Conditions?

blip4383 said:
How do you know how much tire pressure to use on which trails? I usually keep my tire pressure at the higher end of the recommendation. Are you riding 35-40 psi at 6mr because the dirt is softer/looser? Would that mean you would ride 45-50 psi at Chimney Rock because of all the rocks?
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its all personal preference, but when its rockier, i drop the pressure. 45 - 50 at CR would be a very bouncy uncomfortable ride. lower pressures also hook up better when you a grabbing rock with the side of a tire or cornering IMO.

at 6 mile, everything is so smooth, a higher pressure is ok so you can roll faster... but i remember reading some article recently that says lower pressures roll faster, which is real counter intuitive to me.
 
There is no way that lower pressure rolls faster. Why do u think people put over 100 psi in their road bike tires? I run high pressure at 6MR bc it's hardpack and smooth and fast. I lower my pressure when it's wet and slippery to get more grip. Low pressure is especially good on wet slimy roots and rocks. On rocky trails you have to be careful bc lower pressure is more grippy and lessens the harshness of the rocks but it also makes u way more prone to pinch flats. I HATE pinch flats so i tend to run higher pressure than most people do everywhere. I don't think i've ever dropped below 30 psi for XC. DH is a different story...
 
gmb3 said:
On rocky trails you have to be careful bc lower pressure is more grippy and lessens the harshness of the rocks but it also makes u way more prone to pinch flats. I HATE pinch flats so i tend to run higher pressure than most people do
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Tubeless yo.
 
In case you missed it, i am old school so no tubeless. But yes, tubeless can be run at way lower psi than a normal tire. I've never tried tubeless XC tires. On my DH bike though i have tubeless and i managed to pinch flat my TIRE multiple times which sucks even more because those freaking things are expensive. I run tubes in them now.
 
gmb3 said:
There is no way that lower pressure rolls faster.
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Not to start a debate, but ill just say my piece...

When you have high pressure in your tires, every little rock is an obstacle. You feel everything. Drop 12 lbs of pressure and your tires and all of a sudden those rocks are somewhat smoothed out.

I didnt believe it at first either, but I went tubeless and know its all a game to see how low I can go.

I was at Chimney rock with 19lbs in my rear today... that was a little too low, but it was a smooth ride.
 
Lower is better, I agree with JShort. More contact is better. The smoothest trail still has plenty of "stuff" which is why it's counter-intuitive.

There's been plenty of discussion about it. Really fast guys roll low. There's a reason.
 
I was going to say to each his own, but then I said to myself: Self, that would be a bullshit statement.

Lower is better and gives you more control. If I ran 30 PSI anywhere I would want to shoot myself.
 
Whatever guys, I'm sticking with my 40 psi because i've tried lower pressure and hate it. "To each his own" is very true here as it is a matter of preference.
 
^^^ Like a race car tire? The tire expands as you pick up speed? Sorry, I think I was watching days of thunder again....I'll have to pick up a patch kit and another tube before I try out this lower pressure.
 
given identical bikes, riders, tires. only variable is pressures...

a tire with low PSI will deform more, and have a larger contact patch. that larger contact patch creates more friction than would a tire with higher PSI which did not deform as much.

I understand what you're saying about "fast enough" in which case the speed of the wheel's rotation would prevent the tire from deforming, but it would never have less rolling resistance than the super inflated tire...
 
martin said:
I understand what you're saying about "fast enough" in which case the speed of the wheel's rotation would prevent the tire from deforming, but it would never have less rolling resistance than the super inflated tire...
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Yes, rolling resistance is increased, however it is balanced by the ability of a lower pressure tire to absorb small bumps. Higher pressure, while having less rolling resistance, will bounce off of roots and rocks more and slowing you down opposed to if your tire just absorbed some of the hit.
 
Instead of theorizing, just do what I do and time yourself. Go from point A to B with 20 psi, then 30 psi, then 40 psi. Do it multiple times on different days and get an average so you can rule out anomalies. Why would you want to guess, when you can get empirical results?

I haven't done it with tire pressures, but been experimenting with different forks, and plan to do the same with different frames and parts. So after you chart out the spreadsheet, let us know the results so I know what tire pressure to run at 6MR :popcorn:
 
soundz said:
I haven't done it with tire pressures, but been experimenting with different forks, and plan to do the same with different frames and parts. So after you chart out the spreadsheet, let us know the results so I know what tire pressure to run at 6MR :popcorn:
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Why even waste your time, you can't tell me that there is that much of a difference between different part of the same quality. All of this stuff is personal preference anyways.
 
stb222 said:
Why even waste your time, you can't tell me that there is that much of a difference between different part of the same quality. All of this stuff is personal preference anyways.
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Maybe not between different parts of same quality but, there is a difference between a rigid fork vs suspension .. steel frame vs aluminum of the same price range, 20t cog vs 19t vs geared. At least I've found I can be 2 minutes faster on the LM course with a rigid fork vs suspension. That is significant for racing. If I find I can be even 30 seconds faster at 20psi than 40psi, then I might as well do it. Add it all up, it can be a chunk of time.
 
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