throw your tire gauge away.

[thwart]

Well, almost… ;)

More interesting stuff from Mr. Heine:

https://janheine.wordpress.com/2015/01/26/the-tire-pressure-revolution/

[Steve in SLO]

Interesting indeed.
I am not sure I agree with the conclusions, as the 10 to 12% wattage requirement changes with varying pressures shown on the graph might make a heck of a difference on the road.
The wattage requirements look more like each tire has one or two pressure sweet spots rather than having "no relationship" to pressure.
I applaud him for looking into this, but it feels like he has an agenda (surprise) in presenting his data.
It is certainly good for discussion, though.

[FlashUNC]

But how does it relate to planing?

And I'll second Steve's mention. 10-12% is a pretty huge gap in terms of human wattage.

[ergott]

OT, but this is such a cool photo.

http://www.bikequarterly.com/images/fmb_tread.jpg

[christian]

It does not follow that just because the wattage differences between 70 psi and 130 psi are negligible that one can ride a bike with tires at 43 psi and that's the same thing. Also, unless Jan can ride 27.8 mph EXACTLY at a perfectly constant power output at multiple pressures (unlikely), I'd say there's probably enough noise in the data to make the comparison meaningful.

The Compass tires are awesome, but this doesn't prove anything that we didn't all know Jan believed before.

[MattTuck]

You guys are still using pumps? I've switched over to just mounting the tires and using my lungs to blow into the valve to achieve the maximum pressure that god intended. The ride is sublime.

[Grant McLean]

Pretty much anyone who has experimented with tire pressure
realizes there is a 'sweet spot' of pressure for every model of tire.

The amount of pressure for that spot will be different for various
tires in different sizes and types of construction.

If someone has the 'take away' that tire pressure doesn't matter,
they're nuts.

In terms of reducing rolling resistance, the reality is that most
thin and supple casing (clincher) tires in the 25mm size range still
need about 110psi to reach peak efficiency rolling.

Many folks will sacrifice some of this to lower the pressure to 95-100psi
for comfort. But there is a trade off in watts, that's the price.
There is no free lunch.
Tires as wide as 30 or 40mm have benefits, and trade offs too.

-g

[Black Dog]

Pretty much anyone who has experimented with tire pressure
realizes there is a 'sweet spot' of pressure for every model of tire.

The amount of pressure for that spot will be different for various
tires in different sizes and types of construction.

If someone has the 'take away' that tire pressure doesn't matter,
they're nuts.

In terms of reducing rolling resistance, the reality is that most
thin and supple casing (clincher) tires in the 25mm size range still
need about 110psi to reach peak efficiency rolling.

Many folks will sacrifice some of this to lower the pressure to 95-100psi
for comfort. But there is a trade off in watts, that's the price.
There is no free lunch.
Tires as wide as 30 or 40mm have benefits, and trade offs too.

-g

Peak rolling efficiency on a smooth surface. As the surface becomes more irregular then lower pressures are faster than high pressures. So optimal tire pressure has a lot to do with the surface characteristics. There is lots of data out there on this.

[Likes2ridefar]

my knee is my gauge. if it hits the rim with a sharp push towards it, then it's time for more air.

[mrogulja]

pity they didnt test CX tires down in the 20-30 psi range which is race pressure for most of mid-weight racers.

[fiamme red]

https://janheine.wordpress.com/2015/02/17/tire-pressure-data-and-details/

[witcombusa]

Well, almost… ;)

More interesting stuff from Mr. Heine:

https://janheine.wordpress.com/2015/01/26/the-tire-pressure-revolution/


It's your own fault for reading his "stories"

[11.4]

C'mon y'all, Eddy Merckx rode with 21 mm tires pumped to 165 psi. Why are we still debating?

Then, he also rode the big tours with a nice fat ribeye sandwiched between his chamois and his nether parts.

[dolface]

I switched to 28mm Conti's @ 85psi and haven't looked back. #soComfy

[TPetsch]

Earlier I read that crank length doesn't matter.

Now I read that Tire Pressure doesn't matter.

...I hope that 10 pounds I've gained this winter doesn't matter come spring.

[11.4]

Earlier I read that crank length doesn't matter.

Now I read that Tire Pressure doesn't matter.

...I hope that 10 pounds I've gained this winter doesn't matter come spring.

It's OK. Watts don't matter either.

Dear god, is it spring yet?

[ultraman6970]

Go and try to climb switch backs with 60 psi standing your pedals (even seated) trying to catch the group in front of you (or even alone try to accelerate), or try to go downhill 80km/h in a road with a lot of close curves at 60 psi and I will believe what this guy is saying that tire pressure has nothing to do with speed.

Probably with half of the touring population works because they use like 50 mm wide tires but when you go with 23's tubulars, you can tell right away even that the bike handles weird when you go low in tyre pressure.

Almost the same crap a guy came with like 30 years ago in a sports magazine about doing squats with weights and the way you needed to breath to do them correctly to get more power... Yeah.. with 40 kilos maybe, do what he says with 120 kilos and the situation changes night to day.

One of this days somebody will say that is faster and secure to ride with truck tires in the bike and sure a bikes with truck tires will be sold like hot pancakes.

ps: forgot this... as more pressure the less watts you can put?? whatver.

[merckx]

I agree that the tire hysterious that occurs when climbing out of the saddle, or when cornering hard while descending is not accounted for in the roll-down tests. I think that when you factor these events then maybe the ideal tire pressure is higher than what Jan is professing. BTW, I like Jan, and what he does. It adds to the conversation about the enjoyment of cycling.

[Louis]

I have to say that I am somewhat amused by the folks who add air to their tires before every ride. Unless you have a serious leak (latex?) there's really no need for that. I just give each tire a good squeeze with my right thumb (calibrated, of course) and if it isn't noticeably soft I figure I'm good to go. Using that approach I probably add air about once a week sometimes less often. (I typically use Conti or Michelin butyl tubes, sometimes generic Performance, not latex.)

[ergott]

Latex does indeed need air each day.

[Pastashop]

I like some of the stuff Jan Heine does, but caveat emptor...

If you're after judging rolling resistance vs. pressure, this experiment is all noise, virtually no useful data. There's no way to control the experiment as they set it up enough to isolate the effect of rolling resistance. Absolutely no way.

Disclaimer: I studied engineering, including materials science, fluid mechanics, heat and mass transport, etc., for 10 years in the top programs in college and graduate school and do this stuff for a living. So, that's to say, what the heck do I know, anyway?..

[bluesea]

Self-fulfilled prophecy or self serving results, take your pick. :rolleyes:

[MikeD]

I like some of the stuff Jan Heine does, but caveat emptor...



If you're after judging rolling resistance vs. pressure, this experiment is all noise, virtually no useful data. There's no way to control the experiment as they set it up enough to isolate the effect of rolling resistance. Absolutely no way.



Disclaimer: I studied engineering, including materials science, fluid mechanics, heat and mass transport, etc., for 10 years in the top programs in college and graduate school and do this stuff for a living. So, that's to say, what the heck do I know, anyway?..


I agree.