Clydesdales/Athenas (200+ lb / 91+ kg) - Air pressure. Fill to the max for speed or less for comfort?

I have 700c x 28 Continental Gatorback. I will fill them to 100+ psi two times a week or more.

At that pressure, they roll well and minimize the risk of pinch flats. However, the ride is noticeably busy.

After two or three days, the ride quality improves as the pressure drops to about 80 psi.

Should I keep the pressure high at 100 psi, or am I just unnecessarily punishing myself?

I keep mine topped up to the top for the reasons you mentioned. You could always keep them around 80psi if you prefer that - you might find you still only need to refill them a couple of times a week. Ultimately I'd say do whatever helps you get out and ride :)

25c's on my fixed I run at full psi and suffer, for comfy rides I have 32c knobbies on my cyclocross that I run at full psi (85) and don't worry about the 1-2 mph I may lose. The roads are rough in Chicago and I learned my lesson with a serious pinch flat that nearly destroyed my rim thanks to some unmarked road work in the bike lane.

full psi. hate the sluggish feeling when pressure drops.

At my weight, I kind of think they should be at full pressure all of the time.

I have 700c x 28 Continental Gatorback. I will fill them to 100+ psi two times a week or more.

At that pressure, they roll well and minimize the risk of pinch flats. However, the ride is noticeably busy.

After two or three days, the ride quality improves as the pressure drops to about 80 psi.

Should I keep the pressure high at 100 psi, or am I just unnecessarily punishing myself?

Run them at 80 as long as you don't pinch-flat. Testing shows that HIGH PRESSURE= FASTER= MYTH. Your tire is your suspension. Many think that the higher pressure is faster because it feels faster. Which feels faster - a Jeep CJ going down the road at 55mph or a Lexus going down the same road at 85. With high pressure, every time you hit a small imperfection/bump in the pavement, the full mass of the bike/rider has to go up to get over it. The energy required to go up that fraction of an inch is supplied by you pedaling. How many thousands of times would this be on a normal ride? Total them all up and how big of a hill did you just climb? With low pressure, the tire casing flexes and the rider/bike just goes straight. - TF

On my road/commuter I run 110 p.s.i. it helps me prevent flats!

Here's some interesting reading: http://sheldonbrown.com/tires.html#pressure

I keep mine at 120 (23 and 25's). Maybe I'm nuts but I feel no difference when I run lower psi. But I also feel no difference with a cf fork and/or seatpost either when others swear by them!:p

I run my tires at full pressure. Any comfort that may be gained by riding on soft tires is negated by the extra effort it takes to move the bike forward.

I run my tires at full pressure. Any comfort that may be gained by riding on soft tires is negated by the extra effort it takes to move the bike forward.

That's really not true. You're beating yourself up to go slower. - TF

Depends on what kind of riding I will be doing. Riding my MTB with 2.2" slicks, I'll ride around 45-50psi for simple neighborhood cruising, but pump them to the max (65psi) for a serious training ride. The road bike is a bit different, but I know on rougher chip and seal roads in Darlington and Lee Counties I drop them down to 105psi for a somewhat softer ride, but on better roads here in Beaufort County I pump to the max (120psi).

TT, I'm confused by your box vs. bullet comparison (CJ vs. Lexus). The different feeling of speed is primarily the noise of wind hitting all those flat surfaces of the CJ and the (typically) larger lugged tires on the CJ slapping the pavement vs. an aerodynamic shape with tires designed to be smooth and quiet on the road. Not sure how that equates to tire pressure.

TT, I'm confused by your box vs. bullet comparison (CJ vs. Lexus). The different feeling of speed is primarily the noise of wind hitting all those flat surfaces of the CJ and the (typically) larger lugged tires on the CJ slapping the pavement vs. an aerodynamic shape with tires designed to be smooth and quiet on the road. Not sure how that equates to tire pressure.


He was trying to explain that the worse suspension (jeep or high pressure tires on bike) makes you feel like you are going faster than you really are. The smoother ride (lower pressure or Lexus) makes the speed less noticeable.

I keep mine at 120 (23 and 25's). Maybe I'm nuts but I feel no difference when I run lower psi. But I also feel no difference with a cf fork and/or seatpost either when others swear by them!:p

I do the same but I think the cf fork and seatpost do make a difference in reducing the faint buzz alu frames have.

He was trying to explain that the worse suspension (jeep or high pressure tires on bike) makes you feel like you are going faster than you really are. The smoother ride (lower pressure or Lexus) makes the speed less noticeable.

I knew where he was going, just don't think it is a fair analogy as the suspension (AKA tire pressure) is only one of many significant differences between these vehicles leading to the percieved speed.

