Flat fixr

October 19, 2020 § 10 Comments

Today we decided to test the backpacks on the longer but more gentle gradient of Mandeville Canyon Road. I had left the tent and tarp out overnight and they got soaked with fog/dew, so I left them in the yard and rode with a lighter pack, about 35 lbs.

In the meantime we’ve been doing some reading and pseudo research on the physics/physiology of packs, trying to answer a couple of questions, such as: Why would the bike go faster if the weight is on your back rather than on your bike? Because it clearly does.

One answer is in this formula, which I don’t understand because math, but which is also explained in English, which I understand better than math, in other words, some level of comprehension > zero.

I think this means that, all other things being equal, the thing that gets going the easiest goes fastest. In other words, it’s easier to move a 10-lb. bike with a 290-lb. rider than it is to move a 150-lb. bike with a 150-lb. rider.

The physiological aspect is a well-studied one, as people have been carrying heavy loads on their backs for thousands of years. This picture illustrates why a milkmaid doesn’t carry the pails up around her shoulders.

It also expresses another important formula that has held true throughout history: Mother-in-law + shitload of hard work = daughter-in-law carrying the shit x mother-in-law’s supervision.

These pictures show how heavy weights are distributed when people have to carry exceptionally heavy gear over long distances and rough terrain doing strenuous work. The photo where the firefighters are bent over with heavy packs looks similar to the position you’re in when bending over the handlebars.

On the way to Mandeville Canyon Road we saw a guy standing on San Vicente holding up an empty CO2 cartridge and yelling “Do you have a spare cartridge?”

The cyclists in front of us ignored him, but I stopped. “I got one. How long you been here, man?”

“Half an hour at least.”

“And no one stopped?”


I shook my head. He must have hollered at a hundred people in half an hour; this street is the weekend freeway for bicyclists. “Here’s the cartridge,” I said.

But he didn’t take it. “Thanks. The one I have didn’t really work.”

“Oh. How come?”

“I don’t know. I’ve never used one before.”

I looked at his brand new Ultegra disc BMC, shiny, and the tires that had perfect tread. “Have you changed the tube?”

“No. I don’t know …”

“Know what?” He looked at the ground. “Was there air in the tire when you left home?” I asked.

He brightened. “Yep!”

“And how long ago was that?”

“An hour.”

“And then did the tire not have air in it after a while?”


“Then you probably have a flat.”

“Yeah,” he agreed, after some thought. “But I don’t have any tire stuff.”

“We do.” I pulled out a tire and lever and he looked at it in horror. That’s when it clicked. He had no idea how to change the tire and hadn’t brought a spare and levers because, useless. But it didn’t explain the fact that he had a CO2 cartridge that he didn’t know how to use. “So how come you brought the CO2?

“I figured maybe if I ever got a flat I could just air it up.”

“Well you can, I guess. Briefly, anyway. This your first flat?”


“Let me change it for you.”

“Okay!” It was Christmas plus birthday plus bar mitzvah all in one.

I removed the through axle and pushed down on the derailleur to remove the wheel. Too late … my hand was covered in four pounds of blackest chain grease. I got the tire changed and he was, shall we say, grateful. “Can I pay you for all this?”

“Oh, thanks. I couldn’t take a penny less than $300.”

He smiled a bit nervously. “I really appreciate the help.”

“No worries,” I said, desperately trying to remove the grease with some magnolia leaves, which kind of worked.

The entire morning we’d been badassed by every manner of cyclist, but my newfound inner peace and tired legs from the day before allowed me to take the high road and not chase anyone. So I wasn’t surprised when I heard another set of carbon wheels overtaking us on Mandeville. But these wheels slowed …

“Hey, Seth!”

It was Attila, my erstwhile pal from Big Orange. He slowed to a crawl and started talking with us, but his crawl soon had me panting. We got to the top and descended. All the way home he kept it at a lazy and comfortable 17mph, which is to say that with my 35-lb. pack and dead legs I was fucking pinned. But I pretended to be fine. We got to Redondo and Attila, who after 60 miles still hadn’t gotten in a workout, continued on. “I’m gonna do a quick lap around the hill! Good seeing you guys!”

Then he dialed it up to his normal tempo pace and vanished in a puff of smoke.

We got back and checked our speed. Total elapsed average was 13 mph, faster than I went any single day in almost three months with panniers. The day before, with lots of climbing and chasing, we’d averaged 14, almost double my pannier speed on climbing days.

My shoulders were tired as hell even with the low-slung pack, and the suspender buttons on my pants as well as the pocket buttons on my jersey had bored painful holes into my back. Mental note: Take those bastards off.


Tagged: , , ,

§ 10 Responses to Flat fixr

  • I see no other option than to agree with you regarding positioning of the pack. That doesn’t look very comfortable to me, but when I see the firefighters working, I can clearly see that if those packs were high up on their backs, they would be fucked. The principles of backpacking, and the principles for fire fighting in the woods packing, are not the same principles.

