Jim’s Tech Talk
By Jim Langley
Proper tire inflation is all important for a comfortable ride and pinch flat protection. It also protects rims and ensures optimum performance.
So, when I received an email from regular RBR commenter “fixieguy,” asking what psi to pump his new tires to, I was eager to help. Here’s his expertly explained question and after is my response. You’ll see that I need an assist.
Please read his question and my answer then, if you have used the tires fixieguy has and have inflation recommendations, it would be great if you posted your wise words in a comment.
Fixieguy wrote
I suspect you’ve addressed this subject in the past in Road Bike Rider or elsewhere, and I’ll be happy enough if you just send me a link to a prior piece of yours that addresses my question.
The question involves a pair of new Vittoria Corsa Graphene 2.0 tires (700 x 25) that I recently bought. I had reacquired a beautiful 1990 celeste Bianchi SLX fixed gear bike that I had sold to a friend back in 2015 and I wanted some tan wall tires to reflect the style of its vintage. These tires were well rated.
It happens that the recommended tire pressure is 85-147 psi. My usual tire is the Michelin Pro Race 4, which recommends 73-109 psi. In my young and foolish days, I would pump to the max, which usually was 120 pounds, until I was enlightened to the joys and benefits of bringing the psi down by a lot by your predecessor on RBR, Uncle Al.
It’s my custom now to pump to the midpoint of a recommended range. On the Michelin that is to 91 psi, which I find comfortable (BTW, I weigh 180 lbs.). The midpoint on the new Corsa tires is 116 psi, which just seems high. Now, I realize the simple solution is to ride the bike and try different pressures until I find whatever feels right; but that seems too subjective and I like objective criteria when it is available.
Besides that, it’s still winter in New England, and I’m riding my winter bikes with 30mm cross tires for now. I won’t take the “new” bike out until mid-March when the sand and salt is off the roads and I need not be concerned about ice patches.
Notwithstanding, I’d like your advice generally on the subject. I do not race so marginal differences in speed are not important. Comfort, tire wear, puncture and pinch flat avoidance are important. Other than the trial and error method, what is a better way to decide the tire pressure to use on these new Corsa tires or, for that matter, to choose to use generally?”
My answer
Thanks for the email and great question, Martin. What I’ll do is use it for my column this week. And that way readers should weigh in with comments on what pressure they run and hopefully for the same tires you’re using.
Unfortunately I have no experience with that specific tire to help me and I’m a 150 pound rider, which doesn’t help either. I did grow up in New England so I do know about winters there.
But at your 180 pounds and with the tires being 25c – fairly narrow by today’s trends (I still ride 25c) – I’m thinking 95 psi. That ought to give you a reasonably comfortable ride with plenty of pinch flat resistance. I have ridden other Corsa tires in 28c and they were supple tires that rolled great.
In case you haven’t seen them, there are at least a couple of online calculators for tire pressure. One is based on the late former Bicycling Magazine technical editor/engineer, Frank Berto. (I worked with Frank when I was with Bicycling 1988 – 1999.)
As far as I know, his was the first published research into tire pressure testing. It resulted in a chart you could use for determining your optimum psi/bar. Now, it’s available as an online tool at the link below. (Frank Berto is deceased so I have no idea whether there’s any affiliation).
Frank’s chart is older and his research was done before road rim and tire widths started changing so much and so frequently. Yet, you’re asking about a rim and tire width he would have studied so his data should be good.
Here is the Frank Berto online calculator:
https://roubert.name/joakim/pressure/
Jan Heine in his publication Bicycle Quarterly also published and used Frank Berto’s chart and wrote about how to choose the best tire pressure. Here’s a link to his take:
https://www.renehersecycles.com/tire-pressure-take-home/
And, Silca recently came out with their pressure calculator. That only makes sense for a company selling awesome pumps. That’s their gauge in the photo. An accurate one is key to ensuring accurate pressure settings and theirs is among the best.
https://info.silca.cc/silca-professional-pressure-calculator
I also recommend Josh Poertner of Silca’s blog posts on all things tires. Start with this one titled Tire Size, Pressure, Aero, Comfort, Rolling Resistance and More! https://blog.silca.cc/tire-size-pressure-aero-comfort-rolling-resistance-and-more.-part-1-how-we-got-to-now
I hope something here helps you find pressure perfection fixieguy. Now, it’s your turn readers. Thank you!
Ride total: 9,927
Jim Langley is RBR’s Technical Editor. A pro mechanic & cycling writer for more than 40 years, he’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Tune in to Jim’s popular YouTube channel for wheel building & bike repair how-to’s. Jim’s also known for his cycling streak that ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.
There is also a phone app based on Berto’s tyre pressure calculator. I don’t know if there is a version available for iPhone, but the Android app works pretty well. I have the details of all dozen or so bikes in our garage stored in it, as when I come back to ride a bike after not having ridden it for a month or three, I find I’ve usually forgotten what tire pressure is best for that bike:
https://play.google.com/store/apps/details?id=com.edisongauss.bertotirepressure
I’m running Continental 4000s2 and 5000. I’ve gone from 23s to 25s. Back in the day I ran 120 like most everyone else. But went to 100 with the 23s. And now with 25s and 170 lbs. I reduced gradually to 80 psi which is working very well without pinch flats. Works for me.
I ride 25mm Conti 4000S2 tires on “old school” narrow rims (18mm external width). At my weight of 170-175 pounds I run 70/80 psi, front/rear. I’ve never had a pinch flat, despite the somewhat unforgiving roads I ride in NH and MA. On wider rims, the same pressures should work for Fixieguy or perhaps 5 psi higher if he’s running narrow rims on his vintage bike.
Running lower front pressure has always made sense to me as much more weight is on the rear. I would probably run a 15 or 20 psi difference. Another “crazy” option I have used is a larger rear tire at the same pressure.
