#1
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Online Tire Pressure Calculators
I'm trying to establish a rough idea on what my tire pressure should be and I am relying on some online tire pressure calculators. Issue is there is a major variance on what is calculated.
Wheels are Zipp 202 FC - running Conti 5000 TL 25mm tubeless Body Weight - 168lbs Bike/Gear weight - 18.5 SRAM Calculator generates - Front 75 PSI and Rear 78 PSI Silca Calculator generates - Front 91 PSI and Reat 94 PSI I am leaning towards the SRAM amounts. Understanding that part of pressure is personal, I'm looking for a "safe" starting point and the above variance does not provide any comfort. Thanks for your thoughts. |
#2
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The SRAM values seem about right, Silica values are too high given your weight and going tubeless.
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#3
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I'm roughly the same weight. The SRAM values seem idealized IMO.
With the state of the roads today, I would surely nuke a rim in short time. |
#4
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Different calculators give different pressures because there is no “correct” tire pressure. Start with something in the middle and experiment. You might find that one calculator gives results that match your riding preferences, and that becomes your “go to” source.
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#5
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Quote:
Tubeless tires high performance Moderate speeds Worn pavement Remember that the 25mm GP5K TL will probably blow up to an actual width of 26-27mm on the FC202s. If you use different inputs you get a different tire pressure - 26mm Tire You get 86/88 Front Rear That said, a reason for the numbers varying so much from Silca to Zipp is in what each calculator is trying to do. Silca's intent is included at the bottom of the calculator page: Quote:
But I'm unable to get your numbers in the SRAM calclator. Using the following inputs, the output is similar to the Silca: 168+18.5 weight 25mm labeled (not actual) tire width 21mm internal width Thin casing tire Hooked Clincher Dry conditions 81.4/86.6 front rear If you change the casing to standard (which I don't think the TL qualifies as) then you get figures of 74/78.8 So sram/zipp goes by labeled size, and they probably use the inner width to then judge what the actual width will be, unlike Silca which just uses actual width. Also the sram/zipp is only for zipp wheels, so probably has some level of safety margin built in. Another decent tire pressure suggestion is the Enve chart, which gives numbers similar to the above - 82-85 psi on 21mm inner rims with a 25mm tire: https://www.enve.com/learn/tire-pressure/ |
#6
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Sram is about what I, at 165 + 19 bike, run. The other seems high
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#7
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Quote:
Greg |
#8
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I've always used standard casing in my Zipp calculations. I use Michelin or Pirelli tubeless.
Using thin casing increases my 62 psi to 68. I used 60 on my last ride and all seemed fine. I've never felt the need to increase the suggested pressure. The Zipp calculator is not just for Zipp products. There are variables to cover just about any combination you can think of. I did a test recently where I increased the pressure on my 28mm Michelin tubeless tires on 19mm IW hooked rims from my normal 62 to 80. Now I remember how awful the ride becomes with such high pressures, which some people still think reduces rolling resistance. I've used 72 psi with 25mm tubed Michelin on 17mm rims. The ride wasn't terrible, but I did get a couple of pinch flats. Zipp recommends 77/82. |
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