function compute(form)
{
if (form.dt.value<6.0 ||form.dt.value>22)
{       form.dt.value="Gear Not Available";}
if (form.ar.value<2.00||form.ar.value>9.99)
{       form.ar.value="Gear Not Available";}
if (form.td.value<10.0||form.td.value>99.0)
{       form.td.value="Gear Not Available";}
if (form.sr.value<900||form.sr.value>1100)
{       form.sr.value="Gear Not Available";} 
calc = ((form.dt.value * form.ar.value * 20168) / (form.td.value * form.sr.value));
if (form.td.value==0)
{       form.dn.value="Gear Not Available";}
if (form.dn.value>45.0)
{       form.dn.value="Gear Not Available";}
form.dn.value = Math.round(calc)
return;
}
function clear(form)
{
form.dt.value = "";
form.ar.value = "";
form.td.value = "";
form.dn.value = "";
}
 
function findheight0(form)
   {
   //return formatvalue(parseFloat(form.widthmm0.value / 25.4 * form.aspect0.value / 100 * 2) + parseFloat(form.diameter0.value), form.rsize);
   formatvalue(parseFloat(form.widthmm0.value / 25.4 * form.aspect0.value / 100 * 2) + parseFloat(form.diameter0.value), 5);
   }
   
function formatvalue(input, rsize)
   {
   var invalid = "**************************";
   var nines   = "999999999999999999999999";
   var strin   = "" + input;
   var fltin   = parseFloat(strin);
   if (strin.length <= rsize) return strin;
   if (strin.indexOf("e") != -1 || fltin > parseFloat(nines.substring(0,rsize)+".4")) return invalid.substring(0, rsize);
   var rounded = "" + (fltin + (fltin - parseFloat(strin.substring(0, rsize))));
   document.tire.height1.value = rounded.substring(0,rsize);
   //return rounded.substring(0, rsize);
   
   }
function clearform(form, x)
   {
if(x==0)
      {
      form.widthmm0.value  = "";
      form.aspect0.value   = "";
      form.diameter0.value = "";
      form.height0.value   = "";
      }
 }
function clearvalue(name)
   {
   name.value="";
   }
   
function update(form, x)
   {
   if (x==0)
      {
      //form.height0.value = findheight0(form);
	  findheight0(form);
      }
  }

<!-- set conversion factors for each item in form.
document.forms[0].rsize  = 5;  // rounding size, use same as size
 -->