By any definition of bicycle design, Slingshot’s ‘Sling Power Technology’ frame design is unusual, to say the least. By completely replacing the down tube with a spring-loaded braided steel cable, Slingshot claimed that the bikes would not only be faster but more comfortable, too. That such an idea was able to take hold in the Wild West early days of mountain biking is no surprise, but the fact it’s still available today might be.
Slingshot’s SPT design flew in the face of every piece of conventional thought when it came to frame and suspension design. There are no conventional mechanical pivots, there are no claims of ‘travel’, and no separate shock. In fact, there’s essentially zero vertical movement built into the chassis at all.
Instead, a ‘flex plate’ built into the top tube (just ahead of the seat tube) works in conjunction with the spring-loaded steel cable to let the bike’s overall length increase slightly with load. Think of how an inchworm crawls along a leaf and you sort of get the idea.
The idea was that such movement would allow the frame to better conform to the terrain than a fully rigid frame, yielding improved traction and rider comfort. In effect, what Slingshot created was a Unified Rear Triangle design with an exceptionally high pivot (and just a simple undamped coil spring for the shock).
A flexible fiberglass plate is bolted into a gap in the top tube
More key to the Slingshot’s unique appeal, though, were the company’s claims on how the design made the rider faster. According to Slingshot, the coil spring that anchors the steel cable stored pedaling energy that was otherwise wasted during the power stroke and then returned it into the drivetrain when the pedals were in the ‘dead zone’. In addition, bump forces that would normally rattle the rider instead are transferred into the spring and then returned into the drivetrain, supposedly turning every obstacle into forward motion.
Nevertheless, removing the down tube has obvious negative effects on a frame’s torsional rigidity, and despite the top tube growing continually in size, the words ‘lateral stiffness’ and ‘Slingshot’ were rarely uttered in the same sentence. Since one major section of the main triangle was missing, Slingshot still had to reinforce what remained so the frames ended up being quite heavy.
The Syncros cockpit is about as classic as it gets
The build kit on this particular example – a 1992 Team Issue – is a veritable wish list from the time. In addition to the highly desirable SunTour XC Pro transmission and cantilever brakes, there’s a full suite of Syncros bits from when the company was still very much a boutique, niche player (and well before its acquisition by Scott Sports). The aluminum two-bolt seatpost and TIG-welded aluminum stem are classic and relatively common but far more rare are the titanium handlebar, the Steer Horns bar ends with their novel clamp design, and – best of all – the tubular chromoly Revolution crankset spinning on the company’s own titanium bottom bracket.
Rolling stock consists of Sun Chinook rims laced to SunTour XC Pro hubs with DT Swiss Champion straight-gauged stainless steel spokes, all wrapped with Continental Comp Pro 1 rubber. Finishing off the build is an Avocet O2 saddle, lightweight foam grips, and a 1in threaded Chris King headset.
There aren't many of these still in service
Did SPT work? Well, Slingshot’s decidedly loyal band of enthusiasts certainly believes it did, so much so that the company’s doors are still open today, complete with a full range of down tube-less frames. Missed out on a Slingshot frame back when you were a kid? Well, now you’ve got a second chance.
For more information, visit www.slingshotbikes.com
Complete bike specifications:
- Frame: 1992 Slingshot Team Issue
- Fork: Chromoly steel unicrown
- Headset: Chris King threaded, 1in
- Stem: Syncros
- Handlebars: Syncros titanium, 570mm
- Grips: Foam
- Front brake: SunTour XC Pro
- Rear brake: SunTour XC Pro
- Brake levers: SunTour XC Pro
- Front derailleur: SunTour XC Pro
- Rear derailleur: SunTour XC Pro
- Shift lever: SunTour XC Pro
- Cassette: SunTour PowerFlo 8-speed, 11-28
- Chain: SRAM PC-850
- Crankset: Syncros Revolution, 175mm, 26/36/46T
- Bottom bracket: Syncros Titanium
- Rims: Sun Chinook, 32-hole
- Hubs: SunTour XC Pro Grease Guard
- Front tire: Continental Comp Pro 1, 26x2.125in
- Rear tire: Continental Comp Pro 1, 26x2.125in
- Saddle: Avocet O2 Air 40R
- Seatpost: Syncros
- Pedals: n/a
- Weight: 11.30kg (24.91lb, without pedals)