Correct and tested too.
Triathlon Forum
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Re: ENVE claims disc wheels are not for triathlon [lyrrad]
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Re: ENVE claims disc wheels are not for triathlon [lyrrad]
[ In reply to ]
lyrrad wrote:
I agree with Tom A. A disc on the back makes it easier to handle a deep front wheel.
Here is what I hypothesize might be happening.
With a disc on and you get a strong side wind, the first reflex is to lean into it.
At the same time the front wheel is blown in such a way as it automatically makes you lean into it by countersteering to initiate the turn because of the larger surface area in front of the steering axis.
So the large force on the disc is actually a stabilising force acting upon the bike compared to a shallow or medium deep rear wheel.
i don't disagree with this. but i'm not smart enough to know. on the one hand you could refer back to the center of pressure argument. but i don't know how robust that argument is because the bike is pretty solidly anchored to the ground at the contact patches. if a sailboat only had a headsail, a jib and a spinnacre the center of pressure would be well forward of the boat's centerline, to bad effect. but the boat isn't anchored in the water quite the way a cyclist is anchored to the pavement, i don't think. so i just don't know.
Dan Empfield
aka Slowman
Re: ENVE claims disc wheels are not for triathlon [Tom A.]
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Tom A. wrote:
I've always thought that a good solution to front wheel stability and deep wheels would be to implement a Hopey steering damper (intended for MTBs) which damps excursions away from center, but allows free movement back to center. I still want to build one of these into a TT bike someday and try running a front disc :-)i remember these. might have been better of triathalon was spelled right ;-) i played with this back in the day. i was unswayed (no pun intended).
remember, sidewinds act in 2 axes, rotational around the line between the tire's contact points, and rotational around the steering axis. so, if you're pushed over (rotated around the contact points) you need to countersteer - steer in the direction of the wind - to place your CG between the line you're tracking and the line you want to regain. this, so that you can now lean in the direction you want to go.
if you place a device on the bike that inhibits your countersteer, i don't know that this is helpful.
Dan Empfield
aka Slowman
Tom A. wrote:
In regards to the surface area on the rear, don't forget that a force that tends to tilt a bike will tend to cause it to steer away from the direction of the gust (push a bike by the saddle, tilt the bike and see which direction it steers), which will be counteracting gust steering torque trying to turn the bike into the gust (due to "countersteering" effects). This is MY speculation why running a rear disc tends to add stability to the system. BTW, the deeper the front wheel used with a fork that adds surface area behind the steering axis, the less effective it will be. Think of it this way...in the limit (i.e. running a front disc) the area of the fork is within the outline of the wheel, and thus no additional side area.
I've always thought that a good solution to front wheel stability and deep wheels would be to implement a Hopey steering damper (intended for MTBs) which damps excursions away from center, but allows free movement back to center. I still want to build one of these into a TT bike someday and try running a front disc :-)
http://www.hopey.org/tt-triathalon.php
I'm intrigued. Cool find!