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a question about tire pressure

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a question about tire pressure

Old 04-20-10, 10:58 AM
  #1  
Inertianinja
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a question about tire pressure

because of my limited experience, i usually inflate the tires to somewhere inbetween the min and max listed on the tire.
my Vittoria Rubino Pro's say Min 100psi, Max 145psi; I inflate them to 130psi.
my Hutchinson's say min 100, max 125. i inflate them to 115.

i'm 175lbs. not a "light" rider. i'm worried that inflating them to the max + pothole = boom.

considering my weight, is this a good rule to go by?
should i go less? could i go more?
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Old 04-20-10, 11:03 AM
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You should be fine anywhere in there. I find the ride harsher with higher PSI, I'm about the same weight as you. I run 115 in the rear and about 105 in the front. Less weight on the front. You might experiment some. Try riding at 100 psi. Then jump up to 130 and see if you can feel the difference. Less pressure will allow for more tire "flex" and to a point more traction.

Someone had a web page that talked about determining your actual weight on front then rear tires and had a graph for "optimum" tire "flex". It was lower than I currently ride.
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Old 04-20-10, 11:11 AM
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175lbs is light compared to some of us, say, like me, for example! I have had no problem with Vittoria Rubino Pro at 140+ psi.
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Old 04-20-10, 11:17 AM
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Originally Posted by Inertianinja View Post
because of my limited experience, i usually inflate the tires to somewhere inbetween the min and max listed on the tire.
my Vittoria Rubino Pro's say Min 100psi, Max 145psi; I inflate them to 130psi.
my Hutchinson's say min 100, max 125. i inflate them to 115.

i'm 175lbs. not a "light" rider. i'm worried that inflating them to the max + pothole = boom.

considering my weight, is this a good rule to go by?
should i go less? could i go more?
130psi is way too high for a 175pounder. I weigh between 210-215Ibs, and I usually now run my rear 110-115psi, and front about 100psi. It makes for a more comfortable ride. I'll suggest you experiment with tire pressure and pay close attention to how you feel physically, post-rides.
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Old 04-20-10, 11:26 AM
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Yes, 130 is too high. Check out Sheldon Brown's page on this.
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Old 04-20-10, 11:28 AM
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Originally Posted by Inertianinja View Post
because of my limited experience, i usually inflate the tires to somewhere inbetween the min and max listed on the tire.
my Vittoria Rubino Pro's say Min 100psi, Max 145psi; I inflate them to 130psi.
my Hutchinson's say min 100, max 125. i inflate them to 115.

i'm 175lbs. not a "light" rider. i'm worried that inflating them to the max + pothole = boom.

considering my weight, is this a good rule to go by?
should i go less? could i go more?
Hey OP, I'm about 170lbs +/- and run at 120lbs pressure on the back & about 110lbs on the front my Continental 4000's after a series of pinch flats on a century last August when I ran a little less. I think there's some science & charts to rider weights & tire pressures somewhere (not sure), but I found that this is what works for me.
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Old 04-20-10, 11:37 AM
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From Psimet's Tip of the Day thread...

Tip 1 - Inflate your tires before every single ride. Know what the proper inflation pressure should be for your tires. Inflation requirements will vary by rider, bike, tires, conditions, etc.

Below you will find equations that you can use to help determine an appropriate starting point using your weight and the tire's size. Adjust from these baselines to suit needs and conditions.

Proper inflation is the easiet way to avoid flats.

Tire Width=20: Pressure(psi) = (0.33 * Rider Weight in lbs) + 63.33
Tire Width=23: Pressure(psi) = (0.33 * Rider Weight in lbs) + 53.33
Tire Width=25: Pressure(psi) = (0.33 * Rider Weight in lbs) + 43.33
Tire Width=28: Pressure(psi) = (0.33 * Rider Weight in lbs) + 33.33

Tire Width=32: Pressure(psi) = (0.17 * Rider Weight in lbs) + 41.67
Tire Width=37: Pressure(psi) = (0.17 * Rider Weight in lbs) + 26.67


Example: You are 150lbs running 28's

Pressure (psi) = (0.33*150) +33.33 = 82.83psi (rear)
Front Pressure = .9*Rear Pressure = .9*82.83psi = 74.55psi front\


So for 23s run 112psi in the back and 101psi in the front.
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Old 04-20-10, 12:17 PM
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interesting how nonuniform the responses are - some say "no prob!" some say 130 is too much.

these calculations / charts - are they based on the "correct" PSI w/r/t the individual tire max, or is it the universal "correct" PSI based just on rider weight?
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Old 04-20-10, 01:04 PM
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Originally Posted by Inertianinja View Post
interesting how nonuniform the responses are - some say "no prob!" some say 130 is too much.

