Plow13

so i am making the switch from 25c to 23c tires and i remember seeing a formula where u put in your weight and tire size and you do some math and get the "suggested" tire pressure....i used the search function for the forums but couldn't find it...anyone know it?

Szczuldo

pump to 120, too rough for you, deflate to 115, still not the way you want it? 110, but i wouldn't go below 100.

Plow13

hrm i did a little more detective work and found one of psimet2001's old post and there were the formulas...


Tire Width=20: Pressure(psi) = 0.33 * Rider Weight in lbs + 63.33
Tire Width=23: Pressure(psi) = 0.33 * Rider Weight in lbs + 53.33
Tire Width=25: Pressure(psi) = 0.33 * Rider Weight in lbs + 43.33
Tire Width=28: Pressure(psi) = 0.33 * Rider Weight in lbs + 33.33

Tire Width=32: Pressure(psi) = 0.17 * Rider Weight in lbs + 41.67
Tire Width=37: Pressure(psi) = 0.17 * Rider Weight in lbs + 26.67


Example: You are 150lbs running 28's

Pressure (psi) = (0.33*150) +33.33 = 82.83psi (rear)
Front Pressure = .9*Front Pressure = .9*82.83psi = 74.55psi front

anfieldmx5

I like mine at 130psi

RHOsbrink

what if you are running the high psi vredestein tricomps (175)? or just the fortezza (145psi)?

Psimet2001 

Thanks. I thought I was going to have to find my old notes.

clausen

You will have to try different pressures to find out whats best for you. Depends allot on the type of roads you ride on and make and model of tires your using. for example I use 120 psi on one make of 23s and 110 on another make, same manufacture but different TPI in the tires.

https://www.sheldonbrown.com/tires.html#pressure

SPlKE 

OK, when I first read the thread title, I rolled my eyes, me not being a big believer in formulas.

However, the formula "Tire Width=23: Pressure(psi) = 0.33 * Rider Weight in lbs + 53.33" works out to 116 and change for me, which after numerous experiments up and down the psi scale during the past month, is pretty much my optimum pressure, front and rear. I pump to just past 120, and when I check it with a gauge, it has settled back to about 115-120.

Psimet2001 

Funny you should mention this link. That's where the interpolation for the formulas came from.

The formulas work very well, especially for those who really don't have a good understanding of what is going on, or a good baseline to draw from. I have used them many times to help newer riders.

As I mention in almost all of the posts I have made about the forumlas they serve as a baseline. Modify as needed depending on the tire, your terrain, and preferences.

Oh...and I actually ride at the pressures that calculate out for me. Turns out they are right on the nose.

serpico7

So the 150lb rider on 23s should ride ~103psi rear and ~93psi front. That seems low relative to what I've seen people post. Maybe the majority of us tend to overinflate? I'll try running the pressure the formula suggests.

Treefox

On the back of Pro2Race packaging, there's a nice little graph, which I find really quite nice.

Though I ignore it and pump them to 120 anyway.

Psimet2001 

Yes. Most just read the max on the sidewall and figure that high pressure = fast so they pump it up to the max. Ask yourself though if you - at 150lbs - should be riding at the same pressure that a 200lb cyclist is riding on.

There aren't any good guidelines out there to help people find what the pressure should actually be. That's why I went looking. The formulas are what I came up with. Give it a shot. Adjust to fit your own riding style as needed.

johnny99

Those numbers sound reasonable to me. I know much heavier people who use 100 psi front and rear in 23mm tires. If you start getting pinch flats, then you should increase your pressure.

Psimet2001 

I just realized that new BF software is replaceing double spaces at the beginning of each sentence with single spaces - probably to "save space". Makes the text look like poo.

I'd rather have spellcheck.

SPlKE 

I use same in front as in rear.

I do a lot of climbing where I'm standing leaning forward and bearing down on my front tire.

Psimet2001 

Yeah, but which tire wears out first - shows signs of wear earlier? Even if you climbed out of the saddle all day long your weight distribution for the ride would place more weight on the rear. That's why there is a higher pressure for the rear, because there is more weight being supported there....even if you are climbing.

johnny99

fyi - this tire pressure chart is printed is printed on the box for Michelin tires. The metric numbers translate to about 100 psi for a 140 pound rider or 115 psi for a 175 pound rider.

https://two-wheels.michelin.com/2w/fr...154733&lang=EN

San Rensho 

What is most important for me is the difference in pressure front to rear, since the front tire carries relatively little weight, it takes less pressure.

This is what I do. I get on my bike and then using a bathroom scale, record the weight under the front tire of my bike and under the rear tire and calculate the ratio front to rear. Then I select what pressure I want to use for the rear and apply the ratio to calculate the front tire pressure.

irish pat

pump your tires to the recommended psi, get on your bike and ride!! jokes
Are we a little anal before we start biking or are we only like that about our bikes? me included.

Psimet2001 

I am anal. Hear me roar.

SPlKE 

It's hard to say which is wearing faster since I changed up my tire combo and pressure regimen recently.

I used to run GP 3000 then GP 4000 F&R, with 10 - 15 more air in back. The back still wore faster than the front so I'd generally rotate tires at about 1000 mi.

Now I run GP 4000 rear with around 120 and Vredestein Fortezza Supelite on the front also at around 120.

After about 1000 miles on this combo, they seem to be wearing evenly, but I need to get up close and personal with the tires to find out for sure.

Since I had a rim strip related flat yesterday on the front, I'm going to pull the Vredestein to replace the rim strip and at that time, I'll give the tire a real good examination for wear.

Plow13

i heard that was a terrible idea to rotate your tires....

littledjahn

Do these formulas apply only to clinchers?

SPlKE 

I can't imagine why if you're running the same tire front and back and you make sure you don't reverse the rotational direction stamped on the tire itself.


(I wouldn't rotate my GP4000 / Vredestein combo, though.)

San Rensho 

Because the rear tire gets squared off as it wears. If you put a squared off tire on the front, the bike will handle very poorly.

And by the way, the direction of travel only affects the tires ability to shed water.