Descending with deep section front wheels

Question

Would a deep section front wheel improve stability and control in descends? And if yes would the benefits outweigh the potential danger of side winds? (We usually don't get more than 15kmh winds here)

Answer 1

I believe the depth of your rim would not have much direct impact on the amount of stability on descent. Most stability is going to come from body position, hand placement on your handlebars and the speed at which you are descending along with road quality.

Let's ignore road quality and focus on the three you can control: body position, hands and speed.

Body position affects your center of mass while riding. As you tuck lower, you are moving your mass lower to the ground which in turn means greater lateral force is needed to affect your balance.

Hand position affects how much force is needed and hand movement is needed to turn the wheel, the further away from the steering tube your hands are, the more stable you will become - as long as your hands are still on the handlebars ;-).

Speed - This is where your wheels really come into play and relies on your wheel's angular moment. Check out a bit more on Angular Momentum. Essentially, the faster your wheel spins around its axis (the wheel hub) the more the entire wheel feels a force pulling perpendicular to the direction of motion. Weight does play a role in angular moment, but is most noticeable when accelerating or decelerating because that is when you are fighting against the wheel's inertia.

Bottom line: deep rims won't harm your descending stability excluding outside factors like wind and road surface but it also won't help you bike stability either. For descending can be hairy due to wind without deep rims, using deep rims on descents could just blow you off the road literally.

Answer 2

I'm not sure I understand the question. Hopefully this answers it.

I have descended fast, including turns, on box section, 30mm, 45mm and 50mm deep wheels and not found any of them to be unstable such that it was a problem. Off course the deeper wheels are prone to being pushed by cross winds but this has never really troubled me, and down hill then the higher speeds make the whole bike more stable. Although I am quite a bit heavier than you and perhaps with 80mm+ wheels then it would be more of an issue.

Answer 3

Would a deep section front wheel improve stability and control in descends?

Yes. Deep section wheels are heavier. The heavier the wheel, the higher it's angular momentum at a given speed. Higher torque means the wheel will take more force to turn, therefore leaning into the curve will require more force. Leaning into curves will be smoother and less jerkier which even improves traction.

It's the same physical principle that makes Diabolos work.

Would the benefits outweigh the potential danger of side winds?

No. A Deep section wheel might weigh 10-20% more. The forces they experience in crosswinds however are multiples of what shallow wheels experience.

Answer 4

Front wheel is there for steering and braking. Rear wheel is there for acceleration and keeping the track.

More stable front wheel will make it harder for you to turn and keep the desired track. On the other hand, rear wheel is fixed to the frame (exluding its rotation) and its enhanced stability also stabilise the bike and you.