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What To Do With The Japanese Bicycle Interior

A lot of Japanese surplus bicycles end up in the streets of Metro Manila. With these bicycles are interiors that are Japanese made. They are not Schrader nor Presta but they are simply called Japanese valves (some call it the Dunlop valve as well).

What To Do With The Japanese Bicycle Interior
photo cred: https://bikexchange.com/presta-vs-schrader-valves/

The Japanese interior is often called the Dunlop valve or Woods valve (from the inventor of the valve, CH Woods). A lot of bicycles from Japan still use this kind of interior so expect it to come along with a Japanese surplus bike.

Japanese Bicycles From Japan

We acquired a mini velo for it is perfect for my wife. It has 20 x 1 3/8 tires, mudguard, single speed, light and easy to pedal. It has a few rust spots here and there, but it works perfectly. It came with the Japanese interior so that was the challenge.

We got the bike in perfect working condition, all the brakes were working, bearings were well greased and it ran excellently. After storing it for a few weeks, we noticed that that the air in the interior escaped. I had a presta adaptor so I screwed it on the valve and put air into it. After pumping it up, the air would not hold inside and soon became deflated.

Why The Air Escapes From the Interior

I had to consult some of the Marikina Jap bikes Masters and found out about more about the Dunlop interiors. The inner core which held the air inside was wrapped by a tubular rubber which allowed air inside the interior when pumping. That same tubular rubber was also responsible for NOT letting the air escape from the interior.

What To Do With The Japanese Bicycle Interior
core of the Dunlop/Woods Interior. Must be wrapped with rubber

You pump air through the screw top area and the air passes through the small hole you see. You have to wear the tubular rubber on to the lower part of the core so that air goes in, but does not go out.

What To Do With The Japanese Bicycle Interior
the rubber holds the air in place inside the interior.

It’s simple right? Old school technology to hold air inside an interior. The problem is, the rubber deteriorates over time and disintegrates, (especially during summer days, due to heat) so you have to occasionally change the rubber lining of the core valve.

It is tricky to find that rubber inside, but you can order online a long stube and just cut it to size. They also include the rubber in patch kits which they sell in bicycle shops around the city.

What To Do With The Japanese Bicycle Interior
standard patch kit sold for less than 100 pesos. Please do not pay more than that!

Once you have inserted the rubber into the valve core, your interior is good as new. Since the tubular rubber is rare, one bike shop near us sells the rubber for 30 pesos! I can’t believe the mark up. But to pump air into the interior and get the bike back up and running, I had to pay.

Just assemble back the core into the interior, screw the holder and if your air pump cannot hold the Japanese valve, use an adaptor to pump air.

What To Do With The Japanese Bicycle Interior
core, screw and blue adaptor

Alternative To Changing the Rubber is…

Easy does it. If you do not like the hassle of changing the rubber once in a while, change the interior of your bicycle into the Schrader type of interior. Works fine, with no adaptors needed. That is the alternative solution in this Japanese interior puzzle.

We hope that helps, and always ride hard! Do not forget to wear a helmet.

Live life with balance!

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