MTB tire pressure?

I was recently out riding with a group. One guy got a flat and we were eating huckleberries while he was fixing it talking tire pressure. The flat guy was running about 20psi and the others were runnig about 25psi. After all the snake bites I got this spring I've been running about 40-45psi. I recently softened up my suspensions and took the tube out of the back tire (mofo dh) my front tire has a heavy enough sidewall (Rokko ceramic) that I can almost ride with no air so I left the tube in. So what pressure would be a safe pressure to prevent flats but yet give me some traction on the rocks. 45psi sucks on rocks.

I hate to be that guy but it totally depends on the tire, rider, terrain, etc.

Lower it 3psi at a time until you start getting flats, then go back up a few psi.

I run 26.57 back, 23.21 front. Yup.

45 uphill and 18 going down. I don't get snakebites till about 12 lbs, on 2 ply tires. But I don't do drops either. :biggrin:

Might want to also consider the strength of your rims and their width.

Front Range XC, whats the general psi to run? 45?

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Originally Posted by GT40

45 uphill and 18 going down. I don't get snakebites till about 12 lbs, on 2 ply tires. But I don't do drops either. :biggrin:

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I've rolled tires almost off the rim anything below 20. It's scary when all the sudden you have 0 traction. :eek:

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Originally Posted by AfroMullet

I've rolled tires almost off the rim anything below 20. It's scary when all the sudden you have 0 traction. :eek:

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The beads on the tires are so locked, that I have to use metal levers to try to change tires. The sidewalls do fold a little when I ride, but no flats or bent rims.

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Originally Posted by AfroMullet

I've rolled tires almost off the rim anything below 20. It's scary when all the sudden you have 0 traction. :eek:

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This is very important to keep in mind. Less pressure does not always equal more traction.

I run 22psi in the front with a Michi Comp32 on a D521 rim and 26 in the rear with a Comp16 on a D321. I weigh 175lbs, and this is for straight up downhill riding.

I found that (on narrow rims) anything ~18 psi or under, and the tire won't pinch flat because there's not enough pressure to blow it out when it pinches. It works well, but you run the risk of damaging the rim. In my experience, with normal tires and tubes, 20-40 psi is the danger zone.

Go tubeless (or Stan's or Ghetto Stan's) or get heavier duty tubes. The thorn resistant tubes work well and aren't as heavy as DH tubes.

What exactly is Ghetto Stans?

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Originally Posted by powwrangler

What exactly is Ghetto Stans?

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A tubeless setup where you use a normal rim and tire, tape up the spoke holes, and pour in a liquid latex solution to seal it. Cheap, light, drives some people crazy but works well for others.

Ghetto Stan's That's what I've done to my back tire. Two days, 1 ride, and I've still got 20psi.

My trail tires are at 35.
My DH tires are around 25-28.

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Originally Posted by descender

My trail tires are at 35.
My DH tires are around 25-28.

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Yeah, pretty similar. My trail bike has a pretty beefy Nokian NBX 2.35 UST up front that i run at 30, conti vert pro rear UST 35 psi.

My freeride, 25 front and rear. with stan's tubeless. I don't change pressure from climbing to descending. 25 seems to be good for both.

As already stated, the terrain, the tires, UST vs tubes, rider weight; all factor into tire pressure. There is alot of fine tuning involved depending on those factors.

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Originally Posted by Z

Front Range XC, whats the general psi to run? 45?

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depending on your riding style and weight. I weigh 180, when i run less than 33 psi, I tend to get pinch flats. To be safe i am usually around 40psi in the rear, 35 in the front on non-UST.

I rarely get flats and of course last weekend i got 2 in the same day, but i believe the goat head was still in the tire causing the second flat, also from some drifting high speed airs which may have put some pressure on said goat head.:rolleyes:

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Originally Posted by Crinkle

depending on your riding style and weight. I weigh 180, when i run less than 33 psi, I tend to get pinch flats. To be safe i am usually around 40psi in the rear, 35 in the front on non-UST.

I rarely get flats and of course last weekend i got 2 in the same day, but i believe the goat head was still in the tire causing the second flat, also from some drifting high speed airs which may have put some pressure on said goat head.:rolleyes:

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yeah, i remember you saying that... Been playing around lately, think around 40 is best...

15-25 for DH, depends on conditions. On my old bike w/doublewides, you could easily run under 10. Those suckers would NEVER blow off the rim.

40+ going uphill on roads or smooth trails, lowered to 25-30 for the descent.

Don't forget to factor in the tire casing width you're running.

Road tire: 700x23c: 120 psi - but you can still squeeze the sidewalls
Mtn tire: 26x1.0 street slick: 90 psi - hard as a rock
Mtn tire: 26x1.95-2.1 XC knobby: I need to run tires of this size around 38-45 psi depending on terrain, or I'll get pinch flats.
Mtn tire: 26x2.5 DH/FR knobby: never ridden tires of this size, but since the volume is higher, a lower tire pressure = firmer tire.

My point is that a mtn XC tire at 40 psi is pretty firm due to its casing volume; a road tire at 40 psi is unrideable. So we can't just compare psi without including the type of tire, as well as the other factors (type of terrain, weight of rider)

-Karl

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Originally Posted by Beaver

Ghetto Stan's That's what I've done to my back tire. Two days, 1 ride, and I've still got 20psi.

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11. Mix your liquid latex (most Mold Builder will be far too thick…..dilute it with warm water so that the end product looks like Creamo, Half-and-Half or Light Cream.



can you just uses stans for that???

bump for my question ...

I believe when Stan's first came out they included mold builder instead of the sealant used presently. I remember having to mix something.

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Originally Posted by AfroMullet

I believe when Stan's first came out they included mold builder instead of the sealant used presently. I remember having to mix something.

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so now, just use stan's in the cheap set up?

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Originally Posted by mntlion

so now, just use stan's in the cheap set up?

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We just use Stans.

Mold builder is cheap. I got enough to do about 100 tires for $15cad. Even cheaper on ebay


I went out yesterday with about 15psi in the back tire. I felt a couple rocks hit the rim but nothing too hard. I might put in a couple more pounds.

thanks I have stans at home so I'll be trying this soon

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Originally Posted by Beaver

Mold builder is cheap. I got enough to do about 100 tires for $15cad. Even cheaper on ebay


I went out yesterday with about 15psi in the back tire. I felt a couple rocks hit the rim but nothing too hard. I might put in a couple more pounds.

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How much do you weigh and what tire are you using? If I ran that little pressure in a full DH tire I'd be getting tire roll.

for general trail riding (on a Blur w/a 2.4 MotoRaptor upfront and a 2.24 in back) I usually start my ride w/them at 40 psi (IF CLIMBING TO START), then gradually decrease the psi on the trail as i get into more DH sections to around 35 to 32 psi. this set-up has always worked for me, but as many have stated, just depends on where/how/what you are riding....