Now if he said a Lexus with underinflated tires got better mileage (ie: used less energy to move the vehicle down the road) than one with fully inflated tires, that would have been a fair analogy.

I run mine (23 and 25) at 120 and I really don't consider the ride quality that bad...until I get on my commuter with the 32c TT2000s. ;)

Keep them pumped up to a level appropriate to your weight to prevent pinch flats.

Now if he said a Lexus with underinflated tires got better mileage (ie: used less energy to move the vehicle down the road) than one with fully inflated tires, that would have been a fair analogy.

Yes, but that would not be correct. I think the analogy is bad either way, but I have never seen anything to support better gas mileage at a lower tire pressure than recommended.

My Buick gets better mpg with PSI Maxed Out in the tires.
So I do the same on the road bike.

Keep them around 90 - 95 psi. 80 seems a little low and may be prone to pinch flats.

Yes, but that would not be correct. I think the analogy is bad either way, but I have never seen anything to support better gas mileage at a lower tire pressure than recommended.

Thanks. That was the point I was was hoping someone would get. Why would it take LESS energy to move a bike with underinflated tires when it takes MORE energy to move a car with underinflated tires? Regardless, I know I am slower when my tires are down 20 psi. Don't need a guage to tell me they are low, I can feel it when I ride.

10 Wheels has a point there. I don't see how having lower tire pressure could equal the efficiency of having higher tire pressure. Even in a car, you'll get noticeably lower mpg if you have lower tire pressure even by 5 psi. Your engine has to work a little bit more because their is more tire making contact with the road. Same formula would apply to a bicycle. TurboTurtle, you can't convince me that having lower tire pressure is equal to a higher one. The less contact a tire makes, the more efficient the motorThat's why hybrids and high fuel economy cars have tires that make less contact with the road. This same formula would apply to a bicycle, being that the vehicle is the bike and the motor is the rider, each pedal stroke would benefit more from having fully inflated tires. Of course, the trade off is rougher ride, but that would depend on the individual's taste.

Michelin tires says if your over 180 to fill to the max as on the sidewall

Ok, maybe I'm a physical oddity, but I seem to get better speed and more comfort with my tires at around 80-90psi (panaracer pasella tg, 28 or 35c depending on the bike I'm on). I also notice a notable level of discomfort above that psi range (I think they're rated at 120 psi).

Find what works for you, and stick with it. Its your butt in the saddle after all.

I run around 110 - 120. The difference down to 80 is terrible for speed difference, and also too easy for a pinch flat with my 23's.

I have 700c x 28 Continental Gatorback. I will fill them to 100+ psi two times a week or more.

At that pressure, they roll well and minimize the risk of pinch flats. However, the ride is noticeably busy.

After two or three days, the ride quality improves as the pressure drops to about 80 psi.

Should I keep the pressure high at 100 psi, or am I just unnecessarily punishing myself?

It really depends, what it really comes down to, is squish factor, typically the larger the tire, the less pressure needed to eliminate squish, it all comes down to the contact patch. With a 200lbs rider and a 30lb bicycle you have a load of 230lbs, 75% of that is on the rear tire, or 172.5lbs, at 100 PSI you have a contact patch that is roughly 1.725 square inches, the square root of 1.725 is 1.31 inches or 33mm this is the width of tire you need at 100 PSI to eliminate squish.

However that eliminates squish completely, which has the lowest rolling resistance, and is fastest. Now that is true, on glass smooth roads, however if the road is frost heaved, cracked, potholed, chip seal or worse, then the excessive buzz and bumping around of a rock hard tire, means that your are probably intentionally slowing down a little for relief. The other method of relief from imperfect roads is to lower the tire pressure and take advantage of the air-ride suspension built into your tires. You should be fine on pinch flats at somewhere around 80 - 90% of the squish free pressure. It also means that you can run your front tire at a lower pressure then your rear tire, what some riders do, is run the rear tire at the squish free pressure, and the front tire at 80% of that, which reduces the buzz on the bars where it is most bothersome.

It also raises another question, I wonder how much of numb bum is from excessive saddle buzz, due to the insistence of running the tires at a higher pressure then is warranted for road conditions. I got this idea this morning sitting on the bus, in the seat directly over the engine compartment, where there is more vibration from the engine, then in many other seats.

I run 5 pounds over the max on all my tires. Running low pressures suck all the fun out of bicycling.

TT, I'm confused by your box vs. bullet comparison (CJ vs. Lexus). The different feeling of speed is primarily the noise of wind hitting all those flat surfaces of the CJ and the (typically) larger lugged tires on the CJ slapping the pavement vs. an aerodynamic shape with tires designed to be smooth and quiet on the road. Not sure how that equates to tire pressure.

