Re: accuracy of gauges, accuracy and resolution are all well and good but so long as you always use the same gauge, good repeatability is good enough. Obviously, an accurate gauge must have good repeatability, but a gauge which gives consistent results (i.e. good repeatability) need not be particularly accurate.

Most track pumps have gauges that read to 150psi or more, but the nature of a mechanical gauge means you’ll never get particularly good/accurate/repeatable readings if you’re only using the first 25% or so of the scale – I wouldn’t generally trust a reading from a mechanical gauge much below 50% of full scale deflection.

Pretty low pressure in my tyres – my pump leaks a bit so gauge not accurate but usually under 20psi. Tube but a heavy duty one and it’s on a wide rim. This on a steel 456. I’ve felt the rim on rocks plenty of times (reminds me to be a bit lighter on the bike) but went almost a whole year without getting a flat.

Help me out here…5psi on a gauge, is that 5psi above atmospheric pressure i.e. nearer to 20psi, or 5psi inside the tyre in which case atmospheric pressure approx 14.5psi makes the tyre (ignoring construction strength) pretty much flat before you start?

It’s the difference between atmospheric pressure and that in the tyre so 5psi above atmospheric.

Don’t forget, as soon as you attach the pump to an inflated tyre to read the pressure you get a small drop instantly as the tube of the pump fills up.

I’ve worked with pressures around 18 and been fine as well… though pressures in the 35 range are a big ridiculous. The only time I’d even consider close to that is if I was on a mountain epic and simply couldn’t afford a puncture, having used my spare inner tubes as trades for a meal of hot lamb testicle soup from a tibetan monk.

Surely Bryceland is putting a whole lot more force through his tyres than us mere mortals so needs a few more psi to cope with the G’s maaaan.

We have very accurate gauges, a 0-20psi, 0-30psi, 0-50psi, here due to racing (cars and bikes) that are tested each year, so confident there are correct. First thing that stands out is we have three track pumps, all half decent, on reads nearly 10 over, one nearly 10 under and one so close we use it in the pits and rarely check it.
The gauges on track pumps read 0-120/150 so, as said above, in the first 25% of range they are usually not particularly accurate.
We both come in under 80kg in kit and run, DH 22-25psi, Fatty 8 in snow to 12psi, 29ners 32-38psi depending on tyre size etc, 34 in Ardents, 26ers usually mid 30s. I’m amazed what range one can get away with unless jumping or clobbering rocks and roots.

Pepole should say if they are running tubeless or not…

…and whether or not it’s a hardtail, the type of terrain they ride and what weight they carry around and, and…

timba – absolute pressure is relative to vacuum, gauge pressure is relative to atmospheric.

It’s possible – though unlikely in the case of a bike pump – that the gauge is calibrated in absolute pressure. In this case, the gauge would read 14.7psi/1bar at rest (at sea level). I’m defining at rest to mean not hooked up to a tyre/thumb over valve and pumping/whatever. This should really be clearly identified by appending an “a” to the units (psia, bara).

Assuming the gauge reads “0” at rest then it’s calibrated in gauge pressure. Strictly speaking, this should have “g” added to the end of the units (psig, barg). But because it’s what we’re on about with tyre pressures, this is usually missed off pressure gauges on pumps car/bike/shock pumps. Gauge pressure is effectively the differential pressure between atmospheric pressure and the pressure within the pressurised body (e.g. tyre, shock, fork) that you’re interested in.

If you thing about it… a tyre at a pressure of anything less than atmospheric pressure (14.7psia at sea level) would not resist the atmospheric pressure bearing down on it and would be crushed. As a result, it wouldn’t be at all effective as a tyre.

Knard (3.0) on a Dually (29er+) …… 6.5psi (Front)

must feel like riding with a flat tyre surely? I’ve got knards on RH’s and 15psi seems to be the sweetspot (for me at 82kg)

Always run around 30 in the front and a bit more in the rear. I hate that mushy rolling feeling you get with a soft tyre, and the inevitable bent rims with rocky descents

Currently running 25psi in my front Magic Mary with Snakeskin sidewalls and tubes, usually 30psi in my rear Minion (Exo casing) but will happily drop a few psi if things get skittery at the back….tubed also and on a hardtail.

Most of my riding this year has been push up local level DH stuff, the odd day at Rogate-DH and then as many uplift days as I can afford/fit in at BPW, FoD and Black Mountain Cycle Centre.

Touch wood no flats yet, ditched my rear Ardent as I couldn’t get it to work at any pressure!

@whitestone and hopskinsgm
Thanks both. It’s what I guessed (but didn’t know)

Rule of thumb I was told when young, a tyre should deform about 15% when you’re sitting on the bike.

We didn’t have gauges back then, and even had to hollow out our own tubes and make our own air… 🙂