Caution, this bike is no longer available: The Street Machine Gt recumbent with steel frame and rigid seat has been replaced by the Street Machine Gte. These pages are only online for archive purposes.
The Street Machine Gt's rear suspension
The heart of the Street Machine Gt design is the strong frame with the extraordinarily rigid rear wheel swinging arm in our No-Squat-Design. While a well designed suspension has to be able to react sensitively even to small unevenness of road surface, the frame and suspension pivot should be as rigid as possible, so that you can control the bike and accelerate the wheel without loss of energy or steering precision.
Modern frame building: a sophisticated egineering task.
The frame is welded from drawn tubes of 4130 Cromoly steel in an inert gas environment. For the rear swing arm we use butted tubes, which are ovalised according to the direction of the load. The pivot is a maintenance free unit consisting of a strong, 20mm wide, one-piece aluminium axle, which is kept free from play with teflon bushes.
There are several good reasons for using bushes on the swing arm pivot: on a touring and everyday recumbent the rear swing arm pivot must function reliably without continuous maintenance and servicing. At the rear swing arm only a relatively small movement occurs, although it is constantly oscillating within the spraying area of the tire. Bushes have a much greater surface area than bearings, which tend to concentrate the load on a few small points, and are much better able to deal with torsional loading. They also weigh much less and are easier to replace.
Finally bearings react very badly to being run without lubrication. With bushes this isn't a problem; the bushing material contains self-lubricating teflon particles which lodge themselves in the pores of the special anodising layer of the axle.
The triangulation of the rear swing arm results in a light but extremely rigid framework to mount the rear shock. We offer two types of rear shock units. With the standard damper DNM DV-22, the damping rate is fixed. The preload can be adjusted however, by hand turning the knurled knob. This tightens the spring to adjust the suspension to different loads.
We recommend adjusting the spring so that under static compression (sitting on the bike) about a third of the travel is used up, i.e. around 25 to 30mm. This gives plenty of space for the suspension to 'unload' if you go over a dip in the road, and generally makes for the most comfortable ride.
The optional DT Swiss XM180 air shock unit has external damping adjustment, allowing you to adjust the release rate for different road conditions.
Travel the easy way.
For the standard shock units DV-22 different coil springs are available. The selection of the spring rate depends mainly on your weight and the additional load. We recommend that to take full advantage of the suspension design you choose a spring that allows you to use as much of the available travel as possible, since the No-Squat-Design ensures no loss of performance on hills or under heavy acceleration. However your personal preference may also be taken into account. By changing the spring rate you can adjust the ride of the Street Machine Gt from extremely comfortable to sportily hard. No matter how you choose to set it up, our No-Squat-Design ensures that the suspension operates independently from the pedalling action of the rider.
As a reference point for the selection of the spring rate we have had good experiences with the following values:
- up to 80 kg weight of rider and luggage = > soft spring (labeled 350 lbs/inch)
- up to 100 kg = > standard spring (labeled 450 lbs/inch)
- up to 120 kg = > hard spring (labeled 550 lbs/inch)
These spring rates are valid for the Street Machine Gt. On the Speedmachine, the suggested spring rates are 100 lbs/inch harder, i.e. the standard spring on the Speedmachine is 550 lbs/inch.
With the optional air shock DTSwiss SSD225, you do not need to change any springs. The spring rate is set with an air pump. By setting the pressure in the pressure chamber, you can individually adjust the suspension feel and comfort.
Want to go for a test ride? Check out our dealer list to find out where you can start you personal shock therapy. Or find out more details about the Street Machine Gt.