The difference is the supension. Even with road tires and ear plugs, that rough ride is going to 'feel' fast. - TF

Thanks. That was the point I was was hoping someone would get. Why would it take LESS energy to move a bike with underinflated tires when it takes MORE energy to move a car with underinflated tires? Regardless, I know I am slower when my tires are down 20 psi. Don't need a guage to tell me they are low, I can feel it when I ride.

A car tire is rounded when over inflated. A bike tire is rounded at the recomended pressure. A car has suspension. The tire is the suspension on a road bike.

Also, you are talking about under inflating the car tire vs. over inflating the bike tire. The recommended pressure from Michelin is 58 - 85 psi (depending on weight) for the OP's tire. What are you recommending?

Do a search. Look at the tests. Over inflation is slower.

TF

10 Wheels has a point there. I don't see how having lower tire pressure could equal the efficiency of having higher tire pressure. Even in a car, you'll get noticeably lower mpg if you have lower tire pressure even by 5 psi. Your engine has to work a little bit more because their is more tire making contact with the road. Same formula would apply to a bicycle. TurboTurtle, you can't convince me that having lower tire pressure is equal to a higher one. The less contact a tire makes, the more efficient the motorThat's why hybrids and high fuel economy cars have tires that make less contact with the road. This same formula would apply to a bicycle, being that the vehicle is the bike and the motor is the rider, each pedal stroke would benefit more from having fully inflated tires. Of course, the trade off is rougher ride, but that would depend on the individual's taste.

Since this forum hides posts below a certain level, I will quote what I posted above-
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A car tire is rounded when over inflated. A bike tire is rounded at the recomended pressure. A car has suspension. The tire is the suspension on a road bike.

Also, you are talking about under inflating the car tire vs. over inflating the bike tire. The recommended pressure from Michelin is 58 - 85 psi (depending on weight) for the OP's tire. What are you recommending?

Do a search. Look at the tests. Over inflation is slower.

TF
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I have nothing vested in convincing you and will leave you with the myth if you like.

TF

A car tire is rounded when over inflated. A bike tire is rounded at the recomended pressure. A car has suspension. The tire is the suspension on a road bike.

Also, you are talking about under inflating the car tire vs. over inflating the bike tire. The recommended pressure from Michelin is 58 - 85 psi (depending on weight) for the OP's tire. What are you recommending?

Do a search. Look at the tests. Over inflation is slower.

TF

Yes, to over inflate (i.e., ABOVE the recommended tire pressure rating) bicycle clincher tires causes the tire to deform and will actually increase rolling resistance. Plus it is dangerous and can cause a rim split which can be deadly at speed.

However, to run the tire at the higher end of the recommended inflation pressure versus to run it under inflated will reduce rolling resistance and make it less energy consuming to ride.

Best advice is to run the tire within the recommended inflation pressure range and to check the pressure occasionally while out riding. Warming ambient temperatures can cause the air pressure to rise and if you have inflated the tires during the cool morning to max psi, you will likely be over inflated during the hot afternoon part of your ride.

TT, I never said over inflate only running at max pressure vs. less than max.

I left my old bike standing in full July sun once - and it blew the rear tube:) They were old but ever since I always put the bike in shade.

TT, I never said over inflate only running at max pressure vs. less than max.

Then what would your answer be to the OP?

And do mean maximum recommended pressure or the maximum SAFETY pressure that is stamped on the side of most tires.

TF

105-110 in my 700x23s is a very good compromise for me, weighing 235. My speed definitely suffers below about 90.

Then what would your answer be to the OP?

And do mean maximum recommended pressure or the maximum SAFETY pressure that is stamped on the side of most tires.

TF

I looked at the 22 bicycle tires currently in my garage and could not find a maximum SAFETY pressure stamped on any of them. They either say "inflate to max. X psi" or "inflate to min X psi / max Y psi". As for the OP, I'd recommend max.

Ok, maybe I'm a physical oddity, but I seem to get better speed and more comfort with my tires at around 80-90psi (panaracer pasella tg, 28 or 35c depending on the bike I'm on). I also notice a notable level of discomfort above that psi range (I think they're rated at 120 psi).

Find what works for you, and stick with it. Its your butt in the saddle after all.

Just FYI, the recommended pressure on the Pasella TG 700x35 is 90 PSI. I put a pair on a week or two ago, so I still recall that specific detail.

Personally, I don't agree with the sentiment that lower PSI is more comfortable. I find I am MUCH more comfortable with higher tire pressure... I don't know much, other than a mushy ride, with lower PSIs in terms of physical comfort, but I appreciate the psychological comfort from being able to feel what's happening down on the road. Maybe when I'm older and have old man bones I will find the lower pressure more comfortable, but for now I'm just as happy to let my body take "the blow"
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