Tire Pressure

[Michelle T]

I'm 4'10" and weigh about 100 pounds. I'm going to buy a bike with tires that will take 120 psi. I've heard that lighter riders don't need and can be uncomfortable with the maximum tire pressure. How do I know what tire pressure is right for me?

[indysteel]

Just experiment. I'm 120 and ride at 100 psi on tires that can hold up to 120. I'd start with 90 psi if I were you and see how that feels.

[Xrayted]

Never go to max pressure on a tire, bike, car or otherwise. That is the upper limit. I would go, in your case, about 20lbs less than max to start. Get on it, see how it feels and how it LOOKS. Have someone look for you from the side as you go by. If it is compressing too much, put a little in. If it seems hard and you're feeling the road too much, taking into account what kind of frame/seat you have, then take a bit out. The biggest thing is to find a pressure that isn't harder than needed, so soft it won't give you a pinch flat and check the pressure at least twice a week depending on how much/how far you ride normally. :) If you only ride on weekends, then absolutely, check it everytime you ride. If you ride to work everyday, then every other day give it a quick check.

I just hate seeing someone riding around on 1/2 the air needed, almost on the rim. The rest of the air must be lodged between their ears. :p

[Dogmama]

I'm 118 pounds & I've always run on 120 pounds of pressure (20 years of cycling.) I use Continental tires. I notice more rolling resistance at less PSI.

[indysteel]

On the often rough roads we have in Indiana, I'm willing to have some extra rolling resistance if it makes for a more comfortable ride.

[Catrin]

On the often rough roads we have in Indiana, I'm willing to have some extra rolling resistance if it makes for a more comfortable ride.

Hmmm, I am 138 pounds and have kept my Trek's psi at 110. I am wondering if I should drop that to 100 and see if the ride is a little more comfy on my country roads? With my weight would 90 pounds be too low?

[Chicken Little]

I keep them maxed for wear and flat protection.

[artifactos]

My tires have an optimum range of 100-120 psi and I keep mine right in the middle of that.

[OakLeaf]

I'm 122# and I keep my Conti GP4000s at 110 front and rear. I definitely notice the increased rolling resistance if I go lower. There is a tradeoff in efficiency when the roads are so rough that your drive wheel is losing contact with the road surface - but those are also the times that a pinch flat is most likely. So just experiment.

Also, I air my road bike tires every ride. High-pressure road tires and tubes lose almost as much pressure just sitting around as they do being ridden. On the fat-tire commuter, once a week is plenty.

Out of curiosity, does anyone run their tires at different pressures front to rear? If so, how do you like it?

[indysteel]

I run the same pressure front and rear. I'd note that I've never (knock on wood) had a flat.

[OakLeaf]

Whoa, whoa, whoa, do you mean you've never had a pinch flat (neither have I, that I can recall - I think they're pretty rare when you're under 150 lbs)? Or you've never had a puncture, a leaky valve, any kind of flat????

[Dogmama]

Whoa, whoa, whoa, do you mean you've never had a pinch flat (neither have I, that I can recall - I think they're pretty rare when you're under 150 lbs)? Or you've never had a puncture, a leaky valve, any kind of flat????

Oh man. Never say never. The Flat Gods will visit you frequently. I've had one pinch flat & honestly - it had been two weeks since I'd aired up my tires & I was probably running about 80 pounds (I'm 118 pounds.)

[indysteel]

I have never had a flat of any kind. I guess I've been lucky thus far.

To the OP, there was a thread last year that gave a formula for determining psi, along with a link to a Sheldon Brown article. I'd provide a link to the thread, but I'm on my Blackberry and can't. It's from May of 2009, and was titled "tire inflation and rider weight" if you want to do a search.

The bottom line I took from it is that you should just experiment with psi to see what you prefer.

Sheldon Brown's article indicates that you should run the rear tire at a higher psi (by about 10 percent).

