// JavaScript Document

			var g_StartOfFormElements = 9;
			
			function autoTab(input, len)
			{
				if(isNaN(Number(input.value)))
				{
					input.value = input.value.slice(0,-1);
					alert("Please enter numbers only");
				}
				
				else
				{
					if(input.value.length < len)
						return true;
						
					else if(input.value.length > len)
					{
						alert("Please enter " + len + " numbers in this field.");
						input.value = "";
					}
					
					else
					{
						var inputIndex = getIndex(input);
						
						if((inputIndex + 1) > input.form.length)
							inputIndex = g_StartOfFormElements;
						else
							input.form[inputIndex+ 1].focus();
					}
				}
			}
			
			function getIndex(input)
			{
				for(var i = 0;  i<input.form.length; i++)
				{
					if(input.form[i] == input)
						return i;
				}
				return g_StartOfFormElements;
			}
			
			function roundToTires(n)
			{
				var tires = n * 100;
				tires = Math.round(tires);
				strTires = " " + tires;
				len = strTires.length
			}
			
			function getdiameter(form)  
			{	
				var ommwidth = parseFloat(form.origwidth.value)
				if (isNaN(ommwidth))
					{ommwidth = 0};	
			
				var oratio = parseFloat (form.origratio.value)
				if (isNaN(oratio))
					{oratio = 82};	
			
				var oirim = parseFloat (form.orim.value)
				if (isNaN(oirim))
					{oirim = 0};
			
				var ospdread = parseFloat (form.ospeed.options[form.ospeed.selectedIndex].value)
				if (isNaN(ospdread))
					{ospdread = 0};
				
				var ammwidth = parseFloat (form.alterwidth.value)
				if (isNaN(ammwidth))
					{ammwidth = 0};		
			
				var aratio = parseFloat(form.alterratio.value)
				if (isNaN(aratio))
					{aratio = 82};		
			
				var airim = parseFloat(form.arim.value);
				if (isNaN(airim))
					{airim = 0};	
			
				var oinchwidth = ommwidth/25.4;
				
				if(ammwidth !=0)     
				var ainchwidth = ammwidth/25.4;  
				
			
				
				oinsidew = oinchwidth * oratio/100 ;
				roundToTires(oinsidew); 
				form.OINSideWall.value = strTires.substring(0, len - 2) + "." + strTires.substring(len - 2, len);
			
				roundToTires(oinchwidth); 
				form.OINTireWidth.value = strTires.substring(0, len - 2) + "." + strTires.substring(len - 2, len);
			
				ointired = oinsidew * 2 + oirim;
				roundToTires(ointired); 
				form.OINTireDia.value  = strTires.substring(0, len - 2) + "." + 	strTires.substring(len - 2, len); 	
				
				oinradius = oinsidew + oirim / 2;	
				roundToTires(oinradius); 
				form.OINTireRad.value = strTires.substring(0, len - 2) + "." + 	strTires.substring(len - 2, len); 	
					
				ointirec = (oinradius * 2) * Math.PI;
				roundToTires(ointirec); 
				form.OINTireCir.value = strTires.substring(0, len - 2) + "." + strTires.substring(len- 2, len); 	
					
				orevpermile = 20800 / form.OINTireDia.value;	
				if (isNaN(orevpermile))
					{orevpermile = 0};		
			
				roundToTires(orevpermile); 
				form.OREVMile.value = strTires.substring(0, len - 2) + "." + strTires.substring(len- 2, len); 	
				
				orevperkm = 39346.56 / ointirec;	
				if (isNaN(orevperkm))
					{orevperkm = 0};		
			
				roundToTires(orevperkm); 
				form.OREVkm.value = strTires.substring(0, len - 2) + "." + strTires.substring(len- 2, len); 
				
				form.ASPERead.value = form.ospeed.value;		
			
				
				if(ammwidth !=0) 
				{
					ainsidew = ainchwidth * aratio/100 ;
					roundToTires(ainsidew);
					form.AINSideWall.value = strTires.substring(0, len - 2) + "." + strTires.substring(len - 2, len); 
				
					roundToTires(ainchwidth);
					form.AINTireWidth.value = strTires.substring(0, len - 2) + "." + strTires.substring(len - 2, len); 
				
					aintired = ainsidew * 2 + airim;
					roundToTires(aintired);
					form.AINTireDia.value = strTires.substring(0, len - 2) + "." + strTires.substring(len- 2, len); 
				
					ainradius = ainsidew + airim / 2;	
					roundToTires(ainradius); 
					form.AINTireRad.value = strTires.substring(0, len - 2) + "." + strTires.substring(len - 2, len); 	
				
					aintirec = (ainradius * 2) * (3.14159);
					roundToTires(aintirec); 
					form.AINTireCir.value = strTires.substring(0, len - 2) + "." + strTires.substring(len- 2, len); 	
				
					arevpermile = 20800 / form.AINTireDia.value;	
					
					if (isNaN(arevpermile))
						{arevpermile = 0};		
			
					roundToTires(arevpermile); 
					form.AREVMile.value = strTires.substring(0, len - 2) + "." + strTires.substring(len-2, len); 
			
					arevperkm = 39346.56 / aintirec;	
					
					if (isNaN(arevperkm))
						{arevperkm = 0};		
			
					roundToTires(arevperkm); 
					form.AREVkm.value = strTires.substring(0, len - 2) + "." + strTires.substring(len-2, len);
			
					aspeedread = (orevpermile / arevpermile) * (ospdread);	
					
					if (isNaN(aspeedread))
						{aspeedread = 0};	
			
					roundToTires(aspeedread); 
				form.ASPERead.value = strTires.substring(0, len - 2) + "." + strTires.substring(len - 2, len);  
				
					perctdiff = ((aintirec - ointirec) / ointirec) * 100; 
				
					if (isNaN(perctdiff))
						{perctdiff = 0};	
				
					roundToTires(perctdiff); 
				form.PERDiff.value = strTires.substring(0, len - 2) + "." + strTires.substring(len - 2, len); 
			
					diffside = ((form.AINSideWall.value) - (form.OINSideWall.value));
					roundToTires(diffside); 
					form.DIFFside.value  = strTires.substring(0, len - 2) + "." + 	strTires.substring(len - 2, len); 			
				  
					if (0<(diffside))
						{diffside = diffside + "+"};		
			
					diffsect = ((form.AINTireWidth.value) - (form.OINTireWidth.value));
					roundToTires(diffsect); 
					form.DIFFsect.value  = strTires.substring(0, len - 2) + "." + 	strTires.substring(len - 2, len); 			
				  
					if (0<(diffsect))
						{diffsect = diffsect + "+"};	
							
					diffdia = ((form.AINTireDia.value) - (form.OINTireDia.value));
					roundToTires(diffdia); 
					form.DIFFdia.value  = strTires.substring(0, len - 2) + "." + 	strTires.substring(len - 2, len); 			
				  
					if (0<(diffdia))
						{diffdia = diffdia + "+"};			
					
					diffcir = ((form.AINTireCir.value) - (form.OINTireCir.value));
					roundToTires(diffcir); 
					form.DIFFcir.value  = strTires.substring(0, len - 2) + "." + 	strTires.substring(len - 2, len); 			
				  
					if (0<(diffcir))
						{diffcir = diffcir + "+"};				
			
					diffrev = ((form.AREVMile.value) - (form.OREVMile.value));
					roundToTires(diffrev); 
					form.DIFFrev.value  = strTires.substring(0, len - 2) + "." + 	strTires.substring(len - 2, len); 			
				  
					if (0<(diffrev))
						{diffrev = diffrev + "+"};						
				}		
			}