rolling radius.... yes i'm bored

[dummi]

just trying to work out errors for the speedo if they would be significant finding the following

1741.7 mm rolling radius @ 225/40/18
1791.96mm rolling radius @ 245/40/18
1714.99mm rolling radius @ 245/35/18

225/40/18 said to be commonly used as stock, use 245/40/18 as an upgrade


100 kph @ + 50mm

+ 3.1mph @ 62mph

+ 3.49 mph @ 70mph

not sure if thats correct but if it is not a lot in it

 

[AndyMac]

It's more to do with the gearing rather than speedo accuracy

 

[imported_VaulterTim]

[ QUOTE ]
just trying to work out errors for the speedo if they would be significant finding the following

1741.7 mm rolling radius @ 225/40/18
1791.96mm rolling radius @ 245/40/18
1714.99mm rolling radius @ 245/35/18

225/40/18 said to be commonly used as stock, use 245/40/18 as an upgrade


100 kph @ + 50mm

+ 3.1mph @ 62mph

+ 3.49 mph @ 70mph

not sure if thats correct but if it is not a lot in it

[/ QUOTE ]


How did you you work out those rolling radii Dummi?

I make them as follows...

225/40 x 18" rolling radius - 637.2mm or 63.72cm or 24.88"
245/40 x 18" rolling radius - 653.2mm or 65.32cm or 25.72"
245/35 x 18 rolling radius - 628.7mm or 62.87cm or 24.75"

Maybe I'm wrong there but I can't see how an 18" wheel could have a rolling radius of 170-odd cm... or 60+ inches... that's 5 feet! /ubbthreads/images/graemlins/confused.gif

Are the wheels on a monster truck? /ubbthreads/images/graemlins/wink.gif

T

P.S. Those figures are actually rolling 'diameter' since it is the total of two tyre sidewalls plus the height of the wheel... radii would obviously be half those figures...

 

[dummi]

lol yer that would be a bit silly, i think thats the circumference i worked out distance covered in 1 rotation then worked out % difference at 70mph in rotated distance at those rolling radii, i think, forget why i did it now though lol

 

[imported_VaulterTim]

/ubbthreads/images/graemlins/laugh_roll.gif

Absolute nutter!

I love it /ubbthreads/images/graemlins/grin.gif