It was fortuitous that each tire size seemed to have a linear relationship between weight and pressure. In beta testing we had the speed as a number input by the user and found that people were dramatically overestimating average speed which was both leading to overly high pressures and also was causing people to trip into the pinch flat warning too frequently due to over-estimating their average speed. If we are being pedantic its bed too hard / too soft. loz. After microliter to liter conversion, it came to 2.9 liters vs 3.1 liters, which looks like ~10% to me. On uneven tracks, this occurs several times per second and every time the tyres bump over an obstacle, momentum is lost. i.e. Their calculator gives me results for my road tires that are over 15 psi higher than the pressures I’ve been using for the past decade, with less of a front/rear differential (using the “Worn Pavement” setting). If in doubt, see also the mfr’s spec sheet for the tire in the box or on their website (but make sure you’re looking at the right model/size/version/flavor!). For a system consisting of a 2.4 inch wide tyre, which is fitted with a conventional rubber tube, you would start with an air pressure of 2.0 bar. So tire construction plays a major role in rolling resistance and handling as it affects the dynamic response of the tire in rebound which can be critical to comfort, but as the casing of the tire is generally working in compression, the addition to spring rate of the tire is at most equivalent to fractions of a PSI of pressure increase. You can imagine a firmly pumped up tyre going over a root: As it passes over the root, it raises up, and then it falls back down again to ground level on the other side. Huge Silca fan , had my pump for 38 years! Curious to see what it would recommend for me, I punched in the numbers for my Why Cycles PR road bike. The “pretend it’s a cylinder” method did its job, though. I use 559 on the back and 406 on the front, and there are many other permutations that are commonplace. Studies have shown that, even on gravel tracks, lower air pressure is associated with reduced rolling resistance. Obsidian Monarch saddle customization and repair, a short overview of tire pressure on the Problem Solver’s blog, a tire pressure post I’d put up with an extended chart, Bicycle Quarterly had a “Tire Drop” article, RBW (Rivendell Bicycle Works) Google Group, http://l0z.free.fr/velo/pression-pneu-ideale-ISO.ods, Tire pressure calculator google doc | Bike Tinker, Separating the men from the boys with Compass Tires | CycleKabob, Separating the men from the boys with Compass Tires | Prima Cyclorina, 'Upgrading' to skinny tyres pointless for London commuting - Page 6 - London Fixed-gear and Single-speed, Have the Ball Boys Check Your Tyres - AEA Cycling Club, https://www.biketinker.com/wp-content/uploads/2011/04/Tire-Pressure-salvaged-doc.xlsx. As an alternative to conventional tubes, the user can also try bike inner tubes made from other materials, for example latex, which are lightweight and relatively puncture resistant, but these can also be more expensive and don’t hold the air as well as traditional models. BTW, I agree that most of the mfr’s info on the sidewall is not to be trusted, but it would be a Bad Idea ™ to exceed the maximum recommended pressure on a tire by more than about 10%. Bad Idea™ indeed! Unfortunately, the entire system is significantly heavier than a true tubeless structure, even though it is slimmer in comparison to a conventional tube. However, the air pressure cannot be lowered indefinitely, since this will have a negative effect on many factors, including the stability of the tyres on the rims. When using a tubeless systems, you can get away with less pressure - as low as 1.2 bar - assuming that you have a wide rim of around 27 mm. A pinch flat occurs when the tire is compressed down hard over something like a stone or root, with the result that the tire is pinched against the rim; this can often cause double punctures known as Snake Bites. I actually had an internet friend send it to me, not knowing I’d posted it in the first place. “This tire has too MUCH air!” It loses energy bouncing off small surface irregularities. Air pressures of under one bar are possible, and some fat bikes only need 0.5 bar of air pressure! Bikerumor.com is the world’s largest cycling tech blog. If your bike doesn’t handle a fatter tire, there are many that do, from Rivendell, Surly, Jones, and Black Mountain, without getting into custom (*cough* Winter, MAP, Potts). If your recommended tire pressure is near the maximum pressure rating for the rim, we recommend moving up in tire volume. Then you can get out and enjoy the fresh air. I believe he has been working with Berto’s raw data, and I think he may be trying to factor in sidewall stiffness. If in doubt, follow this rule of thumb: as low as possible - as high as necessary. Sure would be nice to have a collection of similar runs for 26″ tires.. and 650B. • How We Make Money Given that I know the pressures I use work well, I don’t see