[Closed] How wrong was I ..... Tyre pressures .....

What condition are all your rims in? 😯

Perfectly true and as new!

I rode MM with these pressures too!

If you're not getting rim strikes and the tyres aren't rolling about all over the place, you're not running them too low. I wouldn't bother increasing the pressures as clearly what you're running suits your riding style on your usual trails.

Bit more air if you go anywhere with sharp rocks though, I reckon.

Ardent (2.25) on a DT 470 ............ 19.5psi (Front)
SB8 (2.2) on a DT 470 ................ 17.5psi (Rear)

😯

I'm 75KG and anything under 25-30 on the rear puts me at serious risk of burpage or pinch flatting, have successfully ridden/nursed lower through a race before but do you not notice the tyre folding and squirming off the rim at that pressure whenever you corner hard or land anything?

I went for a ride the other day and as soon as I set off I though my tyres felt a bit low but I had amazing traction. I didn't realise how low until I landed from a 10" ladder drop. I checked when I got home and the rear was about 9psi and front about 11. The tyres are magic Mary front and hans dampf rear. With normal riding they were fine but push them a bit and the rear was a bit squirmy. I think I could of climbed any hill with how well the rear was gripping.

How do you know the digital gauge is correct?

I take it your not a chunky monkey?

Was interesting reading about Brycelands pressures when he races DH, you'd expect low pressures as forums are full of people advocating sub 20psi pressures at the moment....Josh runs 30psi by the way, when asked why he said he hates the feeling of the tyre moving around on the rim.

Shows the massive skill difference when forumites on here are advocating super low pressures for grip on their typical XC type rides yet a pro can get down a track that would likely put most of us in hospital while using seemingly rock hard tyres!

Yeah but the OP isn't a pro and isn't having a problem at the pressures he's running, so why change it? (unless he wants less rolling resistance or might be doing different trails that will get him punctures/rim damage obviously)

I run psi in the early 20s and am a skinny whelp at around 60kg. I destroy rear rims far too quickly though so probably not the best to advise on how hard your tyres should be.

larkim - Member

How do you know the digital gauge is correct?

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I have to trust the gauge to be the gauge .....

Yeah but the OP isn't a pro and isn't having a problem at the pressures he's running, so why change it?

Going from about 20-25 on the Salsa to 35 or so made it way more responsive in handling and with power input, a lot nicer to ride despite being bumpier.

Good point, molgrips. Worth experimenting. I guess as I tend to get millions of pinch flats at lower pressures I've never had much issue with low pressures making handling worse, or rolling any worse on the trials. 30psi front 35 rear is as low as I dare go on tubeless HT.

he hates the feeling of the tyre moving around on the rim.

^ This

The lowest I ever go to is 30 psi on the front and around 40 psi on the rear and this doesn't seem to slow me down much (2.25" tyres and 80kgs). Even then I've been known to get pinch punctures in really rocky places.

I simply cannot stand that horrible squirming about feeling that comes with all these low pressures you weird lot rave about.

You must be very light on the bike. I'm the same weight and put a dent in my rolling Darryl rim with bud at 10psi on a pretty tame trail, let alone 5 psi 😯

15-20 psi max and im a skinny XC type! Cant stand rock hard tyres.

I go to 20psi in floppy Schwalbe 2.1" XC tyres and find it ok for my 68kg. Generally run about 25. Agree that if you like how they rode and weren't walloping your rims there's little reason to change just because you now have a number alongside that.

Tubeless or tubed? Can run lower pressure tubeless, and it can still feel fine. I tend to run 25psi tubeless as there's bags of grip and no pinch flats, but i am careful on rocky stuff and am 70kg

I've normally run 32psi F and 36psi R on my Whyte T-130 which has Maxxis Ardents setup tubeless on ROAM40 wheels. When I checked recently I'd gone down to 24psi F and 18psi R due to lots of small thorn punctures which had sealed but lost a few psi each time. The bike felt awful when running so low, it really felt like the rear was going to roll off the rim!

As always if it works for you why change it?

I have no idea how people get away with low pressures. I feel rim against rock sometimes at 30lbs!

On my Solaris I usually stick to 35psi.
(Tubed)

All the aforementioned just shows how variable pump pressure gauges can be.

On the big bouncy SB66, 19 front, 21 rear. No squirming, and I'd only ever chuck in 2psi for lakes/Munro days. I'm 6'3" and 16 stone.

No squirming, rims are fine.

30psi and I'd be skittering about.

And that's on both my schwalbe and my mates topeak digi gauge.

Good point, molgrips. Worth experimenting. I guess

Oh I should add it depends on tyres. Old fashioned skinny sidewalls need more pressure to handle well, as well as avoid pinch flats. Modern tubeless ready ones seem to have more sidewall support so are better lower.

How do you know the digital gauge is correct

because like many people the OP confused "precision" with "accuracy".

Anything under 30psi (ish) and my tyres feel like they're squirming and folding as I corner. Do not like. The GF runs hers done to 18-20 at times by comparison

Tom KP.

bloody hell some low pressures here!

Spesh Enduro Elite 26" wheels 40 psi front and back, I may drop the front down a little to 35 ish if really mucky and soft.

Spesh Carve HT 29" wheels 50 psi front and back may push to 55 psi if lot of road riding involved.

I run 22 on the front and normally 25 with a tubeless setup and no squirming on the Spitty. Anything over that and the bike feels awful.

Mmmmm 90kg - 17.5 psi in a 2.1 tyre- no rim damage or pinch flats- I remain unconvinced....

On my Alpine Five, 22front and 30 rear or for a big day out 30 front and 40 on the rear, running with tubes and I weigh about 105kg all kitted up, not had a puncture for about two years now, touch wood.
I've put a curse on myself now haven't I 😯 😆 .

It's the squirming on the rims that I don't like with low pressures. I have recently gone back to tubeless and find this feeling even worse with what seems equivalent pressure.

Pumped the rear tyre on my Fortitude up to 25psi and it feels waaaaay to firm.

Will give it a bash though.

I'm more like 96kg at present 😉

I love low pressure from a grip / feel perspective, but I usually pinch at <30psi on the rear. However I'm experimenting with heavier tyres and lower pressures which is working for me. Recently I've been down to 24psi and touch wood no punctures yet.

Who am I to say that Bryceland is wrong... But that's mental. You'd have thought he'd be on the limit of grip all the time and always looking for ways to improve it.

I find a good rule of thumb for pressure is twice your weight in stone - and then add more if it squirms or pinches and let air out if it skitters. More air for skinnier flimsier carcasses and vice versa.

Pepole should say if they are running tubeless or not. 20psi tubeless is fine, it's mental with tubes.

I think where you ride is as big a factor as what and how you ride. I run 35psi with tubes around Cannock chase and never get a flat, but any ride in the peaks seems to result in at least one snake bite.

People should also says which size tyre and wheel size, no?

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... 🙂