Pressure gauge changed my life ! Read this!

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This srsly has changed my life; my bike is insanely more comfortable, and safer.

My emergency braking distance has shrunk by 50 - 75%.

I’m a very sciencey person, and I’m deeply disappointed in myself that I’ve now been riding & racing seriously for 10 yrs, and didn’t know this: Pressure gauges on pumps are garbage. All of them. Even the “good brands.”

They are +/- 10 - 30% or more.

Also: We are riding our tires over - pressured, and it’s making us miserable !! :slightly_smiling_face:

Again; so self - disappointed !

We would never crank the pressure on our car tires up to the max allowable on the sidewall; we go by the car’s pressure, on the doorframe.

Why the heck was I doing this w my bike; 95 - 105 PSI ?!?!

It really is pretty simple: We need tire pressure to protect the rim from damage, when it goes over bumps. Whatever compression force is created, we need a slightly greater pressure.

Anything above this is just making the tires harder, and harder, and harder, for no reason.

It’s highly dependent on the wgt of the rider & load. A 5 kg backpack / panier can make a huge difference in needed pressure.

I’m now running around 75 PSI !!! It’s insanely more comfortable; the vibration and bumps into my butt & hands are reduced massively.

My road contact patch has increased in size at least 2 - 4 x, and the grip and handling on smooth pavement in corners is insanely better, especially down hills. Emerg braking is way shorter.

Online calculators are available to calc your ideal tire pressure.

You need a pressure gauge that is excellent quality & accurate, and allows you to clip it on, and then release air slowly until you’re bang - on.

I will prob run 95 ish for race days, because my brain won’t let go of the idea that it’s 0.5% “faster”, but I know functionally it’s near zero, and the advantage in safety & comfort is way worth the trade off.

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I run 55 psi on 28s at 165-170 lbs, even 75 seems pretty crazy high to me.

Are you sure that 95 would even be faster? I thought higher pressure = faster is an old myth that was busted with testing.

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I’m 205lbs / 93kg and run 58psi front and 62psi rear on 32c Continental GP5000 S TR tires. Some field testing has shown these are faster than other sizes on my Roval Rapide CLX II rims (front is 35mm external width, wider than the 32c tire).

Without aero considerations here are some rolling resistance tests:

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Article here:

On the topic of pressure gauges. I have some of those SRAM valve stem pressure gauges, and my Specialized floor pump reads the same as the electronic gauges. Not garbage.

FWIW. I realize you are excited by your discovery.

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As someone who did metrology for a decade I can confidently tell you that the floor gauges are still garbage. If they had a snubber and were liquid filled I might have a bit more confidence in them, but such gauges are more expensive than a high end floor pump.

A snubber greatly reduces pressure spikes and pulsations that wreak havoc on a pressure gauge, especially when the pressure suddenly drop to zero.

In a traditional dry gauge like you see in a floor pump, prolonged mechanical movement and sudden pressure drops damage the links, pivots, and pinions.

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All garbage, okey dokey.

:rofl:

My floor pump has a button to slowly release air, and it reads the same as the SRAM valve stem gauges and a good quality gauge. Maybe all 3 are garbage and agree, I dunno.

Back to your story - 75psi sounds a little high but maybe you ride on a concrete track/velodrome and/or run small tires on narrow rims or you weigh more than I do.

What do you get

using this calculator?

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Slow release of air is good. Having the needle wack against the stop is really bad for gauges. It still doesn’t help for the pulses every time that you do a stroke of the pump.

The Specialized gauges are cheapies, rated at 2% or 3% accuracy depending on the model when new. The accuracy is a percentage of Full Scale Deflection, so for the best model you would be looking at is +/- 2% of 120 PSI → +/- 2.4 PSI and the worst would be +/-3% of 180 PSI → +/-5.4 PSI. But these style of gauges simply don’t retain anywhere near that level of accuracy when out in the field for this style of application. I have tested thousands of pressure gauges and I do have a fair idea as to what gauges survive in what environments.

In my experience, digital gauges are typically pretty good when its comes to accuracy. The SRAM Quarq TyreWiz is rated at +/-2% with a maximum rating of 150 PSI, so that gives an accuracy of +/- 3 PSI. I’d be much more likely to trust the reading of these after a prolonged period of use compared to a floor pump.

So keep doing what you are doing, but just keep an eye out for discrepancies in readings.

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engineer and math major.

