kinda a math question

[ghosthunter]

What is the approx. RPM of a car's wheel travelling at 100KPH?

Wheel size 15 inch mags with 195/55/15 tires.

[mbt]

what's the equivalent overall diameter of a 195/55/15 wheel and tire?

[the_wildthing]

Hmmm...If we assume 100Km/h is the "true" speed, and not just what the speedometer shows, which is sometimes inaccurate, and we assume also that the 195/55/15 is inflated to make the radius of the tire precisely the ff:

195mm x 0.55 = 107.25mm
Diameter of rim: 15in x 25.4mm = 381mm
Diameter of wheel: 381mm + (107.25mm x 2)= 595.5mm
Circumference of wheel: 595.5mm x 3.1416 = 1870.82mm approx.

Now, 100km/h means the car is travelling 100,000,000mm per hour.

So the car is travelling 100,000,000mm / 60 = 1,666,666.67mm per minute.

1,666,666.67mm / 1870.82mm = 890.87 revolutions per minute, assuming a relatively smooth surface and a straight line. We all know that when turning, outer wheels travel farther than the inner wheels, hence more turns. Also, going over bumps or potholes may affect wheel spin.

Of course, I am not a math wizard so the above computation could be wrong.

[mbt]

tama na siguro yan hehehehe :bwahaha:

[baiskee]

Originally posted by mbt
tama na siguro yan hehehehe :bwahaha:

hahaha...naalala ko yung prof ko na tamad mag-check.

[flakez]

hahaha.

hanggat wala pang mas matiyaga kay wildthing tama na yan. hehehe

[mbt]

teka, ano ibig sabihin nung 25.4 mm sa "diameter of rim"? hehe

hindi ba dapat, 15 inches x (300 mm/12 inches) = 375 mm ?

[the_wildthing]

1 inch = 2.54 cm = 25.4 mm, di ba?

[JAYarc]

may nakalimutan pa kayuuu hehe Tranny ratio pa..hehe
>>

kakatamad tignan yung figure!

paro sakin 195/55/15 60mph*sub2000rpm

[ghosthunter]

Originally posted by the_wildthing
Hmmm...If we assume 100Km/h is the "true" speed, and not just what the speedometer shows, which is sometimes inaccurate, and we assume also that the 195/55/15 is inflated to make the radius of the tire precisely the ff:

195mm x 0.55 = 107.25mm
Diameter of rim: 15in x 25.4mm = 381mm
Diameter of wheel: 381mm + (107.25mm x 2)= 595.5mm
Circumference of wheel: 595.5mm x 3.1416 = 1870.82mm approx.

Now, 100km/h means the car is travelling 100,000,000mm per hour.

So the car is travelling 100,000,000mm / 60 = 1,666,666.67mm per minute.

1,666,666.67mm / 1870.82mm = 890.87 revolutions per minute, assuming a relatively smooth surface and a straight line. We all know that when turning, outer wheels travel farther than the inner wheels, hence more turns. Also, going over bumps or potholes may affect wheel spin.

Of course, I am not a math wizard so the above computation could be wrong.

Thanks for the compute... I need to verify something kasi.

[109]

890.8756958920456
tama nga si wildthing, nahilo pa ko pagcompute :bwahaha:

JAYarc, what's about tranny ratio?

[cyclone]

imho lang. parang mababa ang 890.87 rpm.
for me i can't run my car up to 100kph without
getting over 1000 rpm. try ninyo kaya in
actual and give your feedback.

[conzky]

sir the_wildthing:

your computation is correct.very well done.

[jim]

galing ni sir wild hehehehe. sir cyclone yung computation ni sir wild based sa 'ideal' situation. syempre pag may external elements (friction, air pressure sa tire, wind force, etc.) na involved gaya sa 'actual' tataas yung rpm value......

[the_wildthing]

Cyclone and JayArc,

I think what ghosthunter is asking is RPM of the wheel and not the engine, hence tranny ratio is not a factor. And yes, at 5th gear, in most cars at least, engine crank will be turning more than 2000RPM at 100Km/h.

HTH.

BTW, the result is an approximate value also due to rounding (e.g. Pi can be 3.14 or 3.141592654), aside from other "real world" factors.

[cyclone]

wilthing, your right, question nga is RPM of the
wheel, i mistook it for the tacometer RPM.

[ghosthunter]

yup... wheel rpm. I'm trying to do preliminary research on an idea that might be a very good product for us motorist.

Hint: it can save gas AND increase performance depending on how you drive.

[Ungas]

Hmmm... mukhang may kalaban na sa market si Alegre Exhaust.

[Kicker15]

ang complicated naman nung tanong

[kimpOy]

yan ang tsikoteers!!!