Tire Inflation & Rider Weight

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05-13-2009, 07:26 PM
ACiveE

Tire Inflation & Rider Weight

Greetings, ladies!

I am wondering if someone can provide me guidance on how high to inflate my tires. I never really thought about it and just inflated to around 100psi but I recently had a big tire failure and it got me thinking about it. My tire failure may have had little to do with inflation(I think) as I have a nice clean 3" slice through my brand new tires and tube. After reading reviews on the tires I have, I opted to purchase a whole new set and after dropping that $$ I'd like to properly inflate them to a level that avoids puncture as much as possible.

So, I'm no featherweight rider :rolleyes:. I weight in at around 170-180lbs and ride on 23cm tires. I purchased some vittoria rubino pro tires after reading their many praises for a cheapo tire and they have a max inflate rate of 120psi. Should I have gone with a higher max rate?

How high should I inflate them to? I know the higher psi, the faster, but at my weight how high is high? And how high makes them too puncture prone?

Thanks so much!
05-13-2009, 08:24 PM
Pedal Wench

My BF just sent me this:
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
05-13-2009, 08:36 PM
SadieKate

Quote:

Originally Posted by ACiveE

I know the higher psi, the faster, but at my weight how high is high?

Not necessarily. Lots of factors go into the "speed" of a tire. And you might find that 25mm tires give you a lot more comfort and durability. Your weight and max psi don't correlate. Max psi has to do with the tire construction, just like the rolling resistance.

Over-inflated tires are susceptible to gashes and have a harsh ride. Under-inflated tires are susceptible to pinch flats.

http://forums.teamestrogen.com/showt...ycle+quarterly

PW, that chart is pretty good! I just ran the numbers and they is spot on for Bubba and me.
05-13-2009, 08:50 PM
ACiveE

Many thanks!

So how close to max psi should you go? My calculated psi is like 110psi and the max for the particular tire is 120. Should I have gone with a higher rated(?) tire?

...this is all too complicated. I just want to get on my bike and riiiiiide!
05-13-2009, 08:58 PM
SadieKate

Use Pedal Wench's chart and go ride.

Don't worry about the max psi.
05-14-2009, 05:02 AM
AnnieBikes

PW,

Your chart is super! I have always wondered what inflation amount I should use. I always heard that I should make them 100-110 to avoid flats but based on "the chart", I should be about 96, so though 100 is close to it, I am often just "pumping up" and go to 110 or 115. I guess I will use the 100 and see how it goes.

Thank you so much for this very informative piece of information. :D
I love this forum!!!
05-14-2009, 05:11 AM
HoosierGiant

ACK! Following the chart puts my tires under 85 psi -- at that pressure I'd feel like I was riding through wet concrete!
05-14-2009, 05:43 AM
indysteel

I don't flat much (well, at all, knock on wood), so I could be terribly wrong, but my understanding is that underinflation can lead to "pinch flats." A 3-inch gash in both your tire and tube suggests to me that you ran over something nasty.

For what it's worth, I run my Rubino Pros around 100 psi. According to the chart, I should run them at 92 psi.
05-14-2009, 06:30 AM
Cataboo

I run my tires around max, so 120. The chart says I should be running less than that, but I can't say that I find the ride harsh.

I used to run about 90-100 psi and I was having pinch flats constantly.
05-14-2009, 06:39 AM
SadieKate

Quote:

Originally Posted by HoosierGiant

ACK! Following the chart puts my tires under 85 psi -- at that pressure I'd feel like I was riding through wet concrete!

I have plenty of wider road tires that I run below that. They're meant to be.
05-14-2009, 07:51 AM
OakLeaf

I definitely notice increased rolling resistance if my 700x23s are below 110 psi.

Does higher pressure really make tires much more susceptible to cuts? I might be persuaded to take the pressure down a notch if that's true.
05-14-2009, 07:54 AM
Biciclista

i have purchased tires which had a weight chart on the packaging.
Since i am a light weight, I keep my tires under 100psi.
05-14-2009, 02:47 PM
TxDoc

Hi ACiveE,
I am no expert but here's my personal experience: usually I inflate tires very close to the max. And, I tend to buy high pressure tires: Vredestein tricomp (clincher tires) and Vittoria Crono EVO (tubulars). My weight is under 130lbs and I've never had problems. A couple of my riding buddies are heavier (in the 190-230lbs range), and they also use mostly Vredestein tricomp or fortezza and inflate their tires close to the max.
Hope this helps :)
05-14-2009, 04:45 PM
salsabike

Quote:

Originally Posted by HoosierGiant

ACK! Following the chart puts my tires under 85 psi -- at that pressure I'd feel like I was riding through wet concrete!

Multiply it this way: (.33 x rider weight) + whatever number. It'll work that way. I tried it the other way first too, and thought....no, 75 can't be right....
05-14-2009, 05:22 PM
HoosierGiant

Quote:

Originally Posted by salsabike

Multiply it this way: (.33 x rider weight) + whatever number. It'll work that way. I tried it the other way first too, and thought....no, 75 can't be right....

That is the way I did it. (Please Excuse My Dear Aunt Sally and the Order of Operations reign supreme!)

Anyway, tire pressure, like shorts and saddles, is a personal thing. What feels like sloggin' through the mud to me might be someone else's comfort zone...
05-14-2009, 06:18 PM
ny biker

I came up with 99 from the equation, but I've been inflating my 700x23 tires to the max of 120 psi for several years now with no problems, and I prefer them with max pressure. When I has the Vittoria Open Corso tires, I inflated them to 130 which I think might have been below the max.
05-14-2009, 09:20 PM
Grog

I can't remember who but it was someone here who said that the max inflation printed on tire is the result of an argument between the marketing people (who want a higher number there because the racers willing to pay $$$ for tires want to put 140 psi in there) and the legal people (who don't want to be sued because people see their tires poppin' off their rims when they're too inflated).

Made a lot of sense.
05-15-2009, 08:51 PM
Heifzilla

Quote:

Originally Posted by Pedal Wench

My BF just sent me this:
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

My tires are 26x1.95 so what size is that? Inches to mm? Bike tire sizing is a new world to me at this point, kind of confusing.

Does anyone have an inflation chart for larger tires like mine?
05-16-2009, 07:56 AM
Grog

Quote:

Originally Posted by Heifzilla

My tires are 26x1.95 so what size is that? Inches to mm? Bike tire sizing is a new world to me at this point, kind of confusing.

Does anyone have an inflation chart for larger tires like mine?

Just inflate them to the max that's printed on the sidewall.
05-16-2009, 08:14 AM
OakLeaf

Fat tires are multi-surface tires.

I'll leave it to people who actually ride off-road to discuss the subtleties of tire pressure selection. :rolleyes: Definitely max pressure for road riding, and generally the softer the surface, the softer the tires.
05-16-2009, 08:36 AM
salsabike

Sheldon said....

http://sheldonbrown.com/tires.html#pressure
05-16-2009, 08:37 AM
Heifzilla

Quote:

Originally Posted by OakLeaf

Fat tires are multi-surface tires.

I'll leave it to people who actually ride off-road to discuss the subtleties of tire pressure selection. :rolleyes: Definitely max pressure for road riding, and generally the softer the surface, the softer the tires.

Does the rider's weight have any bearing? I am not exactly a lightweight.

Thanks. :o