erico2k2:

your shaft and wheel revolves at same speed, same time, now this is different from distance traveld
Speed= Rate of change of the wheel remember I said Rate
if you look at teh diagram bellow its a typical rear axle car
Now explain how the size of the Tyre would influence the speed of the gear.
The gears by the drive shaft is constant it does not change unlike the gears in the gear box hence the output speed at any point is constant btw the wheel and the drive shaft.

Mr Einstein
Speed = distance covered over time.
If your drive shaft completes a revolution in 10sec (assumption) that means any size of tyres installed will also complete their revolution in 10sec.
Now assume your current tyre's circumference is 1m, that means in one revolution which is in 10sec, your Tyre will cover a distance of 1m, then speed will be 1m/10sec = 0.1m/s
If you install a bigger tyre let's say a circumference of 1.5m, that means in one revolution which is 10sec, your bigger Tyre will cover a distance of 1.5m, then the speed will be 1.5m/10sec = 0.15m/s
As you can see, even though the same drive shaft spin both tyres at the same rate (10sec per revolution), the distance and speed differs, the bigger tyre will always result to a higher speed, likewise a smaller tyre will result to a lower speed.

Do you need more explanation?

abes:

Mr Einstein
Speed = distance covered over time.
If your drive shaft completes a revolution in 10sec (assumption) that means any size of tyres installed will also complete their revolution in 10sec.
Now assume your current tyre's circumference is 1m, that means in one revolution which is in 10sec, your Tyre will cover a distance of 1m, then speed will be 1m/10sec = 0.1m/s
If you install a bigger tyre let's say a circumference of 1.5m, that means in one revolution which is 10sec, your bigger Tyre will cover a distance of 1.5m, then the speed will be 1.5m/10sec = 0.15m/s
As you can see, even though the same drive shaft spin both tyres at the same rate (10sec per revolution), the distance and speed differs, the bigger tyre will always result to a higher speed, likewise a smaller tyre will result to a lower speed.

Do you need more explanation?

You still do not get it . The speed of a vehicle is.measured by a speed sensor . ......,,,this is what you see in your dash board . Since tyre size does not change the speed at which the gears /shaft rotates it simply means yoyr speedometer will read same for whatever size of wheel you pit there . .The veriables in this narative is not how far a car can go in time.but rather the time it takes to.attain a certain speed . My car does 0 to 100 in 6 seconds . If I keep it at that speed is constant . Your car might take 10.secs to attain 100 kmh but once reached the distance btw me and you will B Constant .
NB I'm not Einstein . I'm a mechanical Engineer and I actually did teach physics in Nigeria for a year 1999 . So I ha e Co. E across this question loads of time

erico2k2:

You still do not get it . The speed of a vehicle is.measured by a speed sensor . ......,,,this is what you see in your dash board . Since tyre size does not change the speed at which the gears /shaft rotates it simply means yoyr speedometer will read same for whatever size of wheel you pit there . .The veriables in this narative is not how far a car can go in time.but rather the time it takes to.attain a certain speed . My car does 0 to 100 in 6 seconds . If I keep it at that speed is constant . Your car might take 10.secs to attain 100 kmh but once reached the distance btw me and you will B Constant .
NB I'm not Einstein . I'm a mechanical Engineer and I actually did teach physics in Nigeria for a year 1999 . So I ha e Co. E across this question loads of time

abes:
Still on No 4: Tyre size and effect on vehicle speed.
By default, the actual speed of a Bugatti travelling at 80km/h(speedo reading) is the same as an "Ijapa" travelling at 80km/h(speedo reading), now I said 'by default', that is they are using the manufacturer's recommended tyre size. But if the tyre size of one car is changed, the actual speed will be different from the speedo reading.

For example, let's say the recommended tyre size for a 2008 Camry is 215/55R16, by default, the actual speed will be the same as the speedometer speed (i.e factory calibrated). If you change to bigger set of tyres for example 215/65R16, then the actual speed will be more than speedometer speed, Speedometer reads 100, but the actual speed is 107 km/h.

You can calculate speedo error from this site for your own vehicle http://www.tyresizecalculator.com/tyre-wheel-calculators/speedo-error-calculator

So No 4 in NOT a myth as long as car owners can still change their tyre sizes.

