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.
https://axs.sram.com/guides/tire/pressure
https://silca.cc/pages/sppc-form
https://cycling-sport.com/en/resources/tire-pressure-calculator
https://www.renehersecycles.com/tire-pressure-calculator/
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.
Perhaps the biggest reason there are so many opinions on optimal tire pressure is that many typical bike pump gauges are quite variable.
I have two respected brand name pumps (both with Presta & Schrader heads) and tested them to ‘top off’ a large truck tire to pump-gauge-indicated 100psi. Then checked with a separate calibrated gauge (unlike a narrow bike tire, should be minimal relative air loss with gauge-checking a large tire). There was a consistent 7-8 psi difference between the 2 pumps. Soooooo- My preferred INDICATED pressure for 25c tires (under my 180# body) is 90psi with one pump but 83psi with the other.
Given that variability I agree 100% that a pump-indicated 85-90psi for 25c tires is a good rule of thumb for most cyclists.
I too have noted differences between floor pump pressure gauge readings. I forgot my pump for one group ride and borrowed someones pump to air my tires. My usual 90 psi on my pump left my tire way over filled using the borrowed pump. I stopped before I even got to 90 psi on their pump based on the feel of the tire.
We’ve reviewed the Topeak digital pressure gauge in the past, which is very good.
https://www.roadbikerider.com/topeak-smartgauge-d2x-review/
George raises an EXCELLENT point- periodically feeling the tire during inflation- especially when using a pump you haven’t used before. I watched a guy literally blow a tire when hurriedly using a borrowed pump just before an event. After the tire blew the pump’s owner sheepishly said- “Oh yeah. I forgot to tell you the pump’s needle jams at around 5o psi”. DOH!
… 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.” . . . as noted in the article, as well as tire details, the appropriate tire pressure is largely based on weight (combined rider/bike/water etc), as well as tire width. I weigh 140 lbs, and my “sweet spot” tire pressure for 25c tires is 65 psi, with 60psi in the front tire.
Thanks for addressing an important topic.
A comment from a 200 lbs. rider. My weight ranges between 200 and 208 lbs. I ride only continental’s best tires and over the years have found 95 to 100 psi works well for the rear and 90 psi for the front. I use 25c on the rear and vary the front between 23c and 25c depending on road conditions. My bike is a 2010 Trek Madone. H2 with carbon forks. I usually ride around 5000 miles a year. Hope this helps a bit in your decisions.
Remember Uncle Al? He did the mechanics section years ago. In an article he suggested 85 psi as ideal. I’ve continued with that as I’ve moved from 23-28 cm tires over the years and find it very comfortable.