Old thread, and I'm the last poster...but have a question on this.

I have some older Shimano 105 9-speed shifters on one of my bikes, paired with some Tektro RX-5 v brakes, which have 85 mm arms. After I originally built the bike up, I added fenders. The problem is that when I pull the brakes, the pivot piece where the brake cable enters and is secured (side opposite the anchor bolt) hit the fender, hangs up, and doesn't return. This causes the right pad to stay right on the rim.

I need brakes with a longer arm, but I'm not sure how I can tell which brakes will work with my levers, without any add-on gadgets required. Looks like the Tektro RX-6s have 90 mm arms, but I'm not sure 5 mm will be enough to raise the cable enough to properly avoid the fender top.

Is there a formula, or a chart, to assess brake lever/v brake compatibility? I think arms around ~100 mm will be enough to safely clear the fender, with Tektro M730s being 102 mm.

Thanks!!