Tire pressure/speed
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2015-05-25 12:58 PM |
439 nashville, Tennessee | Subject: Tire pressure/speed Throw out a number. In your opinion/experience, how much difference would air pressure make if you did the exact same ride, same road(smooth pavement) conditions etc, with 60-80 psi vs 110-120 psi? |
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2015-05-25 1:07 PM in reply to: mchadcota2 |
Elite 7783 PEI, Canada | Subject: RE: Tire pressure/speed Weight of the rider? Someone that is heavy might take a long time on the 60 psi as it would likely pinch flat on the first pothole they hit. |
2015-05-25 1:57 PM in reply to: #5117913 |
439 nashville, Tennessee | Subject: RE: Tire pressure/speed How bout we say 170 lb cyclist on 80 psi vs 120 psi? Any speed difference over 20 miles? |
2015-05-25 3:41 PM in reply to: 0 |
Extreme Veteran 3025 Maryland | Subject: RE: Tire pressure/speed yes, at 170 lbs i would recommend around 100-105 psi on 23mm tires Edited by dmiller5 2015-05-25 3:41 PM |
2015-05-25 3:43 PM in reply to: #5117913 |
439 nashville, Tennessee | Subject: RE: Tire pressure/speed Not recommendations. How much difference does it make speed wise, 80 psi vs 120 psi |
2015-05-25 5:03 PM in reply to: mchadcota2 |
Extreme Veteran 3025 Maryland | Subject: RE: Tire pressure/speed Originally posted by mchadcota2 Not recommendations. How much difference does it make speed wise, 80 psi vs 120 psi this question is unanswerable without a ton of information and a ton of physics. it also doesn't matter. do it correctly and then you don't need to find the answer |
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2015-05-25 5:15 PM in reply to: #5117941 |
439 nashville, Tennessee | Subject: RE: Tire pressure/speed Awe cmon Dave. Give it a try. I promise it's answerable. |
2015-05-25 5:20 PM in reply to: 0 |
Extreme Veteran 3025 Maryland | Subject: RE: Tire pressure/speed whats the roughness coefficient of the course. whats the actual width of the tire, whats the width and contact area of the tire under loading at each discrete pressure value in your selected range. what is the average speed of the racer, what is the median speed of the racer as described by time traveled at that speed. what is the external barometric pressure, what is the temperature of the tires, what is the ambient temperature, what is the temperature of the road. and with that you can find the rolling resistance and calculate the traveling speed at a given power. do that for a set of power values now do this for every different type of tire and you can find your answer Edited by dmiller5 2015-05-25 5:24 PM |
2015-05-25 5:33 PM in reply to: 0 |
Extreme Veteran 5722 | Subject: RE: Tire pressure/speed Originally posted by mchadcota2 Awe cmon Dave. Give it a try. I promise it's answerable. difference in rolling resistance at various tire pressure will depend on tire and road surface difference in speed will depend on rolling resistance and speed you are rolling at in other words....it depends Edited by marcag 2015-05-25 5:39 PM |
2015-05-25 5:39 PM in reply to: #5117913 |
439 nashville, Tennessee | Subject: RE: Tire pressure/speed Haha! How bout this. If you were about to do a 20 mi time trial, and you're tires were at 80 psi, and you didn't have access to an air pump, what would be concerned that it would slow you down? |
2015-05-25 5:41 PM in reply to: 0 |
Extreme Veteran 5722 | Subject: RE: Tire pressure/speed Originally posted by mchadcota2 Haha! How bout this. If you were about to do a 20 mi time trial, and you're tires were at 80 psi, and you didn't have access to an air pump, what would be concerned that it would slow you down? no I tested between the difference between 90 and 105psi and it made no measurable difference on relatively smooth asphalt Edited by marcag 2015-05-25 5:42 PM |
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2015-05-25 5:51 PM in reply to: #5117913 |
439 nashville, Tennessee | Subject: RE: Tire pressure/speed Thanks! |
2015-05-25 9:01 PM in reply to: mchadcota2 |
643 | Subject: RE: Tire pressure/speed Check this out too: http://www.bikequarterly.com/images/TireDrop.pdf Now I sort of feel bad since of my 2 rides I've done outside, I've been pumping to ~115 psi. I know my tire is 120 PSI max. I'm going to play with that chart next week and see how I fare. |
2015-05-25 10:03 PM in reply to: Blastman |
Member 131 | Subject: RE: Tire pressure/speed So, am I reading this right? 170 pound guy with 23mm should inflate front to 80lbs and rear to 100lbs for optimal comfort and speed? |
2015-05-26 6:29 AM in reply to: scottficek |
Pro 5892 , New Hampshire | Subject: RE: Tire pressure/speed Originally posted by scottficek So, am I reading this right? 170 pound guy with 23mm should inflate front to 80lbs and rear to 100lbs for optimal comfort and speed? No… more than likely, 80psi is too low for the front. I would say somewhere around 95-105psi is probably about right. The smoother the pavement, the higher the pressure, the wider the rim, the lower the pressure, the heavier the rider, the higher the pressure, etc. etc. etc. And then you have personal preference in there as well... |
2015-05-26 7:19 AM in reply to: scottficek |
