Everyone seems to say 30-35 PSI for general riding. I was wondering if people use higher than that for XC racing, or not?

if your running tubeless then lower pressures is usually nicer, depends on terrain and conditions. anything from 30psi to 45 psi for me

Whatever works for the course – anything between about 25 and 40psi.

which air for XC racing though? I know that Canadian air is preferred for AM/FR but what's best for long arduous lycra cad hill climbs and fire road descents?

I know that Canadian air is preferred for AM/FR but what's best for long arduous lycra cad hill climbs and fire road descents?

🙄

around 40psi. Thats what i ran this weekend at cyb

35-40 psi for speed. Skinny tyres don't like low pressure.

Ok, interesting. Anything up to 10psi more than recreational/trail riding then.

I run between 50 and 60psi depending on course – 1.8 speed kings. I also have lower back problems…

😆 60 bloody hell

which air for XC racing though?

Air?! You commoner. I use helium. Purified of course.

Its completely dependant on the volume of the tyre. Unless everyone is running identical tyres, comparing pressures is pretty pointless, as a 1.8 tyre at 35psi will feel pretty soft compared to a 2.5 tyre at the same pressure. (and yes, I know you'll be highly unlikely to be racing on a 2.5, but hopefully you get the point)

I would use the far more accurate method of measuring pressure, which is the patented thumb-press followed, by quick sucking of air through the teeth, then 'yeah, s'bout right' 😉

this is of course tosh, as every pressure dial in every pump gives a different reading?

even my two shock pumps give readings miles out from each other.

to this end, i would suggest that the pressure i run in my 2.2 racekings (which are awesome btw) is about, this much :

>>……………….<<

25 / 40 psi for me

60 bloody hell

Speed Kings Supersonics are recommended for a minimum of 50psi. I run them at 50psi on my Epic (just for general trail riding as I don't race) and they work pretty well like that.

As low as I can get away with. 25-30 psi.

this should explain everthing.

http://www.singletrackworld.com/forum/topic/fatality-at-whinlatter-today

25 rear, 20 front. Up 5psi on both ends if the course is particularly rocky.

GavinB, how can the same pressue feel different in different size tyres ?

Its pressure after all, not quantity of air. So 30psi is 30psi in any size tyre.

30 pumps of air in a big tyre is going to be less than 30 pumps of air in a small tyre.

Dont confuse quantity with pressure.

depends on the course, if its a trail center (like laggan) then 65, nobody makes significant time up on the downhill, so firetrack speed is obviously everything.

other courses depend on how much FT there is and the chance of puncturing on things, I can run pressures quite low because I weigh 60kg (makes 65psi seem like a lot more) and still not puncture…

i put 34psi in a 2.3 (schwalbe sizeing)

tyre pressure can drive you daft

i run anywhere from 25-50psi in 2.1 schwalbes (NN/RR) i find that with a RR on the front anything lower than 40psi gives me pinch flats on rocky stuff

"nobody makes significant time up on the downhill"

Have you done an XC race recently?

Thanks Trimix, very helpful.

What I was trying to say (not very clearly perhaps), was that different tyres will feel very different at the same pressure. There are so many other variables, such as rim width, tyre volume, tyre compound etc. All I was trying to say was that how a tyre 'feels' can be a good indication, rather than purely going on pressure.

Somewhere between 18 and 35 psi on Schwalbe tyres run tubeless on Stans.

Trimix – Member

GavinB, how can the same pressue feel different in different size tyres ?

Its pressure after all, not quantity of air. So 30psi is 30psi in any size tyre.

30 pumps of air in a big tyre is going to be less than 30 pumps of air in a small tyre.

Dont confuse quantity with pressure.

Because it's pounds per square inch.
ie if you have a tyre with a contact patch of 1 square inch at 30psi, it will take 30 pounds to start to compress it.
If it's a bigger tyre with a contact patch of 2 square inches, then 60 pounds will be required.

That's why road tyres need 100+ psi, and car tyres only need 30psi despite having 3 or 4 hundred kg on each.

Isnt that a total contradiction glenh???
Your saying that my road tyre has a larger contact patch than my car tyre?

Surely the same volume of air in my car tyre and my road tyre would give the 70psi difference between the two?

Well the lowest you can get away with would be fastest according to this

28-30psi suits me, run tubeless

avdave – that is a decent bit of research but does tend to go against my experience. I notice it only tests at low speed – I wonder if at higher speeds the sidewall flex and tread flex takes enough energy to negate the good effects from running soft and wide tyres.

I also wonder about how hard the ground was and if that makes a difference

I remain convinced that higher tyre pressures run quicker for me and my riding

gee – Member

"nobody makes significant time up on the downhill"

Have you done an XC race recently?

sorry i should have made it clearer, At the XC race at laggan, which is very easy (red, but not hard at all) people who would normally make lots of time up on the downhill had less of an advantage. Seriously… take a chill pill. 😆