PSI for road bike tires?

[esmorin]

So I am having tire floor pump issues.

I bought a Topeak Joe Blow, but couldn't pump my thin bike tires. I asked a guy at a LBS and he said I needed a pump with a smaller air cylinder.

So, I bought a Specialized pump at another LBS today. This one has a narrower pump cylinder, and is much easier to pump. However - my tires are now rock hard (as they should be), but the pump says that I am at 60 PSI. The recommended PSI on the tire says 117. I even check with the Joe Blow, and that gauge also says that the tires are at 60 PSI.

So now I am stumped. I got a pump that worked, and my tires feel right, but the dial says that I am at half the PSI that I should be. Should I keep pumping until I am in that 110-115 range? Will I blow out my tire? Am I neglecting to notice something else?

Has anyone else had pump/tire issues?

[aicabsolut]

Yes, keep pumping to around 110, give or take some depending on your weight. It is very difficult to determine road bike tire pressure by feel with your hand. Use the gauge.

However.....when you pump up the tire, is the needle moving up high and then falling back down? Perhaps you don't have a good seal in the pump and aren't getting an accurate reading. You might also hear air leaking from the valve if this is the case. I doubt that the same thing would happen with both pumps, though.

[nscrbug]

I'm confused...:confused: I have a Topeak Joe Blow pump and have never had a problem pumping my road bike tires. I don't understand why you were told that you needed a pump with a smaller cylinder...doesn't make any sense to me. I pump my tires up to 115psi before every ride, and DH pumps his to 120...all using our Joe Blow pump...great pump, BTW. Are you sure that you are turning the little threaded tip on the presta valve all the way to the top of the valve before inserting the pump valve on?

[esmorin]

nscrbug, yes, I am unscrewing that little threaded part on the presta valve. And the narrow vs wider pump cyclinder was explained to me this way at the LBS: a large cylinder means that you trying to push a higher volume of air into the tube in one pump, which makes it harder. A narrower cylinder means that you are pushing less air in one pump. So, it would take a higher number of pumps, but the actual pumping would be easier. He was telling me that it's some physics principle. it sounded good to me! And, I have to say that my narrower specialized pump IS way easier to pump.

aicabsolut, at first the needle was going up and then back down, and I resealed the pump and it stopped doing that. And the tube was definitely getting fuller. I was nervous about going any higher than 60, because the tires felt so firm.

So, you ladies are saying I should trust the dial? it seems really unlikely that BOTH my pumps -bought at different shops- would be broken or inaccurate to the exact same PSI - right?

[Possegal]

I remember calling my brother in law when I was first putting air in my bike's tires and saying to him - should it really feel like if I put more air in these things may explode? And he said yes. :) So I just kept putting air in until the gauge read correctly. And nothing exploded.

You are not alone - I laugh now, but initially I kept thinking you need a dang PhD to put air in your tires. Then I realized I have one, so I just soldiered on. :)

[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.:confused:

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.

[esmorin]

Thanks. that's what i was finding. I solved my problem, it seems, by buying a Specialized floor pump with a narrower cylinder. I got my tires up to 115 PSI or so...after the repsonses in this thread. Thanks!

[Crankin]

I routinely pump my road tires to 120 psi with my Joe Blow. I am a petite person, too and while I can't do it in 3 strokes, like DH, it's fine. We have 2 other floor pumps that while they pump fine, the valve attachment isn't as nice.
And the pressure meter goes up to like 160 on my pump.
Pumping tires takes a good deal of upper body strength, which cyclists are notoriously lacking. I've never heard any of this stuff before.

[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_s_in_a_tube__1034.html

and here.
http://www.michelinbicycletire.com/michelinbicycle/index.cfm?event=airpressure.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.

[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).

[OakLeaf]

the gauge is pretty accurate too.

Where did you get it calibrated? I guess you have to live near a major pro race team or event?

[ridebikeme]

After reading this topic again, I decided to do some research concerning Topeak pumps. Topeak actually does make a mountain bike pump, so the PSI rating only goes to 75. All of their other pumps have a rating of 160.

So I think the lesson for the day is for each of us to make sure we are buying the pump that we need, and if we're not sure, simply ask staff at your LBS.:o

At any rate, glad to hear the discussion on pumps, and hopefully we have all learned something as well... I know that I have!:D

[ScaldedCat]

Where did you get it calibrated? I guess you have to live near a major pro race team or event?

When I say pretty accurate I mean that is checks out with other trusted guages, when it says 120psi its around 120, not 105 or 135. That's reasonable for an analogue guage on a £20 track pump.

[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? :confused:
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 (http://www.slowtwitch.com/Tech/Tires_and_wheels_for_timed_cycling_events_226.html)

[OakLeaf]

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

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.

[OakLeaf]

Try it out for yourself.

As I said before, I'm right around 120#, and if I put less than 110# in my tires, I may as well be riding my 35# commuter with 1-1/2" knobbies. It's like pushing a tank.

Once in a while I do get on roads that are so rough that it really will bounce and beat me up, and I know lower pressure would help me there, but I'm never on those kinds of roads long enough to make it worth changing the pressure.

[aicabsolut]

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.