Member 1748 Exton, PA | Subject: RE: Tire pressure/speed Originally posted by scottficek So, am I reading this right? 170 pound guy with 23mm should inflate front to 80lbs and rear to 100lbs for optimal comfort and speed? I weight 165lbs riding on 23mm tires and inflate my front tire to 90psi and rear to 100psi. Even in early season when I'm up at 170+ I keep the tires about the same. Road surface range from smooth to practically unpaved, and I have only had 1 pinch flat in the last 3 years. (Additional pressure would not have stopped that flat, lucky I didn't dent the rim). |
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2015-05-26 9:28 AM in reply to: mchadcota2 |
Not a Coach 11473 Media, PA | Subject: RE: Tire pressure/speed |
2015-05-26 11:01 AM in reply to: 0 |
1509 Cypress, Texas | Subject: RE: Tire pressure/speed If your tires are really under inflated you are going to feel like you are riding though mud. I did two 45 minute rides with the tires at about 45-55 PSI (no pinching flats either since I didn't go over anything too bumpy). I averaged 16 MPH. Then I made some adjustments to the fit (it was a new bike) which involved raising the seat height and raising the seat angle. The following ride with the seat adjustments and tires inflated to 90 PSI I averaged 17.2 mph over a 90 minute ride. I think a lot of this had to do with the seat adjustment, but the tires were rolling noticeable better too. I didn't feel the bike slowing down every time I eased off the pedals. It actually would coast and maintain speed when I eased off the pedals. :-) On rough country roads (the majority of what I ride on) I find that tire pressure that is a little softer (90 psi-100 psi) is a lot more comfortable than higher pressure (110-115 psi). When the pressure is high I can feel every bump in the road and I actually have slower average speeds than I do for lower tire pressures. For me I seem to ride slightly faster (0.1-0.2 MPH) faster on tire at 95 PSI than I do on tire at 105 PSI over my standard morning ride. I usually just set the front tire somewhere between 90-105 PSI and set the back tire at 5 PSI higher and don't worry about it to much. In an event I don't know the course as well as I do my morning route that I do multiple times every week so trying to guess what pressure is going to be the best for the road surface of the race isn't possible so I just go for comfort and don't fret the 0.1 mph difference that tire pressure could make.
Edited by BlueBoy26 2015-05-26 11:03 AM |
2015-05-26 1:29 PM in reply to: mchadcota2 |
74 Post Falls, Idaho | Subject: RE: Tire pressure/speed Depends on tires, as some have a bigger difference in rolling resistance at variations in pressure, some have very little variation with pressure. Depends on course, as rougher courses will be slower at higher pressures due to bike deflection robbing energy. Last week I swapped out 32mm lightly cross hatched (not knobby) cyclocross tires at 80psi to a slick 25mm road tire at 100psi on my commuter bike and it feels like someone removed a dragging brake, I gained about 2mph and it's much more responsive... but that's a combination of tire weight, tread difference, and pressure, not a single variable. |
2015-05-26 3:20 PM in reply to: mchadcota2 |
8 | Subject: RE: Tire pressure/speed Is there any issue with going too high other than roughness? I'm about 155 lbs rolling on 23mm Veloflex Masters and have been riding on the paved bike paths at 120psi and they seem fine to me and way faster feeling then they did at 90. Been meaning to push them to their max of 145 just to see but I've never inflated any tire that high! Of course a race could be on any matter of road, I'd probably want to run the actual coarse to see how the tires feel but besides roughness is there any other issue of going high? Are they going to wear out a lot sooner like a car tire would? |
2015-05-26 3:28 PM in reply to: T-Stew |
Member 1748 Exton, PA | Subject: RE: Tire pressure/speed Originally posted by T-Stew Is there any issue with going too high other than roughness? I'm about 155 lbs rolling on 23mm Veloflex Masters and have been riding on the paved bike paths at 120psi and they seem fine to me and way faster feeling then they did at 90. Been meaning to push them to their max of 145 just to see but I've never inflated any tire that high! Of course a race could be on any matter of road, I'd probably want to run the actual coarse to see how the tires feel but besides roughness is there any other issue of going high? Are they going to wear out a lot sooner like a car tire would? http://www.bikequarterly.com/images/TireDrop.pdf Did you read this? 145 psi is just plain crazy unless you are a track rider. 120psi may feel faster however it is most likely slower unless you ride on all super smooth newly paved roads. |
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2015-05-26 5:54 PM in reply to: mike761 |
