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Deliberately running the tires at less than min pressure

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Deliberately running the tires at less than min pressure

Old 07-13-20, 04:17 AM
  #1  
cubewheels
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Deliberately running the tires at less than min pressure

I am 132 lbs so I figure I'm on the light side. My bike has 20 x 1.95" wheels tire pressure, 40-65 PSI.

Safe to run this at 30 PSI? Not for comfort but for strength and endurance training by deliberately increasing rolling resistance. I used to inflate it at only 40 PSI but after 1 week, no pumping, pressure goes down to 31 PSI. I ride it and still feels like 40 PSI even though it's actually 30 PSI.

I'm already wearing loose / baggy quick dry apparel to also increase aerodynamic drag. The bike itself is quite heavy (35 lbs) and using all-terrain tires, really draggy.

I'd like to increase power and speed but without actually going fast in training. Quite dangerous in a crowded city with plenty of jaywalkers and bad motorists.

And finally, does having a large basket up front increases the bike's aerodynamic drag? Sounds like a stupid question but with my OCD mind, I realized that a large basket can create a large, low pressure wake (recirculation) behind it which can reduce the drag of the rider and every bicycle components behind it. Just a thought. But I'm rather confused if it will increase drag overall or even reduce it, given I'm wearing loose, baggy clothes.
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Old 07-13-20, 04:53 AM
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At some point you will become susceptible to getting pinch flats without sufficient pressure. How about pulling a small parachute or a lawn roller behind the bike?
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Old 07-13-20, 05:00 AM
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set your brakes to rub
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Old 07-13-20, 05:54 AM
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Originally Posted by dsbrantjr View Post
At some point you will become susceptible to getting pinch flats without sufficient pressure. How about pulling a small parachute or a lawn roller behind the bike?
Lawn roller, seriously?? No way!!

Parachutes....Maybe, I've seen a PRO cyclist use a small parachute for training. But looks totally weird. I hate to turn heads so probably not an option.
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Old 07-13-20, 06:04 AM
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Originally Posted by dedhed View Post
set your brakes to rub
No need to, I already use the brakes A LOT. I live in a crowded city in a 3rd world country. I'm already quite worked out just by braking a lot of times in the very disorderly traffic, horrible road conditions, and unsynchronized traffic lights.

Conserving momentum is a joke around here. 20 mph -- 0 mph -- 20 mph -- 0 mph, repeat 100x!

...Thinking about the parachute option... Perhaps, an oversized mudflaps at the end of the fenders might be a reasonable option to increase drag!
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Old 07-13-20, 07:23 AM
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Rather than running at less than minimum pressure, your idea of a basket is a better idea. Also could add a large seat bag, or rack, maybe put some heavy objects (fishing weights, brick, whatever) to add more weight to the bike. Another idea is a large piece of plastic (maybe like plexiglass attached to the front of the bike-could drill holes and attach to the bars and headtube with zip ties). Probably wouldn't have as much effect at slower speeds, more weight seems the best idea to me.
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Old 07-13-20, 07:31 AM
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Nothing will slow you down faster than a flat tire and running below minimum pressure is a good way to insure that will happen. Add drag other ways.
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Old 07-13-20, 09:41 AM
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I second the idea of some sort of mechanical resistance. Drag from poor aerodynamics decreases quickly as your speed drops, so the slower you go, the more drag you need to add. Seems much easier to just put something on to rub on your tire or wheel to create resistance that's closer to linearly proportional to speed. If you don't want to set up your brakes to drag all the time, you could just attach a flat piece of flexible plastic to the front side (meaning closer to the front of the bike) of the rear brake bridge so that it presses against the surface of the tire. The plastic will wear out quickly, but you can just replace it. Or use an old school generator that rubs on the sidewall.
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Old 07-13-20, 11:49 AM
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Originally Posted by cubewheels View Post
I am 132 lbs so I figure I'm on the light side. My bike has 20 x 1.95" wheels tire pressure, 40-65 PSI.

Safe to run this at 30 PSI? Not for comfort but for strength and endurance training by deliberately increasing rolling resistance. I used to inflate it at only 40 PSI but after 1 week, no pumping, pressure goes down to 31 PSI. I ride it and still feels like 40 PSI even though it's actually 30 PSI.

I'm already wearing loose / baggy quick dry apparel to also increase aerodynamic drag. The bike itself is quite heavy (35 lbs) and using all-terrain tires, really draggy.

I'd like to increase power and speed but without actually going fast in training. Quite dangerous in a crowded city with plenty of jaywalkers and bad motorists.

And finally, does having a large basket up front increases the bike's aerodynamic drag? Sounds like a stupid question but with my OCD mind, I realized that a large basket can create a large, low pressure wake (recirculation) behind it which can reduce the drag of the rider and every bicycle components behind it. Just a thought. But I'm rather confused if it will increase drag overall or even reduce it, given I'm wearing loose, baggy clothes.
underinflation is just going to end up with flats

no way anything you do like wearing baggy shorts or putting a basket on is going to make any significant difference in effort if you are going as slow as you have indicated........ (what is average speed) Try finding hills and doing repeats (up the hill, down, back up the hill) or a place to go faster
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Old 07-13-20, 12:58 PM
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if bike is 25 lb and you are 132 then i'd say the pressure is alright at 30 psi.

