Advanced Custom Fields Filtering Relationships by Tax

I have the following code to list posts. But i need to filter them by a tax called scale. How would I add that to this code:

<div id="masonry-loop" >

			<?php 

			$posts = get_field('cars_under_this_group');

			if( $posts ): ?>
			    <?php foreach( $posts as $post): // variable must be called $post (IMPORTANT) ?>
			        <?php setup_postdata($post); ?>

			        <div class="masonry-entry small-6 columns singleGroup">
			        	<div style="background: #ffffff; border: 2px solid #333333; margin: 0 0 20px 0;">
					<?php 

					$posted = get_field('car_under_id');

					if( $posted ): ?>
						<div class="row">
						<?php foreach( $posted as $p ): // variable must NOT be called $post (IMPORTANT) ?>
						    <div class="small-6 columns">
						    	<a class="glow" href="<?php echo get_permalink( $p->ID ); ?>">
						    		<div class="productListThumb" style= "background:url(<?php the_field('thumb_image', $p->ID); ?>) no-repeat center 30%; display:inline-block; width: 100%; height: 155px; background-size: 97%; margin: 10px 0;"></div>
						    	</a>
						    </div>
						<?php endforeach; ?>
						</div>
					<?php endif; ?>
					<div class="row" style="padding: 0 30px 15px;">
						<h2 style="margin: 0;"><?php the_field('name_of_rcs'); ?></h2>
						<p style="margin: 0;"><b><?php the_field('detailed_title'); ?></b></p>
						<p style="margin: 0;"><?php
								$age = get_field('age_group');

								if( $age == '8+') {
									echo '<a href=" ' . get_site_url() . '/ages/8/">' . 'Ages: ' . $age . '</a>';
								} elseif ( $age == '6+') {
									echo '<a href=" ' . get_site_url() . '/ages/6/">' . 'Ages: ' . $age . '</a>';
								} elseif ( $age == '4+') {
									echo '<a href=" ' . get_site_url() . '/ages/4/">' . 'Ages: ' . $age . '</a>';
								} else {
									echo 'Ages: ' . $age;
								}
								?></p>
					</div>
				</div>
			        </div>
			    <?php endforeach; ?>
			    <?php wp_reset_postdata(); // IMPORTANT - reset the $post object so the rest of the page works correctly ?>
			<?php endif; ?>
		</div>