Tom Kunich wrote:
On Thursday, August 29, 2019 at 1:46:16 PM UTC-7, Frank Krygowski wrote:
On 8/29/2019 4:03 PM, Sir Ridesalot wrote:
On Thursday, 29 August 2019 15:46:47 UTC-4, Frank Krygowski wrote:
On 8/28/2019 12:25 PM, Sir Ridesalot wrote:
On Wednesday, 28 August 2019 12:18:21 UTC-4, Tom Kunich wrote:
On Tuesday, August 27, 2019 at 9:22:23 PM UTC-7, Frank Krygowski wrote:
On Tuesday, August 27, 2019 at 5:51:20 PM UTC-4, Tom Kunich wrote:
Because of several things, I ended up mounting the Vittoria
Roubino Pro G+ tires on the LeMond.

Sunday I did an easy 40 mile ride and I was exhausted at the end.
These tires did ride well - they smoothed out the roads quite a
bit th9ugh they appeared to have a lot of rolling resistance. I
couldn't figure out if it was my imagination and finally came to
the conclusion that I am simply on the low side of my fitness
cycle. The difference in rolling resistance is so small compared
to the wind resistance that I can't see how you could possibly tell.

I did a hard 40 miler today with a lot of climbing. I used the
Colnago which has the Vittoria tubeless racing tires on box
tubeless times. Now the Colnago is an aero bike but since this
ride is mostly all climbing or very twisty downhills the aero hardly seems
significant.

But I did 3400 feet of climbing and the tires seemed to make a
rather extraordinary difference. I DID NOT get good sleep last
night so it isn't as if I recovered.

I think that it would probably be a good project to make a rather off-hand
experiment on types of tires and how they seem to run and ride.

Both of the Vittoria racing tires - the Corsa G+ And Corsa G2
tubeless feel very good. Better than the Michelin Pro4 Endurance
which is pretty good. All of these tires have good puncture
resistance which is necessary around here. I think that I'll pull
the Roubino Pro's off and replace them with a new set of
Gatorskins I have laying around. It's been so long since I've
ridden Gatorskins that I can't remember their rolling resistance.

On another set of wheels I did a couple of metrics on a set of
Continental GP5000TLR tubeless tires. I wouldn't exactly call
these things low rolling resistance. They have a tacky compound
that screws up any directional stability the tires may have. While
the bike goes exactly where you point it with the Vittoria Corsa
G+ you have to watch the GP5000's closely. But in a corner the
Continental is probably better. Riding these metrics I was often
confronted with a decreasing radius turns. On the Vittoria's I
would slow a little and complete the turn. With the Continentals I
would just ride through it.

My experience with the Continental tires is that you have to wear
them through to the thread before throwing them out. The Vittorias
are different. It didn't appear to have much wear on the tread
facing but the rubber sidewalls were peeling away and that made me
nervous so I threw them away.

I guess I'll have to experiment to see if the non-aero LeMond is
what the problem is or the rolling resistance of the tires.

Seems to me if you want to get a handle on the rolling resistance of your
various tires, you might find a hill with a long, gentle slope and keep track
of speed results when coasting down it.

I've done just a little of that. One thing it taught me was that it's harder
than it seems to gauge rolling resistance just by "feel."

- Frank Krygowski

Rolling test aren't accurate either because humidity, pressure and
wind make a far larger contribution than rolling resistance. The
only practical way is either pure feel or to make a testing machine
which I do not feel like doing.

Take your bike and put training wheels on it. Take the bike to a long
downward trending straight grade. Attach a cord to the handle bar on
each side and then attach the cords to the seatpost or frame so that
the handlebar can not turn. Allow the bike to start rolling on its
own = no pushing it to start it. Time how long it takes to get to a
certain point. Repeat within a short time with different tires, tubes
and/or pressure in the tires.

You need a representative load on the tires to give any validity to this
test. The easiest way to arrange that load is to have a rider on board.


--
- Frank Krygowski

It'd be better to fasten weight to the bicycle because then when you
switch tires everything is the same. With a rider a slight difference
in position could create a more aero setup t hereby negating any change
the tires might make. You want the test to be repeatable as much as possible.

I think if the test were done at a slow enough speed, minor differences
in air drag would be negligible. It would be nice, though, to have an
indoor asphalt surface for the test. Climate control concerns, including
wind, would be removed.

I often wondered too about those old tests, circa 1980s, for
aerodynamic components and just how much difference the components made
on a bicycle with the rider pedaling.

As I've mentioned, I used to be an aerodynamics freak. It actually
started when I was a teenager interested in fast cars. It carried over
to motorcycles, then to bicycles.

So during the 1990s, I played around with a variety of minor aero
improvements. No Shimano AX components except their flat water bottle.
But over time, I tried disc spoke covers for the rear wheel (and used
them in some time trials), bladed front spokes, some use of a Zzipper
front fairing, handlebar bags shaped for a bit less air drag, Tailwind
panniers, clip on aero bars, and a few other details. And more basic, I
shunned clothing that was loose and flappy.

I had fun with that for years, but only a few items seemed to make
enough difference to be worthwhile. Flappy loose clothing slows a person
down. The Tailwind (aero) panniers tested well when coasting alongside a
friend with conventional panniers on a tour. And the aero bar is a
definite help.

In one issue of Bicycle Quarterly, they rented a wind tunnel and tested
different tricks using a randonneur bike (not a time trial bike). That
included different riding positions, as well as the presence or absence
of fenders, choice of bags, etc.

One major conclusion was that the Drag Coefficient of bike+rider
calculated out to the same value (about 1.0 IIRC) no matter what you
did. IOW, for any halfway conventional bike, you probably shouldn't
worry about "streamlining" the shape of the components. Just work on
lowering the frontal area.

Before some people squeal: This doesn't mean a Cervelo time trial bike
gives no benefit over, say, a touring bike. It just means the difference
is small enough to matter only in a tightly competitive time trial.
You're very unlikely to really "feel" it.

--
- Frank Krygowski

Isn't it true that aerodynamic drag is a 3rd power factor? So even tiny
differences in speed screw up your tests.

There are also different factors - worn vs new tires - a worn tire is
significantly wider than a new one. Rim width also changes tire shape.

All in all, if you are attentive I believe that you can learn more by
feel than most testing that isn't on a level of a testing laboratory.


I don’t actually disagree with that. In practice, you have head winds and
elevation gradients that have a much more noticeable effect than rolling
resistance. Well within norms anyway.

The new concept is that wider tires have less rolling resistance due to the
change in the contact patch. But for me, wider tires feel muddier in the
turns so I prefer my 23s.

I know, not scientifically valid but I just did 100km with 500 meters and
managed an average of 31km/h. We had winds in the 30s. Rolling resistance
was not an issue. Cornering in some twisty descents was still noticeable.



--
duane