High Axle Blues

Back in Danzig mode with a vengeance. Or a small grudge. Or just some constipation and a headache. Either way, all free time diverts to some design work I have to be doing right now. As in “at this moment, instead of doing this.”

But this round of design revisions has me remembering the original reasoning behind the placement of the lower pivots, and there’s a brief, half-assed kind of story around that.

I’d dissected the work Steve Domahidy and company had done on Niner’s CVA suspension. See, a 29er has an axle that sits above the center of the bottom bracket, unlike a 26-inch wheel bike–those have axles that are almost in line with the bottom bracket center. From a full-suspension standpoint, a 29er is basically a 26-inch wheel bike that’s already halfway through its travel. Makes it tough to get any real travel out of them, as all early 29ers FS designs realized.

By dropping the lower link below the bottom bracket shell, Niner was able to drastically reposition the center of curvature of their rear axle path. The whole arc has to be mellower with a 29er, in order to leave you room for any actual travel. Incidentally, this is one of the reasons single-pivot 29ers have their pivots further forward–often in front of the bottom bracket.

It was trying to figure out how to accommodate the bottom bracket drop (higher axles) that got me thinking about a lower link that sat in line but tracked along the chain’s path, moving with it. That position, a little radical compared to everything else that’s been done, allows for a lot of axle path options for bikes with bigger wheels while still keeping the whole system very tight and compact.

It’ll be interesting to see what tracking along the chainline even as the suspension moves will do for the ride of the bike, though. Smart people have suggested this is a very good thing, and it certainly looks that way to me, too. Tape a laser pointer to the lower rocker on Danzig and it’ll stay pointing to the place your chain makes contact with our cassette all the way through the first two-thirds of travel. Sure, it’s affected by which exact gear combination you’re in, but much less so than a lot of other systems out there.

Back to work.