Originally Posted by
SesameCrunch
I actually have this situation. My black Fuji Team Issue is a carbon fiber 17lb bike with full Dura Ace drivetrain. My Dahon XX Anniversary Helios is also right around 17 lbs.
They're both excellent bikes and fun to ride. I have not done "scientific" tests on them for performance difference, but here are my anecdotal and honest thought about their differences:
- Flats - Probably very little difference. Although, I feel that 700C wheels roll more efficiently at higher speeds due to the higher angular momentum. Also, the Dahon's top gearing was around 95 gear inches with its stock setup, so it was a little disadvantaged when the paceline is going faster than 25mph or so. But, that is easily remedied.
- Climbing - As I said earlier, I actually do believe that smaller wheels are better for climbing,due to the fact that it spins up faster. My Rolf wheelset on the Dahon weighs 995 grams (!), the Easton wheelset on the Fuji weighs 1550g. Factor in the angular momentum impact and one can certainly see how it is harder to spin up the big wheels.
- Descending - I definitely feel more stable on the 700C wheels than the 406's. Maybe it's just my poor riding skills, though ..
- Sprinting - The Fuji wins again, I'm afraid. The hinges at the handlebar and mid-frame take a significant toll on rigidity when stomping on the pedals and pulling on the 'bars. There's no way around it. On a one-piece full size frame, it's a very confident feeling when I stand and pull on the bars. On the Dahon, particularly the Helios design, I just cannot pull as hard.
I have been on a two year search for a "portable roadie" - a folder than can keep me in the hunt on my weekend rides with the group. However, I have abandoned that idea because I simply have not been able to find one. That's why I put the Dahon up for sale and it is on its way to a new home. Maybe the Moulton TSR will come close, but it will weigh 24lbs.
Don't mean to start any wars here, just noting my honest observations about the bikes.
Your observations are consistent with my beliefs about the physics of cycling and the state of small wheel technology.
That said, I personally would like to know more about the relationship between fork trail and contact patch shape when it comes to self-correcting steering at high speeds ("stability descending"). Since contact patch shape depends on wheel diameter and trail can be adjusted independently of wheel diameter and both influence "stability" what I'm curious about in particular is to what extent trail can be used to cancel the rounder contact patch of smaller diameter wheels. Is it like inertia where the higher gearing can exactly cancel the size difference in all circumstances or is it like the frequency of oscillation when hitting a bump which Jur showed can be mostly (though not exactly) canceled out with wider tires?
I personally think that at lower speeds the rounder contact patch of small diameter wheels is more "stable" because it gives you more leverage to hold the wheel steady when a bump or pothole tries to turn it (which is far more likely to cause a crash than endoing without the wheel turning). However, I suppose at higher speeds one wants the opposite effect where the longer contact patch gives the force of friction of the tire against the road more leverage against you so that the wheel holds itself steady despite the input of the rider. The question is, to what extent can one get the best of both worlds? The first low speed affect should be independent of trail, while the other is closely related to trail. Can adjustment of trail produce exactly the same affect as adjustment of contact patch shape? If not can trail be used to approximate a longer contact patch at all speeds? If not, can trail be used to approximate a longer contact patch at one or more target speeds?