OK Mr notEinstein

If your car is a FWD, jack up the front so the two front tyres do not touch the ground, go inside your car, start it, put it in Drive then throttle down. You'll notice your speedometer will be doing James Bond while your car is stationary. Why is that? Your speedometer through the vss measures the rate at which your shaft spins and not the actual speed of your car. What determines the speed of your car is that entity that is in contact with the ground, in this case, the tyres. If you can get your shaft to be in contact with the ground then your car speed will be determined by the shaft (try it ).

There are two speeds involved, the Speedometer Speed(sdsp) and the Actual Speed of the car(acsp). Now at the factory, the speedometer is calibrated using the original tyres (factory fitted tyres) to make sdsp = acsp. Once you change the tyres to a bigger or smaller ones, unless you recalibrate the speedometer, sdsp will never be equal to acsp.

Check out the site in the post I quoted to see the effect of changing your tyres to a different sized ones.

From the example in my quoted post, using two camrys, camry A with the original fitted tyres 215/55R16 and camry B with not factory fitted tyres 215/65R16. If both cars are going at 100km/h sdsp, after one hour, camry A would have covered 100km while camry B would have covered 107km. Obviously camry B is faster even though both speedometers read 100km/h.

Do you need more explanation?

abes:




OK Mr notEinstein

If your car is a FWD, jack up the front so the two front tyres do not touch the ground, go inside your car, start it, put it in Drive then throttle down. You'll notice your speedometer will be doing James Bond while your car is stationary. Why is that? Your speedometer through the vss measures the rate at which your shaft spins and not the actual speed of your car. What determines the speed of your car is that entity that is in contact with the ground, in this case, the tyres. If you can get your shaft to be in contact with the ground then your car speed will be determined by the shaft (try it ).

There are two speeds involved, the Speedometer Speed(sdsp) and the Actual Speed of the car(acsp). Now at the factory, the speedometer is calibrated using the original tyres (factory fitted tyres) to make sdsp = acsp. Once you change the tyres to a bigger or smaller ones, unless you recalibrate the speedometer, sdsp will never be equal to acsp.

Check out the site in the post I quoted to see the effect of changing your tyres to a different sized ones.

From the example in my quoted post, using two camrys, camry A with the original fitted tyres 215/55R16 and camry B with not factory fitted tyres 215/65R16. If both cars are going at 100km/h sdsp, after one hour, camry A would have covered 100km while camry B would have covered 107km. Obviously camry B is faster even though both speedometers read 100km/h.

Do you need more explanation?

Facts
Two different tyres different speed
Two different distance different speed .
Same tyres same distance same speed .
Your example above is of two different speed .

erico2k2:

Facts
Two different tyres different speed
Two different distance different speed .
Same tyres same distance same speed .
Your example above is of two different speed .

My example is of two different actual speeds but the same speedometer speeds

abes:


My example is of two different actual speeds but the same speedometer speeds

TWO DIFFERENT TYRE SIZE CANNOT GIVE SAME SPEED READINGS,YOU SAID SO YOURSELF.
What we are talking here is same speed.This is where you are getting it wrong, A jet bomber traveling @60mph will get to a village 60 miles away in 1 hrs
A car traveling @ 60 mph will get to a village 60 miles away in same 1 hour.
Reason they are both traveling at same speed ie 60mph

abes:


My example is of two different actual speeds but the same speedometer speeds

The actual speed of a car which is not constant can only be measured by an external device hence speed guns and speed cameras have tolerance of about + or - 2/3.
The speed of a car is variable cos it depends on so many factors hence for the case of research we use Average speed instead.

erico2k2:

TWO DIFFERENT TYRE SIZE CANNOT GIVE SAME SPEED READINGS,YOU SAID SO YOURSELF.
What we are talking here is same speed.This is where you are getting it wrong, A jet bomber traveling @60mph will get to a village 60 miles away in 1 hrs
A car traveling @ 60 mph will get to a village 60 miles away in same 1 hour.
Reason they are both traveling at same speed ie 60mph

Maybe you don't understand what I'm trying to prove with respect to No 4 of the OP myth list.
According to No 4 myth, two cars can never overtake one another as long as they are doing the same km/h (speedometer km/h).
My argument is that is true as long as both cars still has their stock parts especially the tyres.
But if one of the cars has its tyres changed to a bigger ones then the car with bigger tyres will be faster than the car with stock/original tyres despite the same speedometer km/h.

Check this site http://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/speedometer4.htm

http://www.tyresizecalculator.com/tyre-wheel-calculators/speedo-error-calculator

Also research on effects of Tyre size on speedometer, check Google.

Have a nice day/night