Rear tire starting pressure recommendations on Silca calculator for my bike:

rear pressure initial recommendation pavement
66psi new
63psi worn
58psi chipseal

At 60psi a +/-2% margin of error is 59psi to 61psi.

At 60psi a +/-3% margin of error is 58psi to 62psi.

Those initial recommendations are all within the margin of error.

So you can see my skepticism on your claim these pumps have garbage gauges, because practically speaking the gauges are fine. I ride outside all year, there is a mix of new and worn and chipseal on every single training ride. And lately there has been a lot of road work to install new water mains in the rural agriculture area where I do most of my training, so for the last 6+ months the roads also include gravel and dirt.

YMMV and all that.

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Mechanical Engineer here. Pressure gauge accuracy is expressed as a percentage of the Full Scale Deflection, not as a percentage of reading!

At 60psi a +/-2% margin of error in a gauge that reads up to 120 psi 56.6 to 62.4 psi.

At 60psi a +/-3% margin of error in a gauge that reads to 180 psi is 54.6 psi to 65.4 psi.

The first is within the recommended pressure range the second is not (even then the accuracy is optimistic, because gauges are typically designed to be placed vertically, are to be tapped before reading, need to be tested between 18 °C to 22 °C etc.), but my take home point is that you can’t rely on these gauges to maintain that level of accuracy. The only reason I chimed in on this post was because on the weekend I just found one of my floor pumps was out by 20 psi!

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Is the error random, or consistent? MTB tire pressure for me is around 20psi, and I find it hard to believe that it’s sometimes 17.6psi and sometimes 22.4psi. That’s a huge difference!

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Most are consistent, except maybe the cheapest obscure ones. Some are so badly made that they are leaking at the valve connector.
While you may not be able to transfer your specific value to someone/something else, if you consistently use the same gauge of decent quality and know from experience what works best for you, you are OK.
If you have multiple gauges, agreeing on the values, then you’re most likely also accurate.
What I don’t see clearly in the above posts are the following guidelines (some more obvious then others):

  • The heavier you (and your gear) are, the higher the pressure
  • The narrower the tire, the more pressure you need
  • In wet conditions, reduce pressure by a couple PSI to increase grip
  • TLE can be ridden with slightly lower pressure
  • Rougher roads/terrain need a bit more then super-smooth tarmac

If at some point you would loose speed because of higher roller resistance, you’ll gain that again by being more planted while cornering and you will feel more safe in high speed corners. The higher comfort of lower pressure also makes you perform better at the end of long events when fatigue settles in.
Best practice is too start a bit high and then reduce until you notice problems like hitting the rim or unstable cornering caused by collapsing side walls. Go back up a couple of PSI and you have your reference value.
I have a tubeless setup with 30mm tire at the front and 32mm at the back since the end of 2024. This is sooo much more comfy then my former bike with both tires at 25mm. And it’s at least as fast.

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fixed the last one for you.

Something else - wider is faster but your road bike frame may be the limiting factor.

A couple of interesting tidbits:

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Source: Dan & Josh: A Hookless Discussion - Slowtwitch News

FWIW my Tarmac SL7 has Roval Rapide CLX II wheels, the front rim is 35mm external and rear is 31mm external. I’ve done some field tire testing that agrees with NorCal Cycling field testing on the same wheels:

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no offense but everyone has known this for years

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it won’t be

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I actually did not phrase that correctly. What I meant was damaged roads with holes and bumps or when riding off-road, terrain with more vertical obstacles. That would require a bit more to reduce puncture risk.
On non-damaged rough pavement, you are absolutely correct that less pressure is better.

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It’s a weird thing with rough roads and tyre pressure. Lower pressure is both better and worse. Sure it would be nice to run lower pressure, but if you do the tyre can bottom out giving the wheel a hard knock and giving you a pinch flat if running tubes. Fortunately wider tyres allow us the best of both worlds. A low enough pressure to be smooth and comfortable, whilst still having enough air volume to avoid bottoming out. Interestingly, since switching to 28/32 GP5000 on my road bike I have yet to experience a pinch flat with TPU tubes, even though I’m running the same pressure that I did when I ran them tubeless.

I agree with idea of running gravel wheels on a road bike. I have my kids on 28/32 mm GP5000s on Lun Grapids that are 25 mm internal and 32mm external. The fronts have that toroidal profile that was mentioned. The Flo Cycling article isn’t a great example as their road wheels are really out of date. I do like the choice of the Roval Rapide CLX II, but I’m not sure why they are only 21mm internally?