Optimal tire pressure
 

My wife and I ride cyclocross bikes with 32cc tires. We inflate them to about 80 lbs - midway in the recommended range on the tires. I thought that was a good compromise but I just listened to an interview with the editor of Bicycle Quarterly that says research shows we are way over inflated. Here is a pdf with charts showing optimal inflation against tire size and weight (on the wheel, not total). The results are surprising - more so for wide tires like ours than for narrow which may need more inflation. If you want to hear the interview it is here.

Good article. Most people overinflate in the expectation of better performance.......................it doesn't work as well as normal inflation.

Everybody has an opinion.

If I tried to use that chart, I'd be under the recommended minimum of the tire manufacturer. Not good! Me and the bike are pushing 250#.

I inflate to gain handling and sure footedness. In my case, with a 35 on the front, and a 40 on the rear, that works out to 85 PSI in both tires.

I've tried less, and the tire starts to feel "loose" when going around tighter corners and curves. At 85, everything feels nice and secure. (I start to tell a difference at 75, and it is very noticable at 70.) 85 also keeps pinch flats at bay, and it still rides nice (most likely due to the tire size.)

Interesting - I am pretty close to ideal acording to this, I am on 23s and run about 110psi, I could drop 10 - 20 on the front wheel. I am a little over inflated on my commuter - I run about 35-40 in those tires.

I wonder if there is also a dependency on wheel radius - the smaller the wheel the more the tire has to flex for the same tire pressure. I would think smaller wheels would want to carry a little higher pressure, probably proportional to the radius.

Yeah, I tend to keep 'em high, I'm no light weight. It's an interesting chart, I like his take. I've seen others not as good. Seems though, that lots of writers lean towards the whole avoiding the over inflating theory. Sound theories, I've experienced plenty of pinch flats, you know "snake bites ".
I can see it more on a +32mm tire or extraordinary conditions; sandy pavement, lots of pebbles. small bumps or washboard surfaces. Can't see the load-aspect, doesn't pertain to other vehicals anyway.
I max or close to max them and have never had tires within 5lbs. dif. either way cause problems.
I get very few flats and have yet to bend a wheel other than REALLY goofy times as a younger man.

Looks like I am right in there - 700x25's - 215 - 220lbs for me + about 25 for the bike = ~240 total or thereabouts - I keep tires at 115-120 psi

I like to ride at 70-80 psi, but sometimes ride at 60. According to your chart, that works for my rear tire, but my front is overinflated. Rivendell has been promoting wider tires at lower pressures for years. In general I've found that to be good advice for me. Wider tires at lower pressures roll really nice. I run 1.5" tires on both of my bents and have no intentions of going any narrower.

One popular bent tire is the Schwalbe Big Apple, available in 2" and 2.35" versions. Those usually are run at 40-50 psi and they roll very nice at those pressures.

According to that article I should run 32mm tyres at around 50 PSI on the front and 70 PSI on the back - would this not increase the risk of pinch flats? Also on tyres such as the Specialized Armadillo Nimbus with a slightly harder sidewall, would the increased tyre drop cause sidewall damage?

(At the moment I run 23mm and 35mm at over 100 PSI and don't like the rough ride!)

Thanks

Daven

Biggest road bike tire I use is 28mm Armadillos, these I keep just a little lower, bike's not right here but as I recall... up to 8lbs below max on account of the sandy pavement around my neighborhood where I ride this particular bike. More ambitious rides, another bike with 25mm (too skinny really) I keep 'em maxed.
MBs... matters little, I fiddle with 'em according to mood.
Shootin' from the hip daven1986 ; given the size/brand tire...seems OK. The front's low but OK too.
the REAR TIRES have given me the troubles I'd stated.
I'm a little neurotic over under-inflating, sew-ups will do that to a person.

Thanks "old and new" I am in 2 minds really as I want a more comfortable ride as I think this may increase my speed as the roads aren't brilliant around here, however I DO NOT want flats! So far my tyres have been good for over 5000miles combined (Armadillos 23mm and Nimbus 35mm) so I was going to go for a 32mm on a new build but if I have to pump them up to max then I may as well go with a 23/25. Might give it a shot on my 35mm and see what happens!

Thanks for the tips

Higher inflation does not necessarily mean less rolling resistance. You don't have to beat yourself up on rough surfaces to get best performance. At least, not if you're rolling on 40mm tires and weigh less than a lot. I've backed off on pressures after reading about this recently - hasn't slowed me down and feels smoother. (Sorry; no hard data.)

I began messing around with tire pressures last year, and experimented in earnest starting this year.

I'm 170 lbs and both my bikes are 28 lbs. My primary bike, an '06 Trek Portland, gets two-thirds of my miles, and in the three-seasons runs 28mm Bontrager Race Lite Hardcase. The Hardcases include some sort of "anti-pinch flat technology", whatever that may mean. Yellow Bike gets the remaining one-third of my mileage, and runs 25mm Continental Ultra Gatorskins.

I found the sweet spot for the Portland to be 70F/80R, although on grocery day I add more to the rear to carry the load. On Yellow Bike, it's 80F/90R.

On both bikes, the ride improved tremendously. And neither bike seems to suffer for it in the speed, perceived effort, or coasting departments.

