The world's first belt-driven collapsible bicycle

Bridgestone Picnica

Very cool. Japanese market does see many interesting innovations coming and going with various degrees of practicality.

Interesting. But … “the world’s first belt-driven collapsible bicycle”? Excuse me?? Or is this an old (like 25 years old) advertisement?

Yes, these are catalogues of 1985 and 1990:

And what we can’t see. under that crankwheel guard, is the incredibly clever Bridgestone automatic tensioner that ensures the harder you pedal, the tighter the tension. No cog-slipping possible and a long, long belt and sprocket life!

I know, because I have a Bridgestone Lacrosse commuter bike as well as my cool neon-green Strida. if only…

Oh well.

cheers, Minkair.

PS Anyone who wants some light bedtime reading, I have the Bridgestone patent.

Here’s how that Bridgestone automatic belt tensioner works (the picture is from my full-size 27" wheel Lacrosse commuter bike, but they’ve used the same idea for 25 years in Japan):

Notice the teeth engagement point (internal geared crankwheel) is approximately North West on the compass dial. As more tension is applied through the pedals, say riding at slow speed uphill, the teeth engagement point swings around automatically to the East, thus tightening the slack side of the belt and completely preventing skipping or cogging of the belt. Most of the time the belt runs slack for long life. Brilliant!

I have 8,400 miles on my original Bridgestone belt, rear pulley, front crankwheel assembly, with no apparent wear and still silky-smooth operation. The front pulley/gears are plastic, the rear pulley metal - a winning combination. The front pulley/gears are all protected from dirt by a cover and rubber gland, removed in the photo.

Surely having an extra gear will reduce the efficiency, and having the belt in tension whenever it is powered will do the same ??

I think a snubber which only contacts the back of the belt to prevent skipping in extremes is better {as used on Strida} because for the majority of time the belt is running at a relatively low tension - which is most efficient and avoids high forces on bearings etc.

Hi Guest.

I may have confused you with my description. By the way, there is a typo in it - ‘North West’ should have read ‘North East’.

The Bridgestone runs slack 95% of the time when pedaling, it only ‘tightens up’ under extreme hill pedaling or standing start acceleration - when you need that extra tension to prevent skipping. You set the belt loose on the bike, it’s not critical at all. Millions of commuter bikes are running around Tokyo right now with this design.

As to how well it works - I think 8,400 miles commuting with no visible wear on the drive train or bearings says it all…

You are probably right that there is a few % efficiency loss from the extra internal gear - that is a small price to pay for never having to buy replacement rear pulleys or belts at $90 a pair.


My wife just brought one of these home from the flee market. Nice little bike, clever design.