How do I get the loose rear derailleur cable tighter on my road bike?

find the 'adjuster' [[not the main cable screw]] make it LOOSE before you get cable tight \ \ttighten the cable same as b4 now the adjuster increases tension more [[note-the rear will b e slack on smallest cog]] wle

You want to shift to the smallest gear on the back. Turn the barrel adjuster in all the way. Loosen the cable clamp, pull the cable tight and re tighten the clamp. That should do it except for some fine tuning with the barrel adjuster. The best way to clean the cable is to put the chain on the largest rear sprocket. Now without pedaling shift to the smallest gear. That will give you enough slack to pull the cable housing out and and wipe down the cable. Moving the housing around you can clean the whole cable. While you are at it clean the cable guide that is under the bottom bracket. I like to put grease on the guide to keep dirt out and lube the cable. I like to use Triflow on the cable and derailer pivot points. It should shift better then new.