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Tire pressure/recommended psi and rider's weight
I've searched the archives but can't find a straight answer...
I ride Avocet 25mm road tyres. Recommended 110psi. I weigh 195lbs. I ride a fixed gear road bike that weights less than 20lbs. I commute with a carradice saddle bag. Does the 'recommended' tyre pressure change with the differences in rider + bike weight? I find that with 110psi, the tires feel too soft sometimes, but then I was riding 120psi 23mm until recently. Thanks for a straight answer. Joss |
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Tire pressure/recommended psi and rider's weight
Joss Winn wrote:
I've searched the archives but can't find a straight answer... I ride Avocet 25mm road tyres. Recommended 110psi. I weigh 195lbs. I ride a fixed gear road bike that weights less than 20lbs. I commute with a carradice saddle bag. Does the 'recommended' tyre pressure change with the differences in rider + bike weight? I find that with 110psi, the tires feel too soft sometimes, but then I was riding 120psi 23mm until recently. Thanks for a straight answer. The rating on the sidewall is a guide determined by the lawyers and marketing department. It's unlikely that the tyre will blow off the rim at even 50% above that. However, 110psi sounds about right if they are genuinely 25mm wide. I'm 20lb lighter than you and I use 120psi rear, 100psi front in 20mm tyres. |
#3
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Tire pressure/recommended psi and rider's weight
"Recommended" pressures are pretty flexible. They're subject to a lot
of factors, not the least of which is how you feel riding on them. Weight definitely enters into it, too. Sheldon Brown discusses it better than I could ever hope to: http://sheldonbrown.com/tires.html Look about 2/3 of the way down the page for the pressure discussion. |
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Tire pressure/recommended psi and rider's weight
Joss Winn wrote:
I've searched the archives but can't find a straight answer... I ride Avocet 25mm road tyres. Recommended 110psi. I weigh 195lbs. I ride a fixed gear road bike that weights less than 20lbs. I commute with a carradice saddle bag. Does the 'recommended' tyre pressure change with the differences in rider + bike weight? I find that with 110psi, the tires feel too soft sometimes, but then I was riding 120psi 23mm until recently. Thanks for a straight answer. Jos Don't worry-go ahead and use the inflation pressure that gives you the best comfort and performance (within reason, of course). My 700x24mm Veloflex tubulars are rated at 6-7 bar. That is only 90-103 psi, however, I generally run the rear tire at 120 psi with no problems. |
#5
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Tire pressure/recommended psi and rider's weight
"Joss Winn" wrote:
I've searched the archives but can't find a straight answer... I ride Avocet 25mm road tyres. Recommended 110psi. I weigh 195lbs. I ride a fixed gear road bike that weights less than 20lbs. I commute with a carradice saddle bag. Does the 'recommended' tyre pressure change with the differences in rider + bike weight? I find that with 110psi, the tires feel too soft sometimes, but then I was riding 120psi 23mm until recently. If these are the newer (black sidewall) Avocets that measure a true 25mm, then at your weight (I weigh the same) I'd run 100-110 psi. No way 120 psi. See: http://www.precisiontandems.com/phot.../tirechart.jpg Art Harris |
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Tire pressure/recommended psi and rider's weight
Joss Winn wrote: I've searched the archives but can't find a straight answer... I ride Avocet 25mm road tyres. Recommended 110psi. I weigh 195lbs. I ride a fixed gear road bike that weights less than 20lbs. I commute with a carradice saddle bag. Does the 'recommended' tyre pressure change with the differences in rider + bike weight? I find that with 110psi, the tires feel too soft sometimes, but then I was riding 120psi 23mm until recently. Thanks for a straight answer. Joss Run about 105 psi as during heating, they will rise in psi. This psi is to prevent them blowing off the rim. Do not exceed. If they feel soft, get a higher psi rated tire, like a conti tire. |
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Tire pressure/recommended psi and rider's weight
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Tire pressure/recommended psi and rider's weight
Thanks for everyone's advice. I'm running them at 110psi and will try
