PSI for road bike tires?

[Biciclista]

depending on your weight you don't need 115 pounds of pressure. Some tires come with a graph, and if you weigh about 120 pounds they tend to show you need more like 90 pounds, much easier to pump to that level. 60 sounds low unless they are larger (wider) tires.

[ridebikeme]

I am VERY confused. We use the Jow Blow pumps in the shop, and have for many years... without any problems. Although we own an air compressor in the shop, we pump everything by hand. So you can imagine how many times the pumps are used. We also have been selling these pumps for many years, and have never heard of any issues.

Although this sounds like a stupid question, was the employee that you spoke with at your LBS familiar with the Joe Blow pumps? Even if you had a problem with yours, there are repairs kits available to replace any of the working parts.

At any rate, good luck with your new pump.

[Eden]

Another person who thinks the advice about Topeak pumps is questionable.... We use ours to get TT tires up to 140 - and even 105lbs of me can do that....

But anyway - I think you are fine, you're just not used to road bike tires. They *should* be hard - hard enough that your thumb cannot dent them, hard enough so that your entire body weight on the bike just starts to deform them a little. It does depend on your body weight and the psi ratings of your tires and rims just how far or how low you can go - generally you'll see a range printed on the tires. If you are light the lower end of the range, heavy the upper end.

[esmorin]

the advice i was given was not about Topeak pumps in general - and am not speaking to their quality or anything. i am just talking about the specific Joe blow one that i got...(note: there are several different Joe Blows with differenr PSI max ratings - I got the lowest one, with 120 max PSI).

The advice about the pump cylinders being narrower or wider was good, I think. It helped me, anyway. I guess my question originally was more about the PSI on the dial vs. feel.

[nscrbug]

Okay...maybe I just need some clarification here. Are we talking about a Topeak Joe Blow FLOOR PUMP? Or are you referring to a FRAME pump? Perhaps this might be why some of us are confused regarding the cylinder size.

[esmorin]

Ahhh, Yes, this is a floor pump. Sorry!

[Pip]

I have a Joe Blow floor pump and can't get my tires over 80 PSI. I just physically can't get them any higher, even jumping on the thing and using all my weight. I have to get my husband to check them. I weigh around 60kg and keep them at around 100.

[Seajay]

depending on your weight you don't need 115 pounds of pressure. Some tires come with a graph, and if you weigh about 120 pounds they tend to show you need more like 90 pounds, much easier to pump to that level. 60 sounds low unless they are larger (wider) tires.

Yes! Thank you Biciclista. Follow the graph. Not the max pressure. It's based on rider weight. Over pressure is slow among other bad things. The tire needs to deflect. It's designed that way. Cervelo says most of their MENS race team are at around 95-100 psi.
A good link here
http://www.slowtwitch.com/Tech/What_...ube__1034.html

and here.
http://www.michelinbicycletire.com/m...rpressure.view

[Crankin]

Well, I know it's a personal choice, but I think keeping the pressure at the upper range is the reason I have had 3 flats in 10 years.

[OakLeaf]

It's really dependent on road conditions and riding style as well as rider weight.

Think about how you would adjust fully adjustable suspension. Rider weight is a starting point, but only a starting point. Then realize that your tire pressure is your ONLY suspension adjustment on a road bike.

The rider weight charts basically look at one thing only: what pressure will prevent pinch flats ("bottoming out") on average roads?

There's much more than that involved in suspension setup, obviously - rolling resistance, braking and turning performance, comfort and handling over particular road conditions, tire wear, etc.

I'm 120#, I ride probably average roads (a fair amount of chip-seal, but not a lot of cracked/potholed asphalt), and I prefer my 120# max 23c tires at 115psi. Anything below 110 I really notice the increased rolling resistance. I have a cheap-ish carbon frame, so that does soak up some of the vibration that someone on an aluminum frame would have to rely on their tires for.

[Seajay]

The rider weight charts basically look at one thing only: what pressure will prevent pinch flats ("bottoming out") on average roads?

Oakleaf. Love the analogy of tuning a suspension.
But... Where do you get the fact/opinion that charts are based only on preventing pinch flats?
I find it hard to believe that the engineering that goes into making a tire casing perform the way it does is all based on pinch flat prevention.
Tire Tech

[OakLeaf]

But... Where do you get the fact/opinion that charts are based only on preventing pinch flats?

