Since the Raleigh XXIX has hit the scene in the 29"er world the question of "suspension corrected forks" and what the effects of mounting a suspension fork on a rigid forked bike might be have cropped up. I would like to address that here in this post.
"Suspension corrected geometry" was a terminology used quite heavily during the mid-ninties to describe a hardtail mountain bike that allowed for the use of a suspension fork without lousing up your angles and handling. It fell out of common use when almost every bike sold for off road had a front suspension fork mounted to it. The reason being was that all frames were designed to run a suspension fork by the late nineties.
Now with the advent of the popularity of 29"ers, some of the formerly held "standards" for frame and fork geometry are being revisited and revised. Thus the confusion created when Raleigh introduced the XXIX with a non-corrected front fork. Questions began to be raised such as, "Will using a suspension fork on a XXIX ruin the handling?" Ahh! A question that takes me back over ten years ago! How fast we forget! (Or we're too young to remember!)
The XXIX has a front end geometry based on a fork with an axle to crown measurement of 430mm. (The measurement is taken from the center of the front wheels axle to the base of the headset crown race) Compare that to a "suspension corrected" measurement of 470mm for a Karate Monkey frame and rigid fork and 480mm for an Inbred 29"er frame and fork. You can see that by adding a Reba suspension fork for 29" wheels to a XXIX is going to raise the front end up with it's sagged axle to crown measurement of 465mm. That is going to do funky things to the handling of a bike like an XXIX.
Not only that, but you will also change the way the bike fits too a small degree as well. So, the XXIX is sort of a retro-grouches delite in that it doesn't allow for the proper handling characteristics because of it's lower axle to crown height. Not that you couldn't mount a suspension fork- it just wouldn't be much of an improvement, that's all. In fact, you might say it would kill the handling of the bike.
So, why would a company like Raleigh do such a thing? Well, that is a two fold answer. One: the front end is automatically lowered, which helps negate an oft heard complaint of 29"ers having too high a front end. Secondly: 29"ers are noted for smoothing out the trail just by virtue of the bigger wheels alone. So why even mess with suspension? It plays into the single speed thing, which dictates simplicity above all else, as well.
That's basically it right there. Rather simple, but forgotten, perhaps with the plethora of suspended bikes these days. Remember your history folks, or your doomed to revisit it!