Back in the Olden Days, people used to ride with huge 1" (25.4 mm) pitch chains, and 3/16" (4.8 mm) wide sprocket teeth.

As time went on and materials improved, by the 1940s, most bikes converted to 1/2" (12.7 mm) pitch chain, with 1/8" (3.2 mm) thick sprockets. When the first "10 speed" bikes appeared, in the late 1950s, with 5 sprockets in back, chains and sprockets were thinned to 3/32" (2.4 mm) but they stuck to the 1/2" pitch dimension.

In the early 1980s, Shimano tried to introduce a slightly smaller 0.3937 pitch chain (10 mm) but nobody wanted that metric junk, and it really wasn't that much smaller anyway.

That was all back before anybody who matters was even born, and now it's time for the first 21st century drive train: "Nanodrive/Quarter-Twenty". This new modern universal standard cuts every dimension of a traditional chain in half! 1/4" (6.35 mm) pitch, with sprockets just 3/64" (1.19 mm) thick. In addition to cutting the weight of your chain and chainwheels in half, it also lets you fit twice as many sprockets as the old fashioned systems!

Real mountain bikers don't need any more than the present standard 27 speeds, but can greatly benefit from improved ground clearance and reduced weight.

That's why Rivendell Bicycles chose Nanodrive for their new flagship Downhill model, shown above.

The Nanodrive MTB system sticks with 9 sprockets in back, 3 in front, because extensive research has proven that this as many as the human brain is capable of comprehending, and not everybody can even do that many.

As you can see on the latest Rivendell downhill model, Nanodrive makes a huge improvement in chainring clearance, allowing the skillful rider to jump even bigger logs without fear of damaging expensive chainrings. In addition, the narrower width of the NanoNine (TM) drivetrain permits wider hub flange spacing and thus increases the bulletproofness of your wheels.

Although the new system has 20 rear sprockets instead of only 10, they fit in the same space, since everything is half the thickness of the old junk! Thus, they'll work with any standard frame.

The only parts you need to replace are the rear wheel, the front derailer, the rear derailer, the cassette, the crankset and chainrings, and the shifters! Nothing to it!

You may wonder what effect the smaller size will have on chain and sprocket wear...? Glad you asked!

Nanodrive is a revolutionary new high performance system, and we do mean system. For correct results you must use all genuine Nanodrive parts, and only genuine Nanodrive parts. You'll find Nanodrive provides the smoothest riding, smoothest shifting you've ever experienced, with a unique combination of stiffness and suppleness, high performance and low weight.

We're sure you'll be delighted with the Nanodrive, and that's why we offer our unique Nano-guarantee!* .

Typical old-fashioned road gearing would feature two chainrings, 53 and 39 tooth, and a rear cassette of 11-12-13-14-15-16-17-18-19-21 teeth. Here are the Gain Ratios of this typical gear setup:

	11	12	13	14	15	16	17	18	19	21
53	9.5	8.7	8.0	7.5	7.0	6.5	6.1	5.8	5.5	5.0
39	7.0	6.4	5.9	5.5	5.1	4.8	4.5	4.3	4.0	3.7

Now there are a couple of problems with a setup like that. First of all, the jumps are too big--look at the huge gap between the 11 and 12! The 12-13 jump isn't much better.

In addition, the gear range is too limited. You really don't want to go any smaller than 11 teeth for smooth pedaling, and only weaklings need a sprocket as big as 21.

This system doesn't have even one gear as high as a 10 Gain Ratio. Now, take a look at a typical "Quarter Twenty" Nanodrive drive setup:

Note that the 106 and 78 tooth chainrings are exactly equivalent to 53 & 39 respectively. The 17 tooth sprocket is equivalent to an 8 1/2 tooth sprocket for old-fashioned 1/2" chain, and the 36 tooth is equivalent to an 18.

In addition to giving much tighter spacing, this gives you 5 whole gears above the pitiful 53/11 top gear on the old system from the last century!