diameter of a dry tyre can’t exceed 660mm, with a wet tyre allowed to be 10mm larger.”

    Imagine if a 10,000-12,000 rpm engine running a formula one with 15", 19", or 22" rim (i use rim because the word wheel could be confusing), that car will be flying LOL. Limiting rim size is a indirect method to keep formula 1 speed within design specs of the track. Without mechanical limits, formula racing will be a technological race instead a test of driver ability. Same goes for IROC.

    Taneepak, u cannot pull examples from indy car (or Yonex )and say it's the best application. Just like badminton and golf, there are rules on equipements. If 'Cooler' brand (made in japan too )come out with a 30mm longer shaft and larger frame racket but disallowed in IBF tournaments, would u go saying that Cooler brand racket is inferior because that's not what the pros use?

    There are illegal golf balls and clubs that are banned in PGA tournaments. They are illegal because they have much more superior performance over regulation balls and clubs.

    GM and Porcshe have no engine or wheel restriction(but restricted by other parameters like noise, CAFE, and emission for example). They design what's best for the money and consumer demand. The speed is limited by posted highway signs.

    On forged rim, i should have said forged rim is denser. Forged rim is lighter because less material is used and also better (lighter) material is used. With same composition, dimension and thickness, forged rim is heavier than casted and stamped which is what i had assumed that comparison was on same composition, dimension and thickness rims.

    Of course if rolling radius is unchanged, COG won't change. However, going to lower profile tires usually lowers the car a bit. I had provided the example above already for a minor changeover from 195 to 185.

    In my 1976 olds, i had 215/75R15 stock tires. I bot 255/60R15 to upgrade handling. I had lowered my car by 8.25mm. My car weighs 4000 lbs.
    Last edited by cooler; 08-09-2004 at 01:29 PM.

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    LOL, I did it again
    http://www.badmintonforum.com/forums...ighlight=hutch

    Neil, your hunch is right. There ARE RULES. One of it is:

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    lol, cooler=car mechanic

    Now we are jumping into the world of F1...and I am just enjoying reading this whole thread

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    The best way to find out is to try it out yourself. If you have a car with steel wheels, try to borrow a similar size set of alloy wheels that are at least 4lbs lighter on each wheel and have a test run. Or better still, if you own a hot hatch or sports car, check with your fraternity about using lighter vs heavier large diameter wheels.
    Also, a tyre's contact patch size is strictly determined by 1. weight on the wheel, and 2. tyre pressure. A wider tyre doesn't make the area of the contact patch larger. It only changes the shape to wider but shorter longways. Also size of the contact patch is not relevant to grip, which is dictated by the coefficient of friction of the rubber compound used in the tyre.

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    You may find this site www.caterham.co.uk/aftersales/upgrades/mar03.htm an interesting read. Caterham is a fantastic manufacturer of very light and unsual sports cars.

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