Your method of setting correct tyre pressures
 

What method do you use to set the ‘correct’ tyre pressures on your bike(s)? And how do you know you’ve finally hit the right pressures?

The method I’ve been using so far is to check the max PSI on the tyre wall and inflate to a value close to, but slightly below, the max pressure. However, I think that this is probably not giving me the best ride quality given that there is a variation in fore and aft load on the bike wheels. Am I right I thinking that the rear tyre should probably have a slightly higher tyre pressure than the front, and bike weight plus body weight also play a role?

inflate until the tire explodes, then back it off about 5 psi

There's no such thing as correct tire pressure. Optimal pressure depends on the specific conditions, including the tire itself, the rider's weight, road surface, weather, and rider's personal preference about ride quality.

So instead of thinking about numbers, think about how pressure affects the ride.

Lowering the pressure will make for a softer ride, which is nice, especially on bumpier roads. But it increases friction and slows you. It can also allow you to bottom on bumps, causing pinch flats and denting rims.

Higher pressure lowers friction which is nice, plus makes for very crisp handling. But less friction, also can mean less traction, especially on wet roads or when cornering. It also makes for a harsher ride, especially if the road isn't glass smooth.

So start at some arbitrary pressure, say 90% of the tire's max. Ride that a while and think about the ride. Then add 10psi and ride that a while making not of what's better or worse. If it felt better overall, try 10psi more, and do this until the good isn't getting better, but the bad is getting worse. You now have an upper limit.

Repeat the process going down from where you started until you find your lower limit. IME the lower limit tends to be more obvious.

So you now have a band, probably 20-30 psi wide, and have a good sense of where within it you're happiest. As you gain a sense of how pressure effects ride, you'll make small adjustments based on specific conditions.

With more weight on the rear axle, particularly with my cruiser bike for example, should the rear tyre pressure should be higher than the front?

I have started experimenting a bit now, whereas previously I would just inflate both tyres close to the max value stated on the tyre wall. I notice that on my Fat Frank tyres theres a minimum and a maximum range of 20-55 PSI.

""What method do you use to set the ‘correct’ tyre pressures on your bike(s)? And how do you know you’ve finally hit the right pressures?""

I use the gauge on the pump to set the correct pressure. When the gauge says 90 psi, I know it is the correct pressure.

• Inflate tire until bead snaps into place
• Measure tire height
• Multiply tire height by 15%
• Adjust my sag gauge to (tire height x 15%)
• Orient valve stem so I can reach while sitting on saddle
• Place sag gauge on rim
• Reach down and let air out until sag gauge shows level
• Get off bike and take pressure reading to note for future

Alternatively one could use the Frank Berto chart and fudge the different tire pressure required for tires of different casing stiffness.

1. Inflate tires to what I think is about right, with the front a bit lower.
2. If I don't like the ride adjust as appropriate
3. Ride more, worry less.

+1. Since experimenting with the Frank Berto recommendations years ago, I have not been disappointed. No pinch flats, and the ride is much more comfortable than when I simply aired up the tires to the max pressure rating.

This calculator makes it easy: Bicycle tire pressure calculator (I use the "Weight of (Fully-dressed) Rider & Bike" option and select the 45%/55% weight distribution for any road-style bike.)

trial & error

Step 1. Pump up tire
Step 2. Ignore gauge on pump
Step 3. Check pressure (i.e. tire 'hardness') with gauge of the thumb of my right hand
Step 4. Repeat steps 1-3 as necessary
Step 5. Ride


Dan

Don't worry about whether you gauge is accurate. Just make sure it is consistent. No matter how you go about calculating what it "should" be, you will still have to adjust up or down depending on you and your ride conditions. So with any gauge that gives consistent readings you'll know how to inflate your tires for the ride you want irregardless of whether the gauge is telling you the truth about the pressure.

What sag gauge to you use?

Do you find that you have to adjust for riding style (race vs casual ride) or surface (gravel vs paved)?


-Tim-

I ride with much less pressure in the front.

I ride my tires on the low side. Grip and comfort mean more to me than outright speed.

The "Best" pressure is a compromise.

Experiment a lot. Pay attention (document if needed) to the changes in performance and ride quality.

Too high and you lose grip and the ride is harsh. Too low and it sucks power from you.

Find your happy middle ground.

On a bike, 10% less than the max listed on the side wall. Allows for pressure increase on hot days, and helps prevent snake bite punctures. On Tadpole Trikes some what less on the two front tires. I run 65 on them and 80 in back on 100# tires.

I made my own out of some scraps of wood and a tiny bubble level, I can post pics a little later when I'm home. It's not that impressive but it gets the job done.

Definitely, it's terrain and tire dependent. I try to stay between 10-25% depending on the terrain/weather. For races/events I'll often overthink and add too much pressure on race day - it probably ends up faster but less comfortable. Most of my casual mixed terrain rides are such a smaller percentage of gravel overall that I stopped messing with pressure/sag and just ride it at my road pressure/sag as the segments are rarely longer than 10-15 minutes and mostly flat/smooth.

I've only been really paying attention to this for a few months. I'm still experimenting and figuring out just how much change in sag makes a difference in tire feel/speed/reduction in pinch flats. I think 2-3% is noticeable but I'm still not sure it's worthwhile to be so quantitative.

Riding through dust on an otherwise hard road (or marking the tires with chalk before riding) can give a good visual indication of the contact patch of the tire, too. If it's just a narrow strip down the middle of the tire, you're probably running too much pressure. Ditto if you find that your rear tires wear thin at the centers when there is still thick rubber at the shoulders of the tread.

From https://janheine.wordpress.com/2016/...ompass-tires/:

This was the poor man's tire pressure guage for sports cars back in the day.

One would mark the shoulder of the tire with chalk some distance up the sidewall and into the tread. If the chalk is wearing off the sidewall then pressure was too low. If chalk is left on the outside of the tread area then pressure is too high.

It was surprisingly effective.


-Tim-

I start with the 15% tire drop pressure from the calculator above and go from there. Works best to first weigh you and your bike front and rear to find out the load on each wheel and the F/R distribution. Two of my bikes are about 30/70 F/R so considerably less pressure for the front tires. (Both long wheelbase recumbent bikes.)

IDK if it is just coincidence; From my experiences with my bike, with a higher PSI in the tube the more prone a spoke is to break.

Good call on recumbents being different.

I take a guess at what pressure risks bottoming out on my rims. Let's say that's 30 psi with 32mm tires. 40 psi is the pressure I want to ride at. Then I inflate to 50 psi, because the tires will seep air, and I don't want to reinflate frequently. When it feels like I'm below 40 psi, I reinflate.

I like this method.

It completely avoids anything which might require thinking, minimizes the need to do actual work and justifies it all using hypothetical numbers and acronyms.

Only a seasoned IT pro can come up with a system like this. :p


-Tim-