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How low can I go on tire pressure on my tires?

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How low can I go on tire pressure on my tires?

Old 12-04-13, 10:08 AM
  #26  
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Originally Posted by djb
I've mentioned this before about these graphs and calculators-in my experience and opinion, the suggested pressures are too low......
Everyone has hos own opinion about tire pressure, and each is entitled to his own. The tire drop analysis isn't about finding a magic ideal pressure, but the best pressure from the single standpoint of rolling resistance.

Things like having enough freeboard (rim/ground distance) to protect rims from bumps, handling, tire flex in cornering, and so on weren't factored.

OTOH, those concerned about these can adjust tire pressure or change tire width to address them. Finding one's personal ideal pressure is a matter of judgement based on experience. Guides like the tire drop chart are simply starting places.

One thing the data shows, along with other data from other sources, is that the lowest rolling resistance isn't necessarily with the narrowest tire, and many (most) riders can benefit from tires wider than the 23-35mm that has been dominant in recent years. Unfortunately too many frame builders haven't seen the light and a good portion of high end bikes cannot clear anything larger than 25mm.
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Old 12-04-13, 10:27 AM
  #27  
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I see your points, and in fact these graphs got me thinking about tire pressures that I had never really thought about before, but as you say

Originally Posted by FBinNY
Things like having enough freeboard (rim/ground distance) to protect rims from bumps, handling, tire flex in cornering, and so on weren't factored.
I do think its important to mention the aspects I brought up just so that someone with less riding experience is aware that the suggested pressures should be used as a guide, and in my opinion too low for real world riding, as we all have to deal with potholes and such.
Again, I did a lot of riding and touring and never really thought of tire pressures, just tended to put them to the high rating on the tire when I did pump them. Due to touring, I was usually more careful about lower pressures with the added weight, but when commuting they would invariably go down but never had pinch flats.

The thing that impresses me is how lower pressures can really change the comfort of a bike, and improve cornering too (compared to using the high end of tire pressures).
As you say, its great for riders to experiment with pressures and see how it feels.

PS, off topic-don't you find it kinda strange that someone is posting using a user name almost identical to yours? SBinNYC or something? I mean I dont know you, but the stuff you write seems to be helpful, well thought out and balanced (especially about chain lubes!) so while I havent really read things the sb fellow is writing, it still is a little odd.
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Old 12-04-13, 10:35 AM
  #28  
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Originally Posted by djb

PS, off topic-don't you find it kinda strange that someone is posting using a user name almost identical to yours? SBinNYC or something? I mean I dont know you, but the stuff you write seems to be helpful, well thought out and balanced (especially about chain lubes!) so while I havent really read things the sb fellow is writing, it still is a little odd.
cheers
I don't feel it's odd at all, though not very happy about being "copied". I created my user name by simple formula, my initials, and where I'm from. I didn't invent the format which has been used in places like newspaper letters to editor signatures for decades (centuries?), so I have no claim to it except for the specific FBinNY here.

So figuring that there are plenty of members from NY or NYC, I'm not at all surprised to find others using a similar format for their user names.
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Old 12-04-13, 01:05 PM
  #29  
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I am interested in lowering the pressure to achieve the 15% drop talked about in that Bicycle Quarterly article. But I have two problems:

1. There is no drop provided for a 40 or 42mm tire on the chart.
2. If I go below recommended low tire pressure listed on my tire, will it damage the tire to ride it that way? The low end is 50psii on my tires, and looks like I will be in the 40's from what I see on the chart. .
Try my attempt at capturing that chart with a formula...

But after you compute nominal front/rear pressures, pump up your tires to precisely that, and take a test run in a driveway or parking lot with some obstacles that represent what you might encounter in the wild. Like how about a broom handle (branch in the road?) or try bumping up and down curbs and driveway lips. Ride carefully and pay attention to tire deformation, or have somebody else (your weight) ride and watch from the side. That should give you an idea whether you can tweak the computed numbers in either direction.

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Old 12-04-13, 04:09 PM
  #30  
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Originally Posted by FBinNY
I don't feel it's odd at all, though not very happy about being "copied". I created my user name by simple formula, my initials, and where I'm from. I didn't invent the format which has been used in places like newspaper letters to editor signatures for decades (centuries?), so I have no claim to it except for the specific FBinNY here.

