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Old 01-10-06, 12:56 AM   #1
mjsca07
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Good PSI to run?

I was just wondering what a good PSI is to run when I'm out on some dirt singleteack. It's desert terrain, so I there's no foliage or anything. I read somewhere that you want to deflate as low as you can go wihout getting a pinchflat. What's a good PSI to go with for this? Thanks for any feedback.
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Old 01-10-06, 01:08 AM   #2
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Start with what's reccomended on the sidewall and work down from there. There is no set PSI formula, it's based on personal preference, trail conditions, tire type and body weight. Happy experimenting
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Old 01-10-06, 01:14 PM   #3
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My theory has always been to have downhilling tires. I passed a lot of people on the last michigander while in the sand because I use DH tires. DH tires are well suited for just about anything at max pressure other than taking on a road bike.

I have to replace them more often than regular tires because I ride on the cement a lot, but I think its worth it.
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Old 01-11-06, 12:26 AM   #4
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Pfft I haven't needed any thing past a 2.1 for Florida's sugar sand (Think dry quick sand). Heck the best tires I ever had for sand were a set of Panaracers (Smoke and Dart) in a 1.95. DH tires are over kill for XC epecially if you're turning pavement miles to boot
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Old 01-12-06, 06:52 PM   #5
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agreed. for most conditions that are not extreme 2.1 is about as wide as practical. the 2.25 Cinders I ride are actually less than 2.2 and have done me well from mud to boulders. dry,wet, damp , long steep climbs, 60mph downhill fire roads, name it and they have not been too thin to excell.
I ride them at aprox. 35 psi . if you are my size, ride my bike, with my style of riding you may not like the setting I use. a thicker sidewall tire like the Cinders will give a firmer feel at a certain psi than a thinner walled tire. if I ran my Trailblasters at 35psi I felt like I was riding flat tires. I ran 45psi on them and 35psi on the Cinders feels stiffer than them, epsecially in the corners.
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Old 01-12-06, 08:54 PM   #6
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Quote:
Originally Posted by mjsca07
I was just wondering what a good PSI is to run when I'm out on some dirt singleteack. It's desert terrain, so I there's no foliage or anything. I read somewhere that you want to deflate as low as you can go wihout getting a pinchflat. What's a good PSI to go with for this? Thanks for any feedback.
For hardpack, smooth singletrack, you should just slighty deform your tires when riding. That is, when you are on the bike, you should be able to look down and see that the round edges of the tire are being forced down onto the ground.

For rougher stuff, you want to let out a little more are as it will make your ride more compliant. Make sure that your front tire is about 5-7psi less than your rear.

Try to find a quick little loop at the beginning of your particular trail and ride it once, tweak it and ride it again. It will take some time to determine what is the best configuration for your tire, your weight and your trail.

Finally if your using an odometer, be aware that increasing and decreasing tire volume has the effect of changing the overall wheel/tire radius. When you calibrate, you should measure out on the ground AND apply appropriate load to the tire. Otherwise, you'll be off.
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Old 01-12-06, 09:28 PM   #7
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60mph downhill fire roads
Are you exagerating... I hope your exagerating.
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Old 01-12-06, 10:18 PM   #8
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60mph is possible i would say , i have hit 50mph descending firetrails using 2.0's
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Old 01-12-06, 10:21 PM   #9
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I would say 35 psi would be a good place to start.
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Old 01-13-06, 07:53 PM   #10
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Originally Posted by gattm99
Are you exagerating... I hope your exagerating.
forest service road 274 in Luray Va. it was part of a 23+ mile outing called Duncan Hollow ride that I got from a book called MtBikeVa.
the road had a very high crown and big rocks for gravel. it was a 9 mile fire road . the first 2 miles gained almost 1k feet and the next 7 dropped 1100 feet. some of the drops were huge and some were almost flat. I averaged 45.something mph on that stretch. it led to the BEST singletrack Ive ever ridden including 1 stretch that was 5 miles of nothing but rock gardens with creek crossings thrown in for fun( I stopped counting at 12) that gained 1600feet and the ride ended up with a 2 mile downhill that was so steep they S turned most of it for the forest service 4 wheelers to be able to navigate( lost 1700feet with tons of rocks), a large creek crossing and then back to first 2 miles of the forest road 274 for a nice paved downhill.
I told my wife Id call in 3 hours when I got back to where cell service was available( she dropped me off at 945am. almost 6 hours later I finally hit reception. it was the best ride Ive ever done although I was exhausted and out of water, in July, during Tropical storm Cindy( started raining about 11).

the tires laughed at all the boulders and water and the 35psi was perfect for the conditions.
its a lot easier to lower the pressure on the trails than to raise it so start high and go down

Last edited by iamthetas; 01-13-06 at 08:03 PM. Reason: corrections of facts
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Old 01-14-06, 01:16 AM   #11
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Originally Posted by gattm99
Are you exagerating... I hope your exagerating.
Nope. Heck I used to do that while going down this long deserted access road (bad pavement, random fist sized broken rocks, and gravel spots) that went up to the old taconite processing plant in my hometown. This was on a old ten speed with crappy brakes that I used to have when I was in high school So doing it on a modern mountain bike on a fireroad that may actually be smoother than what I used to ride doesn't sound far fetched at all.

Come to think of it I miss that old hill, too bad I was trespassing everytime I climbed that hill, and my dad would have had to arrest me or kicked my ass for being there (probably both) but the decent was worth it!
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