AJW2W11E

My tires on my 2016 Giant Defy got softer through the winter and I let them stay that way. It rains out here a lot in the Pacific Northwest and I use a lot of uneven roads and sidewalks and it gives me a factor of safety. When the roads get really bad, I use the Trails. After all its a Giant Defy. So I think they may be at 60 psi now. Of course I use Schwalbe Marathons, the world's heaviest tires, because I don't want to deal with flats. It's spring now and time for service. I'm no speed demon but when I put some air in my other bike's tires, my rides got easier.Where should I be at?​​​​​​​

tFUnK

Here's a calculator.

freeranger

So many variables that guidelines are just that, similar to trying to get the right size bike from the sizing guidelines from the mfrs. Just don't run your tires at max pressure listed on the sidewall. Maybe start 10-15 lbs. less than max and go down from there until you find the best pressure for your tires, your weight, and road surfaces on which you ride. Of course, don't go so low that you risk pinch flats. And your rear tire carries most of the weight, so it can be a bit higher psi than the front. Experiment, you'll find what is best for you.

Leisesturm

Seriously? Life is too short (YMMV) 25mm - 100psi; 28mm - 90psi to 100psi (or max press. on sidewall) Everything doesn't have to be made hard (swidt)

PeteHski

The calculator makes life very easy. Clever people did all the hard work for you.

GhostRider62

Go by feel. For 32 mm tires, it is a smidgeon (55-60 psi), 28mm tires a dash (70-75 psi), and 25 mm....just a pinch (85-90 psi). The odd thing are the sizes, the actual widths vary considerably compared to the label, so, much like baking, you must adjust

Chuck M 

I run my tires somewhere between the max pressure on the sidewall and what the voices on this forum tell me.

Seriously though, inflation pressure is a dead horse that has been beat to death as long as I've owned bicycles and I'm kinda old. The calculators on the internet range from the simple inputing your weight and tire width to adding so many variables it seems like you are trying to make financial plans for retirement. I suggest trying one of the calculators ( I didn't even look to see which one was recommended earlier a few replies up) and make adjustments from there.

Wildwood 

As always = Depends.
Tire width, rider weight, surface ridden, type of tire. Etcetera.

Iride01 

It varies by the road surface you are riding on. So just pick a number and start with that. After a few rides change the number up or down. Ride a few more rides and see if you do or don't like that compared to the first number. Adjust accordingly till you find your PSI number.

If you get pinch flats, you've gone way too low for your road conditions regardless of how comfy the ride may have been.

wolfchild

I just go by feel according to the conditions that I am riding in, no need for any fancy calculations.

PeteHski

Come on, there are not that many variables. It takes about 10 seconds to use the SRAM/Zipp calculator linked above and it gives you a decent starting point.

The other thing I check is if the tyre manufacturer has a specific pressure guide for their tyres. For example Pirelli road tyres come with specific pressure recommendations for rider weight, rim width, speed/comfort priority and wet/dry conditions. But some manufacturers are not so specific, sometimes only stating maximum pressures.

Chuck M 

That's pretty much what I was saying. There are so many calculators, I didn't look at the one above to see how many details it asked for, use one to find a starting point and take a few test rides to find what works.

Even the SRAM calculator states that it is a starting point. Yet in regular internet fashion, someone is going to come along and argue not all calculators factor in this, that and the other thing and without a digital tire gauge accurate to within .01 psi you can't get the correct tire pressure and riding with the wrong inflation will cause your babies to be born naked and without teeth.

ofajen

Yet another option, split the total weight between wheels and find reasonable starting points for front and rear wheels off this chart:




I run 32s on my road bike, total weight is 210 pounds but I figure more even split because I stand a lot. I end up running about 57 front/60 rear.

Otto

zandoval 

Gee... I just go at least 1/2 Bar - 7 PSI under the max pressure embossed on the side of the tire.

I guess I should really be paying more attention to using the correct pressure. I am sure if I were carrying a heavy load on a tour it would be critical...

Wonder what his pressure

flickr.com/photos
is?

Leisesturm

I did take a look at the calculator. There's like 20 fields?! And maybe I only have to make the calculation(s) each time I change tire brands but am I really supposed to check my tires with a gauge before every ride? Guaranteed the pressure changed since the last one. When did a practiced thumb get kicked to the curb by a digital gauge accurate to 1psi?? I don't know about your gauge but it's really hard not to lose at least 5psi, even 10psi, just getting the pump head to seat properly with mine. Really not sure when the obsession with a particular pressure for x, y and z parameters supplanted the thumb.

Leisesturm

So you totally blow off that chart then. I weigh just under 200lb myself. That chart is decades old and biased to 20 somethings. Why is it here?

shelbyfv

Get a decent pump with a gauge and use it before each ride. Not complicated.

shelbyfv

The chart is per wheel....

wolfchild

That's too simple.....We need math, science and complex charts to determine proper tire pressure before we can go out for a bike ride.

PeteHski

There are 11 variables on that Zipp calculator and they are all very simple things. Like how much you weigh and what width tyres and rims etc. So it gives you a meaningful pressure target to use as a starting point rather than just guessing. I think that's what the OP was asking for.

How you set and check that pressure is another story. But at least knowing what pressure you should ideally be running is a good start. If you are running 90-100 psi on 28 mm tyres then you are almost certainly well above the optimum unless you are very heavy. It would only take you a moment to check on that calculator.

PeteHski

You can dumb it down as much as you like.

ofajen

No, just a slight tweak on percentages. Besides anything like this is just a starting point. My actual tire pressures are based on many, many actual rides. I have no clue what you mean about 20 somethings.

I did my own static measurements of weight distribution in various riding positions and found that it can be 70% on the front wheel when standing or 60% on the back wheel when back on the saddle.

Trying recommendations from the chart seemed too soft in front so I based tire pressures on the lowest pressures that didn’t cause issues in feel or handling. I’m riding crushed stone so I want the lowest pressures that work well, to improve comfort.

Otto

Wildwood 

One of the main determinants will always be the rider's perception of a 'nice feel'. Some want a cushy cloudlike road ride, others want a very firm tire, others may pump to near tire max for smooth pavement rides.

7up

I usually go by the pressure on the side of the tire minus a few pounds less.

Fredo76

The stiffer the sidewall, the more energy is lost in flexing it, so higher pressure is a benefit. Try 90 psi in your Schwalbes and see if they don't roll easier.