A Second Spin 1987 Mantis X-frame/Valkyrie

One of the things I love about our content here on the Radavist are features like this. Martin runs a hobby company called Second Spin Cycles, an outfit we did a Shop Visit on a few years ago, and this is his 1987 Mantis X-frame, aka a Valkyrie. Check it out in detail below with words by Martin…

A bike like the Mantis X frame of Valkyrie as it would come to be called, would no doubt turn heads if it showed up at NAHBS this year, that is if NAHBS were happening. But just imagine it’s 1987 and virtually every bike on the market is a standard double diamond with any exotic flair coming in the form of maybe Aluminum construction or a wild paint job.

Enter Richard Cunningham with his crazy twin lateral reinforced cross tube design. Not only was the concept wildly different from every other bike at the time, but RC built the X showcasing his skills with a torch by fillet brazing the frame but leaving the fillets unfiled. The end result remains of the most unique mountain bikes to ever hit the market, that is if you consider making 15-20 bikes really ‘hitting the market’.

The concept behind the design wasn’t brand new, most notable was the SE Racing Quandangle BMX but it was the first and last of its kind to be applied to a mountain bike. The main idea behind RC’s concept was that you can use smaller diameter tubing in place of the more commonly used sizes to create a measurably stiffer and stronger bike without sacrificing weight.

The X is not all show though; this is a real rider’s bike though it’s not a tame one for sure. The short 41.5″ wheelbase coupled with a steep (for the time) 72º headtube angle makes for a snappy handling bike that rewards the focused rider with a sublime though sometimes exciting ride. Much like many other builders of the time, Mantis offered a matching fork, stem, and Aluminum handlebar to complete the frameset.

This particular example is finished in a custom black/white fade with some wispy black splatter with a pop of red on the laterals and fork. The build is composed of Shimano’s original 6-spd XT group with WTB Speedmaster brakes (Toggle Cam in the rear solves the unique brake cable routing problem) and grease guard hubs with Campy QRs as well as Cook Bros cranks and bottom bracket.

Early mountain bike drivetrain favored large bailout gears demanding long cage rear derailleurs. However, those preferring a tighter rear cluster and desiring snappier shifting often used road bike rear derailleurs, which is the case here with a Shimano 600EX rear derailleur moving across a custom-built 12-28 rear cluster using a Dura-Ace freewheel body and 600EX cogs.

Like most of these older bikes it’s hard to compare the ride characteristics to anything modern, but when compared to other bikes of the era the Mantis resides in rarefied air with the likes of Cunninghams, Manitous and the occasional Merlin. Though when it comes to the uniqueness of design and execution style points there are few bikes that can compare.