No flats either, despite hitting some pothole edges that I just knew would pinch-flat. They didn't.

Encouraged by this, on the new wheelset I just bought for the Portland, I went from 19mm wide rims to 24mm wide rims. The buzz on wider rims is that they yield a wider tread profile and the increased air volume allows lower pressures. Using the very same tires and tubes, I'm still experimenting, but I'm currently running that bike at 60F/75R, again finding improved ride at no perceivable loss in speed or coasting.

FWIW, Velocity's new A23 rim is supposed to provide this same improvement for users of 23mm tires.

YMMV.

This is my chance to recommend, for the 100th time, getting a subscription to Bicycle Quarterly. Even if you don't agree with everything they write, Jan's approach to bicycle components is well thought through and interesting.

His views on wide tires vs. narrow tires are particularly controversial; data from his tests conclude that the width of a tire is not particularly important in determining rolling speed - it's construction, tirewall construction, weight, etc.

There's a *long* thread about his view on fat tires over on the Long Distance Cycling forum.

Those tyre presuures Are just about right- For the Tandem. Possibly just a bit lower than we would run. But road bike on 23's and I am above what they recommend. If I came down to the suggested pressures- I would be getting Snakebites- I know as I tried those pressures before.

Sorry- just adjusted mty thoughts- If I go down a tyre size and put on 20kgs- I could be somewhere near right.

Tyre pressures are what you find best for you. And I have even found that two different bikes with the same set of wheels and tyres WILL require different pressures. Its just what you want to ride and how.

Funny, I can tell when I forgot to top off and am running only 15 PSI under max. on 23C road tires. Yeah, it's that sensative. I run the max allowed by the tire manufacturer on all road bikes except vintage bikes with chrome rims. Then I only run 75 PSI because I don't want to blow the tire off the rim that doesn't have clincher rims.
ON MTB tires when I'm riding a gravel MUP it takes about a 20 PSI drop to feel the difference. .

It is MUCH more difficult to get a pinch flat on a 32mm-35mm tire than a 23mm-25mm one. For one thing, most 32-35mm tires have significantly thicker sidewalls ... this is especially true if you are running a city or hybrid tire. With the taller tire with a strong sidewall, it is much less likely to hit something hard enough to compress the tire against the rim.

For the most part, on hybrid type bikes with 35mm to 40mm tires, pinch flats are almost non-existent. Even if you are running your tires at 60 psi.

Tyre pressure should take into consideration total weight and road surface (as well as tyre size, of course).

As I've mentioned before (concurring with Jan's tests and recent manufacturer's statements) "Wider tires roll easier, yield higher mileage and offer more comfort and grip." ~ Continental.

There's a link to tyre pressure chart on my Fix a Flat page.

I am glad a few of you mentioned the importance of carrying a bit more pressure (5 to 15 PSI) in the rear tire than the front. I run nominal 28mm (physically more like 26mm) Contis on the Bianchi, typically around 90 front / 100 rear. I run about 85 front / 90 rear in Capo #1's 28mm (again, more like 26mm) Vittorias, which are rated at 85PSI, and cannot say I notice any performance difference in the tires. I go even lower, about 75 front, 80 rear, on the Peugeot's non-hooked rims, to avoid a blowout. When I ride the mountain bike on the street, I put 70 PSI in the rear tire, which is rated at 65 PSI.

Thanks, I am waiting for a response from specialized (I asked if running the low psi would damage the sidewall on the armadillo tyres) and if they say it is ok that will be my new pressure :)

Read a version of that article in Adventure Cycling. I run 26x1.25 Pasela TGs on my LHTs, and had been running them at max sidewall- 100PSI. Without weighing the bikes, dropped pressure to 80 F&R on both bikes. No difference noted in rolling resistance/speed, but a very big difference in ride quality. Checked the wheel weights on mine- I should be running 50 front and 80 rear, but so far have left it at 80 80. Am now in the process of trying to convince so of my "gotta run max, 2 grams will really slow me down" riding buddies.

Ok, I'll bite. WHY?

SP
Bend, OR

I have 23C GP4000 tires. I've been running 95 front, 105 rear for over a year with no problems. It helps a lot on rough roads, and seems just as fast. I think the flexible sidewalls in the tires help, too. The usual 110 in both tires isn't any faster for me, but there's a lot more vibration.

I'm around 170 and 20 lbs of bike, and the chart is very close to those pressures.

EDIT -- I tried weighing my front wheel while on the bike and get somewhere between 44% and 48% of total weight on the front wheel. (It's hard to get an accurate measure) So the chart says 90 front and 105 rear. Maybe I'll try that on the next ride.

We need the power tap users in the road forum to replicate Jan's tests and report their findings.

I'm off the chart on the right side on my rear tire. I think I have 70%-80% of the weight there. I think they are correct in that I could run 35-40 psi on the front tire. I can pump the rear tire up to the maximum for the tire and still get people asking me if my tire is going flat.

daven1986-your Armadillos have a range starting at 75 psi. I would drop them to that and see how the ride feels. If you want something with similar flat protection, you could try the Vittoria Randoneur tires with the triple shielding. They have a range of 60-70 psi.

Thanks Dchiefransom.

Just got an email from specialized, they said it was too low for the armadillo nimbus and that I should try 70psi on the front and 90psi on the rear.