It's a conclusion (I don't know whether that counts as "fact" or "opinion" ) based on three things:

* the charts don't take into account road conditions;
* the charts don't take into account rider preference for comfort vs. performance; and
* the pressures they give are well below what I need to minimize rolling resistance.

The only reason any road tire needs a "minimum" pressure is for pinch flat prevention. Other factors yield a range of pressures for a given rider weight. Tubeless tires are becoming popular mostly because they allow riders to run much lower pressures than tubed tires.

[Seajay]

Oakleaf...Thanks for the stimulating conversation on a boring day. I should be working.

Consider that a tire is designed to take up load/bumps (energy) at the front of the contact patch...and release that energy at the end of the contact patch.

If your tire pressure is above that on the engineered chart.... the energy will not be taken up by the tire...it will pass THROUGH the tire, into the fork, frame and YOU where you absorb it (convert it, actually) with your body (same as a tire with a very stiff sidewall (like an Armadillo) ....THUS never being returned to the road through the back of the contact patch = HIGHER rolling resistance not lower.

The other consequence here is that the weight of the bike and your body are forced to travel up/down/up/down with every imperfection in the road as opposed to that mass traveling on an even plane.
My turn for conjecture... it must take MUCH more energy to have you and the bike move up and down than it does to move it smoothly down the road.

[Seajay]

From Zipp Tech without changes except highlights.
OK I'm a tire geek. I admit it.

The Corsa Evo CS will be perfect for that wheel, and I would recommend 100-125 psi (6.9-8.6 bar) depending on your weight. You will want to run 0.2-0.5bar more in the rear than the front to account for weight bias. I personally weigh 155lbs (70kg) and run my tires at 105 psi front (7.2 bar) and 110 psi (7.6 bar) in the rear. When I was racing and lighter I ran them at 100/105, but now that I'm heavier it is safer to run a few extra psi and I may go even higher on bad roads, which has worse rolling resistance, but better protects the wheels from damage in the event of hitting a pothole or something else which could damage a rim or tire. The better option is to run a wider tire at lower pressure on rough roads, but that is just not always feasible, so I would rather have higher rolling resistance and protect the wheels than lower rolling resistance and increased risk of damage to the wheel.

Higher pressure is definitely slower on anything other than perfect surfaces. Think of it in terms of a bunch of 1mm tall bumps in the road. If you have a lower tire pressure, the casing of the tire will deflect over each bump (we'll assume the casing deflects the entire 1mm) converting a small amount of energy into heat as the casing deflects, but the amount of energy necessary to compress the air is almost non-existent. Now at a higher pressure, we will assume that the tire deflects half as much. Now the bike and rider are lifted by 0.5mm and the casing deflects by .5mm, the energy necessary to deflect the casing by .5mm is less than it takes to deflect it by 1mm, but is nothing compared to the amount of energy necessary to lift the bike and rider by 0.5mm, so the end result is that the total energy requirement for the high tire pressure condition is much greater.

The other thing that happens is that on smoother roads, high tire pressures keep the casing from deforming over and into small cracks and crevices and over pebbles, which means that some of the deflection is transferred into the tire tread, which is not as elastic as the casing. Excessive tire wear comes about as the tire rubber begins to fail in shear as it is deformed by the road surface, and this generates heat as well as breaks down the cross-linking within the tread material.... overall, you are using more energy to go slower and you're wearing your tires out faster. The problem is that high tire pressures feel fast as your body perceives all the high frequency vibrations from the road surface as being faster than a smooth ride.

Lennard Zinn had a great analogy when he said that 100kph in a Jeep will scare the crap out of you but 200kph in an S class Mercedes feels effortless...the same is true of bike tire pressures, but it's just hard to convince ourselves of that. As athletes we tend to buy into the 'if some is good, more must be better' philosophy, but this is rarely true. Of course the tire manufacturers have given up on this and continue to try and make higher pressure tires as that's what the consumers demand, as I think that they've decided that it is easier to just give people what they think they want than to try to educate and argue with them :-)

[ScaldedCat]

I use a Topeak JoeBlow Sport, we've had it around seven years and it's been a great pump, the gauge is pretty accurate too.
I have no problem pumping my tyres up to 120 psi, this is the pressure I've found works best for me and my set-up. I did try pumping up to the recommended max pressure for my tyres of 135psi as an experiment but got annoying pinging from my newly built wheels as though they hadn't been stress relieved (they have).