[redrhodie]

Indy, you are lucky! Maybe I should run lower pressure (I usually go to 118, and I weigh 123). Although, that probably wouldn't have helped when I ran over the wood screw. :rolleyes:

Drift--I patched a flat a couple of weeks ago, and it (the patch) failed this week. What did I do wrong? I used a self stick patch, and sanded the tube lightly, as per the instructions. The hole was on a seam, which is where the air ended up escaping from under the patch. Should I have sanded more, or used another kind of patch?

[OakLeaf]

Patching over a seam is tough. It's possible that it just wasn't going to happen... but things I do are sand the seam extra to try to bring it closer to the level of the rest of the tube ... and be extra careful that there isn't a glob of wet glue up against the seam when I apply the patch.


ETA - I missed that you used a self-stick patch. I don't have a lot of experience with those, but I've heard they're not as reliable. I carry them for on-the-road repairs, but if I have the luxury of mounting a spare tube and patching the hole at home, I use the kind with the separate rubber cement.

[Thorn]

I'll join the "never run max pressure" chorus....because (hrrmph) it is right :)

Seriously. If you won't believe Sheldon Brown, try the guys over ad Road Bike Rider.

You want your tires to have enough pressure to avoid pinch flats and no more. For most riders (and they're basing their logic on avg male weights) 90-95 is plenty.

If you run a high pressure, your bike will bounce over little bumps (oh, like say chip seal). You get the impression that you're moving, but, in reality, your wasting energy bouncing up and down instead of rolling forward.

If you run a lower pressure, your tire can deform around those small bumps. You don't lose energy bouncing up and down and you get the side benefit of a more comfortable ride.

The Road Bike Rider guys will also say you're less prone to puncture flats if your tires can deflect around some of the road debris. If the tire cannot deflect, the glass will go through the casing.

[tctrek]

Hmmm... riding at lower pressure seems to make sense. I've always done 100-110 psi, but I am soooooooo flat prone. True the choices of where I have to ride suck and I end up on roads that have lots of crap on the side. But I ride with DH most of the time and I am always the one with the flat. I might try the 90-95 psi and see if I could ride a few weeks without a flat!

[Dogmama]

Hmmm... riding at lower pressure seems to make sense. I've always done 100-110 psi, but I am soooooooo flat prone. True the choices of where I have to ride suck and I end up on roads that have lots of crap on the side. But I ride with DH most of the time and I am always the one with the flat. I might try the 90-95 psi and see if I could ride a few weeks without a flat!

I also got to thinking - it might make a difference depending on the brand of tire. I ride Conti's and they seem to have a rather soft rubber in contrast to, say, Michelins. So, maybe my 120PSI is similar to a 100PSI Michelin in terms of comfort and handle-ability...? But, I'm probably going to lower my PSI because the roads are hot & heat increases tire pressure.

[Bike Goddess]

I've been riding 100PSI on any tire I put on my bike. I seldom have flats. When I do, I have 2 new tubes in my seat bag along with my bike tools. Usually I give my flat tire to a friend who will use it on his rides. I'm too lazy to fix a tube. :)

I do suggest that you always carry 2 tubes with you. Also, if you put "baby powder" on them, it will make it easier to put on the rim.

[Skierchickie]

I have never had a flat of any kind. I guess I've been lucky thus far.

Wow! I want your tires! What are you using?


Drift--I patched a flat a couple of weeks ago, and it (the patch) failed this week. What did I do wrong? I used a self stick patch, and sanded the tube lightly, as per the instructions. The hole was on a seam, which is where the air ended up escaping from under the patch. Should I have sanded more, or used another kind of patch?

A few years ago the owner of my LBS sold me some of those self-stick patches, saying they were fantastic. Most people around here, including him, are primarily mountain bikers. I used one on my road bike, and it failed. Tried a few times, and they always failed the same way. The sticky part isn't strong enough, and the air (at road bike tire pressures) forces a path out to the edge. It just creeps along, following the path of least resistance. I don't think you did anything wrong - and it chose the seam to travel along, as the easiest path, but I'm pretty sure it still would have failed.

I haven't used them in 10 years, so maybe they've been improved, but those things really should be labeled with a maximum suggested pressure, in my opinion. Give me the old kind (with the glue that sometimes evaporates out of the sealed tube :rolleyes:) any day! I think I have the self-stick kind in my mtb seat bag, but never again on the roadie.