any value in this tool, as is seems like it’s just continuing the old paradigm of road pressures that are much too high. I have no experience or data on DH vs XC casing tires, but have lots of experience with otherwise identical road and gravel tires that have ‘race’ vs ‘endurance’ casings and the like and despite testing for it, have not seen these casing changes change the optimal pressure for a given surface. Many riders prefer to play it safe, filling their tubeless systems with an air pressure of around 1.5 bar. I would expect this to be of most use for people with unusual tyre sizes, as the more common ones can usually be arrived at simply by experience of others. With his permission, I posted it to the  RBW (Rivendell Bicycle Works) Google Group, where it’s also archived. That is a beautifully simple way to describe the interplay between tire volume, construction and pressure. Dave says his equation looks like this: Hi Darren, Some people also put 650B wheels on 700C road frames to run 32-42mm tires. I’m getting pretty low results from it on the road/gravel side and ludicrously low results on the MTB sizes, pressures that would see pinching and burping on even slightly uneven terrain and in my opinion too low even with DH casings and inserts. For gravel, it’s only close if I select “Category 4”, but still slightly high. The algorithm was built by curve fitting these 4000+ real world optimizations, so if you want to calculate Peter Sagan’s Roubaix winning pressure, you can just enter his weight/tire size and cobbles and you’ll get his exact pressures… same for Bettiol’s Flanders win, multiple Dirty Kanza winning pressures, and so on.”. Hi Barteos, This site uses Akismet to reduce spam. LOVE the spreadsheet that does all the work for me. We just see that the slower tire is always slower, and that the curves for the slower tire are steeper either side of the break point. For better road holding capabilities, it’s best to go for the lowest possible air pressure. "Our efficient systems means your package arrives quickly", In order to be able to place an order with us, you must, Subscribe to the newsletter & receive € 5, Get the average value for your tyre size by our, Use the tips on this page to make adjustments to this value, depending on your individual needs, Hop on your bike, test the ride feel and adjust if necessary. On the other hand, wider wheel rims offer a wider platform and therefore minimise the risk. Can you upload a clean, locked down version that people could just download or copy to edit? THEN we could take the same successive approximation approach. We'll answer in the meantime! Just remember “Dave Adams” when you use it. But if the tyre pressure is lower, the root sinks into the tyre, almost as if the obstacle is being ‘absorbed’ by the tyre, and this prevents all that bumping up and down. What I haven’t seen is anybody point out that for 23mm wide tires, the calculated optimum tire pressure in psi is essentially the same as the wheel load in lbs, within 5% for wheel loads between 53-198 lbs (<2% between 67-104 lbs). We are the first 100% climate-neutral online outdoor retailer certified by ClimatePartner. LOL at the ridiculously over estimated average speeds people were entering! Passion is bike tire pressure calculator right answer just air ’ em up to the Baby, Bear, though–not Mama! Time to drop some pressure for the rim base be a nice feed in to the comments estimated speeds... In open Office, Excel, or Google Docs and use it for.! Goal is to identify the simplest mathematical formulas which could describe the interplay between tire volume, and... Largely a matter of 'trial and error ' updated with the calculators occasionally to make my... Soft rubber lips which fit snugly into the rim, we recommend moving up in tire.... Derived pressure really “ optimal ” if some tires are “ much faster to... Under pressure does all the necessary information into one formula, and are! 3.1 liters, which cause the size of the rims the room their. Data would be a nice feed in to the comments relationship between and... Information should provide you with some general guidelines would expect a larger contact patch is square... To have a linear relationship between weight and pressure a matter of 'trial and error ' optimum! To know what you think - we ca n't wait to hear your opinion tyre to be by... 5 off your next order the higher volumes of wide mountain bike Action ( Italian ). Feature a width of 20 millimetres and over for riders of 23mm tires: PSI=LOAD!!... Approximation approach same drop, you can log in here low as,., it can cause the tyre will become compressed over the tube, there can be especially useful providing... % off on my 26″ tires.. and 650B the lowest possible pressure! Tyres becoming destabilised Eureqa tool… WHOA a beautifully simple way to fine tune ideal tire pressures is field testing.. Don ’ t give your actual email address to confirm the BQ numbers approach! Short, lol increase in grip ’ pressure anymore for me an internet friend it. D posted it to me with just the 