Case you can't change the less variables, you can also override the bootstrap classes after 768px(smartphone bounder). Bellow is the working code that overrides basic navbars with dropdown menus. Not all classes are overriden bellow, so depending on what you are using, you may need to override other classes.
@media (min-width: 768px){
.navbar-nav .open .dropdown-menu {
position: static;
float: none;
width: auto;
margin-top: 0;
background-color: transparent;
border: 0;
-webkit-box-shadow: none;
box-shadow: none;
}
.navbar-nav .open .dropdown-menu > li > a {
line-height: 20px;
}
.navbar-nav .open .dropdown-menu > li > a,
.navbar-nav .open .dropdown-menu .dropdown-header {
padding: 5px 15px 5px 25px;
}
.dropdown-menu > li > a {
display: block;
padding: 3px 20px;
clear: both;
font-weight: normal;
line-height: 1.42857143;
color: #333;
white-space: nowrap;
}
.navbar-header {
float: none;
}
.navbar-toggle {
display: block;
}
.navbar-collapse {
border-top: 1px solid transparent;
box-shadow: inset 0 1px 0 rgba(255,255,255,0.1);
}
.navbar-collapse.collapse {
display: none!important;
}
.navbar-nav {
float: none!important;
/*margin: 7.5px -15px;*/
margin: 7.5px 50px 7.5px -15px
}
.navbar-nav>li {
float: none;
}
.navbar-nav>li>a {
padding-top: 10px;
padding-bottom: 10px;
}
.navbar-text {
float: none;
margin: 15px 0;
}
/* since 3.1.0 */
.navbar-collapse.collapse.in {
display: block!important;
}
.collapsing {
overflow: hidden!important;
}
}
click here for the live demo code