29 psi is the minimum tire pressure for a 75kg (165.5 lb) rider for 24x2" wheels.
https://www.bergfreunde.eu/bike-tyre...re-calculator/

i'd say you may go even lower than that.
just be sure it does not drop to 27 psi, that would mean it starts to get too low if lower than that. that would be the allowable minimum for the combined weight of 132+25lb.

you may find out that at 30 psi your speed is improved over other higher pressures, your tire wear would be improved also.
i'd say get a pump and get your wheels up to 35 psi twice a week until you replace the inner tubes that are defective; they are either porous or the valve.is defective
or just fix/replace the valve.

this site recommends 33/32 rear/front tire pressure for 47mm tires:
https://info.silca.cc/silca-professi...ure-calculator

this says 39/32 (rear/front) for 37mm tires and 60kg rider weight:
https://oniony.com/cycling/calc/pressure/

i use 36 psi for 622x50 rear and 43 psi for 622x42 front (29 and 28 inch respectively) and the total combined weight with the bike is 214lb (97kg). i also make sure pressure does not drop to less than 85% from the initial values. the rear wheel is under 55% of total load, the front supports 45%.


.
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Old 07-13-20, 01:44 PM
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As squirtdad said, find a hill and work it! He was aright about the aero idea: you aren't going fast enough to use that as a significant source of resistance.
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Old 07-13-20, 01:50 PM
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With a total weight of 183 lbs I keep my Kenda 26 x 1.95" tires @30 - 35 psi front & 36 - 42 psi rear. According to psicalculator.com I should use 27 psi front @ 45% weight distribution, and 36 rear @60% weight distribution. The tire is marked for 40 - 65 psi. So I won't go under 30 psi.

I do perceive a slight difference in speed with more preasure. While at 100 psi a bike tire might roll faster with less, these wide tires roll better with more pressure then the calculator suggests. So resistance will go up slightly with less pressure, But I don't suggest compromising safety for an extra 3% rolling rolling resistance.

You could use the full knobby tires used on mountain bikes, perhaps 2.3" if they'll fit. This will increase rolling resistance. Climbing hills and biking through sand is great workout.

Fat bikes are an even better workout. Those 4.5" tires are so hard to motivate my neighbor, a senior, bought an electric assisted bike. Fat bikes probably aren't a good choice for someone getting back into biking after many years

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Old 07-13-20, 03:45 PM
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Run at 40, get a cheap bike computer, change the gearing, and find some hills.

John

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Old 07-13-20, 04:04 PM
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Attach 20 or 30 cards like this. Will increase drag and sound cool too.
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Old 07-13-20, 04:31 PM
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Run them low and if you get punctures up the pressure a bit.
Anyway with all the stop start you will soon get fit
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Old 07-13-20, 04:39 PM
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Just tape a giant cardboard to the front of your bike.
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Old 07-13-20, 05:23 PM
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ride it in the most difficult gear combo. if it is a fixed gear, swap the crank gear for a larger one. if done right, anything from 0 mph to 10 mph will require a good amount of leg umph.
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Old 07-13-20, 06:16 PM
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Tubeless is subject to 'burping' in corners.. losing the bead contact & all the air at once..
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Old 07-13-20, 06:37 PM
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Originally Posted by freeranger View Post
Rather than running at less than minimum pressure, your idea of a basket is a better idea. Also could add a large seat bag, or rack, maybe put some heavy objects (fishing weights, brick, whatever) to add more weight to the bike. Another idea is a large piece of plastic (maybe like plexiglass attached to the front of the bike-could drill holes and attach to the bars and headtube with zip ties). Probably wouldn't have as much effect at slower speeds, more weight seems the best idea to me.
Like the idea of plexiglass with zip ties! .

Small parachute seems to be what the pros use but it's only going to attract a lot of unwanted attention! Parachute can generate a lot of drag even at low speed, doesn't add weight to the bike (so the bike's handling is unaffected) Maybe sidewinds are going to be a problem though. I would love to use one if I only live in a sparsely populated area but I live in the middle of a densely populated city!
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Old 07-13-20, 06:47 PM
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Fill the tubes up to 90% with *slime. No flats & it'll increase the resistance.
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Old 07-13-20, 06:52 PM
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Originally Posted by AeroGut View Post
Or use an old school generator that rubs on the sidewall.
Sounds like a great idea. For the generator to make significant resistance though, it must also run electrical devices. I'm thinking of old, incandescent automotive lamps and artificial noise generator - a speaker simulating the engine noise of a motorcycle for example. That would also help anyone on the road to announce my presence!
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Old 07-13-20, 07:07 PM
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Originally Posted by cubewheels View Post
Sounds like a great idea. For the generator to make significant resistance though, it must also run electrical devices. I'm thinking of old, incandescent automotive lamps and artificial noise generator - a speaker simulating the engine noise of a motorcycle for example. That would also help anyone on the road to announce my presence!
then you'll gain that unwanted attention that you mentioned before.
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Old 07-13-20, 07:19 PM
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Originally Posted by squirtdad View Post
underinflation is just going to end up with flats

no way anything you do like wearing baggy shorts or putting a basket on is going to make any significant difference in effort if you are going as slow as you have indicated........ (what is average speed) Try finding hills and doing repeats (up the hill, down, back up the hill) or a place to go faster
Today I'll find out my speed if the computer arrives today.

I get across three small hills in my route. The hardest one by far is the nearest one. I've been tempted to repeat that hill several times a day. Unfortunately, the route to the hill goes through a poor neighborhood and it can be dangerous to catch attention in that area.
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Old 07-13-20, 07:23 PM
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Those old tire rubbing generators create a lot of resistance even without a load on them. I actually prefer the playing card (vintage sports cards work in a pinch) and clothespins. The more cards=the more resistance. Win win (See Tyrion's post above)
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Old 07-13-20, 07:24 PM
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Originally Posted by tyrion View Post
https://www.youtube.com/watch?v=krPQ1PMM00Y

Attach 20 or 30 cards like this. Will increase drag and sound cool too.
Brings back memories...
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