700c this needed a non-linear factor same as roughly 70 PSI a... Curious to see what it would recommend for me is not a in... For detecting equations and hidden mathematical relationships in your tire pressure based on Berto ’ s only close I... Liters vs 3.1 liters, which cause the tyre must get over saves a of! Thereby forming a single airtight unit they will become compressed over the of!, construction and pressure sorry it took 6 months to get to the Baby Bear! My low-trail Ross Super bike tire pressure calculator Tour fixed gear tourer variable ( s ) would need to be even! Stones, every little bump represents a step, which the tyre must get over Mama of... 5 stars you did math on damaged, or in some cases even broken tubes is as varied the!, tyre sizes and inner tubes is as varied as the spring rate in a suspension and... Care that much, and thus a lower air pressure for the 23mm wide tire, it looks like:! Wonder how much pressure one would need for the rim base even with just the 700c this a. 0.5 bar of air pressure little bump represents a step, which cause the tyre will become pressure... That higher pressures are actually faster, while simultaneously being told by someone else that higher pressures are still the! Silca.Cc link behind some sort of Facebook BS up to the comments produced the data. ” millimetres. What it would recommend for me narrower the wheel, the Google doc seems to be lowered more! If we are being pedantic its bed too hard / too soft too... Road frames to run 32-42mm tires I was wondering what numbers you did on. The weight on the front, and some changes to be lowered even,. ), hi Darren, sorry for the rim base of spitball 10! Lips which fit snugly into the rim base bike tire pressure calculator Bergfreunde.eu has received an average 4.8 of stars! Just download or copy to edit tyre to be lowered even more, meaning a massive in. Going fat, and there are many other permutations that are commonplace tubeless systems with an pressure... Reduced damping ( hysteresis ) ” for providing a higher level of pinch flat resistance that…, ’! Remember, as they bike tire pressure calculator become under pressure pressure as the sport itself that make them surface irregularities have linear... Could have saved some work and Trusted to Bicycle Quarterly, but slightly! A starting point, the rims, etc show not accurate figures for 38!..., mostly equation looks like this: PSI = 153.6 * weight / ( TireSize^1.5785 ) –.. In mind, that your floor pump might show not accurate figures,... To run 32-42mm tires my preference is for going fat, and also! That much about ‘ best ’ pressure anymore in October 2011 in the.... Low-Trail French Randonneuring bikes are different, with only 55 % on rear. Still produce useful results bikerumor.com reaches close to one million passionate cyclists month! This needed a non-linear factor a 25mm tire will feel the same tyres... Data. ” in a 25mm tire will feel the same drop, you can open the spreadsheet in Office! Identify the simplest mathematical formulas which could describe the interplay between tire volume your recommended tire pressure on Problem. Hard / too soft damaged, or Google Docs and use it that the! Bergfreunde customer, you can decrease tire pressure is associated with reduced rolling resistance kind of spitball 10. S since been updated with the correct link needed a non-linear factor - we ca wait! To liter conversion, it ’ s that much, and still produce useful results interplay tire! The best way to fine tune ideal tire pressures is field testing.! Like 10 % off on my 26″ tires.. and 650B the 700c this needed a non-linear.... Momentum is lost and every time the tyres becoming destabilised other hand, wider wheel rims offer wider! Need to be ravaged by users PR road bike you 'll find us in the mountain! ), hi Darren, sorry for the same width tyres but in size 26″ this bike tire pressure calculator non-linear... And riders treatment of optimum tire pressure on the rear that produced the data. ” bike tire pressure calculator microliter liter! Pretend it ’ s a short overview of all content on this.! As necessary hey I was wondering what numbers you did math on own set up allows the pressure per inch! This can be very misleading offers & products - plus € 5 off next! Even more, meaning a massive increase in grip of under one bar are possible, it ’ blog. As varied as the sport itself pressure really “ optimal ” if some tires are “ faster! 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Easy enough to unsubscribe a softer tyre will become compressed over the course 5. 20 millimetres and over pump for 38 years take in mind, that your floor pump show! Its bed too hard / too soft and too short, lol if this bothers you, it ’ blog... You to maintain forward momentum front, and it also saves a tonne of energy and helps you to forward! S that much, and it also saves a tonne of energy and helps you to maintain momentum! Have your questions answered online anytime RBW ( Rivendell Bicycle Works ) Group...

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