[makbike]

Does the "never inflate to max" apply to tubeless tires too?

[maillotpois]

Does the "never inflate to max" apply to tubeless tires too?

even more so, I believe. and they run at much lower pressures. I was a 115 - 120 psi on tube tires and 90 - 95 on tubeless.

[OakLeaf]

Give me the old kind (with the glue that sometimes evaporates out of the sealed tube :rolleyes:)

drifting...

You raise an interesting point. With the rubber cement, it's immediately obvious when it's gotten so old that it's dried up. With the self-stick patches, you don't know until you go to use one. Or you wind up discarding them just because a certain amount of time has passed and they could be stale.

Yeah... I guess if my second spare tube has failed, either my riding buddies have already left or they'll be willing to wait an extra 90 seconds or so for the glue to dry, even though it does seem like fer-frickin'-EVER even when you're doing it at home with no time pressure. :p

[indysteel]

Wow! I want your tires! What are you using?


I use Vittoria Rubino Pros.

[ny biker]

I have a friend who sent me a bunch or articles showing that lower psi is better than high psi. There is no measurable increase in rolling resistance but your ride is smoother and more comfortable. In fact lower pressure is better for when you hit bumps, because your tires roll over them more easily so your momentum keeps going forward instead of being interrupted by the bump. If I can find them I'll post the articles here, but I have to warn everyone that they will make your eyes glaze over -- it's very dry reading.

Anyway, I used to keep my tires at 120 psi. I agreed to experiment with lower pressure and I'm averaging the same speed at 110 psi. One of these days I will drop it to 100 psi and I won't be surprised if it makes no difference in speed. I also mentioned the experiment to the mechanic at the LBS and he said he wouldn't go above 100.

[OakLeaf]

I'd think you'd need a power meter and laboratory conditions to really know the difference. Most everyone I know says they can feel the difference in rolling resistance - myself included - but of course that's subjective, even for individuals using a power meter outside.

But it's well known that higher tire pressure always increases fuel efficiency in cars. There's just a tradeoff in traction on imperfect roads, that becomes more apparent the worse the road gets.

I would think that the theory is no different for general road riding than it is for racing or mountain bike riding - the smoother the road surface and the better the traction, the higher the pressure should be for best efficiency. There's never any "one size fits all" for tire pressure. It's just that paved roads are more uniform than unpaved trails.

[ny biker]

I'd think you'd need a power meter and laboratory conditions to really know the difference. Most everyone I know says they can feel the difference in rolling resistance - myself included - but of course that's subjective, even for individuals using a power meter outside.

But it's well known that higher tire pressure always increases fuel efficiency in cars. There's just a tradeoff in traction on imperfect roads, that becomes more apparent the worse the road gets.

I would think that the theory is no different for general road riding than it is for racing or mountain bike riding - the smoother the road surface and the better the traction, the higher the pressure should be for best efficiency. There's never any "one size fits all" for tire pressure. It's just that paved roads are more uniform than unpaved trails.


Yes I thought the same thing but my friend is a persistent statistician. And really, I've actually tried it and am riding the same speed without working harder.

[redrhodie]

So, I ran lower pressure today, 108 instead of 118, and I felt like my brake was rubbing. I actually stopped and checked to see if my brake was rubbing, then I remembered it was the tires.

Hard to say if I was any slower. I don't use a computer, and although my time was a little off, I did get a few more red lights than usual. Maybe that was because I was slower. Eh, I'm going back to 118. I didn't like how it felt.

[Crankin]

I'm with Red. I keep my tires at 120 and I have had 2 flats in 10 years. Generally, the roads here are OK; no chip seal. I do feel the bumps, but, to me, it's part of riding. I also ride Contis, and I've never seen anything about 120 being "dangerous." My DH has different Contis that are actually rated up to 135, which is what he uses.

