The unusual design was pioneered by Mark Groendal of Grand Rapids, Michigan, after he one day in the 70s rode his dirt bike when it broke. He didn't notice it at first, but felt that the bike became smoother to ride at one point. When he later discovered that the frame actually was broken after a tube snapped, he started thinking that he could construct a frame with similar qualities. The design that eventually worked was a combination of sail boat technology and an old ski. The wires were mounted in the top tube section and mounted with springs in the bottom bracket area, and these wires should hold up massive amounts of force, Groendal said about 1700 lbs each. The ski was cut into small pieces and one piece was mounted in the top of the seat tube section to make a sort of hinge - the ski was flexible the right way and very rigid sideways. The system actually works, although a bit unusual and scary at first.
What to say about the ride? Well, it’s clearly a interesting concept, and it works. I haven't tested the limits of this bike at all, because it’s so extremely rare and I’ve never seen another 86 model out there (but there is a few 87s). I have no reason to believe that the bike will fall apart though. The rear part of this bike is attached through a flex board, and the rear end isn't as rigid as on other bikes. It takes some time to get used to, and it’s necessary to attack the bends differently because the rear end doesn't trail like normal. It’s scary, but also very fun.
The frame may be bonkers, but the parts are lovely and classic. All parts helps the bike to be as good as is gets. Suntour hubs and double roller cams, Magura brake levers, Shimano Deer Head shifters and derailleurs. IRD seat post and a Selle Italia Turbo seat.
At first I believed that this bike was a prototype or so, since it doesn't have a serial number. I bought it from the MOMBAT-collection, and it was stated as a 1986 model. I know that these MTB models debuted in 1985, so I believed it could be a 1985 model. After some investigation it’s clear that it isn’t - the different model years are very different to each other and the concept was clearly developed constantly over the years. See picture of the different models in slideshow at the bottom of this post.
These crazy ideas is something we all should appreciate since it’s one of the reasons that modern bikes are very good.
Frame: Slingshot, double cable - Cro-Moly
Fork: Chrome tipped cro-mo unicrown
Rims: Araya RM25 hard anodized
Hubs: Suntour XC
Tires: IRC Racer X1 Pro
Pedals: Suntour XCII
Crank: Shimano FC6206
Rear Cogs: Suntour 6 speed freewheel
Bottom Bracket: Suntour
Front Derailleur: Suntour XC
Rear Derailleur: Shimano M700 "Deer head"
Shifters: Shimano M700 "Deer head"
Handlebars: Alloy, shimmed
Grips: Grab on
Stem: Suntour XC
Headset: BMX 1" GT Epoch
Brake set: Suntour roller cams
Brake levers: Magura
Saddle: Selle Italia Turbo
Seat Post: IRD