Champion 9407 Montague Gold Mines, Nova Scotia | Subject: RE: Tire pressure/speed Originally posted by mike761 Originally posted by T-Stew Is there any issue with going too high other than roughness? I'm about 155 lbs rolling on 23mm Veloflex Masters and have been riding on the paved bike paths at 120psi and they seem fine to me and way faster feeling then they did at 90. Been meaning to push them to their max of 145 just to see but I've never inflated any tire that high! Of course a race could be on any matter of road, I'd probably want to run the actual coarse to see how the tires feel but besides roughness is there any other issue of going high? Are they going to wear out a lot sooner like a car tire would? http://www.bikequarterly.com/images/TireDrop.pdf Did you read this? 145 psi is just plain crazy unless you are a track rider. 120psi may feel faster however it is most likely slower unless you ride on all super smooth newly paved roads. The last sentence is key - just because it feels faster doesn't mean that it is. For years, most riders would inflate the the max on the sidewall and the harsh, jarring ride felt faster so they kept doing it. However, with careful analysis, one can easily see that lower pressures are actually faster and more comfortable. Shane |
2015-05-27 9:47 AM in reply to: gsmacleod |
Pro 6582 Melbourne FL | Subject: RE: Tire pressure/speed Originally posted by gsmacleod Originally posted by mike761 The last sentence is key - just because it feels faster doesn't mean that it is. For years, most riders would inflate the the max on the sidewall and the harsh, jarring ride felt faster so they kept doing it. However, with careful analysis, one can easily see that lower pressures are actually faster and more comfortable. Shane Originally posted by T-Stew Is there any issue with going too high other than roughness? I'm about 155 lbs rolling on 23mm Veloflex Masters and have been riding on the paved bike paths at 120psi and they seem fine to me and way faster feeling then they did at 90. Been meaning to push them to their max of 145 just to see but I've never inflated any tire that high! Of course a race could be on any matter of road, I'd probably want to run the actual coarse to see how the tires feel but besides roughness is there any other issue of going high? Are they going to wear out a lot sooner like a car tire would? http://www.bikequarterly.com/images/TireDrop.pdfDid you read this? 145 psi is just plain crazy unless you are a track rider. 120psi may feel faster however it is most likely slower unless you ride on all super smooth newly paved roads. Exactly! This was tested and publicly noted years ago with a chart by a well respected engineer Tom Anhalt. Here's the chart showing what happened in a real world scenario for rolling resistance vs. increasing PSI (blue diamonds) for one set of tires. Note the sharp shift upward in rolling resistance after ~ 120psi that occurred. Again don't always believe what you feel! |
2015-05-27 11:40 AM in reply to: #5117913 |
Master 3127 Sunny Southern Cal | Subject: RE: Tire pressure/speed Good question. I am looking for a stealthy away to slow down my kid. Maybe dropping his tires to 60 lbs. will help. He caught on to the dragging brakes at the top of the first climb, but still beat me to the top anyway. Maybe I could stick some lead inside his frame? |
2015-05-27 1:14 PM in reply to: 0 |
8 | Subject: RE: Tire pressure/speed Originally posted by mike761 Originally posted by T-Stew Is there any issue with going too high other than roughness? I'm about 155 lbs rolling on 23mm Veloflex Masters and have been riding on the paved bike paths at 120psi and they seem fine to me and way faster feeling then they did at 90. Been meaning to push them to their max of 145 just to see but I've never inflated any tire that high! Of course a race could be on any matter of road, I'd probably want to run the actual coarse to see how the tires feel but besides roughness is there any other issue of going high? Are they going to wear out a lot sooner like a car tire would? http://www.bikequarterly.com/images/TireDrop.pdf Did you read this? 145 psi is just plain crazy unless you are a track rider. 120psi may feel faster however it is most likely slower unless you ride on all super smooth newly paved roads. I should rephrase. They didn't just feel faster, but I actually went faster, I mean I almost always record my trip on gps. That article mentioned balance of comfort and speed. So sounds like what you should set up your road/touring bike for right? I'm talking about my racing bike, comfort isn't nearly as important in the equation, and yeah I usually only ride on smooth paved roads. Of course if a race happens to be on rougher roads then I'd try to match up to that by doing some test runs and adjusting pressure. Exactly! This was tested and publicly noted years ago with a chart by a well respected engineer Tom Anhalt. Here's the chart showing what happened in a real world scenario for rolling resistance vs. increasing PSI (blue diamonds) for one set of tires. Note the sharp shift upward in rolling resistance after ~ 120psi that occurred. Again don't always believe what you feel! I'm afraid I don't understand the units or how to interpret that chart. What was the weight of the rider and the loading of the tires? Size of the tires? AFM? Looks like there was a big sweet spot at 120psi so if anything it supports that my 120psi sounds like a good idea not knowing anything else about the graph or conditions of the test.. I suppose it would be really easy to test this under my exact conditions. Of course I can't be sure I give the exact same amount of effort for each test but more meaningful test for my bike than any chart could tell. Edited by T-Stew 2015-05-27 1:17 PM |
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