[Thorn]

While I stand amazed at the depth of TE knowledge and the number of women with strong technical degrees, unless one of you must-run-high-pressure people fess up to not being lawyers, but, instead are physicists or mechanical engineers....well, one last time for the masses (like the 100 pound woman I met who has been struggling to get her tires up to 135 pounds when she needs only 90)

Here's Michelin's guide:
http://www.michelinbicycletire.com/michelinbicycle/index.cfm?event=airpressure.view

And, the latest Jim Langely blog where he tells a reader named Pam (ok, fess up which one of you sent the question :rolleyes:) that at 220 pounds she'll need more than he and then references the Bicycle Quarterly article:
http://jimlangley.blogspot.com/2010/06/q-broken-frame-seatpost-binder-best.html

[OakLeaf]

I'd note that the Michelin page says it's a "reasonable guide of where to start experimenting," not a hard and fast rule.

On a hardtail bicycle, your tire pressure IS your suspension, so the optimum will vary according to road conditions, just as you'd adjust your ride height, preload and damping if you had full suspension. (And even with full suspension, optimum tire pressure varies according to conditions. That's why at a motor race, the tire people will post their recommended pressures.)

I'd also note that "recommended" tire pressures for automobiles have much more to do with comfort than efficiency. A lot of people (for unknown reasons ;)) don't like getting beat to death by the roads. The Michelin page also mentions comfort as one of the factors that went into their chart. You know how when you test drive a car at the dealer, if you buy the car, the first thing you do is check the tires and they'll be 5# low? Same idea.

There's a continuum between a plush ride and an efficient one, and every driver/rider has to make a decision as to where they like to be on that continuum. I like efficient. Other people might prefer plush.

Riding style has a lot to do with it, too. On my motos, for general street riding, I prefer fork springs that are very stiff for my weight. If I take the manufacturers' charts, add 30# to my weight and plug in that I'm an expert racer (which I most definitely am NOT :p), I'll come up with the spring rate that is most comfortable for me and gives me the best handling. But in the rear, I'm fine with a pretty soft shock spring, as long as I've got a ton of rebound damping dialed in. All of which points to I just load the front end pretty heavily. Other people might ride differently, with or without a motor.

I'll 'fess up to being a (retired) lawyer, but I think most of the others who've commented are not. ;) AFAIK, none of us here is a suspension engineer, so we're all just going from general knowledge and personal experience. And I'm still waiting for those articles about the laboratory tests... :cool:



And finally... who among us has had her tire pressure gauge professionally calibrated? :cool: Anyone who hasn't, which includes myself, is just going by a vague notion of what tire pressures she's actually running, which could be plus or minus 15# from indicated...

[indysteel]

While I stand amazed at the depth of TE knowledge and the number of women with strong technical degrees, unless one of you must-run-high-pressure people fess up to not being lawyers, but, instead are physicists or mechanical engineers....well, one last time for the masses (like the 100 pound woman I met who has been struggling to get her tires up to 135 pounds when she needs only 90)

Here's Michelin's guide:
http://www.michelinbicycletire.com/michelinbicycle/index.cfm?event=airpressure.view

And, the latest Jim Langely blog where he tells a reader named Pam (ok, fess up which one of you sent the question :rolleyes:) that at 220 pounds she'll need more than he and then references the Bicycle Quarterly article:
http://jimlangley.blogspot.com/2010/06/q-broken-frame-seatpost-binder-best.html

LOL. I'm a lawyer and my husband is an engineer. We both run under the indicated max for our tires. :D

[Norse]

Ok, I am a lawyer, my road tires are Conti GPs and, until about 1 year ago, I used to ride them at just under 120. I now ride at around 105-110 and did it just for the comfort factor - I do seem about 1/2 mph slower but I don't race and the older I get, the more comfort I want! Also, if it's raining, I will lower the psi to 90-100.

Interesting on the front/back difference. I sometimes go slightly lower on the rear for the comfort of my body. Sounds like I am doing that wrong.

[HipGnosis6]

Just for the sake of saying something about running on lower pressures being okay... I run 700x25C at about 110 psi. I'm big, too - 5'11", 275 pounds. I haven't had a pinch flat since I hit a raised metal drain edge at 20 MPH, but I had a whole bunch of them shortly before I came to understand that the higher the pressure the faster the air bleeds out. For me that means checking the tires every time I want to ride.