Tunnel Finger Caliper - For Rear Shock Sag in Tunnel Frames

Okay, let’s be honest. This thing kind of looks like a small piece of junk plastic but it’s the best way we’ve found to measure sag inside frames with tunnel-mounted shocks (like the new Rocky Mountain Altitude, Santa Cruz (VPP), or Forbidden bikes). It’s thin, long, and does the job.

Yes, it's the picture is on a normal bike that doesn't need it. I didn't find a bike to take a picture on yet. To be continued!

What It Does

• Slides inside tight shock tunnels to measure the gap between the damper body and bumper or sag clip
• Helps when no other tool (or your fingers) can reach
• Mostly useful on air shocks

Real Talk

Yeah, it’s a small plastic stick. It’s not impressive, but it works and it’s cheap. If you lose it, break it, or sit on it by accident, you won’t cry. You’re probably only going to use this once anyway, unless you constantly check your sag and lets be real, just have fun on your bike, don't think about this too much.

For many bikes, especially with coil shocks, we honestly recommend just eyeballing sag with your bumper, or even shoving a strip of cardboard in there, that works surprisingly well too. Most people underestimate how much sag they actually have anyway, so try to double-check from multiple angles if you're unsure.

Best Practices

• Push the bumper up before sitting on the bike
• Get into riding position, let the suspension settle, then measure the gap
• Compare with stroke length to get sag%
  
• Use Wheel Sag Calculator to get the correct % for your setup

Compatible With

• Bikes with tunnel-style shock mounts (e.g., Rocky Mountain Altitude, Santa Cruz, Forbidden)
• All brands of rear shocks: Fox, Öhlins, EXT, DVO, Cane Creek, Push, etc.