So figuring that there are plenty of members from NY or NYC, I'm not at all surprised to find others using a similar format for their user names.
gotcha, of course, the 'ol Dear Abby stuff too. Didnt think of that.
My husband keeps passing gas loudly at family functions, and then laughs his head off. I'm aghast with embarrassment and shame, what should I do?
KMinTootsville.

and back to subject, while taking a quick peek at Rubrad's page, I saw your point about this topic, which pretty much addresses my concerns and how to get to a pressure that works for each person:
https://www.bikeforums.net/showthread...width-and-load
post 24, and yes, that quote was kinda the point what I was trying to make.

"Never sacrifice good, on the altar of perfection"
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Old 12-04-13, 07:22 PM
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^^^ All that you said is not true. The pressures the graph uses is all about the 15% drop zone where the best handling and wear is supposedly taking place. More and more pros are once again going back to that same graph and altering only slightly at about 5 psi more then recommended. There are exceptions, just like anything, if you're riding on cobblestones then you may want about 10 to 15 more psi to prevent pinch flatting, but since very few of us do that then the graph is correct.

The rack with panniers is nuts, think about what you said. Loaded panniers have weight thus you must calculate the weight of the entire bike with all accessories you would need to go on a ride, whether touring or not! Thus if for example the panniers, rack and gear weighs 65 pounds then you need to add 65 pounds to the total bike weight. If the weight changes same thing. And if your touring then you are probably using heavy thick tires and heavy thick tubes which means there is far less air loss day by day vs racing tubes, and there is far more leeway in the psi you can handle vs racing/training tires before a pinch flat occurs.

Also keep in mind, as pros are going back to that chart they may alter their tires 5 psi more for better handling as I recall doing back in the early 80's, but there are people who want more comfort and could care less about performance so they might want to drop their psi by 5 from the chart.

At the end of the day it's up to you how you want to run your tires, if you don't like the graph then forget it and do whatever pleases you. I know from experience of racing, and riding mountain roads that the graph worked the best for handling and tire wear. Take that for whatever it's worth.

Here's more on this: https://www.biketinker.com/2010/bike-...-for-bicycles/
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Old 12-04-13, 10:09 PM
  #32  
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The 15% tire drop calculations are generally formulated for use in real world conditions and not perfect, faultless pavements.
The aim is not just lowest rolling resistance, but optimal performance and comfort.
This from the Jan Heine Bicycle Quarterly article:
"Tire pressures that correspond to 15% tire drop will optimize
your bike’s performance and comfort on average road surfaces. On
very rough roads or unpaved roads, it may be useful to reduce the
pressure. On very smooth roads, increasing the pressure slightly
may improve the performance of your bike."

To those of us who "grew up" in cycling being told to always run maximum pressure, less air can indeed feel 'funny'. It's often just a feeling based on a learned norm.
For a couple of years, I've been rolling with less pressure than I was used to and have had no problems but more comfort. I run about 50psi in the front 32mm tire of my long wheelbase bike (30/70% F/R) and have had no pinch flats or squirming cornering at speed. That's largely on real world suburban/rural not-very-smooth-with-the-occasional-pothole roads. 60psi in the front 35mm tire of the short wheelbase bike I use for my suburban/urban commute works fine, too. No pinch flats.

Agree with rekmeyata that "At the end of the day it's up to you how you want to run your tires"
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Old 12-05-13, 08:43 AM
  #33  
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As said before, it's not THAT complicated!
My approach is to inflate tires a bit more than I think is needed and then, based on test rides, lowering the pressure. For example, on my road bike with 23 tires, I started with 100F/110R (total weight about 175). Now I use 90-95F/100-105R. On my hybrid with 37 tires, total weight about 185, started at 55F/65R, now 45F/60R.
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Old 12-05-13, 10:32 AM
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Originally Posted by Reynolds
As said before, it depends on your weight and your riding style, but if you're not too heavy and ride on good paved roads, probably about 30-35 psi.
If you ride on good roads there is no purpose served by very low tire pressure.
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Old 12-05-13, 10:55 AM
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Originally Posted by Don in Austin
If you ride on good roads there is no purpose served by very low tire pressure.
I'm in New York. Decent pavement is rare, and good roads non-existant. On some descents the rearward G-forces generated by hard tires are high enough to eject downtube mounted water bottles.
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Old 12-05-13, 07:09 PM
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Originally Posted by Don in Austin
If you ride on good roads there is no purpose served by very low tire pressure.
I'm not saying the OP should use that pressure, he asked what would be the minimum usable pressure.
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