badger_biker 

I've been a lifelong card carrying member of the "pressure to the max is best" society and religiously topped my tires off before every ride.

However after reading some information both on this forum and other sources that kind of debunked that theory, I thought after my winter hibernation this spring I would try running my tires a little lower to see if it felt like riding in soft tar or if it made little difference in effort required.

After several rides on 4 different bikes I have become a convert to the ride softer contingent. I've tested 1" and 1 1/4" Panaracers, and 25 mm and 1 1/4" Continental Gatorskins and have come to the conclusion that there is no appreciable degradation in rolling resistance but a significant improvement in ride comfort. The rough jarring effect of pavement cracks and bumps is definitely reduced.

A question I have for others who run at lower than maximum pressure is - have you found the sweet spot where the rolling resistance and comfort are optimal?

I've been running at about 80 percent of the maximum rating on the tire and that seems pretty good but I haven't done enough variation to tell if that is the best.

Any comments regarding what pressure you find optimal would be appreciated.

jeirvine 

I generally run 28s at about 75/85 PSI (front/rear), and I weigh 185. I love the ride and have very few flats.

Edit: you've probably come across this, but it's a good guide:

southpawboston

I have definitely adopted a 'pressure policy' that mandates finding the sweet spot for every different tire in my fleet. It really does depend on several factors, mostly total weight of bike+cyclist, type of road surface, width of tire (or more specifically, air volume), and tire construction. Of all those variables, weight and tire width are the two most important ones.

My typical bike+rider weight with a bag and carrying tools, layers and food & water, is around 190-200 lb. On 650Bx42 tires, 30psi front/35 psi rear is the sweet spot for most gravel and dirt surfaces. For strictly paved, I up those numbers to 40/45.

For narrower tires, like 700x32, I find 45/50 good for gravel and 55/60 good for pavement.

For even narrower tires, like 700x28, which are the narrowest tires in my fleet, I need 65/70 for pavement, and I don't ride those tires on gravel.

Also, tires with extra supple casings, like Compass' "ultralight" line, provide even less rolling resistance and superior comfort than their same tires with standard casing. The only drawback is the ultralight casings are more prone to sidewall gashing from sharp objects.

The Golden Boy 

I've been happy with 10 pounds down. For me, it's Pasela Tourguards- 85 in the 1 1/4 and 95 in the 1 1/8.

jimmuller 

I still live in the higher-pressure zone. Whether it makes much difference to rolling resistance I couldn't say. How much benefit you'd get from a softer ride depends on the road. On a sufficiently smooth road not so much. If I'm running too soft on a 23mm tire I'd be afraid of getting a pinch flat. On my commute last year with the sun in my eyes at a busy stoplight I hit a pothole so hard it flat-spotted the rear rim, ruined a perfectly good MA2. But the 32mm Paseala TG running at rated pressure didn't flat and I was able to ride home. FOr that kind of protection I'll gladly pay a slight comfort penalty. Besides, I like the way tires track at higher pressure.

ThermionicScott 

Cue the Viagra jokes!

The 15% drop and 45%/55% weight distribution seem to be the sweet spot for all of my bikes, and my riding enjoyment has never been higher. I keep a little list of my tire pressure settings so that it's easy to top them up just right at home:

Size __ fr/rear
28-622: 65/80
30-622: 60/70
37-590: 40/50
42-559: 35/40
47-559: 25/30

Even though I'm at or below the minimum recommended pressure in my front tires, I haven't had a pinch flat in the 3-4 years I've been using these pressures. Indeed, my only pinch flat to date was on one of my inaugural road bike rides in 2009 before I knew that 25mm tires should be pumped up regularly.

noglider 

Our numbers may not help you, because you have to find what's right for you.

I rode my 32's in the city recently with 30-something psi in the tires. It was remarkably comfortable, and it didn't feel slow, though maybe it was. But it's not safe, and I don't plan to do that again. But that means that 40-something just might work.

I weigh 175.

