Which one sounds right - the 91/114 psi or the 51/51psi?

I'm not sure if my frame accommodates 28s. So far I am loving the "zippiness" of the 25's compared to the 2.25" on my 29'er. haha.

Both. Since there is less weight on the front of most bikes, it makes sense to use less air in front. So I got 91 psi front and 114 psi rear for your numbers, as well.

That said, if you can avoid hitting potholes and other bumps with your full weight in the saddle, you might be able to get away with less pressure. This stuff isn't right or wrong.

Any idea what the max PSI is on a typical 25 tire? I'd check but I'm at work right now. I guess it's just surprising that 114 doesn't exceed the max PSI.

Depends on the model, but mine have been between 115 psi and 130 psi or so. There's some wiggle room around those specs, too.

I weigh about the same as the OP and this is about what I run on 40mm Clements (now Donnelly). I am running tubeless.

Appreciate all of the help! Just got a road bike so this info is very helpful.

That's what I run on my 40mm tires. My loaded down weight is similar to yours. I don't run tubeless.

I wanted to to see what optimal pressure for 35mm tires are, but the calculator doesn't offer that tire width. I find it odd that it jumps from 32mm to 37mm, when none of the other tires differ more than 4mm in width from the previous one.

Just take the average of 32mm and 37mm Close enough.

The reason that it has the sizes it does is that it is based on a study that used those sizes of tires.

One more calculator with more options to play with: https://silca.cc/pages/sppc-form?__h...a-c25cf17e117f

this works out pretty much where I am. I’m ~200# bike + rider, tires nominal 25s, actual 24s, fast group pace on OK roads, F/R weight 48/52 the calculator gave me 99F/102R. I usually run 100 F&R. I think the assumed weight distribution is a little off - given that I wear out rear tires at ~2x the rate of front tires, I imagine my F/R is likely closer to 40F/60R

Don't get too obsessed with numbers....As long as you're not getting pinch flats then your tire pressure is correct.

If you want to find the go-to chart, Google "Frank Berto bicycle tire pressure chart." Using your numbers I get someting like 47 front 53 rear. It's not exact because they don't have a line for a 40 mm tire, but they do have a 37. In any case, some very sharp folks like Jobst Brandt usually just bumped it up to the sidewall max value. I've been comfortable with about 95 psi in 22 mm tubulars for road riding, for several decades. I adjust for comfort and to have enough pressure to prevent bumps from cracking my rims when I forget to unload over them. Same for when I use 42 mm Hetres or 31 mm Strada Bianca. There is no magic failure when the pressure is a few # too low or too high, but you may feel it in your butt or the heels of your hands. When I use the Berto values I feel it is too soft. Jan Heine writes that while that is true, it is not actually slower. I dunno, ultimately I like pedaling to have a balance between zip and cush.

Thanks everyone for your input. Some valuable feedback there. Will definitely do some trial and error to get my optimal setup, but should be able to start with a good starting point at least. Cheers all.

Every comment on this thread has been much higher pressure than I run. I weigh 165 lbs. Riding gravel on WTB Riddler 700x45mm, tubeless. I run 28 psi front and 34 psi rear. I have not noticed significant increase with rolling resistance on pavement compared with higher pressure and tracks better on gravel. I will drop several psi front and back if course is gnarly. I also have a "gravel" tandem. Co-Motion Java. Combined weight is over 300 lbs. I run about the same pressure on 700x50mm tires (also tubeless), may increase pressure a couple psi if mostly paved course. Once read a comment that if running tubeless, you shouldn't exceed the minimum pressure listed for the tire.

Interesting as that's almost the same pressure I run when using 44mm compass tyres, set up tubeless, on mostly road surfaces, F/28 R/30 lbs, and I find the ride quality considerably better across the board, as far as comfort is concerned the difference between dropping to 30 lbs from 50 lbs is night and day (so comfortable), cornering grip on dry roads is similar (no worse) and as a bonus considerably better in wet conditions.

Jan Heine proved that tyre pressure generally has no bearing on rolling resistance, when tested with the rider on the bike in normal riding conditions. Since dropping my tyre pressure considerably across the board on all my tyre/wheel combinations, I have not looked back, and I am definitely not slower, IMO faster due to the extra comfort!

Here are other tyres I use, and the pressures I run in them on road surfaces mostly (all set up tubeless).
Schwalbe Pro One 25mm, F/44 R/46 lbs.
Schwalbe Pro One 28mm, F/41 R/43 lbs.
Panaracer Gravel King Slick 32mm, F/37 R/39 lbs.
Compass Switchback Hill 650b 48mm, F/26 R/28 lbs.
Schwalbe G-One Speed 650b 60mm, F/18 R20 lbs.

The way I generally gage tyre pressure for a given tyre/wheel combination is to continually drop pressure until the tyre starts to squirm slightly when cornering, and then add a few lbs until this sensation stops, and that's how I set the tyre pressure for all my setups, again as I mentioned earlier this is similar to what Jan Heine suggests and he has done extensive quality testing with the rider on the bike and also on different surfaces to back up his theories, and just to make it more interesting which might open up a can of worms, I feel equally as fast on my 60mm tyres as I do on my 25mm tyres (no proof), the only time I seem slower is on really steep climbs out of the saddle, and sprinting out of the saddle to catch catch someone in front of me in a race (I guess due to the extra weight), I have had no problem keeping up on flat roads at A grade race speeds on a converted MTB bike frame with drop bars added, at speeds ranging generally from 40-50 klm, and at times even topping at 60-65 klm with a tailwind, and a lot more comfortable and stable as a bonus!

