# Thread: How much tire pressure?

1. ## How much tire pressure?

On my tires it says a minimum of 40psi but it seems people run much lower than whats listed on the tire. How much air should I put in my Trek 4500. I'm 150lbs if it makes a difference. I've been using around 35psi but I just want to know whats ideal. Also should it be higher if I'm riding on pavement?

2. I used to use 40 when I was a newb. I accidently put in 40 on a ride last month--the ride is harsh--I was pinging off rocks, nearly going down etc. I've found 30-35 is much better.

I think I used to use 40 so as to prevent pinches, but I've found better riding technique and not using the lightest tubes allow even a 215 lb person like me get away with running pretty low pressures.

On d road on my road bike I pump em pretty hard but even here experts say there is a point where harder wont get you any faster.

3. ## I say as low as you can go...

Originally Posted by Mr.Breeze
On my tires it says a minimum of 40psi but it seems people run much lower than whats listed on the tire. How much air should I put in my Trek 4500. I'm 150lbs if it makes a difference. I've been using around 35psi but I just want to know whats ideal. Also should it be higher if I'm riding on pavement?
without:

pinch flatting
tire rolling off the rim
tire feeling mushy or quirmy in the turns

Apart from that, generally the smaller the tire, the more pressure it needs to keep you up. I typically run 33-35 PSI on 2.25 tires or 38-40 on 2.0s, and I weigh around 200#.

Lower pressure will get you better traction (until the tire becomes squirmy) and a smoother ride (until you bottom the rim out).

Higher pressure gets you slightly lower rolling resistance on paved roads, since the tire isn't trying to 'envelope' rocks and stuff.

4. 1/3 of your body weight + 3% x 6 = personal preferance. I run in the 30lb. range depending on the terrain. Try experimenting, lower than 25 psi. may cause flatting.

5. Originally Posted by keen
1/3 of your body weight + 3% x 6 = personal preferance. I run in the 30lb. range depending on the terrain. Try experimenting, lower than 25 psi. may cause flatting.

Are you sure that formula is right? It tells me 494.4psi

240 / 3 x 1.03 x 6 = 494.4

Edit: Ommited something.

6. Originally Posted by Stregone
Are you sure that formula is right? It tells me 494.4psi

240 x 1.03 x 6 = 494.4
LOL....I tried the same thing.

7. Originally Posted by Mr.Breeze
On my tires it says a minimum of 40psi but it seems people run much lower than whats listed on the tire. How much air should I put in my Trek 4500. I'm 150lbs if it makes a difference. I've been using around 35psi but I just want to know whats ideal. Also should it be higher if I'm riding on pavement?

depends on your weight, terrain you ride, tire size and type (UST or tube), and riding finesse (or not).

i weigh about 120 lbs, am usually gravity bound on mid-atlantic singletrack, use Michelin 2.0 or Kenda 2.1 tires with tubes, and think i am ok in the finesse department.

i used to run 35+ lbs front/rear until Shiggy lectured me. now i run 25 front/rear. no pinch flats.

the ride characteristics of any tire vary greatly with pressure (and between tire brands at teh same pressure). you should experiment and see what you like best.

8. Originally Posted by Phil
depends on your weight, terrain you ride, tire size and type (UST or tube), and riding finesse (or not).

i weigh about 120 lbs, am usually gravity bound on mid-atlantic singletrack, use Michelin 2.0 or Kenda 2.1 tires with tubes, and think i am ok in the finesse department.

i used to run 35+ lbs front/rear until Shiggy lectured me. now i run 25 front/rear. no pinch flats.

the ride characteristics of any tire vary greatly with pressure (and between tire brands at teh same pressure). you should experiment and see what you like best.
Try 4 - 5 pound more in the rear than the front for better handling balance and better rolling resistance.

Pimbot had it right above. It depends on the tire size and stiffness of the sidewall and grip of the tread and terrain.

Like you say experiment and find what works best for you. But put a little more presure in the rear than the front for best performance.

9. Originally Posted by Stregone
Are you sure that formula is right? It tells me 494.4psi

240 / 3 x 1.03 x 6 = 494.4

Edit: Ommited something.
I did the same thing and it gave me some weired number.

10. Originally Posted by derby
Try 4 - 5 pound more in the rear than the front for better handling balance and better rolling resistance.

Pimbot had it right above. It depends on the tire size and stiffness of the sidewall and grip of the tread and terrain.

Like you say experiment and find what works best for you. But put a little more presure in the rear than the front for best performance.

ok, i'll compromise with you, i'll try 25F/28R on my next ride. if i like that better, i'll go a full 4-5 more in the rear like you said. thanks.

11. i usually run 2 or 3 lbs more air pressure in the back than in the front. 30 in the front, 33 in the rear most of the time on tubed tires without tubes and a body weight of 185. Rocky terrain.

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