There a few good threads on how to get your iBike setup to work on a mountain bike that took me a while to find:
http://www.ibikeforum.com/viewtopic.php ... ike#p12053
http://www.ibikeforum.com/viewtopic.php ... ike#p10552
http://www.ibikeforum.com/viewtopic.php ... bike#p9544
http://www.ibikeforum.com/viewtopic.php ... mtb#p13789
There seem to be a few big issues with using and iBike on our Mountain bikes, that really aren't so much of an issue. The first is the friction numbers. In the threads above there are a few Crr numbers thrown about. 0.080, 0.088, 0.010, and 0.013. But, as mentioned, people start getting negative numbers in certain places, and the why doesn't seem to have been answered. A bigger issue is simply the difference in friction between hardpack, mud, and grass. The friction values change so much on a course that getting super accurate results seems near impossible. But I feel ball parking it gets you close enough to be useful, especially after reading some of the threads. I also think I read somewhere that Issac won't let you put in MTB tire sizes or high enough friction values? Since I only have an iSport I have no way of knowing. An oversight, or do things get too complex?
The second issue is the suspension. John often refers to it as flex suspension. Call me nit picky, but this doesn't seem like a very good descriptor. Suspension articulates, steel flexes. Here's where I begin to question a bit what I have read. Suspension is designed to suspend something, in this case a bike. The goal is for the fork and swingarm to move over or through bumps or ruts without affecting the frame. I would think that a rigid bike would cause the iBike more problems than a full suspension bike on the same trail. Now, the fork compressing under braking, or the bike bobbing under hard acceleration I can see throwing things off. Anther issue is sag and tilt cal. If you tilt cal your bike while you are not on it, then when you get on it'll be off. On my bike it's off by 3 degrees usually. So, you have to carefully do a tilt cal while sitting on the bike in your normal riding position. I have only managed to do this once, and it was recently. It took me a bit. I also wonder about the wisdom of doing a cal ride with the suspension locked out. You would have to be very careful about compressing your fork under braking, but if you lock your suspension out, it is supposed to be only when the shock and fork are fully extended (I think this has changed a few times over the years though) so your aero profile will be off, but how far off could it really be? Personally, my rear shock bobs more when locked out than when not. I know it means I'm not pedaling as smooth as I should be, but oh well. If you have the ability to lock your suspension out at your sag level, then you have life way easier than I.
The last issue I have been able to gleen is the tilt sensor, its ability to keep up, and that darned 5 minute re-cal based on altimeter readings. It seems to me the ability to turn that automatic recalibration off would be darn useful. At least until the sensors and processor reach a point they can keep with a mountain bike course.
Really, it does what I want it too. I don't have it dialed, but I get a general tss, if, np, etc, ft climbed, peak and average power, accurate mileage, speed (and now cadence, yeah!), temp, blah blah blah, and power on the climbs and flats. Sorry, but it seems to me if you're watching your power meter on the descents, you're either really good or slow.

Now, for the crazy thought I had. What if you had position sensors for the suspension? They have this for world level racing motorcycles. If they were ANT+ they could talk to the iBike. Really, if the suspension was dialed, they would probably do more harm than good, but suspension guys would go nuts with recorded travel data. Well, the ones that have a chance at interpreting it anyway. Kind of wondering if you get false power readings with a dfpm with some of the force and weight that gets applied throwing the bike around.
The last thing I have been wondering is if any of the new things about the Newton and Issac lend themselves to better dealing with the mountain biking.