One of the recent developements in the history of 29″ers that has caused more confusion and questions than probably the existence of 29″ers themselves is the change in fork offset by prominent suspension manufacturers to “tune” the handling of 29″ers. Why was this done? Is there an “old 29″er geometry” and a “new 29″er geometry”? Can you mix and match forks and frames from different design philosophies? And the questions go on. In these posts I will try to briefly touch on some facts and try to dispel some myths about the current state of affairs as it relates to handling characteristics of 29″ers.

Fact: A 29 inch front wheel will have more trail because of its size. This is the reason for everything that follows and the first thing one needs to understand to be able to follow along. Fork trail is the measure that helps one determine the relative stability/instability of an inline wheeled vehicle. Simply picture a shopping cart wheel or a dolly wheel. The “pivot” that attaches to the cart/dolly is the steering axis. The contact patch of the cart/dolly wheel follows this axis as you push the cart/dolly along. The distance from the centerline of the steering axis to the wheel contact patch is a measure called “trail” or in the case of a bicycle, “fork trail”.

This “trail” measurement increased when modern 29″ers were first developed as a direct result of using a larger diameter wheel. (I won’t get into the details of this, but trust me, it is true) While most of the other critical front end measurements stayed the same, this increase in fork trail dialed more stability into the front end of the earliest 29″ers. The early adopters liked this trait, and so they did not try to change the front end geometry much if at all.

Fact: Many judged the 29″er against what they knew before- the 26 inch wheeled mountain bike. Some early critics of 29″ers were quick to point out this new 29″er geometry as being “not quick and snappy, like a 26″er”. Thus they panned the new wheelsize for this, (and several other) reasons. Others were interested in seeing if something could be done to “improve upon” the matter at hand, so the first of many “fixes” were applied to 29″er bikes. These were sometimes used alone or in combination with each other. The most popular being to increase the head angle from the 26″ers 71 degree angle to something around either side of 72 degrees head angle. This had the effect of decreasing the trail measurement back closer to a 26″ers and made the front end steer with less effort and lost a bit of stability in the process. Of course most applauded the effort to more closely approximate 26″er handling, but the critics still said, “Too sluggish!”

Okay, that should set the stage for what has happened recently. The big problem was always that you were pretty much stuck with using the fork offset on suspension forks that was developed for 26″ers on 29″ers. This made getting a suspended hardtail or full suspension 29″er to steer with a snappy, quick feel hard to obtain. The idea was that if the slate could be wiped clean, a new offset(s) that would work to make 29″ers more like a 26″er in turn in feel and not be unstable could be obtained. Either that or use the same offset as always, (38mm) and keep steepening the head angle to achieve a more snappy, quick front end. And finally, some companies have elected to keep doing the same type of front end geometry that 29″ers have been using since about 2003, which is a slightly steeper head angle than a 26″er and keeping the offset at 38mm or so. Some would call the first two examples “new” 29″er geometry, and some would call the last example “old school geometry” for 29″ers.

Myth: There are “old” geometry 29″ers and “new” geometry 29″ers This is simply false. The fact of the matter is that there are several types of geometry solutions all being worked on at the same time. This is a time that is marked by ongoing experimentation and research into just what a 29″er should steer like; and quite frankly, it is not going to shake out anytime soon. Nor should it. The situation now days is a blessing and a curse. For one thing, it is a blessing in that we can now “tune our rides”. It is a curse in that now you have to think about this stuff. It is not a moot point like it was back in the earlier days of mountain biking when every hardtail had “NORBA geometry” and you just assumed it would handle like a 26 inch wheeled mountain bike “should” handle. No, now there are options to consider, and the wise 29″er shopper will be aware of these options going in.

Next post: Can you swap around forks and frames to acheive a desired result?, and other 29″er handling questions. Stay tuned!