There are two reasons and it’s because of racecars.
99.99 percent of wheels only have one valve stem because that’s all any normal car owner will ever need. Tires lose a bit of air, fill them back up. But, did you know some wheels have two valve stems?
Wheels have two valve stems for two reasons. First, so you can pump in air with one valve stem and check tire pressures with an attached gauge on the other. And the second reason is to facilitate nitrogen air refilling, one valve stem is used for pumping nitrogen in while the other stem is purging regular air.
Enkei NT03s and simultaneously filling/checking
The most recognizable wheel design with two valve stems has to be the Enkei NT03+Ms.
The NT03 is a popular wheel in the import tuning crowd with a functional design. From 20 feet, the perimeter brace ring, used for wheel strength and to resist deformation, makes them easily recognizable.
More importantly, they have “a racing twin valve design which allows for accurate monitoring while adjusting pressure.” The valve stem holes are right next to each other allowing for both checking and monitoring closely.
Youtuber Evan Shanks demonstrates this pretty well.
Kosei K1 TSs and Nitrogen refilling
Kosei K1 wheels also have two valve stems but with a different design approach and purpose.
The valve stems on K1’s are on the opposite side of each other.
Nitrogen air is widely used in racing because it’s much more stable and not prone to rises in heat during demanding race conditions.
According to TireRack,
The two valve stems help in exchanging ambient air for nitrogen. One stem is used to bleed off the ambient air while nitrogen is put in the opposite stem.
The look was so popular in Japan, Kosei transferred it to their consumer wheels.
Furthermore, Kosei says they designed their K1 TSs with twin valves for “quick access and easy refilling.” Nitrogen aside, even if you were refilling with regular air, having one valve stem close to another makes air refilling that much easier.
It just looks cool
Kosei admits the only reason they installed a twin valve system on their K1 TSs is because customers liked the look. Sometimes people buy things so they stick out and can explain to strangers or friends why their wheels have 100 percent more valve stems.
It’s a flex.
Sure, you can go on and on why they’re functional but normal car enthusiasts aren’t going to go through the trouble of simultaneously checking and refilling or working out how to fill nitrogen while purging air.
Besides, popular nitrogen refilling methods, like Nitrofill, are a set-it-and-forget-it type system using only one valve stem. Computers monitor nitrogen levels and automatically purge through the same valve stem.
Do you have wheels with twin air valves? Let me know in the comments below.