First of all, you don't need those PHP echo commands... you are already inside a PHP block.
As far as getting it to work, you will need to concatenate the result because remember that PHP does not like quotes around numbers. To simplify the code within the redirect, I actually like to store the database result in a separate variable like this:
$idnumber = $row_rsProducts['Rims_RimID'];
$WA_redirectURL = "AddWheelOptions.php?Rims_RimID=".$idnumber."";
The period is the concatenation operator and means to combine the strings that are separated by it, processing each concatenated element individually before combining. This is important because it allows for numbers to remain numbers rather than text strings.
You could just concatenate the recordset result in the same place if you don't want to store it as a separate variable.