Big Bore Tubeless Valves

Big Bore tubeless valves from Muc-Off, an end to Presta valve headaches?

Kudos to the Presta valve! It’s been around for over a hundred years and served us well. However times they are a changing, as someone once said. In this case the change is the switch to tubeless and sealant. While the clever little Presta valve worked well when we were running inner tubes and narrow rims, tubeless throws up challenges that Presta struggles with. Big Bore valves from Muc-Off are one of many options that seek to solve the problems.

What’s the problem?

Firstly there is the narrow stem. While this makes it easier to fit narrow road rims – which are now much wider – the internal diameter restricts the air flow. That’s not a problem when all you’re doing is pumping up an inner-tube. The air just has to fill the closed volume of the inner-tube. Fast or slow, it doesn’t matter, the air can’t go anywhere but into the tube.

When you’re trying to seat a tubeless tyre however, it’s a different matter. While some tyres will inflate with just a normal track-pump, most need an initial burst of air. This usually comes from a booster and the sudden rush of air pops the tyre into place. However the Presta valve’s narrow internal diameter can make this a bit of a hit or miss affair. The situation can be resolved by removing the core first, allowing the air unimpeded flow. You then perform a quick sleight-of-hand to pop the valve back in: hopefully without losing too much air.

Secondly there is sealant, which sloshes around inside your tyre waiting for the inevitable puncture. Sealant has to be added before installing the tyre, as it can’t be inserted through the valve. Once in the tyre the sealant fills any hole it can find and the Presta valve is basically a hole. Sealant finds its way into the valve, clogging up the tiny clearances, eventually rendering it useless. So what to do?

Step forward the Big Bore valve!

Muc-Off took a look at this problem and have come up with their solution. They already had their own Presta valves, which have a few features to help with tubeless set-ups, but they wanted to solve the Presta problem. The Big Bore valve does away with the clever, but fiddly Presta core and replaces it. In place of tiny springs and washers, there’s just a simple ball valve. Turn the lever 90 degrees and the valve goes from closed to open. It’s simple to operate and can be disassembled, if that’s your thing!

While the valve’s stem is that same external diameter as a traditional Presta one, it’s the inside that makes the difference. Removing the valve core, with its tiny clearances, means the air-flow is unrestricted. Open the valve and the air can rush straight through. Muc-Off claims Big Bore “offers up to 230% higher air flow than traditional Presta valves thanks to the straight through bore design.” This should make seating your tubeless tyre much simpler. I’ve had tyres that required multiple attempts to seat, this could make life so much simpler.

It’s not just getting the air in that should be easier with Big Bore either. That straight through design looks like it will make adding or removing sealant a breeze. With nothing blocking the valve, sealant should just flow straight though the stem. The valve’s outlet has holes on the side as well as the end, so running a tyre insert won’t obstruct it. Removing sealant can also be done – if you have a compatible syringe – through the valve. Although I would imagine that will depend on the sealant, some brands will clog a syringe’s pipette.

Some details

The Big Bore valves come in three types, Light, Hybrid and Ludicrous.

LITE: Fitment: Presta Pump | Presta Rim | 230% Airflow vs Presta Valves

HYBRID: Fitment: Schrader Pump | Presta Rim | 254% Airflow vs Presta Valves

LUDICROUS: Fitment: Schrader Pump | Schrader Rim | 264% Airflow vs Presta Valves

Lite and Hybrid come in four sizes and six colours, while we’re waiting to hear about Ludicrous. Big Bore valves are made entirely from 7075 aluminium apart from the valve, which is stainless steel. Included in the pack are spare O-rings, a choice of rubber bases and a plastic spanner. Currently priced at £30 for a pair.

I’ll be trying out the Big Bore valves and will record a video in which, hopefully, we’ll see just how much easier these new valves make tubeless installation! Check them out on the Muc-Off website.