to get used to the softer feel. They are generally more comfortable than my old 120psi 23mm tyres but I kind of miss the sound of rock hard tyres rolling on the road and the feel of smooth tarmac underneath the tyre. These new tyres dampen this experience. It's the first time I've ridden 25mm and the first time with Avocet tyres. I had to import them to the UK as they don't distribute them here. I'm very impressed with the wire bead, non-kevlar type I bought. They look like no nonsense tyres having made no concession to marketing. (i.e black, smooth, bold, informative graphics and a really 'rubbery' feel). Joss Arthur Harris wrote: "Joss Winn" wrote: I've searched the archives but can't find a straight answer... I ride Avocet 25mm road tyres. Recommended 110psi. I weigh 195lbs. I ride a fixed gear road bike that weights less than 20lbs. I commute with a carradice saddle bag. Does the 'recommended' tyre pressure change with the differences in rider + bike weight? I find that with 110psi, the tires feel too soft sometimes, but then I was riding 120psi 23mm until recently. If these are the newer (black sidewall) Avocets that measure a true 25mm, then at your weight (I weigh the same) I'd run 100-110 psi. No way 120 psi. See: http://www.precisiontandems.com/phot.../tirechart.jpg Art Harris |
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Tire pressure/recommended psi and rider's weight
Joss Winn wrote: Thanks for everyone's advice. I'm running them at 110psi and will try to get used to the softer feel. They are generally more comfortable than my old 120psi 23mm tyres but I kind of miss the sound of rock hard tyres rolling on the road and the feel of smooth tarmac underneath the tyre. These new tyres dampen this experience. For fun & revelation, why not time yourself, over several attempts, over a fixed course at say 100, 110, and 120psi. I would say a minimum of three times at each psi, unless the differences are dramatic. If you do it all on the same day (i.e. short course) then you have to pay attention to getting an alternating ordering to check fatigue effects: e.g. first try 100 110 120, second 120 100 110 third 110 120 100, with adequate rest intervals between each rep. This does not cover all possible permutations but it is good enough. (Some would randomize the order but that is unsuitable.) You might be very surprised at which produces the fastest ride average. Of course, the results might very well permute according to the road surfaces, so you might try more than one course. Do report back with any results, if you try it.. |
#10
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Tire pressure/recommended psi and rider's weight
41 wrote: Joss Winn wrote: Thanks for everyone's advice. I'm running them at 110psi and will try to get used to the softer feel. They are generally more comfortable than my old 120psi 23mm tyres but I kind of miss the sound of rock hard tyres rolling on the road and the feel of smooth tarmac underneath the tyre. These new tyres dampen this experience. For fun & revelation, why not time yourself, over several attempts, over a fixed course at say 100, 110, and 120psi. I would say a minimum of three times at each psi, unless the differences are dramatic. If you do it all on the same day (i.e. short course) then you have to pay attention to getting an alternating ordering to check fatigue effects: e.g. first try 100 110 120, second 120 100 110 third 110 120 100, with adequate rest intervals between each rep. This does not cover all possible permutations but it is good enough. (Some would randomize the order but that is unsuitable.) You might be very surprised at which produces the fastest ride average. Of course, the results might very well permute according to the road surfaces, so you might try more than one course. Do report back with any results, if you try it.. Dear 41, Unfortunately, it's unlikely that a series of real-world test-runs will show any speed difference between 100, 110, and 120 psi inflation on high quality tires. This calculator uses Jobst's rolling resistance data to predict exactly that kind of effect: http://www.analyticcycling.com/ForcesTires_Page.html Below are the predicted changes for a 40.0 km ride, using two speeds with the default values and a premium clincher. 5000 3600 seconds @ seconds @ tire 8.00 m/s 11.11 m/s inflation 28.8 k/h 40.00 k/h in psi 17.90 mph 24.85 mph change change in seconds in seconds 140 -14 -7.0 130 -8 4.0 120 0 0.0 \ 110 +11 +5.5 12.5 seconds/3600, 0.35% 100 +26 +12.5 / The range of difference in a 1-hour 40 km ride at about 25 mph is less than thirteen seconds for inflations from 120 to 100 psi. A headwind of 0.2 to 0.3 km/h will slow the 40 km/h rider 9 to 18 seconds over the same 40 km ride. This shows how easily we end up wondering about physical effects too small to demonstrate by just timing a few test runs. Very few riders would expect to finish within a few seconds of the same time on two 25-mile rides on the same bike, but we still keep hoping to distinguish such small equipment differences with a test run or two. This kind of tiny change is why drum spin-down tests are necessary to provide rolling-resistance data and why our impromptu roll-outs are so unreliable. Carl Fogel |
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