This is mostly true. If you run a higher pressure, the ride isn't going to feel as smooth, and some of the shock is going to be transferred to the fork/frame/rider instead of being diffused by the tire. On the road, this is pretty minimal, because you're talking about high pressure tires anyway. This isn't like in cyclocross where on the race course you'd run maybe 40psi in your fatter tubular tire (tubies to help avoid pinch flats you might get with clinchers running over a tree root), but on the road, you'd want to max that tire out at 60psi for a faster ride. The difference felt there is probably much greater than going from 100-120psi on a skinnier road tire. You also need to take into account that there is less rolling resistance (though this depends on the specific tire design) with higher pressure which may translate into a faster ride (make more of a difference in the forward direction) than diffusing some of the vertical shock.

I don't even reduce air pressure when it's wet. I know how my tires grip at their usual pressure, and so I stick with that. Perhaps if I had the cornering benefits of tubulars, I might change that, but then dry condition pressure for road tubulars is higher than what i run with clinchers anyway.

[Seajay]

. You also need to take into account that there is less rolling resistance (though this depends on the specific tire design) with higher pressure which may translate into a faster ride (make more of a difference in the forward direction) than diffusing some of the vertical shock.



Hi Aicabsolut,
Please keep in mind..I'm just having a conversation here....I know forums can seem a tad confrontational sometimes....this is not one of those times.
From the reasoning above...a completely rigid (but lightweight) tire would be fastest. ie something like a rubber coated rim. :eek: Yet no one does this... even in the straight line speed world of human powered speed records.
Speaking with Phil White of Cervelo cycles...he claims his Test Team ride 95 to 100 psi on their road bikes. Just experimenting, I've played around with pressures as low as 60psi and have never felt it was as draggy as you describe.
I guess I'm wondering what evidence you are citing to make your case.
Have a great day ! :)

I guess I should add in that in the unlikely event "we" are riding on a brand new, glass smooth road it would be fastest to run as high a pressure as possible. But this only further makes my case that smooth is fast.

[Eden]

What Sheldon Brown has to say about rolling resistance: http://sheldonbrown.com/tires.html#rolling (cause his stuff is usually pretty well researched)

I weigh about 105. I tend to notice it when my tires get down to about 80psi. Feels a bit logy. I generally run about 105psi, but I'm lazy and don't pump them up every ride.... I've had very few pinch flats - only one I specifically remember and I went over a *nasty* sharp curb with an under inflated tire.

[Seajay]

Good One Eden. Sheldon strikes a nice balance. Regarding his comment
" the rolling resistance at correct inflation pressure is already so low that the infinitesimal reductions gained are more than outweighed by the trade-offs"

I take this to mean that if you are somewhere in the ballpark of the correct pressure...the changes in rolling resistance are so small...that "we" are making up any differences in our heads. THAT...sounds like the late Sheldon Brown

The rest of the article is a nice summary as well.

[aicabsolut]

I'm not trying to attack anyone either--just continuing the discussion. :)

PSI also has a lot to do with the tire and what it's max is. I'd blow out some tires at 120, whereas 120 feels fine in others. And then there are tubulars (which most of the pros use), and varying pressure in tubulars has some grip advantages, but again it depends on the tire (and the rim).

I have no physics data, just personal experience.

There are some people who ride tires narrower than 700x23. There are some who ride lighter tires. Think of the Michelin Pro3 Light tire in 700x20. The narrower tires generally require higher PSI for the rider weight, according to the charts I've seen. These are often used by triathletes who want a thin, light tire that is good for riding in a straight line. The narrower tires can get a bit tricky to ride in tight cornering situations (but lots of people like using them for crits too), and the lighter tire means it has less flat protection. So there are practical drawbacks to using this arguably faster tire.

Because we're still talking about a road bike tire (even at high pressure) and not a MTB or CX tire and not a hard rubber disc, the amount of energy lost bouncing vertically is probably adequately absorbed by the tire, fork, and rider such that it's still going to be a faster tire. It will be less comfortable the more rigid the tire, and, depending on the tire, there may be less grip at times you'd want more grip (i.e., not going in a straight line on a relatively smooth road). At some point, "comfortable" turns to a squishy, sluggish feel, and then you get to a point where (with clinchers), you hit some pretty minor holes and you get pinch flats.

[Seajay]

the amount of energy lost bouncing vertically is probably adequately absorbed by the tire, fork, and rider such that it's still going to be a faster tire.

Yes, Fun conversation. Thank you for continuing it.
I will stand by my theory that the energy the fork, frame and rider absorb (convert) is wasted. Yes, you can run too soft... but with an appropriately inflated tire, energy taken up by the front of the contact patch and returned at the aft is not wasted....thus a faster more efficient set up.
It would be interesting to do the same road with a powermeter and a speedometer. How much power does it take to hold X mph with a range of tire pressures?
We need a tire engineer to jump in here. :)

[aicabsolut]

Yeah, sure it's wasted energy, but I think that it's negligible compared to the vertical shock absorption being done by the tire/fork/frame/rider with a softer tire in light of the differences in propelling forward. The more I think about it, I think you are right that you've got to measure this in terms of power output by the rider instead of just rolling resistance numbers for a tire since travel in the vertical direction would be hard to measure. The fewer watts it takes to go X mph over different terrain with different pressures under the same wind conditions would mean that the tire setup is "faster" because the ride would be more efficient.

I'm not sure how many watts we'd be talking, though. I would guess not that many, based on my assumption that this topic eventually boils down to personal preference for comfort, the road "feel" for a given tire, and the odds of getting a pinch flat due to ease of compressing the tire.

[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 :-)