On Tuesday, July 21, 2020 at 5:10:32 PM UTC+2, Frank Krygowski wrote:
On 7/20/2020 8:10 PM, AMuzi wrote:
On 7/20/2020 6:34 PM, wrote:
I think we had this discussion before but it is time to revisit it. I
have been riding Vittoria Corse G+ 25 mm tires. Somehow I had gotten
the idea that these were faster than the 28 mm tires I had been using
5 or so years ago. Well, Since I have been switching over to clinchers
again I got a set of Michelin Power 28 mm clinchers.

There is a sharp descent and a long slightly downhill section I travel
on regularly. There is a radar speed limit sign on this route so that
I can double check my speedo. My speed through this rough area is
normally 24 mph on the sign and about that on my speedo. I just
changed over to the 28 mm tires and did that section and the radar
reported 26 mph through this section. And the fatter tires at a 10 psi
less inflation pressure rode so much smoother that I cannot for the
life of me remember why I changed to the 25's.

Before I had 23's on my Time and you simply could not ride that Time
with 23's on it unless you had a butt of cast iron. When I changed to
the 28's on the Time it was and entirely different bike.

As you probably know, I am 6'4" and 190 lbs so I'm sure there is some
dividing point though I don't know where that might be since the Tour
riders are using 26 mm sew-up tires on their bikes. But I can tell you
I won't make that mistake again and I will be riding 28's from now on.



I don't know but there are more factors such as ambient air pressure and
humidity, wind etc. Also new tires are definitely faster than worn (flat
center) tires.

I wonder if there's data proving that. It's the kind of thing that's
really ripe for the placebo effect: "I put on new tires and they're SO
much better!"

Sort of related: I remember way back when some tires were sold with a
narrower center belt of rubber that protruded farther than the rest of
the tread surface. That center stripe might have been about 10mm wide on
a 32mm tire. As I recall, they were claimed to reduce rolling
resistance. It may have been Jobst who showed they increased it instead.

--
- Frank Krygowski

I ignore all claims comparing different tire widths if the tires are not the same make and type. Let alone the riding conditions and fitness. That is ridiculous.

Lou