grolby

I've been thinking about this again, since I've been considering changing the bike I use for gravel riding and races to my Ridley cross bike (high BB) instead of my Ritchey (medium-high BB). As I'm thinking about it, I'm really not convinced that a higher bottom bracket would have a negative effect on handling, even though it would certainly feel different. One thing that bugs me is, while the conventional wisdom is that a higher BB has less stability and a lower BB has more, I think this might be exactly backwards. My Ridley feels like my most stable bike in that it wants to track straight and true.

As I said before, the Ridley feels more reluctant to dive into a turn than my CAAD10, or my custom Cysco before that. It takes more work to turn, which is what I'm getting at with my stability comments above. I'm not exactly sure why this is true, but I think it might have to do with the arc movement of a lean. With a higher bottom bracket, a lean of a given angle requires the rider's body to swing through a longer arc as compared to a lower arc. I'm not sure whether or not this changes the amount of steering input needed to make that lean happen, but it has to change the moment of inertia of the whole bike/rider pendulum system.

But here's the thing: if I understand this correctly, this greater arc movement and greater moment of inertia is experienced by any rider who is taller and bigger than me. And yet there are plenty of tall bike riders who are good at cornering. That doesn't mean a lower bottom bracket height, and therefore also shorter and smaller body, isn't an advantage in cornering - in fact, I'm quite certain that smaller riders are intrinsically advantaged in fast cornering, especially off road. What this does suggest is, there's no reason you can't have a higher bottom bracket and still corner just as well. You just need to adapt to the somewhat more energetic movement required to compensate for higher moment of inertia.

For my purposes, this means I shouldn't let the ~6mm difference in BB height between my Ridley and Ritchey make me believe the Ridley is going to be worse on a high-speed gravel descent. It's a small difference to begin with, and the much stiffer front end of the Ridley might be more confidence-inspiring. For your purposes, it might be worth trying out a frame with 50 mm of drop. Extreme as it sounds, once you adjust to the handling, it probably won't be an issue.

Anyway, sorry everyone, this was supremely nerdy even by the standards of this thread, but it's been bugging me.