I also moved from the always-keep-your-tires-hard camp, and I'm enjoying the softer ride now.

jimmuller 

NoG, you may remember when we did our little tour last year, as we were pumping up tires in our front yard, someone, perhaps Mrs. NoG, ask what pressure I preferred and so I answered blah,blah,blah. (Not that our tandem's tire pressure is relevant to the light solo bikes you skinny folk can ride.) Some time later a thought occurred to me. For an outing like that it is worth noting that we won't be carrying that nifty floor pump with the gauge. Frame pumps and CO2 cartridges will do but don't offer the same precision. With no flat prompting anyone to recheck their tires every so often we were all likely to run that entire trip on whatever air we started with. (Wouldn't want to mix air anyway, now would we?) If tires lose a little bit a day, the pressure on our arrival back home could be significantly less than what we started with. Best to start with a bit more as a cushion.

Just something to consider when you won't have a nifty floor pump available.

noglider 

Skinny? You and your beloved are skinnier than I am, for sure. Not that I'm complaining about being overweight.

Agreed; I inflate to 5 or 10 psi over my ideal pressure. I reinflate when I expect to be 10 or 15 psi below my ideal pressure.

rumrunn6

my weight is off the charts, 216-220 nekked, way over that suited up incl bike add-ons, water bottles and rear rack trunk, etc, so I guess I'll stick with the MAX, minus the bleed when I take the air chuck off.

but while commuting with winter marathons I found tweaking the pressure (slightly, just a *psst*), depending on conditions, provided better traction, but that's not this discussion

fender1

I am running Compass Barlow Pass EL (38mm) @ 60psibrear and 55psi front. I weigh 185. I find that bike corners better at lower pressures. The Compass tires and Vittoria Hyper Rando tires helped me understand that lower pressure works fine. No need to makes tires ride like bricks.

nlerner

I weigh 170 and even the bikes that I'm running 25mm tires, I won't put in more than 90 psi on the rear with around 80 on the front. Much softer ride.

randyjawa 

Max recommended pressure, checked and adjusted before every ride. And, though I have no empirical evidence to support my claim, harder is definitely faster!

davester

Well, Bicycle Quarterly has been collecting a lot of empirical data, and if their methods are to be believed (and I haven't seen anything to the contrary) then harder is definitely not faster, especially if there's any sort of roughness to the roads you ride.

Lonesome rider

I run at higher pressure (120 psi), however with Maxxis Re-Fuse 23 mm tyres (which are rough) the difference between properly pumped and lower than usual (say, 7.3-7.5 bar) is barely perceptible. I get no punctures, however last two "psssst" accidents happened due to failed presta valves. Silver Arrow Duros 20 mm can be pumped 7 bar max and these definitely give more "feel". They offer much softer ride but being puncture-prone, you don't wanna deflate them whatsoever. All in all, my small experience is just that: keep the pressure high.

seedsbelize 

I've always been a member of the max pressure club too, until last night's ride. I topped up the tires and suffered mightily on the chipseal roads I regularly ride. It was such a smooth ride the night before.

Rocket-Sauce 

I am a happy 215lbs and am still fast *, **
Using Boyd's (or was it Psimet's?) formula for my 700 x 25 rear and 700 x 23 front:
.33 x rider weight + 43.33 = ~114psi rear.
.9 x (.33 x rider weight + 53.33) = ~112psi front

I am sure a search will bring up the justification for this and the actual formulas and graphs. I just can't be bothered because now that I know what I should pump it up to, I am happy with that much information. It seems to work for me.



* For a dude in his 40s

** For a dude over 200 pounds

dddd

Pressure being proportional to load, I run relatively low pressures for my 150lbs.

1-1/4" or 32mm tires, measuring an actual 29-30mm inflated, I run at 60psi.

23mm wide tires I run at 90-95psi.

And 1-1/8" or 28mm tires (measuring an actual 26mm wide on touring-width rims) I run at 75-80psi.

Tire tread lasts longer at lower pressures, and outer-ply failure of aging tires can be avoided by using lower pressures.

