Tire pressure
 

Thanks for posting. I have steadily moved back down from 100+ PSI and enjoy the improved traction and comfort.

The discussion in this podcast rambles a lot, but buried in the middle is a statement that tire suppleness is even more important than tire width or air pressure. Then he recommends his own brand of tires and says stiff puncture resistant tires are terrible.

Just listened to this podcast earlier today. Hard to argue with a lot of their findings. As a guy who started riding in the mid-80s, I certainly fell into the trap of skinny, harder tires are faster (because they feel faster), but I've come around and am convinced that I was wrong. I have a set of 21mm Vittoria Corsa CX tubulars on one of my wheelsets and can't wait until I wear them out. May just put them to pasture before their time. I like Jan's analogy of a Jeep vs. a Mercedes traveling at high speed: just because one may feel faster (i.e. more rattle) doesn't mean it is. I found it particularly interesting to hear him talk about the watts absorbed by the body itself when the bumps aren't absorbed by the tires.

Also intrigued by the former Zipp wheels technician discussing advantages of latex tubes. About half of my bikes have latex tubulars and half have butyl clinchers. I don't like to be troubled with having to inflate my latex-tubed tubulars and worry about the long-term effects of storing deflated tire casings; however, maybe I'm discounting the resistance advantage of latex tubes.

I didn't mind the small amount of self-promotion regarding Compass tires. I think overall his self-promotion was minimal considering the amount of testing and knowledge Jan Heine has accumulated on the topic. He is developing products that advance performance based on years of science-based research. More power to him and good for the rest of us.

Next ride I am taking some air out. Good thing tubulars aren't prone to pinch flats. :thumb:

(Side-note: I am way over-committed on podcast subscriptions--mostly history-, comedy- and baseball-related.)

I run all my tires at the lowest pressure that will protect the rims, give me good handling, and sufficient lateral stiffness at speed.
IMO, it maximizes tread life, reduces flats, gives the most comfort, and recent rolling tests show it's as fast if not faster than rock hard.

If you ride Compass tires with your hair on fire, you will appreciate anything Jan says.

Wow, "err on the low side". " Under 100 faster than 100-120". Interesting.

But I only listened to about 30 minutes, did they mention anything about front vs rear?

If 140 psi and 23mm tires were good enough for Eddie, it's good enough for me.

I was a 120psi guy like everyone else was until I started dropping it a few years ago. 160lbs I pump my 23's to 75/85. Bigger tires even lower. Haven't had one single pinch flat since and my last puncture was in spring of '14. I had pinch flats all the time at high pressure for some reason.

Actually he did say insanely high pressures showed good results too - 160 lbs or so.

Hmmm. Count me in the skinny, high-pressure group.

I like how they feel. They work well on the roads here. They keep my rims off the pavement but stick to it.

Besides which, if I started my latex-tube, sew-up-tire commute on 100 they would be at 85 or less when I returned home.

This.

Brad

Thanks for the vote of confidence. I guess I went out a few psi high yesterday morning, and noticed an immediate difference in the tires transmitting chatter - primarily when they were cold. And after they warmed up, felt a little bouncy. Every now and then, it's probably good to reinforce why you like your set points.

Jan published this article 10 years ago, and Frank Berto's chart with it:

https://janheine.files.wordpress.com...presschart.jpg

Jan has also published about 2 dozen tire pressure articles since then.

A lot of people use this chart as a starting point and often find themselves backing off from these numbers.
The front/rear tire pressure difference is all about the weight distribution. It's going to be somewhere between 45/55 f/r for a road bike, and 30/70 f/r for fully upright.

If you ride really big hills and find yourself hitting 35-40 mph (and higher) you're going to need to run a little higher pressure than normal road shock and vibration tell you that you need. This is because centrifugal forces stretch the tire, and the tire is actually running at lower pressure at speed - you feel it as a lateral squirm and maybe even a spooky sideways vibration at high speed.

Conversely, when going to gravel, I drop down from my normal set points by 5-10 psi. It improves the endurance of both me and the tires.

There is no way I am going to run only 90psi in my rear tire or 75 in my front. Not a chance.

One thing ignored in all this is that a skinny tire is lighter. I can feel the difference in tire (actually tire plus rim) weight.

I refuse to ride with my hair on fire, Jan or Frank notwithstanding.

I run my 27mm Vittoria Open Pave 90 psi rear and 80 psi front and it's perfect.
Knock your lights out, ride rough, get more flats, shorten your tread life.

I have found that the tire can determine the pressure. I am running high end Vittoria tubulars on my Masi and started the pressure at what I ran when I rode the bike with the same wheels but FMB tires, under 100 psi. Running the FMBs at that pressure, the bike was lively. Running the Vittorias at below 100 psi, the bike felt sluggish. It was only after I upped the pressure to over 110 that I found a similar responsiveness in the Vittorias.

absolutely true - Challenge Chicane 33mm CX tubies are designed to run down to 23 psi.

LOL, I listened to this podcast on Tuesday so today I decide to drop about 10 psi from each of my Vittoria Corsa G+. A mile from home...POP, I just had to laugh having saw the photograph. I 'll chalk this one up to bad luck and try again Saturday, I have a fresh build with some Bon Jon Pass tires that I will try with a little less pressure than I normally use.

Yeah but that is exactly what the podcast warns against, making a judgment on how the bike feels rather than hard performance data. In other words the lively feeling bike is not always the faster bike. In order to give the theory a fair shot ride a month or so with both tire pressures and check the data.

to a lot of people, chatter = speed - that feeling of riding with your hair on fire.
Jan's point was that feelings people equate with speed may actually be slower - chatter is your tire losing rotational momentum

Do actual weight measurements, and you might be surprised.
On my 64cm road bike, I found I had 2/3 of my weight on the rear, i.e. 33/67 distribution.
My 5'3" ex-GF had a perfect 50/50 distribution on her bike, (with drop bars).

For measuring, I put a bathroom scales under one wheel, and a stack of wood under the other to keep the bike level, then balanced on it with hands on the drops.

(I've since gone to a zero-setback post on that bike for a better fit, which also improved the distribution a bit.)

I dial everything based on performance, especially shock on bumps and stability at speed - I live on Big hills.

Just because he's hawking his own tires doesn't make the statement untrue.

My commuter has 650b 42mm Pasela Tourguards. It rides like an oxcart vs my other bikes with same size tire Hetres. But the Paselas aren't terrible - when I commute I place puncture resistance very high on my list. As an A-B test, I swapped the wheels on both bikes, the oxcart ride followed the tires.

A good argument for "load your bike in the front first", which I read in Bicycling Magazine back in the 70's before the everyone started buying rear racks.

It was especially true with low trail forks that came on almost every bike in the 70s. Not a good idea on your Italian road racer.