    We should be clear about one thing in your equation though. That governs level conversion of energy, where that pesky motherfuggin “G” has no effect. When “G” enters the equation, it takes the same amount of energy to raise the potential energy of M where M is the total mass of everything your skinny little legs are kinetically trying to move forward, whether that shit is on your back or strapped to the bike, or riding behind you in a nice tow-along trailer.

    • fsethd says:

      This makes a great point.

      Principles of wildland firefighting packs: Carrying heavy things long distances for weeks in rugged terrain doing strenuous dangerous work at the limits of human endurance.

      Principles of backpacking: Carrying three cases of beer a mile from the parking lot to stay four days in a heated hut with picnic tables.

      • While carrying in beer for a weekend in the woods is something I have participated in, certainly not at the 3 cases level, I don’t think the fire-fighting weight distribution works for thru-hiking any of the national scenic trails. Comfort there is getting that weight to ride on your hips, and for that weight to be secured closely to your upper back but not relying on your shoulders. It doesn’t work, IMHO.

        However, think of the porters hauling supplies, and the guided’s bags up to Everest Base Camp. Bags laboring under the Tumpline (https://en.wikipedia.org/wiki/Tumpline). Those loads ride low on the back as you describe, and those loads are sometimes 100kg! There is a documentary going around you-tube called Porter where Nate Menninger, a UVA Alum, signs on to be a Porter and document the experience of those that haul everything up those damn mountains.

        I guess with that I could carry in 3 cases of Alcohols, but not sure I would want to.

  • David Evan Atkinson says:

    when is the next adventure starting? Is it a solo endeavor?

  • Ruth says:

    Ten years ago, on my first ride over 8 miles in 25 years, as I toiled up what now is a little bump but then was a huge hill, we passed a 50ish guy in shiny new kit on a shiny, brand new, carbon road bike. He was obviously having problems, and I was eager for an excuse to stop. “Can we help?” His tire was flat, and he’d tried several patches, but he couldn’t get one to stick – to the outside of his tire! (And he wasn’t riding tubeless tires.) Now he was out of patches. My partner explained that the patch went on the tube, which was inside the tire, and offered to show him how to fix his flat. No, he said, he was giving up and calling his wife to come get him.

    I think of that rider from time to time, and wonder whether he has ridden that bike again, or whether the bike is lonely in a basement somewhere.

    Good luck on your trip to Texas. I have barely ridden a bike in Texas, but I remember a great network of lightly traveled, well-paved roads (with 75 mile per hour speed limits for the cars, at least in West Texas, but you can’t have everything). Riding in Texas cities, though, is scary!

    • fsethd says:

      One time in a fit of heat-induced delirium I tried to put an inner tube on outside the tire.

  • Joe Clement says:

    I’m not sure I agree with the firefighter analogy, but it is imposible to work bent over with a heavy pack up high. Not sure low is ideal the rest of the time. Sounds to me like too much weight. How do you get to 40# anyway? My pack, insulated inflatable pad, tent, and down quilt are around 6-1/2# before food and anything else.

  • Anonymous says:

    You can carry a huge amount of weight with a properly fitting/ positioned backpack resting on your pelvic arch, no question. What that does to the rest of your body is another story. VA hospitals deal daily with people back from deployment who’ve humped 80lbs into the field for months and are paying the price now with ruined knees, ankles, feet and spines. All the weight in a cyclist’s lumbar pack is supported by your ischial tuberosities, “sit bones,” and t’aint. How bad that effect is up to you to decide.
    I’ve ridden with a large fanny pack strapped low for decades but I hate the higher CG and the aero effect, particularly in cross winds, that a backpack creates.

  • nealhe says:

    It would seem that if we had ‘load carrying races’ for long distances (for a range of weights of 40 to 50 lbs.) with conventional looking bicycles …. the competitors with a streamlined trailer with one faired wheel or a good set of small low Crr faired wheels would be winners.

    A trailer shaped like this only without the fins and with added faired wheel or wheels:

    A small chest pack when supporting your upper body on aero bars is not too noticable … either aerodynamically or the weight of it supported through your ams to the aero bars.

    But anything strapped to your body takes more energy than when nothing is strapped to your body.

    The differance between the aero drag for a typical pack compared to a streamlined trailer is very large.

    Even at slow speeds … especially when encountering headwinds …

    Get a relaxed position on a bike with aero bars to tow the streamlined trailer you should be all set.

    Texas as a shakedown cruise …. then ’round the world’?

    As Buzz Lightyear said, “To Infinity and Beyond!”

    Noting that the current record for a Human Powered Vehicle is here:

    The current International Human Powered Vehicle Association world records for faired bicycles stand at 133.284km/h for the 200m flying start speed record and 91.562 km for the hour record.

    Aerodynamics counts ..

    As to the difference in speed with a pack on your back vs. gear strapped to your bike vs. a streamlined trailer … check your efforts with a watt meter … your bike doesn’t know where the weight is carried or how it is shaped …. but the wind does.

    Good luck on your trip to Texas.

What’s this?

You are currently reading Flat fixr at Cycling in the South Bay.


%d bloggers like this: