# Tire Pressure



## supps (Jul 9, 2007)

So, I've been riding with my tires around 110 to 115 psi. I got a flat the other day and noticed that the tire stated the recommended pressure was 100 psi (it was written on the side, hard to see when it's on the bike). I tried it out, and I swear I rode faster. 

Any reason why this would be? I would assume 110 to 115 psi would be faster. For example, on my MTB, I ride at a higher pressure when I ride it on the road. The only reason for being faster at a lower pressure is something to do with absorption of the road, though I was never very good at physics.


----------



## david462 (Jan 3, 2008)

the flat most likely didnt happen because of the tire pressure. however, if the tire pressure was really low (lower than the tires rated min) then you can get pinch flats.

i dont really know how much tire pressure from 100psi to 115 will change your speed. usually riders will feel like they go faster with higher pressures cause they feel all the road vibrations more which makes it seem faster.

the tire pressure to run will mostly depend on the tire itself and the rider weight. i forget what the common pressures are per weight, but i usually ride at 110-120 front and back on 23c clinchers. anything over 120 feels too twitchy. i weigh 150lbs, bike weighs 26lbs.


----------



## MerlinAma (Oct 11, 2005)

The old school conventional wisdom was to pump your road tires until they were about to blow off the rim. After all, those track guys run 150 plus psi, right?

On real roads, things aren't so smooth. Those rock hard tires start to bounce around a little (chatter?) and that slows you down.

At 165 plus a 17 lb bike, I've been running 100 front and 105 back in my Prorace2 tires. It makes the ride much more plush and I notice no reduction in speed at all!

There has been a lot of discussion about this in the past several years, The guys over at roadbikerider.com were the ones who convinced me to drop the pressure.

The max psi printed on the tire sidewall is for legal purposes, not a recommended pressure.


----------



## mohair_chair (Oct 3, 2002)

A drop of 10-15 psi in a road bike tire should have no significant impact on your speed. In some rough road situations, theoretically, lower pressure could make you faster, but I doubt you would ever notice. (Plus, who rides on really rough roads very often? Do you?) It's nothing to worry about. Find the pressure you like, for whatever reason, and stick with it.


----------



## normalnorm (Jan 16, 2006)

A sales rep. said once..."pump to the max reading on the tire". Mind you, I'm a clydesdale.

That said, I feel slower with lower pressure.


----------



## Michelin Bicycle Tech (Nov 14, 2007)

I think one of the biggest problems in the bike industry is this exact conversation. It has always been to "pump them up to the max then go 5 psi more" theory. So wrong.

When a tire is at the right pressure for the rider's weight, the tire is the suspension of the bike. If you can imagine, when you roll over something, the tire "sucks" the object in, conforms around it and spits it out the back keeping you riding smoothly. If there is too much pressure in the tire, basically the tire "skips" over the object in the road. At that point, you aren't just going forward (horizontal) but you are also going up and down (vertical) and therefore losing momentum. Also, when you are overinflated, you are more prone to get punctures. There is also the issue of a contact patch, which is more of a safety issue. When a tire is at the right pressure, the contact patch is only about the size of 2 nickels side by side standing on edge. Thats not a lot of rubber touching the ground at any point in time. Having not enough pressure will make the bike feel like you are riding in mud or wet sand and make the tire prone to pinch flats.

Here is a chart for tire pressures for different weights when dealing with Michelin Tires.


----------



## mandovoodoo (Aug 27, 2005)

Experimentation helps on tire pressure. Ride, add a little, ride, add a little. There's a point where bounce starts to hurt. Back off a bit from that. The other direction works, too. Let air out little by little until it's clearly too soft. I suspect there's really a fair bit of latitude. 

Conditions play in as well. There are rides where I'll run lower pressures because of the pooor road surface. Not a lot less, but less. 

I'm 160 to 165 lbs and I normally run 100 / 105 lbs. Used to run harder, but that's enough. That's on 23 mm tires. On 28 mm tires I run 90 / 95 just fine. With 21 mm on the track I'd be running 125 in the old days. Same weight etc. Different tires, different uses.


----------



## danl1 (Jul 23, 2005)

mandovoodoo said:


> I'm 160 to 165 lbs and I normally run 100 / 105 lbs. Used to run harder, but that's enough. That's on 23 mm tires. On 28 mm tires I run 90 / 95 just fine. With 21 mm on the track I'd be running 125 in the old days. Same weight etc. Different tires, different uses.


I run those pressures (even softer, sometimes) at 180-185 lbs. Might not be as efficient as it could be, but it's comfortable and I don't get pinch flats. I haven't personally seen evidence in my riding that it's a significant difference. I do know that I'm riding stronger after 50 miles of chip seal at a slightly lighter pressure, and I believe it more than makes up for any additional effort it required along the way. 

Could be wrong, but I've been unable to prove it either way.


----------



## Dinosaur (Jan 29, 2004)

Tire pressure depends on the tire you are using, body weight and type of roads.

I usually inflate mine to a couple of pounds below the max recommended psi listed on the sidewall. Too high will cause premature tire wear and a harsh ride. Too low can cause pinch flats and I've had tires feel really squirrelly..


----------



## ECF (Aug 19, 2003)

*I'm past a clyde...*

I'm around 260 right now. Been losing about 10 pounds a year the past two years. I run a 25c rear at 90-95 and a 23c front at around 100 and have never had a pinch flat. Very comfy ride. Lower pressures are highly recommended by me... 

Eric


----------



## footballcat (Jul 8, 2004)

116 psi - im a big boy 86kg


----------



## Kuma601 (Jan 22, 2004)

For me at 155#'s and my bikes, I've noticed that at 78-82% or max rated inflation seems to work well for the roads I ride. Too low and I feel the tire rollover on a corner...I would describe it like driving a car and feeling the sidewall flex on initial turn-in hence a bit sluggish to steering input. Too high and it's a stiff ride.


----------



## jjp (Mar 3, 2005)

Well, I might as well through my $.02 worth into the mix! I'm usually around 185lbs (84kgs), and I ride Continental Sprinters, which are tubulars. The maximum recommended weight is, hold your breath, a whopping 170psi! Even at 140psi you can feel the grains of sand! It was recommended to me by a couple of reputable dealers in the city that 130-140 will seriously reduce tire puntures, as opposed to 120, which is what a lot of riders pump the at. Over the last two years, with thousands of kilometers on my bike, riding at 130-140, I have had 4 punctures, which I don't consider bad at all, considering that I do a lot of my riding on the very unforgiving streets of Toronto.


----------

