Thanks everyone for the suggestions. I ran Schwable Stelvio which normally pump to 145, so only ran 105 psi. The chip and seal was three days old and they did a good job sweeping it, however there were some loose gravel spots/lanes throughout. Almost bought it on the initial entry turn in to the road were the gravel was very loose. Compared to a rough patched and pot holed section that wasn’t chip seal yet, the new surface wasn’t bad! I had latex tubes but didn’t use them. They are about 10 years old and didn’t want my first use of these to be during a race. Are they still good?
I ran Schwable Stelvio which normally pump to 145, so only ran 105 psi.
Why in the world did you run your tires at 145 psi? Do you weigh over 350 lbs? Are you aware that running your tires at that high of a pressure will slow you down significantly over rough roads?
I ran Schwable Stelvio which normally pump to 145, so only ran 105 psi.
Why in the world did you run your tires at 145 psi? Do you weigh over 350 lbs? Are you aware that running your tires at that high of a pressure will slow you down significantly over rough roads?
No, I ran them at 105 psi, but normally run them at 145 on typical roads.
I typically inflate to the tire pressure listed on the sidewall, never saw that chart before and always thought higher pressure was faster.
I typically inflate to the tire pressure listed on the sidewall, never saw that chart before and always thought higher pressure was faster.
The whole point of the air chamber within a pneumatic tire is to serve as suspension. If we wanted to make tires as stiff as possible, we’d just run solid strips of rubber straight on metal rims.
Ideally, the tire should be pumped soft enough that it mostly deforms around surface irregularities. If the tire does not deform around an irregularity, rolling over the irregularity causes the bicycle and rider to be vertically deflected. This vertical deflection costs energy, and this energy is stolen from your forward motion. Even if you’re on a fairly smooth road surface, and the vertical deflections are a subtle buzzing, it can be costing you some watts. (It does also cost energy for a tire to deform around an irregularity, but usually much less than what it costs to vertically deflect the bicycle and rider.)
The rougher the surface, the squishier a tire needs to be pumped in order to serve effectively as suspension.
Now, going too low on pressure can also increase rolling resistance. When a section of the tire rolls onto the ground and becomes the contact patch, it gets deformed under the rider’s weight, which costs energy; when it leaves the tail end of the contact patch and springs back to round, some (but not all) of the previously-lost energy is converted back into forward motion. By pumping a tire stiffer, less of this deformation occurs in the first place, and so less energy is lost from this effect.
BUT
Typically, you need to pump a tire really darn squishy before this effect gets very dramatic. It’s typically much better for performance to err low on pressure to avoid suspension problems, than to err high on pressure to minimize the constant tire deformation at the contact patch. (And that’s even without accounting for the comfort benefits of erring low.)
The reason that beefy bombproof tires have more rolling resistance than supple racing tires is that they tend to be constructed from stiff materials that don’t spring back very lively. So when a section of the tire becomes the contact patch, it costs more energy to deform it against the ground, and you get less of that energy back when it springs back to round at the tail end of the contact patch. You can try to “solve” this by pumping the tire really stiff, but then it suffers from a harsh ride and poor suspension performance, so it’s still slow.
Here’s a good article:
https://blog.silca.cc/part-4b-rolling-resistance-and-impedance
always thought higher pressure was faster.
Wrong. Read the Silca link provide above and and study the charts in that link.
So this chart says I should be riding my 700x23’s at between 110-115psi (I weigh 178 lbs) for a ‘normal’ road?
Boring response to echo all above, but another person that is NZ based and so rides chipseal most of the time. For racing over the last 10 years I’ve used** Vittoria Corsas clinchers with latex tubes**.
I went to this exact setup (28c) this year, and couldn’t be happier. Lot’s of chip seal around here. The Corsa/latex combo takes most of the buzz out of “set-in” chip-seal roads, handles newly sealed sections confidently and, knock on wood, has been quite reliable thus far.
Yes, 111-112 psi for a fairly smooth normal road.