Conbtinental has come out with a GP5000S and a GP5000TL

On Fri, 22 Feb 2019 14:25:49 -0500, Frank Krygowski
wrote:

On 2/22/2019 1:39 PM, wrote:
On Friday, February 22, 2019 at 6:31:09 PM UTC+1, wrote:
On Thursday, February 21, 2019 at 1:46:38 PM UTC-8, Frank Krygowski wrote:
On 2/21/2019 4:27 PM, wrote:
On Thursday, February 21, 2019 at 1:10:42 PM UTC-8, Frank Krygowski wrote:
On 2/21/2019 12:52 PM, wrote:
On Wednesday, February 20, 2019 at 4:32:10 PM UTC-8, Frank Krygowski wrote:
On 2/20/2019 6:30 PM, jbeattie wrote:

Another thing about these tires is that they have a pretty high recommended inflation pressure for a 32mm. IIRC around 90 PSI, which makes the ride like rocks, but if they are under inflated, they ride like slugs. A 10-15 psi difference really affects the perceived "speed" of the tire.

It might be interesting to try some simple coast-down tests. If you have
any hills with pretty consistent slope but not too steep, you could run
them at (say) 75 psi and coast down noting your time between two
landmarks. Then ride back up, inflate to 90 and repeat the trial. If
done on a day without wind, you'd probably get a realistic estimate of
how rolling resistance varies with those two pressures.

You say you don't use cyclometers. But those with cyclometers mounted
might just use the speeds indicated to tell the difference.


--
- Frank Krygowski

Remember that I was describing the coast down test I had up in Cull Canyon where I would coast down a really rough section of road and then it would flatten out and when I hit a 100 yard long patch of new and very smooth pavement the bike would actually accelerate? Everyone wanted to argue that wasn't possible but I did it again and again. As the summer wore on the asphalt aged and got rougher and though it was still pretty smooth the effect had disappeared.

When you say the road "would flatten out" do you mean it was horizontal,
instead of downhill? Or do you mean the bumps went away and it remained
downhill?


--
- Frank Krygowski

It went downhill on a very rough road, flattened to horizontal or at least the 0% grade indication on my altimeter and then it climbed a bit before descending a bike. The increase in speed was immediate upon entering the smooth section and not a slow build up of speed as would come from a declining road.

OK, if you were coasting and you had no tailwind that exceeded your
speed, you had nobody pushing you forward (which I've done for people
many times), and you had no rope towing you or some other weird situation...

And your bike actually accelerated when the road was horizontal? Yes,
that's impossible. Sorry, Tom, this is basic physics.

(And I had to include the rope tow because that was Jute's "deus ex
machina" on his first weird braggart tale here.)

Your story does, however, indicate the power of suggestion and how it
can mess with our perceptions.

--
- Frank Krygowski

Frank, if this is against physics why haven't you actually explained this to us?

To my way of thinking if E = 1/2M*V^2 and you reduce the rolling resistance you coast for a longer distance to expend the energy. But that isn't what happened. As I said - when I hit the smooth pavement the bike increased its speed.

This was not a single case but multiple experiments and as the smooth pavement degraded over the summer and grew rougher the increasing speed disappeared at least to the level where it wasn't detectable.

I think what Frank tries to say is that to be able to accelerate there must be a driving force, one of Newtons laws. If you are coasting on flat terrain without a tailwind there is no driving force.

Exactly. In fact, there are retarding forces, those being air resistance
and rolling resistance, at a minimum.

And as to Tom's question, why haven't I explained it? I guess I
foolishly persist in believing that some things are obvious to educated
people.

Or even to uneducated people who keep their eyes open :-)

--
Cheers,
John B.