these calculations / charts - are they based on the "correct" PSI w/r/t the individual tire max, or is it the universal "correct" PSI based just on rider weight?
You know what they say opinions are like, eh?
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Old 04-20-10, 01:17 PM
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Originally Posted by Inertianinja View Post
interesting how nonuniform the responses are - some say "no prob!" some say 130 is too much.

these calculations / charts - are they based on the "correct" PSI w/r/t the individual tire max, or is it the universal "correct" PSI based just on rider weight?
As Psimet says in in his preface, use the equations as a starting point...
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Old 04-20-10, 01:28 PM
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i also ride vittoria rubino pro and I'm heavier than the OP. I used to pump them up to 115 and i've been experimenting with pressure and i think i've finally found the perfect combo. 104 in the front and 120 in the back. lovely ride.
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Old 04-20-10, 01:31 PM
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Originally Posted by Tsuru View Post
You know what they say opinions are like, eh?
Yep. pearl izumi wants to put a 4D Chamios on our opinions.
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Old 04-20-10, 01:37 PM
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Originally Posted by Inertianinja View Post
Yep. pearl izumi wants to put a 4D Chamios on our opinions.
The 4th D is time? Or, most likely, money.
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Old 04-20-10, 01:40 PM
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Here's a link to the article with the graph-based formula: http://www.vintagebicyclepress.com/images/TireDrop.pdf
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Old 04-20-10, 02:47 PM
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I have a bad habit of overinflating for my weight. Usually 115-120 on the back and 110-115 on the front (i'm 150lbs). I just like em hard, you know?
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Old 04-20-10, 03:22 PM
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Originally Posted by graphs View Post
I just like em hard, you know?
That's what she said.
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Old 04-20-10, 03:25 PM
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Originally Posted by dperreno View Post
As Psimet says in in his preface, use the equations as a starting point...
Yup....no matter what you use it's a starting point.

FWIW - my equations were generated directly from Sheldon Brown's data. I love how there is usually someone looking at my equations and then saying - no....go use Sheldon's page.

If you pay attention almost all of the guides give you about the same numbers. Adjust to suit.
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Old 04-20-10, 03:26 PM
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Originally Posted by Inertianinja View Post
Yep. pearl izumi wants to put a 4D Chamios on our opinions.
i was just referencing that Pearl Izumi commercial where they keep saying they want to "put their new 4D Chamios on Uranus"
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Old 04-20-10, 03:30 PM
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Originally Posted by Yellowbeard View Post
Here's a link to the article with the graph-based formula: http://www.vintagebicyclepress.com/images/TireDrop.pdf
by that site, i should be running 75psi front / 110psi rear.

note that my tires have a minimum inflation of 100psi. something's gotta be wrong here. maybe its me.
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Old 04-20-10, 03:46 PM
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I use 100 front/110 back with no problems (168lbs). I figure that the back wheel is carrying the heavy, fleshy parts.
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Old 04-20-10, 03:52 PM
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I'm 175, ride gp4000s with latex tubes. 90psi front 110 in back. very smooth ride, feels good to me.
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Old 04-20-10, 04:01 PM
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I've never seen anyone have a tire failure as a result of too much pressure (assuming they stay within the sidewall guidelines) but I've seen a ton of flats from not running enough pressure. Don't worry about a tire going BOOM from too much pressure (stay within the sidewall guidelines). But you CAN go softer, and there are benefits to doing so.
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Old 04-20-10, 04:06 PM
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Originally Posted by Chris_F View Post
I've never seen anyone have a tire failure as a result of too much pressure (assuming they stay within the sidewall guidelines) but I've seen a ton of flats from not running enough pressure. Don't worry about a tire going BOOM from too much pressure (stay within the sidewall guidelines). But you CAN go softer, and there are benefits to doing so.
I went BOOM once. I couldn't believe how loud it was. I thought it was an assassination attempt until I saw my front tire in shreds. I don't think it was my fault, it was one of those Specialized tires. Can't remember what I did on pressure that day, pretty sure it was around 100. Nothing to be done.
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Old 04-20-10, 04:56 PM
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Originally Posted by Sourpuss Magee View Post
I thought it was an assassination attempt
Well, doesn't somebody have an inflated ego!
(Sometimes, the hail of bullets isn't about you!)
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Old 04-20-10, 07:49 PM
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Originally Posted by Inertianinja View Post
by that site, i should be running 75psi front / 110psi rear.

note that my tires have a minimum inflation of 100psi. something's gotta be wrong here. maybe its me.
I don't know, it gives me the same numbers, and it felt very nice when I tried it. That said, I've been putting 85 to 90 in my front since then. It definitely seems weird putting so little air in a 23.
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