physics question

[JohnRoberts]

I don't know why, I always overinflate significantly. I don't use a pressure meter, I just pump until it feels hard to the touch. I think it's a combination of easier pedalling (I'm not a masochist, I use my bike for utilitarian tasks, like doing errands) and more positive steering.
Yes, essentially flat when you walk (or run), but riding you feel the incline when you leave the French quarter for the upper neighborhoods. But the real issue is the road surface; I wished I could post pictures of the streets that go east from the FQ to Marigny. Imagine it's paved with 4-inch Lego's. And the streets that go up to Treme have potholes 12-inch deep. Add to that that I have a foldable bike with 20" wheels...

Yup I recall from running the miles between quarter and Audubon park that streets were not kept in very good shape.

I am noticing more tire noise (I think) from higher pressure which suggests scrubbing at the contact patch is consuming energy. The tire noise sounds different on different surfaces, whiter the smoother the road is, more LF the larger/rougher the surface details.

Intersting...

JR

 

[abbey road d enfer]

I am noticing more tire noise (I think) from higher pressure which suggests scrubbing at the contact patch is consuming energy. The tire noise sounds different on different surfaces, whiter the smoother the road is, more LF the larger/rougher the surface details.

Are you aware of porous asphalt? Originally designed to help with draining the road surface under rain, it also showed a significantly reduced rolling noise and better mileage. The explanation is quite simple: compressing bubbles of air between tyre and road consumes energy, which is dissipated in noise. Making it porous fixes this issue. It was very popular at a time, but it turned out it was much less durable than standard tarmac.
Not sure how much it matters when pedalling.

 

[JohnRoberts]

It didn't take very long, but investigating a new noise I noticed that my rear tire was slowly self destructing. The noise I heard was a fat section of the tire rubbing on the kick stand every time by.

I lowered the pressure but still rubbing and I am reluctant to ride miles away from the house on them, so new tires are on order.

While the tires clearly said 40-65 PSI on the sidewall, they didn't say 65# for how long. 

I found some tires almost the exact same size (1.85 vs 1.90 width)  and rated for 89# max, so maybe they'll last longer with decent pressure, I was really getting used to the lower rolling resistance @ 65#.

I found some tires on the WWW rated for >>100# but they were skinny speedsters and might not even fit my rims, or my lifestyle.

Nice weather but no ride today...  or tomorrow,  , or

JR

 

[joaquins]

Are you aware of porous asphalt? Originally designed to help with draining the road surface under rain, it also showed a significantly reduced rolling noise and better mileage. The explanation is quite simple: compressing bubbles of air between tyre and road consumes energy, which is dissipated in noise. Making it porous fixes this issue. It was very popular at a time, but it turned out it was much less durable than standard tarmac.
Not sure how much it matters when pedalling.

  Court case, people to the motorway concessionaire for excessive noise, a friend was one of the experts in charge of measurements and simulations, they ended changing the asphalt for a more porous one, they archived 1dB lower noise levels after expending several M$$$, it didn't make either of the parts happy...

  About the tire pressure, usually higher the more efficient, is not much what you get back from the tire as usual compounds have tons of hysteresis since that makes the grip. Note that HF (once every rock) hysteresis is what you need for better grip and LF (once every tire revolution) hysteresis is what chews energy there aren't many materials that behave that way, while F1 motivation might provide some development in that respect it might take years to get to consumer bike tires. In either case, the averaging on the surface shouldn't be efficient as that losses is what makes the grip, and you don't want your bike going sideways and probably much less understeering. Is good to have some suspension to smooth the roughness. Also the bigger the tire the better (easier to get over rough surfaces) and thus there are some 29 inchers around.

JS

 

[PRR]

Off-your-chart data-point:

A snow-blower tire looks the same at 20psi or zero psi, but the rig sure turns easier with ~~16psi.

The heavy carcass does not sag under the blower's weight even no-air. But yanking to change direction deflects the carcass rather than skid.

 

[JohnRoberts]

Off-your-chart data-point:

A snow-blower tire looks the same at 20psi or zero psi, but the rig sure turns easier with ~~16psi.

The heavy carcass does not sag under the blower's weight even no-air. But yanking to change direction deflects the carcass rather than skid.

Snow blowers... I remember them.  8)

Today was so nice (short sleeve weather)  that I had to ride despite my squirrelly tire.  Lowered the pressure (actually refilled it ) to 35#...  It survived 5 miles but the higher rolling resistance returned...  :-[ oddly it seemed most noticeable on  hills (don't know why?).

New tires should arrive fri-mon so I just need to manage another 3 rides on the old tired shoes. Then I can pressure up.  ;D

JR

 

[joaquins]

...
:-[ oddly it seemed most noticeable on  hills (don't know why?).
...
JR

  Higher load on a single tire, greater deformation, more losses... (that plus you are going up) IIRC the back tire was the problematic one, climbing makes both effects worse.

JS

 

[JohnRoberts]

My new 65# rated 1.5" tires arrived in the mail today so i am back on the road and rollin in style.  ;D

Only pushed them up to 60#  but they seem noticeably quieter than before. I believe the old tread pattern had some intentional scrubbing going on (maybe for better traction). The new tires look tiny compared to the old 1.9" tires and I guess they are kinda.  I don't want to make a definitive call from just one ride, but the rolling resistance at 60# seems a little less than the 1.9" @ 65#, and lots quieter.

I have a set of 89# rated 1.85" tires due in early next week but I may stick with these 1.5" guys for awhile to get a good baseline before taking the pressure up a notch with the next set.

FWIW after i removed the faulty tire, I inspected it carefully looking for a flaw and nothing was visible. I even rolled the tire completely inside out and nothing was visible. I suspect there is a cord hidden inside it broken and the sidewall distortion is only visible under pressure.

Brand new tires are nicer than old faulty ones.  8)

JR

 

[joaquins]

...
Brand new tires are nicer than old faulty ones.  8)

JR

  Yep, that's usually the case, feeling the same in my car right now...

  Tire pattern plays a huge role on rolling resistance, don't take conclusions only over pressure and width... Slick tires are a breeze to go when dry, don't pretend to avoid a collision on the wet. Semislick are usually fine for normal urban conditions, not good for mud or long road trips. My cousin used to travel a LOT on bike, 1000+km roundtrip once a year probably, no support vehicle. He used two set of tires or one fixed semislick and swap the other. He would swap tires whenever the road meets the dirt.

JS