Ideal Bike Tire Pressure? How Low Can You Go!? Commute BikeBlogger

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• published: 21 Sep 2016
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What is the ideal tire pressure for a comfortable bike ride with minimal risk of flats? For road riding some believe the ideal pressure to be about 15% less than the manufacturer's rated maximum pressure. There is a mathematical formula, of course. Formula: P = 600*L / (W*W) + 0.75*W - 25 (P) pressure in psi (W) width in mm (L) load weight of bike + cyclist on that wheel in pounds Example: W = 25 mm tire L = 60% of 180 pound weight on rear wheel = 108 pounds P = 97.43 psi for rear tire One popular guideline to find your ideal tire pressure is the Tire Drop method. Links below. Tire drop is how much the tire deforms vertically (sag). http://www.bikequarterly.com/images/TireDrop.pdf http://www.dorkypantsr.us/bike-tire-pressure-calculator.html Tire drop is different for the front tire and the rear tire because it depends on the rider's weight distribution on the bike, for example, 40% weight on the front wheel and 60% weight on the rear wheel. More weight on the rear wheel for a city bike (upright sitting position). How do you calculate your ideal tire pressure? 1. Find the tire's recommended min and/or max pressure range (printed on the tire sidewall). Sometimes only max pressure is printed. 2. Calculate your total body weight + bike weight + cargo. 3. Multiply step 2 by 40% to get weight on the front wheel. Multiple step 2 by 60% to get weight on the rear wheel. 4. Use the chart (or calculator) to find the ideal psi for each weight fraction (front and rear) and a specific tire width. 5. If the psi number is greater than the tire manufacturer's rated max psi, choose a wider tire. If the psi number is less than the rated min psi, choose a narrower tire. Using the Tire Drop method I can estimate the ideal inflation pressure on my tires, but I also add a 5-10 psi safety factor to the calculated ideal pressure. My inputs: Rider weight = 150 pounds Bike weight = 20 pounds Cargo weight = 10 pounds Total weight = 180 pounds Weight distribution = 40%/60% Front wheel weight = 72 pounds Rear wheel weight = 108 pounds Safety factor = 5-10 psi My ideal tire pressures: 23mm tires = 80 psi front / 120 psi rear 25mm tires = 65 psi front / 100 psi rear 32mm tires = 50 psi front / 70 psi rear 35mm tires = 45 psi front / 65 psi rear This method suggests I can safely use a 23mm rear tire but a heavier rider/bike/cargo would be better suited to something wider. I would probably be best suited for 25mm tires, or 23mm front and 25mm rear. Tip 1: Less tire pressure provides more comfort, more traction on crumbling roads, and less tire wear. Lower than ideal pressure though and you risk more flat tires (or if you just ride aggressively or on bad roads). Tip 2: It is best to match tire widths with the closest matching wheel rim widths (overall) for best ride handling capabilities. Road cycling wheel rims generally come in three sizes: narrow, medium, and wide. Tip 3: Tire widths and construction can vary between manufacturers and models, so the only way to find the true tire width is to carefully measure it when fully inflated on your wheel rim. A 23mm tire may actually be 24mm etc. Tip 4: Modern thinking suggests rolling resistance is less on 25mm tires than 23mm tires, although 23mm tires accelerate a little faster and have a little less air resistance (front tire most critical). Note: The internet credits this guy for inventing the stop sign. Oddly enough he is also credited with the much better, although rarely used in my country, roundabout (traffic circle). https://en.wikipedia.org/wiki/William_Phelps_Eno Video - Stop Sign v. Cyclist Effective Cycling Commuting Bike Blogger https://www.youtube.com/watch?v=EL2Ws1YzLwg Video - Exploring Deer Creek Railroad Tunnel Bike City BikeBlogger https://www.youtube.com/watch?v=7nMOr39JD5U VIdeo - Dead Ends! Baseball! Dirt! UPS Estimated Arrival? Commuting Bike Blogger https://www.youtube.com/watch?v=BvuDrEdb1M0 Subscribe to BikeBlogger http://www.youtube.com/subscription_center?add_user=BikeBlogger Bike Blogger Channel http://www.youtube.com/BikeBlogger Bike Blogger Website http://www.bikeblogger.com