Joined: Aug 2009
Posts: 7,699
Likes: 4,066
From: Berkeley, CA
Bikes: 72 Cilo Pacer, 72 Gitane GT, 72 Peugeot PX10, 73 Speedwell Ti,l, 75 Peugeot PR-10L, 80 Colnago Super, 81 Zinn, 85 ALAN Cross, 85 De Rosa Pro, 86 Look 753, 86 Look KG86, 89 Parkpre Team, 90 Parkpre Team MTB, 90 Merlin
That tab (also sometimes referred to as a "horn") is there to help guide the rear wheel/hub into the dropout. Also provides a place for your fingers when aligning the rear wheel. Info gleamed from esteemed forum member verktyg:
https://www.flickr.com/photos/28267220@N05/4675436497/
Last edited by gaucho777; 09-03-14 at 01:24 PM.