This should give you a laugh on a drab Friday. 🙂

Recently decided to get all accurate about tyre pressures as opposed to just casually glancing at the gauge on my cheap track pump. Running 26″ tubeless with 22 front, 26 rear, which apparently is appropriate for my weight.

Have now managed a couple of bizarre slow speed falls on my last two rides on local stuff that didn’t even register as a potential problem before. On both occasions the front wheel has ‘stalled’ on a very minor rut or rock, sending me merrily OTB. I’m baffled…and sore.

Can running lower pressures at the front make this more likely, or am I just shite? Feel free to offer abuse.

What were you running before?

Well, this is it – this is the first time I’ve stuck a gauge on. I was aiming for roughly the same with the track pump, but it is likely it was a bit more – maybe 25-28 perhaps?

Seems like a relatively small difference in pressure to me, but either the handling has changed or I’m doing something radically different technique-wise. Or it’s just weird luck.

Sorry to make things even worse but it is a drab Thursday, not Friday 😆

I switched from some bonty mud XRs which I used to run at about (24/27psi f/r), to a set of x-kings, upon trying to run them as low I found I was struggling, upon looking at the tyres I realised the x-kings have a softer carcass so benefited slightly higher pressures (27f 30r) to get the same feel.

OK..not just me it is still Thursday.

Sorry to make things even worse but it is a drab Thursday, not Friday

🙂 Must have hit my head harder than I thought..

I switched from some bonty mud XRs which I used to run at about (24/27psi f/r), to a set of x-kings, upon trying to run them as low I found I was struggling, upon looking at the tyres I realised the x-kings have a softer carcass so benefited slightly higher pressures (27f 30r) to get the same feel.

This is what I was wondering, whether even a couple of PSI lower can make them deform more when they hit smallish obstacles or drops at low speed, causing the stall. Alternatively I may have got lazy and stopped lifting the front end enough.

Simple solution seems to be to keep putting air in until;

a) you stop stalling on silly slow stuff

b) the tyres explode in a cloud of sealant and rubber debris

or

c) you decide tyre pressure had nothing to do with it and go back to what you started with.

Doubt it’s the tyre pressures.
If anything, the more deformation would help it roll over obstacles.

Either your forks are diving, or you just switched off at the wrong moment.

Go faster?

Can running lower pressures at the front make this more likely

The lower pressure means that there is less air in the tyres. Less air means less weight, so your wheels are now lighter. And obviously this is rotating mass.

So your wheels now have less momentum to carry you over obstacles, and hence your problem, especially at low speeds.

The solution is simple. You need to make the wheels heavier again. I recommend adding more spokey-dokeys until you stop falling off.

You’re just riding differently, concentrating on different things to see if you can tell the difference. You might even have been looking at your tyre to see how much it was deforming over the bumps?

Leave them be, go ride, look up the trail, all of that good stuff. If you don’t notice your tyres, that’s good. If they start doing things that make you notice them – rolling over in the corners, rims clattering roots and rocks, put some more air in.

Slow speed stalls are nothing to do with tyre pressure. It’s all to do with your reflexive brake finger. Death grip through rock gardens for the win.

I find that quite small nominal changes in pressure can make a noticeable difference to how the bike rides. The difference between 22psi and 25psi is 13% after all.

That said, I’d expect there to be differences in grip and / or rolling resistance but would be surprised if you’d actually stall as a result.

Maybe there’s an indirect relationship. I find with higher pressures the bike is a bit more skittish which, in turn, makes me a bit more nervous and as a result a bit more crap. So ultimately – in my case at least – it’s user error inspired by a slightly different set-up.

Are these 2.35 tyres? I don’t use tubeless but put 45psi in my 2.1’s. is that wrong?

Rockape63 – Member

Are these 2.35 tyres? I don’t use tubeless but put 45psi in my 2.1’s. is that wrong?
Depends if you weigh tons or have lots of pinch flats.
I personally run at the lowest I can get away with – I get the odd flat – maybe 5 a year, and I’m ok with that.
I’m not sure I ride with anyone running more than 35psi though.

put 45psi in my 2.1’s

that’s quite high.

Most people run 30-35 tubed and a bit less tubeless.

try it for a couple of rides and see how you get on.

Tyre pressure is a massive compromise between control, rolling resistance and punctures, generally lower tyre pressures are a good thing until you go so low that either the tyres rolls when cornering or you get pinch flats. A couple of psi lower can sometimes make a noticeable difference when you are close to the sweet spot.

My guess would be something else is the cause of you crashing.

You probably subconsciously considered yourself invincible and the ambassador of gnar now you know exactly how much PSI is in your tubeless tyres which provides you with exact amounts of limitless grip and control – so you were leaning forward in an aggressive attack position in anticipation of that fire road coming alive, which shifted your weight forward and made you fall off.

I find that below 24 psi the tyre can squirm about a bit, thats with 1.5 ply exo casing and im 90kg
so thats as low as I go

My guess would be something else is the cause of you crashing.

This is obviously the wrong answer, so I will now have a massive strop. 🙂

Sadly, I can’t even blame my itchy brake finger. These were on the flat!

Perhaps I need some nice 650b wheels to help roll over these tiny massive rocks.

You probably subconsciously considered yourself invincible and the ambassador of gnar.

I ride in the Dales. The very capital of gnarr.

maybe, lower pressures meant you were ‘riding’ lower? – subtly altering the all-important angle of attack…

(i guess it’s possible)

Simple. Empty tyres of all air, refill with helium. Problem solved. 🙂

26in wheels? Come on! 🙄