InstructionsOn the left is your tyre size. You can vary one of Width, Ratio, Rim Size, Squash or Circumference and the java applet will recalculate the item that you have checked. Typically, if you want to find a new tyre that has the same circumference as your current one. Put in the dimensions of your current tyre with the circumference box checked. Then check one of the other boxes so making the circumference constant and vary the other parameters.
The Squash is an adjustment for how the tyre's circumference is effected by the weight of the car on the tyre. Leave as 0 or adjust accordingly if you know the true circumference. Best way of doing this is to put in your tyre details. Go out and measure the true circumference of your tyre (put mark on tyre and ground, push car forward until tyre mark touches ground again, measure distance travelled (in inches)). Check the Squash box, enter your true circumference and the program will calculate your squash factor. Recheck the circumference to fix that factor.
Note that the squash algorithm is not realistic - it is currently implemented as a percentage to reduce the circumference by. It really depends on the structure/material of the tyre and is more related to the stiffness of tyre wall and how that deforms as the tyre sits on the road.
The Tyre Height and Wheel Revs per mile are just there for convenience - you cannot input them.
On the right you have a gearbox and the Miles per hour per thousand revs and the RPM and MPH as seen on the dash board. You also have an accelerator to vary the engine revs.
Select a gearbox and gear and then accelerate to the desired speed. Then choose a different gear. The speed will stay roughly the same and you will see how the revs would change.
This can be used to gauge the effectivenes of your gearbox for staying inside your power range. If you would like another gearbox put in just send me the ratios.
Any Questions/Suggestions - get back to me: Tony.Jewell@Cregganna.Com