I second Jim’s 95 psi opinion. I’ve been riding the Vittoria Corsa 700×25 for a few years now in New England and have found that 90 psi is just right for me (I fluctuate between 160-165lb). So at 180lb, I think right around that 95psi mark is a good recommended “first try” to see how that feels. Good luck Fixieguy!
Frank Berto based his chart on information from several tire manufacturers. They used a 15% tire drop to design tires, as a good balance between resistance and comfort.
The good news is that tire drop is a measurable value and customizes pressure for your particular weight, loading, and weight distribution on the bike. The bad news is that it’s tricky to measure. A friend helps. Set your bike on a flat floor and measure the unloaded distance from rim to ground. Sit on the bike and measure again, aiming for 85% of the first measurement. You’ll have to go back and forth a few times. Obviously 15% of 25mm is pretty small, so measure carefully.
Jan Heine’s research says that flexible high quality tires have a much wider range of usable pressures that don’t slow you down. Going to a 20% drop gives you more cushion, especially for rougher roads.
Anyway, 15% is a good starting point for your own experimentation. Silca’s online calculator seems very good and ends up with pressures very close to what I’ve settled on.
Also – don’t panic because your pressure is a few psi off. Try riding with too-low and too-high just to see what it feels like. You’ll be surprised how far off of the “ideal” value you can be without noticing any difference at all.
Great point.
Jan Heine wrote a terrific article about tire pressure for us a while back that is still very relevant.
https://www.roadbikerider.com/the-tire-pressure-revolution-by-jan-heine-d1/
A very similar question was asked of Lennard Zinn. A response by Vittoria and Lennard can be found at this link.
https://www.velonews.com/gear/technical-faq-minimum-tire-pressure-and-more/
I recall buying some Vittoria 23s years ago and the range was very high. I can’t recall the specifics but I can say that even at the minimum I was bouncing all over the place so I ran them below that at a more normal psi. I should add that I’m a lightweight, so I can go low on tire pressure.
I ride these same tires, although I too am only 150#. I ride with front 80/85 and rear at 90/95. Works well for me, comfort and good traction too!
I’ve been using the Vittoria tire for several years. The pressure depends on how width of the rim. I have fairly wide rims and weigh 180. I run 75 pounds in the front and 90 back. Excellent tires especially with a latex tube.
Choosing the middle of the sidewall pressure rating range makes no sense. Heavier riders need more pressure, lighter riders need less. It was an RBR column many years ago that noted the following points: 1) if you have to go over 100 psi to avoid pinch flats, you either need wider tires or to ride more carefully. 2) don’t be afraid to experiment with lower pressures. 3) lower pressures mean longer tire wear, better traction, and more comfort. What’s not to like? 4) only if you’re getting pinch flats or your tires are squirming in the turns do you benefit from higher pressures.
The Silca online calculator has given me pressures for all my bikes, starting at the mountain bike and ending at all road bikes and one e-bike conversion. Different tires, different sizes, different pressures. Each one delivers what seems to be the optimum pressure for the usages selected in the calculator. I have recommended that calculator to many and most like it. In addition, I have used the roll-down test to find what pressure yields the best performance r0lling down the same hill. Empirical and interesting.
Thanks for sharing your excellent tire pressure tips and recommendations for fixieguy everyone! Very helpful and much appreciated,
Jim Langley
Thanks to Jim and to all who have contributed your responses and advice to my question. Much good information has been offered, and I intend to use it. As Jim stated, he had privately responded to me so I did have a head start on the various links he provided
Respecting specifically psi for the Corsa G2.0, I am pleased to learn that running them at the low end of their recommended range or even lower is recommended in the responses. My concern would be a squiggly feeling much like that when one has a slow leak in a tire, but no one complained of that.
The Silca calculator seems well received by you folks, and I have run the numbers for the tire widths I use most frequently (25 in summer; 30 in winter). I had not previously factored in road conditions and realized just a few days ago that about 80% of my usual ride is on chip seal. For the 30mm tire on chip seal, Silca recommended 65 psi, which is 8 psi less than what I had been using. I tried it; I was initially concerned in that it looked like a huge contact patch between tire and road. However, the bike felt well in control, and it felt like a much more smooth ride than when I was going with 72.
Based on the calculator, I’ve been running higher psi than recommended despite my 180 pounds. I intend to take it down on the warm weather road bikes if we ever get warm weather here (it’s below freezing today and will be tomorrow also).
My only issue with the Silca calculator is that it treats all tires of the same size as equal. The Pro4 that I have been using and do like has only 110 tpi; the Corsa has 330 tpi and a cotton casing; its superior suppleness is recognizable to the touch. The calculator recommends 86 psi for a 700×25 tire on chip seal. Given that the Corsa is obviously more supple, it should be run a bit higher. Its minimum recommended psi is about 16% higher that of the Pro4. I’m going to go with 100 psi for starters on the Corsa, which is 16% higher than the 86 recommended generally. I would not be shocked were I to drop it down to 95.
In the end, after all the measurements and weighing and calculations, it does seem the final decision is subjective and based on what feels right. As we used to say long ago, if it feels good, do it.
Thanks again to all for your thoughts and advice.
I do a “roll-down test” to get a good idea for pressure: coast down a short hill which goes back up just after the bottom, keeping track of the max speed at the bottom. Do this with various pressures. (You can start with 10 psi intervals, going down to 5 psi if you really want to fine tune it.) The fastest is probably close to ideal. (Don’t be surprised if its a lot lower than you were expecting!)
I like Vittoria tires (25) and at 150# I run in the neighbor hood of 75#front and 90#rear. But this is quite a bit lower than the lowest recommended on the tire side wall of most of my Vittoria tires. Should I be concerned?