On most full suspension mountain bikes, the rear shock sits between the swingarm and the main wishbone, with eyelet connectors at each end. The Datum bike is different and supposedly better, however, in that its rear shock slips in the upper frame tube.
Created by Californian bicycle designer Tim Lane, the Aluminum Frame Datum is manufactured by his company Digit Bikes. It was the subject of a successful Kickstarter campaign in August and is now on Indiegogo to raise additional production funds.
As mentioned, its big distinguishing feature is its patented analog rear suspension, in which the front end of the air shock absorber slides into the open rear end of the top tube. According to Lane, this design has several advantages.
First of all, it uses far fewer pivots (and therefore fewer linkages, bearings, and axles) than traditional rear suspension systems. This means that it weighs around 200-600 grams less, offers more room on the frame for things like water bottles, incorporates fewer parts that are likely to wear out and fall out. failure, and its chassis is stiffer – again, that’s because there are fewer suspension components to flex.
Plus, the Datum’s long, straight seat tube can accommodate longer seatposts than many other full suspension mountain bikes.
And most importantly, because its rear shock is about the full length of the top tube to work with, it can be much longer (over 12 inches / 305mm) than a shock that is constrained by pivot points to each end. This translates to 140mm of rear travel which would be much smoother and predictable than that of conventional shorter shocks.
The Datum bike is currently offered as a frame only, the final version of which is expected to weigh around 7.25 lbs (3.3 kg) in a Large size. A pledge of US $ 3,150 will get you one, assuming it reaches production. The expected retail price is $ 4,000.
Lane explains the attributes of the Analog suspension system in more detail, in the following video.
Video of the DigitBikes Kickstarter campaign