For anyone sceptical I suggest try it first, be open minded, and then make up your mind, I think you'll be pleasantly surprised with your findings!

You didn't say what tire you're talking about - they're all different. The PSI range is printed right on the side of the tire, so start there. It has nothing to do with your weight and everything to do with the tires themselves.

Generally, higher pressure gives you less rolling resistance while lower pressure gives you a cushier ride and better grip on some surfaces. Just experiment within the range printed on the side of the tire and you'll be fine.

Wut?

It abso-freaking-lutely has to do with your weight.

No, it has to do with the specifications for that tire. They don't sell different versions of the same tire, depending on the weight of the rider. And there's no scenario where a rider's weight would override the manufacturer's specifications, printed right there on the side.

Optimum pressure is primarily determined (in equal parts) by the tire volume and rider weight. (casing construction and personal tastes also play a role but far behind the first two factors). Without knowing either of these, one is shooting in the dark.

Max tire pressure simply tells you whether a given tire can be run at that pressure. If it can't, you need a different (most likely larger) tire. So in that sense, they DO make versions for heavier riders if a model comes in different sizes.

Perhaps we are saying the same thing or I am completely misunderstanding what you are saying.

For what it's worth, hadn't seen this calculator before, but ran the numbers for my gravel bike.. darn close to what I've arrived at via experiments. Dead on rear, I run a couple of lbs. less in the front.

Maybe we are. My point is illustrated with this example:

My wife's bike has Kenda Small Block 8s, which are rated for 50-85 PSI. My bike has Maxxis Ikons, rated 30-65 PSI. So when we are going to spend the day on smooth hardpack and want to roll fast, I fill her tires up to 85 PSI, and mine to 65 PSI. Body weight is not a factor - we use what's on the tire.

When we want to ride rougher or looser terrain, we reduce hers to about 55 and mine down to about 40, and that gives us each the best results with the tires we're each riding. Still within the manufacturers specifications, but different because they are different tires.

That's why asking what the best tire pressure is, without knowing exactly what tire we're talking about, is pointless. It depends on the tire.

I don't like that at all! Runs counter to the age old advice to new racers. And yes, we laugh because we now know that some of that advice wasn't the fastest. But ... the huge but ... the race veterans and longtime coaches knew that staying upright; not crashing was key to good training and fitness and hence the ability to produce real speed when needed.

A 190 pound rider slamming into a pothole with all his weight on the front wheel (see my post last page) and only 73 psi in a skinny 25c tire? That's not going to end well. In fact, that might cause conditioning issues months later. Being at 85% of one's best because of a bad crash two months ago is a loss of 15% power. Real. 10% more rolling resistance in the front tire because you had nearly the same pressure up front as the back - well, rolling resistance is rarely more that about 20% of one's total resistance. The front is say half the total rolling resistance. So 1/2 X 20% X 10% increase for the additional pressure = 1% change in the total resistance, Yes, measurable but compared to a crash from loss of control because the front tire blew out or the rim collapsed, peanuts.

Those pretty charts are going to get people hurt. We hit potholes, If we ride long enough, we hit them without doing the proper un-weighting of the wheels and we may hit one one day while braking hard. Front tire pressure could make a very real difference. (If you do choose to ride the low front tire pressures, wear a helmet and shave your legs. Both make the ER experience a lot better and speed recovery.

Ben

Nope, it depends on the weight on the tire. Yes, you can fill the tire to the max, but that is not the way it works optimally. The tire is designed to be able to support weight, using air, how much weight it can handle is dependent upon how much air is in the tire. The tire does not need 85psi to hold up lower weights, and handle the way it is designed to handle. Filling the tire to the max, with a low bike/rider weight, you have a smaller contact patch, which will affect traction for braking and cornering. T the same time, the tire will be hard, and not compliant, it will not be able to conform to small bumps, causing the tire to bounce and lose traction more easily. You most likely will never notice, if you are riding recreationally. On a perfectly smooth road, you probably won't notice any issues, but overall, using a lower psi, one determined by the weight of the rider and bike combined, will give you a better ride, and better efficiency.

It is like a car. The tire is designed to carry a max load at the max pressure the tire is rated for, but most cars use a lower pressure for each tire than the max psi the tire is rated for. As an extreme example, the old VW bugs, the ones with the engine on the back, used tires with a max inflation pressure of 35 psi, but, the VW Bug's pressure recommendation in the front, was 16 psi. There was very little weight on in the front of the Bug, so VW recommended 16 psi. That gave you the proper contact patch, the best handling, and best wear for the tire. If you used more, it rode like a buckboard, slid in cornering, the front would easily lock up during braking, and the tires wore in the center of the tread.

Tire inflation has everything to do with the weight the tire has to carry. The inflation range stamped on the tires is simply the minimum psi and maximum psi the tire is designed to be used with, depending on the weight the tire has to support.

And when you put different tires on that old VW bug, everything changes. It is literally impossible to know (or "calculate") the optimum pressure for a tire, without knowing exactly what tire you're talking about. That shouldn't be hard to understand.

When talking about bicycle tires, 45 PSI in one tire may handle and perform completely different than 45 PSI in a different tire. That shouldn't be hard to understand either.