Tyre Pressures

fairhurst, you’re just phishing now.

For tubeless, see the formula here:

http://www.notubes.com/RecommendedTires.aspx

In British that’s weight in stone doubled, -1 for front, +2 for rear. A very sensible starting point for a rider that’s neither fast nor slow, smooth nor heavy. I’d go higher for tubes but not a lot. Obviously if they pinch/squirm go higher. 65psi is just silly.

When I run Conti 1.5s I use 60-65psi but even then it has to be pretty smooth, I’d struggle where I normally ride even at those pressures.
I use 90psi on the CX, I had a pinch flat last year when I let the pressure drop as low as 70.

Wow a lot of high pressure salesmen here!

On 2.4 Conti MKs with tubes, 88kg rider, hardtail, I am running from 22 to 26 PSI front and rear for off road. I love the grip and comfort. I’m not fast on the downs, and don’t hit rock gardens or big jumps / drops, so YMMV.

I run 40 PSI on road for my Schwalbe Supermotos… nice!

My XC bike with 26×2’s is running at 50psi front and rear.

My road bike with 700×23’s is at 100psi front and rear.

I run high pressures to keep the rolling resistance low.

I run high pressures to keep the rolling resistance low.

That only works on road with smooth tyres.

Off road, it is less efficient to have the tyre and bike bumping about over every stone, more efficient to absorb the bumps at the tyre. Also with knobbly tyres, high pressure causes more rolling resistance as tyre ratchets from knob to knob rather than rolling smoothly.

I’m always a bit amused by people who seem to think that they’re inflating tyres to exactly 28psi or whatever. There’s no way the gauges on most pumps are that precise, or repeatable. And if you pump the tyres up in a cold garage and then ride on a hot day you’ll end up with 29psi anyway 🙂

Just to throw the cat amongst the pigeons, how many of you actually know how accurate your gauge is?

I have 4 track pumps and several mini-pumps with gauges.

When I tried to calibrate against a standard (car tyre and 2 garage gauges), I was horrified to see my pumps were just random.

For a real 32psi, I had my pumps showing 22 to 40 psi.

I learned that what I thought was 35 was actually under 20, so no wonder I had a few pinch-flats.

I have calibrated and written what to use on the pumps….not simple but essential. I used a dual-headed pump to calibrate against the car tyre, then a large MTB tyre with a presta, then the other presta-only pumps.

PaulD

Probably depends on lots of things like tyre choice, rim width, riding style etc but i’m a similar weight to OP and generally run between 30-40 F+R (on 2.3″ single ply tyres) for dh/trail use. Closer to 30 when the going is rough. Nearer 40 if relatively smooth. I still get the occasional pinch flat but I don’t like how my bikes handle if the tyres are too soft or hard. My jump bike tyres are rock hard though (70-80psi) but that’s a conscious decision to sacrifice comfort for speed.

I’d say try 35 and see how you get on (bring a spare tube though :D)

I run high pressures to keep the rolling resistance low.

lower pressure = less rolling resistance …

… apparently:

http://www.mtbonline.co.za/downloads/Rolling_Resistance_Eng_illustrated.pdf

I just don’t know ow some of yo can run such low pressures even with tyres with stiff sidewalls – I just hate the squirming and loss of accuracy as the tyre rolls in corners.

GeForce – thats an interesting bit of data but its by no means conclusive – low speed only and not all conditions.

35ish for me (better expressed as the oranges and apples analogy above).

Maybe I’m too much of a geek, but I use a Topeak digital tyre gauge. Also, the original post was regarding 29er tyres, which being larger volume would run at lower pressures anyway.

Nobeerinthefridge – Member

fairhurst, you’re just phishing now.

they seem to be running slightly flat at 50psi so was only thinking of increasing the pressure

the only thing you can deduce from those charts is riding through grass is a bitch and i didn’t need a graph to tell me that ! 🙂

Checked my pump with a digi pressure gauge, its within 1 psi.

Tried 35 front 38 rear today, all ok.

Will go for 35 front and rear next time.

I think the report is fairly conclusive, bar [joke] needing to include a couple more terrain types for completeness, as TJ suggests.

The report is all about the uphill though, not really covering the benefits/risks of lower pressures downhill (or the trade-off) which is as important to the overall choice of pressures.

I think the “gauge accuracy” argument is a strawman; unless different pumps/gauges are used every time alternative pressures are tried, which I’d be surprised by.

I think the effectsof pressure will also be iddiffernt at higher speeds.

As for pressures – different tyre work at different pressures for sure – some contis need a fairly high pressure to stop the knobs collapsing – better grip at 40 psi than 30 – mountain kings for example – rubber queens I can run softer than mountain kings

6psi Front and 7psi rear.

Yes, it’s a fat bike…

Some bloke with most of his arm missing when his tyre peeled off the rim advised me not to run them lower than 25psi. I’m going with that.