QUESTION: What’s the correct PSI for my road bike tires? I recently bought a used Trek Madone and I don’t know how high to pump the tires up on the bike. They say max pressure 125 psi on the side. Should I pump them up to that? – Elliot J
RBR ANSWER: First of all, congrats on buying a new (used) road bike! Welcome to road cycling.
There’s not really a specific number I can tell you for how high to pump up your road tires because it depends on a lot of different variables! How wide are the tires? How supple is the casing? (This is sometimes expressed in the form of how many threads per square inch, also known as TPI, where a higher TPI is typically a more supple and more expensive tire.) How much do you weigh? Are you using tubes or riding tubeless?
In general, a heavy rider is going to need to put more pressure into a given tire size to prevent the tire from bottoming out when you hit a bump and causing a pinch flat, or even just poorly performing in turns and while pedaling.
When I first started cycling in the 1980s, it was common for racers to buy the narrowest tire we could find and pump them up to the maximum pressure, because we thought this was the fastest. It definitely felt fast! But newer research determined that although it might feel faster with rock hard tires, it isn’t actually as fast as wider tires running much lower pressures than the maximum.
So then how do you determine the best tire pressure for you and your specific tires? Turns out that there are many different online tire pressure calculators that allow you to enter in your tire details and your weight and get a precise tire pressure number. Are the calculators perfect? No, but they’re definitely good and a great place to start and a safe number to go with.
Here are a few of my favorite online tire pressure calculators.
Not knowing your personal details, if you don’t want to bother with a calculator and you’re running the standard 700 x 25c tires and you weigh less than 200 pounds, you’ll probably get a fairly comfortable and grippy ride with 85 to 90 psi.