Traction improves at lower pressures, especially when gravel may be present (even in invisible quantities).

Cougrrcj

I've been running 27x1-1/8 tires on my bike for close to 40 years now. Even when I was younger and much lighter (135lbs) than I am today (205lbs), I could feel the difference if my tires were down by 5-10psi from where I usually kept them, which was - and still is - 100psi rear, 90 front. Yes, I could feel the difference in rolling resistance. And also yes, the ride was harsher at 90/100. BUT while I may have been only ever-so-slightly faster on the harder tires (less than .5mph difference), there was no doubt that I could ride farther.

practical

I run 28mm tires with 115r psi. If they go low, I notice. Less than 10 pounds max and I top off.

davester

It's interesting that folks here are referring to running a particular pressure (i.e. a single number). No matter what, to maintain similar contact patches for both tires there should be a difference of about 10 to 20 psi between the front and back if you have the same size tire front and rear. It never makes sense to have the same pressure for identical front and rear tires (other than the idea that one number is easier to remember than two).

jethin

Interesting thread. I'm in the full psi = less resistance camp, but only because it seems that way when I ride. But I'm lazy and often run low tires, which feel marginally slower but definitely softer/smoother. Maybe I'll give this 15% drop an extended trial. I'd love to ride softer tires if there's really no performance loss.

noglider 

@jethin, it could be a placebo effect, but these new (to me) Vittoria Hyper tires are fast as displayed on my computer, and I'm running 50F and 60R!

jethin

@noglider yeah the data is compelling. It seems counterintuitive to me (more tread on road = more friction = reduced momentum) but I'm all for a softer ride as long as it doesn't slow me down. Maybe it's time I replaced my cycling hourglass with one of those newfangled speedometers so I can compile some metrics of my own.

dddd

If one considers that any tire must conform to the road surface, which is far from perfectly smooth, then there are a couple of ways that a tire can conform to this surface irregularity.

A higher inflation pressure allows the casing to deflect less, as the pressure is proportional to the tension in the casing, which helps the casing maintain it's round profile instead of conforming to road irregularity.

But a tauter casing puts higher stress on the tread layer to conform to the road surface irregularity, and the tread has a much higher coefficient of damping than does the pneumatic tire casing, which means you don't gain as much "speed" by using high inflation pressure to limit the tire casing deflection as was perhaps expected. The added "working" of the tread also dramatically increases tread wear, which is more localized within the smaller contact patch.
Racing tires with very thin tread will therefore absorb less energy in rubber flex, but also flex the casing a bit more in conforming to the road surface and of course also wear out much faster and puncture easier than tires with thicker tread layers.

There is also the matter of slippage friction, which comes into play when climbing steeper hills on rougher or dirtier surfaces, as well as when cornering on rougher surfaces.

Finally, you have to consider rider fatigue, both from vibration and from the rider having to exert more effort to keep the bike under control when traversing ever-changing road surface conditions. Surely this physical and mental stress takes some toll on a rider's speed and endurance limits(?).

davester mentioned using lower pressure in the front tire, which makes sense to the extent that the pressures are well above any possible pinch-flatting condition. But for riders seeking to use minimal pressure in minimally-sized tires, the front tire turns out to need nearly the same pressure as the rear tire in worst-case conditions of having to brake over bad stretches of pavement that tend to turn up unexpectedly, and which may force the use of heavy braking, which of course transfers most of the weight to the front tire!
I've also pinch-flatted front tires many times when hitting un-seen rocks, this when running only 5psi less pressure in the front tire than the rear. Objects which may not move out of the way of the rear tire after front tire impact may likely also flat the rear tire though.

BTW, wider rims, to the extent that they position the sidewalls more vertically and to the extent that they flatten the tire's tread cap profile, can allow a somewhat lower inflation pressure with no increase in rolling resistance.
This is because of the reduced drop/rebound distance of the tire under load, and because of a less-sharp bending angle of the tire's tread and casing at the periphery of the contact patch, respectively.