dazco

Specialized FSR with stock wheels and tires. (26"x2.00 roll-X)
I weigh 170 and ride fireroads with often steep downhills and occasional singletracks.

What do you think my tire pressure should be approximatly? Also, what would you inflate them to when riding streets?

Thanks all...

Jim311

On the street, inflate them to the recommended max PSI, or a little bit less if you want less vibration and a little bit more of a cush ride. On the trail, I'd say about 35-40 PSI. You just have to get a feel for it.

moabrider47

I would go a bit more than 35-40 PSI. You don't have real wide DH style tires and you aren't riding over real rough terrain where a wide footprint would be a huge benefit. I would stick to about 45 PSI. I would run about 50 if I was doing fireroads. I weigh almost the same as you. It really comes down to how harsh of a ride you can stand and how much of a footprint/traction you need. The latest mountain bike action had a 2 page section on finding the right tire pressure for you and your riding conditions.
On the street, I inflate them to the max pressure or even slightly above it to get the least rolling resistance and the most ease of pedalling. Knobbies pumped up high, especially to the max pressure, will feel squirmy in the corners on pavement. As long as you don't make and high speed maneuvers with the knobbies on the pavement you should be fine.


-Moab

CrashTestDummy

I run 20psi in the front and 30 in the rear. I'm 220lbs and ride singletrack. My roommate is 180lbs and runs as low as 13 in the front. People who run 45 psi are screwing themselves in the technical climbing areas. Basically run as low as you can without pinching flats or bending rims or losing sidewall integrity on an off camber situation.

Jim311

Oh yeah... if you're riding tubeless it will make a big difference, but I'm assuming he's not. If you're running tubeless, run it as low as you please!

Maelstrom 

Unless you are doing xc and wants loads of speed...then pump those tires up.

I generaly run at 30ish...but then again I am not a tire pressure freak...I really don't worry about it too much...

dazco

Well it seems i'm ok. They were at about 28 front and a touch more in the rear. I thought that seemed awful low being new to MTB'ing. But the bike has handled well and held tight while moving pretty fast downhill. So i guess i'll just leave em there.

While i'm at it tho, what do you think is a good shock PSI for my rear Fox float? I've been using 180, but again i'm new to this and really don't have a feel for whats best yet, and probably won't for a long time.

Jim311

Lower = more traction, but more rolling resistant

Higher = Less rolling resistance, but less traction and a harsher ride


Just a compromise between the two.... I hate nothing more than having to really crank hard just to push against the resistance of my tires, so unless it's really muddy like this weekend, I keep my pressures a little higher.

a2psyklnut

One of the fun aspects of a new bike is "tinkering", (a lost art, I feel)! Set your tires at about 45 p.s.i., then go for a ride. While out there, drop the pressure a bit (small blast) and see how it changes your bikes handling and speed. Keep doing that until you're happy with it, or back to the trailhead. Adjust up and down till you find what you like.

Same thing for the rear shock. I believe Fox states to start at rider weight and adjust up/down for preference!

L8R

moabrider47

Crashtestdummy,

You're running that pressure in tubeless tires, right?? I find it hard to beleive that running a regular tubed setup at 13-20 PSI in an XC size tire wouldn't cause rim damage.

-Moab

BigHit-Maniac

I generally run 35 PSI up front, and 18 PSI in the back. I've found it to be the best possible pressure for trails around here (rocks, and roots), and not pinch flatting. I also run 2.5" Specialized tires with DH Tubes... so I can get away with it. With the lower pressures though it's absolutely amazing how much crap I can just "run over" and not have my bike scooting all over the trail under me.

If you're on fireroads... I'd say 45 up front, 30 in the rear.

You'll be able to corner it pretty good, as the side knobs up front will dig in, and the rear will have a wide foot print to also keep it from scooting out from under you in those fast-paced corners.


Have fun.

-Matt

Singlespeedster

It really depends on your local trail conditions and riding style.

Around here, it is so rocky that running anything less than 30 psi would result in endless pinch flats and ganked rims.

Somewhere between 40 and 45 might be a good place to start, but I strongly encourage rampant experimentation.

A

skdsl

I have to use around 40 to avoid pinch flats. I still get the occasional one though.

Maelstrom 

Its amazing how varried everyone is. I ride around 30ish and never get pinch flats...actually I only had 3 flats last year and it was all because of presta valves blowing

CrashTestDummy

Moabrider47- Not tubeless. I run about 18-20 in the front. My rommate checked his and it was 13 at the end of a ride. He's not running tubeless either. We both run about 30 in the rear. Both bikes are hardtails. Maybe we run a little lower pressure to make up for no rear shock...

There are risks of course. Scott wasted a rim (rear) hitting a rock wrong at high speed a few months ago.

We typically ride about 10 miles up a fire road and then take our pick of singletrack downhills. Occasionally I will pump the rear up a little extra for the climb and bleed a little off before heading down. The downhills are technical singletrack with everything from brutal rocky sections to tight switchbacks to high speed blasts. We ride very fast, generally spanking our friends with dual suspension and full downhill garb.

All I can say is get a pressure gauge and experiment. Anyone who has ever four wheeled or driven in sand can attest to the traction gains from "airing down."

CrashTestDummy

Update on Scott's 13 psi in the front tire: It lost it's grip on an off-camber downhill turn and washed out from under him. His first words after getting up were "I think I need a little more air..." He pumped it to about 20 and we were good to go.

On a side note I managed to launch myself over the bars on a fast rocky section. I was being stupid, jumping off all the rocks and ended up flipping, hitting with the side of my head first. Broken helmet, broken seat, post went in 5cm. I'll be in some serious pain for the next several days for sure. I don't think I broke anything, just feel like I got hit by a car or something