carcentric
|
| posted on 24/3/06 at 11:12 PM |
|
|
Overall gearing change formula?
If you increase tire diameter from 25" to 26.25" (~5% difference), and
increase the ring(crown)/pinion ratio from 3.09:1 to 3.545:1 (~15% difference the other direction) . . .
. . . has the OVERALL GEARING been changed ~10% (TD percentage difference minus RP percentage difference)?
If not, what is the correct formula to determine overall gearing change?
Thanks.
[Edited on 24/3/06 by carcentric]
M D "Doc" Nugent
http://www.carcentric.com
|
|
|
|
|
Mark Allanson
|
| posted on 24/3/06 at 11:52 PM |
|
|
you make my head hurt
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
|
|
|
cossey
|
| posted on 25/3/06 at 12:15 AM |
|
|
speed will now be 91.5% of orginal speed if ive got my maths right ie (26.25/25)*(3.09/3.545)
|
|
|
carcentric
|
| posted on 25/3/06 at 12:23 AM |
|
|
quote:
Originally posted by cossey
speed will now be 91.5% of orginal speed if ive got my maths right ie (26.25/25)*(3.09/3.545)
That was what I thought at first, too, until I considered an example where tire diameter went UP 10% and r/p ratio went DOWN 10%. Using
multiplication, there would be a 1% overall change - but logic would tell me there'd be no change because one change would offset the other . .
. that's why I'm asking.
M D "Doc" Nugent
http://www.carcentric.com
|
|
|
cossey
|
| posted on 25/3/06 at 08:44 AM |
|
|
they dont offset each other and you would get a 1% change.
eg a 25" diameter wheel at 100rpm travels 25*pi*100 inches per minute =7854"/min
a 10% shorte diff means that the wheels for the same propshaft revs now only turn at 90rpm. 10% bigger wheels have a diameter of 27.5" so
27.5*pi*90=7775"/min
7775/7854=0.99 or 99%
|
|
|
