[willywonkax]

I cross country ride mostly, but I hit some pretty big rocks on this one particular trail. I wondering if my tire pressure should be higher or lower. I'm assuming higher, but I'm only assuming. Any thoughts?

Will

 

[shiggy]

As low as possible without frequent pinch flats.

 

[Dan Gerous]

In order to help you, we need more information. What happened when you hit those rocks?

If the tire gets compressed all the way to the rim (causing rim damage, pinch flats if using tubes, tire damage...) use higher tire pressure.

If you are bouncing all around the place on rocks and not getting any traction there, you are probably using too much pressure.

EDIT: Shiggy and I are in sync: his advice is a good one to follow.

 

[BrandonMiller]

I have never had a problem with too low pressure, and everyone says keep it high. Sure seems like I could drop it down.. I ran about 35 or so on my downieville trip last weekend and it was a bit rough, other then bending my rim there were no pinched tubes etc.

I run a 29er cobia, think I should go lower?

thx

 

[shiggy]

I have never had a problem with too low pressure, and everyone says keep it high. Sure seems like I could drop it down.. I ran about 35 or so on my downieville trip last weekend and it was a bit rough, other then bending my rim there were no pinched tubes etc.

I run a 29er cobia, think I should go lower?

thx

If you have never had a problem, you have not approached your lower limit. The only way to know is to try it.

 

[synthesis]

As low as possible without frequent pinch flats.

i run my tires very low for deep sand. The problem I see is that below about 7 lbs, the tire walls begin to ripple which quickly causes angular folds in the carcass. All that flexing must eventually lead to premature failure of the tire wall.

problem is that in the deepest sand, pressures as low as 3 pounds mean the difference between walking the bike or riding it.

ever seen an actual failure of the tire wall from underinflation?

 

[SuperbMan]

I'm not a pro--but I've agonized over tire issues for years-after a lot of experimentation and discourse-here's my thoughts:

Tire pressure should either be really high (over 50 Psi) or
Tire Pressure should be really Low (33 Psi or Lower, in the 20's if you run Tubeless).

All depends on riding style---A Few of the best all-arounders I know (who are on Hardtails btw) run very high pressure on relatively narrow tires--the trend to float, bounce, skip, hop rather effortless, at high speeds through any and all terrain.

Those of us who tend to grunt and grind our way around the mountain run wider tires at lower pressure. I run my schwalbe Alberts at 30-32 psi--with tubes-that is. Works great-for my style of traction loving grinding riding.

What I don't see any point in is running a luke warm, on the fence, psi setting (35-50--where most folks probably keep their pressures)--you sort of get the downsides of the two extremes without their benefits.

So experiment and decide if you're a high pressure or low pressure rider--and then push the envelope of those poles.

Liam

 

[willywonkax]

When I ride I on asfault I feel the tire pressure is low, but when I hit the trials it's fine. I see the tires compress when I hit the rocks but no damage has ever has happened. So, I think I should just keep the pressure where it is. If anything I should go up a couple psi.

 

[shiggy]

i run my tires very low for deep sand. The problem I see is that below about 7 lbs, the tire walls begin to ripple which quickly causes angular folds in the carcass. All that flexing must eventually lead to premature failure of the tire wall.

problem is that in the deepest sand, pressures as low as 3 pounds mean the difference between walking the bike or riding it.

ever seen an actual failure of the tire wall from underinflation?

I usually add "...or the tire feeling squirrelly in the corners." This is not usually the limiting factor in rocky terrain.

The Pugs is a special case. I have never seen a casing failure that could be directly traced to fatigue from extreme low pressures mainly because most tires are not rideable that low.

 

[BrandonMiller]

I will say my frame is down to bare metal on the inside from tire/wheel flex though..

 

[shiggy]

I will say my frame is down to bare metal on the inside from tire/wheel flex though..

Every bike with semi tight clearances I have owned wears the paint off the inside of the stays

 

[Quercus agrifolia]

...Tire pressure should either be really high (over 50 Psi) or
Tire Pressure should be really Low (33 Psi or Lower, in the 20's if you run Tubeless).

...What I don't see any point in is running a luke warm, on the fence, psi setting (35-50--where most folks probably keep their pressures)--you sort of get the downsides of the two extremes without their benefits...

Liam

I gotta call bullsheet here, Liam.

I don't follow the logic in this 'either/or' type of statement. I ride an alum hardtail, so I am frequently messing around with tire pressure (especially the rear). My goal is to get a balance of sufficent traction, a reasonably cushy ride, and low rolling resistence, in that order.

On the techiest of trails I typically run around 25 psi. But even when I 'air up' for fire roads or buffed singletrack I seldom go as high as 50 psi. Traction begins to suffer at these higher pressures (2.4 Mutano on the rear).

I guess that makes me a lukewarm, non-envelope-pushing fence-sitter.

Oh well, to each their own...

 

[SuperbMan]

I gotta call bullsheet here, Liam.

I don't follow the logic in this 'either/or' type of statement. I ride an alum hardtail, so I am frequently messing around with tire pressure (especially the rear). My goal is to get a balance of sufficent traction, a reasonably cushy ride, and low rolling resistence, in that order.

On the techiest of trails I typically run around 25 psi. But even when I 'air up' for fire roads or buffed singletrack I seldom go as high as 50 psi. Traction begins to suffer at these higher pressures (2.4 Mutano on the rear).

I guess that makes me a lukewarm, non-envelope-pushing fence-sitter.

Oh well, to each their own...

Actually--it sounds like, for the most part, you're in the low tire pressure camp--

do you really stop to 'air up' when you get to a fire road???

 

[shiggy]

Actually--it sounds like, for the most part, you're in the low tire pressure camp--

do you really stop to 'air up' when you get to a fire road???

I think he is saying he uses different pressures for different rides, not that he adjusts pressure for different sections during a single ride.

 

[uktrailmonster]

I can see Liam's point, but I think it's way too generalised and what's wrong with compromising somewhere in the middle? Optimum pressure depends on a combination of the following:-

Tyre width and volume (bigger tyres = lower press)
Tyre sidewall construction (stiffer sidewall = lower press)
Rider weight (lighter rider = lower press)
Riding style (less aggressive = lower press)
Trail surface / conditions (smoother surface = higher press, wet/muddy = lower press)

There is no single answer to this, but a good general rule of thumb is to run them as low as you can get away with for maximum grip and traction. Also bear in mind that rolling resistance may be higher with low pressure, but not always on rough ground (see Schwalbe website). Finally higher pressures generally give you better puncture resistance.

Personally, I run mine around 30-32 psi (Michelin AM 2.2 UST, 190 lb rider). I'm not getting any flats and they still roll well, so I might try them a little lower and see if I can squeeze a bit more grip out of them. I used to run the old Michelin Hot S 2.2 (tubed) at around 38-40 psi.