Muc-Off Big Bore tubeless valves replace the usual Presta core with a straight through bore and a lever operated ball valve. This is the 35 mm (medium) length.

What it's for

A standard Presta valve has a small core that restricts airflow and clogs with dried sealant. Big Bore valves have no core. Air passes straight through the stem, which helps seat tubeless tires, and you can pour sealant in through the open valve. Muc-Off claims up to 230% more airflow than a Presta valve for the Big Bore Lite and 254% for the Big Bore Hybrid.

How it works

Ball valve: a stainless steel ball valve inside the head opens and closes the airway. There is no valve core to remove or clog

Lever: turn the lever to open or close the valve. The arrow on the lever shows the position, and arrow pointing up means closed. You can crack it open to let out small amounts of air

Serviceable: the valve can be taken apart and serviced

Compatibility

• Pumps: the Big Bore Lite head works with Presta pump heads. The Big Bore Hybrid head works with Schrader pump heads
• Rim shapes: several rubber bases are included. Use the round base for a curved rim bed and the square base for a square rim bed

Sizing and fit

• This size: 35 mm, which Muc-Off calls Medium
• Other lengths Muc-Off makes: 30 mm, 45 mm, 60 mm, 70 mm, 80 mm
• How to check yours: measure the vertical distance from the spoke hole side of the rim to where the tire meets the rim. Enough threaded stem must stick out of the rim to hold the O ring, the lock ring, and the top half of the valve

Setup and installation

• Step 1: remove the ball valve body, cap, lock ring, and O ring from the stem
• Step 2: pick the rubber base that matches your rim bed
• Step 3: push the stem through the valve hole in the rim
• Step 4: slide the O ring down the stem to the rim
• Step 5: thread on the lock ring and the valve body. Use the 4 mm hex key and the supplied spanner
• Step 6: press down on the valve base inside the rim while tightening the lock ring, until the O ring squashes out slightly
• Step 7: turn the lever to open, then add sealant and inflate

Specs

• Length: 35 mm
• Body: CNC machined 7075 aluminum
• Ball valve: stainless steel
• Colors here: Blue or Iridescent

In the box

• Big Bore valve stems
• 4 mm hex key
• Spanner for tightening
• Rubber bases and O rings for different rim shapes

You will also need

• Tubeless rim tape
• Tubeless sealant
• OMG's bike shop can install valves and set up tubeless tires