Isak Leivsson has a few experimental bike designs to his name. We saw his homemade DH bike
that he raced last season under him at a number of races and originally a tester for Pole's out-there DH bike
, he's quite familiar with geometries that push the boundaries of conventional thought.
His latest steel DH bike is an evolution of his other ideas which are mostly based on geometry. It's the third iteration of homemade bikes for Isak. The first bike was basically a geometry mule with a standard four-bar setup. The second iteration had a high pivot and really progressive leverage rate, as well as a different linkage design. He only rode that bike in a smaller race as the extremely progressive rate didn't turn out to be what he wanted and the linkage design inherently contributed to a lot of lateral flex which couldn't be accounted for without making the bike too heavy.
The third bike, pictured here, is a continuance of the other two, according to Isak. It encompasses his attempts at fixing whatever didn't work in the previous two. Having ridden the bike for three months, he's happy with it and the only thing he would currently consider changing is possibly building a lighter version with butted tubing but, it's not a huge concern at the moment.
The big changes from V1 to V2 were that the bike grew and took on 29" wheels. From V2 experiments, Isak went back to a single pivot design for V3 but he kept the high pivot. The leverage rate was also made more reasonable.
The reach of the bike is 470mm with a 644mm stack. The head angle is 63-degrees and the BB height is 350mm. Chainstays are a massive 510mm and the bike runs on 29" wheels front and rear. Altogether, the bike weighs in at 19kg or, a touch under 42lbs.
Most of the hardware for the bike came from the local hardware store but Isak made the main pivot bolts himself. He feels it's a large part of the process to accommodate for the things he has accessible to him. Fortunately, there are a few good suppliers like Bicycle Fabrication Supply, where he got the headtube, BB, dropouts, and other miscellaneous parts. When it comes to frame building, there aren't as many people who make full-suspension homemade bikes, so the hardware and parts for that purpose he often has to make for himself.
Designing and building the bike didn't take all that long with a few days of design and then a couple of weeks to build. Isak said that since it was a continuation of what he already liked, it was mostly just moving pivot points around in linkage to get it where he wanted. He says there are always more custom jigs and things to make than anticipated so it does take a little while. Without being able to dedicate full-time work to it, the project was spread out over a couple of months and he didn't build it until his Christmas break.
What does the bike like to do best? Speed. What doesn't it do best? Manuals and playfulness. Isak says that those 510mm chainstays don't play.
As far as other set-up goes, he's running a 0mm stem and taller bars to make his riding position more upright and central on the bike. Also, he initially assumed he would need to make a chainguide for the idler, but so far he's not had any issues with the chain falling off.