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Discussion Starter · #1 ·
Is there a general rule of thumb for tire psi increase or decrease with tire size change?

For example, say for your riding and terrain with zero pinch flats you usually can run 25psi in a 2.25 size.

Now say you mount up a set of 2.0 size of the same brand tire. Keeping terrain, rider, etc the same, what increase in pressure would one expect to need in this smaller sized tire to maintain zero pinch flats?
 

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Destroy said:
Is there a general rule of thumb for tire psi increase or decrease with tire size change?

For example, say for your riding and terrain with zero pinch flats you usually can run 25psi in a 2.25 size.

Now say you mount up a set of 2.0 size of the same brand tire. Keeping terrain, rider, etc the same, what increase in pressure would one expect to need in this smaller sized tire to maintain zero pinch flats?
Roughly - VERY roughly - start with +5psi and experiment from there. If you never pinch flat your pressure is probably too high. You need to at least feel the tire bottom out once in a while to know where the lower limits are.
 

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Discussion Starter · #4 ·
shiggy said:
Roughly - VERY roughly - start with +5psi and experiment from there. If you never pinch flat your pressure is probably too high. You need to at least feel the tire bottom out once in a while to know where the lower limits are.
Wow, only ~5psi more? I was guessing it would need like 15psi more at the least. Good to know, thanks.
 

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Destroy said:
Wow, only ~5psi more? I was guessing it would need like 15psi more at the least. Good to know, thanks.
15 psi can be huge. If you're running 30 psi, its a 50% increase and the tire probably only decreased in volume by 10 or 15%....2.25 to 2.0.
 

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i run 45 in my front 2.25 and 55 in my 2.1 rear, but i also weigh like 220 and am 6'3 :p

But wow ive never expected tires to be run that low, mine at that lvl have never even come close to going that low (the part about feeling it bottom out ar some times)
 

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Cheers! said:
Man... I must be nuts. I consistently run 50 psi to 57 psi... I hardly ever venture below 40. And these are on Panaracer FireXC Pro 2.1, X223 mavic rims, and specialized light tubes... I weigh 170lbs
I would bounce off the trail in unpredictable directions if I used your pressures.
 

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shiggy said:
I would bounce off the trail in unpredictable directions if I used your pressures.
Me too and I weigh about 190. The other day I ran my front Conti Navigator 2.1 at 18 psi on some rocky terrain with no problem. The rear Conti Comp Pro 1 2.1 was really soft and I didn't have a gauge at the time. I felt the rim hit a few rocks but no pinch flats. I checked the pressure when I got home.......20 psi. :eekster: This was on a hardtail with about 3 inches of front suspension.
 

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I've gone tubeless with my RacingRalph and Nobby Nic. I used Eclipse sealant on tube type tires.(2.1)
The directions said to run at 30 psi, I was nervous and thought I might burp the air out but it was fine on my ride the other day. The ride is like having another couple inches of suspension travel.SMOOTH.
What affect does the lower pressures have on RR?
 

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4212darren said:
I've gone tubeless with my RacingRalph and Nobby Nic. I used Eclipse sealant on tube type tires.(2.1)
The directions said to run at 30 psi, I was nervous and thought I might burp the air out but it was fine on my ride the other day. The ride is like having another couple inches of suspension travel.SMOOTH.
What affect does the lower pressures have on RR?
It really depends on the surface you're riding on. On pavement or hardpack the lower pressure will increase RR. On sand, very soft dirt, gravel and rocky soil, the lower pressure will usually decrease RR.
 
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