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· Old Fat Guy
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249 Posts
Discussion Starter · #1 ·
As I get used to my fat bike more and more, I'm finding I'm riding with less-and-less pressure all the time.

For the pictures below, the front tire is at about 7.5 psi, and the rear at roughly 8.5 psi (as read on the gauge of a Topeak JoeBlow Dualie).

I'm curious about the contact patch, as you can see where the snow is sticking.

Would it be correct to say that the narrow patch on the front tire would suggest that I could lower the pressure in that tire?

Would it also be correct to assume that that broader, edge-to-edge contact patch of the rear tire is just about right?

FRONT TIRE:


REAR TIRE:
 

· Nurse Ben
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11,989 Posts
That's a lot of pressure, unless you weigh 300#.

5 to 6psi is good for firm snow, 3 to 4 psi for soft snow. Also depends on the tire, Minions don't need as much air because the casing is stiff.

If you don't run hogh enough pressure you'll know because you'll flat or you'll be pushing snow.

Your mileage may vary...
 

· Old Fat Guy
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249 Posts
Discussion Starter · #3 ·
That's a lot of pressure, unless you weigh 300#.

5 to 6psi is good for firm snow, 3 to 4 psi for soft snow. Also depends on the tire, Minions don't need as much air because the casing is stiff.

If you don't run hogh enough pressure you'll know because you'll flat or you'll be pushing snow.

Your mileage may vary...
Thanks from one Ben to another...

I'm not 300lbs, but I was trying to ask if contact patch is a reliable indicator, to take weight/preference/bias/tire brand out of the equation...

I'll keep experimenting...
 

· Registered
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63 Posts
I would agree in this particular instance that your contact patch on the front indicates that pressure could be lower. But to Nurse Ben's point your pressures seem high. Keep in mind that riding in hard packed snow you won't have this snow covered tire to determine air pressure. Air pressure is the one thing that will change day to day, ride to ride, and sometimes during the ride. I haven't found a reliable way to measure outside of a gauge and feel
 

· fat guy on a little bike
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956 Posts
i would not adjust tire pressure based off how much snow is left on a tire after a ride...

tire pressure is very subjective. last night i rode my ICT (bud/lou on clownshoe) on a upper 20's temp, singletrack ride. the ride was 50/50 as far as snow crust/dirt coverage. my pressures were 6 front, 6.5 rear.

for me, pressure needed to be lower on the snow crust for more traction. but, it also needed to be higher on the fast rocky sections as i would get some mushy handling. so, i settled for something in between.

pick a starting pressure, then experiment. what pressure works for one, will not work for another. good luck!
 

· Registered
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901 Posts
I start with a bit much more psi, so I can release air pressure a couple of time to find the sweet spot for that day snow condition. Don't worry, you will feel it when you get it right: more tration, more floatabilty. softer the snow lower the psi.
 

· Registered
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225 Posts
Yeah the snow covered contact patch is not a reliable indicator because the highly inflated tire will sink into the snow - still contacting it everywhere - whereas a lower pressure will float better. 1'm 185 (195 with all the winter gear on I guess) and run 4-5 psi in snow. Maybe even less. Or more if real hard pack. This is on Bud/Lou 4.8.
 
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