Tyre Pressure?

Roadbiker.com had a discussion on tire pressures awhile back. Tires are designed to give their optimal rolling resistances at much less than max pressure, and roll as well as they are going to at 90 psi, or 6.2 bar, for 700x23 sizes. (I saw data for this posted somewhere -- web, magazine, book? -- can't remember.) Cornering traction decreases with overinflation, plus the ride is much harsher on your body at high pressures. I live on rough roads, and have no problem with pinch flats at 90 psi for a 165 lb, or 75 kg, rider.

I use Vredestein Fortezza tires, which advertise 140 psi/9.7 bar maxes. When I first used these tires, I pumped them hard and was noticeably more beat-up, and got less mileage on the tires. I also now understand what a "supple" tire is, as the Fortezzas provide a much more absorbent and comfortable ride than Michelin Races I have tried, without any evident speed detriment.

When Greg Lemond raced for Gitane, one of their philosophies was to run tires around 6.2 bar/90 psi, because it beat-up the riders less. I wonder if Tyler Hamilton would have crashed in the 2003 Giro (or was it the TDF?) time trial if his tires weren't pumped up so darn hard.

Tires pressures make a more noticeable difference on ride characteristics than frame material. Having an extra 10psi/0.8 bar in the tires will be more noticeable than the difference between an aluminum, ti or carbon frame. Back off on the pressure, and enjoy your rides more.

As for measurement systems, the fact we use some of both in the U.S. really means that most people don't know either one. Hell, most people don't understand how to move a decimal point around or how to work with fractions. 😕 A land of educated idiots, I'm afraid.

Well said desertrat!

After the high math conversion table that DHK gave us, now I can say that I run at 8.27586206896552 BAR (or 120 PSI =) front and rear checked daily.
I'm a 79 Kg (174 lbs) cyclist from Mexico and we use PSI too, however we use MKS International System for almost everyting.
Now I'm thinking in droping 10 PSI from back tyre and maybe 20 from front because it's starting to rain here and that is one of the recomedations that I got here in the forum for bike handling under wet conditions.

supergrill said:

Nope. As was previously inferred, the Bar is not part of the internationally recognized systems.

Hi,

I never claimed the Bar being SI. But a kilometre is also not SI and it's so unhandy to tell the people back home the length of your cycle trip in metres. However it is convienient to have a system that uses a factor towards SI.

But let's focuss on the important things and forget about PSI and Bar. That was a mistake by me starting the thread. Probably the value of the poll would have improved when I would have used psi (lazy me).

I think "desertrat" has a point when he says inflating above 6.2 Bar doesn't have any advantage. Like I pointed out before, I'm reading this German scientific book, they are writing a complete chapter about just this subject. I can't find the time to move on with the book, but what I already saw is that above a certain pressure one should not expect much reduce in drag from the tire any more, however the harsh feeling will increase enormously.

The 6.2 value may be perfect for desertrat, but I think it's dependent on the weight of the rider, the type of tire and the type of surface of the road as well.

Regards, Frank.

I use max recomended inflation on my tyres not looking for drag or friction reduction, my main objective it's flat reduction, and it seems to me that high pressure does avoid some puncturing.

cuervo said:

I use max recomended inflation on my tyres not looking for drag or friction reduction, my main objective it's flat reduction, and it seems to me that high pressure does avoid some puncturing.

You dont need to max out to not get pinch flats. I'm 190 on 23's and do 100-105 on front and 105-110 on rear and no flats and i hit some nice ruts and holes.

cuervo said:

I use max recomended inflation on my tyres not looking for drag or friction reduction, my main objective it's flat reduction, and it seems to me that high pressure does avoid some puncturing.

Hi,

Regarding puncture resistance I found out that the cheaper tires are a lot better than the top of the line models.

Usualy I train on Rubino, do competitive cycling on open corsa's (both Vitoria). It was just lately that I discovered a sign on my tires stating that the open corsa tire is weaker than the heavier built rubino.

On my previous competition tires (continental GP3000, vredestein volante, michelin high binergic, michelin pro race (or what was the name) etc.) I probably never noticed a sign like this because most of them were a total loss just after a few rides.

I am a (extremely) fast descender. When you hit a small stone at top speed in the descent the Rubino's have nothing at all, while the expensive top of the line tires are usualy a total loss.

If the open corsa's will also get damaged soon I will just drive Rubino's in the future. I find the very small lack of comfort in the Rubino tires of lesser importance than the enormous price difference with open corsa. A Rubino is just 9 Euro here and an open corsa 24 Euro (a Euro equals about a Dollar). (Don't worry, I don't want you guys also change to the Euro, haha! :p )

Regards, Frank.