As the result of a project that was started back in 2008, Ibis has finally unveiled their newest bike: the 120mm travel full suspension Ripley. Rather than just stuff 29 inch wheels into a stretched out Mojo SLR frame, Ibis reached out to suspension guru Dave Weagle to create a platform that would do the big wheels justice. The result? A surprising remake of the famed DW Link suspension where the two short links have been replaced by 2 small eccentrics.
With a new look, and a boat load of features, Ibis’ 29’er looks like it could be worth the wait.
More details inside!
Much like the Mojo SLR, the Ripley receives just about every feature that techno-geeks dream about: press fit BB92 bottom bracket, high mount direct mount front derailleur, 142x12mm thru axle rear end, tapered 1.125 to 1.5″ headset, Kashima Coat Fox Float RP23 with Adaptive Logic Boost Valve, 160mm post mount rear brake, and all in a full carbon fiber monocoque with sacrificial core molding package. All of that, and I’m still probably leaving something out.
Even with all of the above features, the real story is hidden beneath the carbon on the seat tube. In about the same space that would normally house just the main pivot, Weagle has somehow managed to cram two eccentric pivots into the frame. Weagle is quoted as sying, “We’ve been working on this bike for what seems like forever. Far before it was fashionable or even heard of to have a shock clevis, and one of the first bikes since the I-Drive and Decathlon to use any type of eccentric link. Obviously more is better so we have two of them!”
As far as an explanation of the eccentrics are concerned, it’s probably best to take it straight from the source (from Ibis):
The eccentric world of eccentrics:
When Dave suggested using eccentrics it sounded like a good idea. Eccentrics as an engineering solution are slick and elegant. We’ve always liked the quote attributed to Einstein that says: “Everything should be made as simple as possible, but no simpler”. As it turns out it’s pretty hard to keep this simple idea simple. The picture of the eccentrics above represent the 20th iteration of the design, and each time the design got simpler. We like where it is now.
The thing about dw-link is that it’s based on physics and math. Dave can’t just put the links where ever he wants and slap his name on it. They have to go where the equations that he’s derived tell him to put them. Unfortunately this means that as he shrunk the links they had to get closer together. In order for things to get small enough to use eccentrics the links got so close that we ran out of room for ball bearings. In order to make the eccentrics work we started looking at bushings because of how thin they are. Also, bushings are actually better than bearings at oscillating motion so when designed right they’ll last longer. We set some pretty high standards though: no play, friction comparable to ball bearings, no special tools, lighter than our current link and bearing system, and perhaps most important, field adjustable with standard tools.
As mentioned, as we were beginning the Ripley 29 development, we were finishing up the Mojo HD. During that project we figured out that the first couple of mm of deflection during a stiffness test is actually from play in the ball bearings. The way we solved it on the HD was to use dual row angular contact bearings on the main pivot. There was no way those were going to fit between the eccentrics or be light enough. So we had the idea of angular contact bushings? And then we thought what if we made them adjustable so that as they eventually wore you could take the lash back out? We got in contact with the guys at Norglide and they started showing us some very slippery and durable composite bearing materials. We did some proof of concept experiments and were impressed so we started working out our eccentric design.
It took a while but what we came up with was a sealed, fully adjustable, angular contact composite bearing eccentric linkage system that is field adjustable. As mentioned, the eccentric system weighs 130 grams less than the Mojo linkage system.
We did some durability calculations and we predict that the eccentrics will outlast the bearings in our linkages considerably. We designed them with extra load capacity which provides increased life. The system is sheltered from direct spray by the design of the frame and also fully sealed. When you do go to replace the bearing material it is easier than pressing bearings out and less wasteful and expensive than replacing the entire link. It’s just the cone shaped bushing material that needs to be replaced. Not that you’ll need them in your lifetime, but they will be reasonably priced.
Shown above are the new eccentrics on the right, and the two links that they replace. The eccentrics are obviously smaller, but they are also 130 grams lighter than the links on a Mojo SLR.
In order for everything to fit and still allow clearance for a derailleur and tires, the seat tube had to be heavily shaped to make it all work.
- 29″ wheels
- 120mm rear wheel dw-link travel
- Twin angular contact composite bearing eccentric linkages
- Full carbon fiber monocoque with sacrifical core molding
- Tapered head tube (Cane Creek AngleSet & Chris King InSet compatible)
- Kashima coated Fox Float RP23 with Adaptive Logic Boost Valve technology
- Clean cable routing with molded carbon cable stops and provisions for cable-actuated adjustable seat posts
- BB92/Press GXP style integrated BB is lighter and stiffer and better for molding
- 142mm Maxle rear axle provides high axle stiffness with QR ease of wheel removal and installation
- 160mm carbon fiber post mount rear brake mounts
- High direct front derailleur, mounted to swingarm
- Geometry designed to work with 120-140mm forks
- 34mm fork stanchion approved
- 4 Sizes (S, M, L, XL)
- Weight TBD
- Price TBD but in line with our other frames
- Delivery TBD, but not in 2011