The discussion is really about torque and thrust. Your engine has a torque curve that relates torque to RPM. This torque is multiplied by the gear train (transmission gear x ring and pinion ratio) and appears as a twisting force or torque at the axle. This torque is applied to the road through a moment arm which is the actual distance from the center of the axle to the ground. For the sake of example call this the rolling radius. For any given engine transmission differential instance the difference in torque with various wheels can be calculated as a percentage. This percentage is the difference between the rolling radii of the two wheels in question. EG: Wheel/tire 'A' has a 13inch rolling radius. Wheel/tire 'B' has a 15inch rolling radius. The reduction in thrust by the larger 'B' wheel over the smaller wheel 'A' is the ratio of the two radii or 13/15. FWIW this process also works for retarding force or braking. A larger wheel will lessen the braking force per unit pressure by a similar ratio. QED or something like that, rigorous proof is left as an excercise for those with too much time on their hands. A useful tool in the form of an MSExcel spreadsheet is available for posting to the Vanagon Yahoo group. Tim Smith is the original author. P |
Please note - During the past 17 years of operation, several gigabytes of
Vanagon mail messages have been archived. Searching the entire collection
will take up to five minutes to complete. Please be patient!
Return to the archives @ gerry.vanagon.com
The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.
Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.