Road Cycling - tire pressure question... (dumb question?)

So... after reading much of another tire pressure thread here where folks run different pressures front/back, it occurs to me...

I always inflate to 100 psi because the sidewall of my tires says to do so. Is this 100 psi the...

A. maximum psi?
B. average recommended psi?
C. minimum psi?

:confused:

My mountain bike tires have a range of 45-65. Why doesn't the road bike indicate a range?

I really have no clue here. Does it depend on the tire brand itself? I'm using the tires that came with my (2001) Univega Modo Volare. They're 700 tires. Can't remember which brand offhand...

All the tires I have ever used have a recommended range on them and not just one #. Are you sure there is not another number hiding somewhere. They are very difficult to see on some tires because of small fonts or the color of the tire itself.

Number you see listed is maximum allowed by manufacturer. You can go lower or higher at your discretion. Up to you.

You can play with the pressure some. The manufacturers inflate the tires, until they blow off the rim, a bunch of times and then half the pressure.

One thing most cyclist miss, Rims have a max pressure rating, for example, I ride Mavic T-520 touring rims on the touring bike, for a while I was riding Conti ultra 2000 700-28C tires, the tires have a max inflation rating on the side of the tire of 120 psi, the rims have a max rating of 105 psi. When I first built the wheels I ran the tires at 120 psi, I was riding in the hlls one afternoon and on a section of rough road that was a steep downhill, the braking caused enough heat to expand the air in the tire and blow it off the rim, I didn't crach but came close. After that I did some research and found the both tires and rims have max ratings, Mavis recomends riding the tires at 95 psi, I have been doing this and my ride is better, the bike seems to handle better and I don't worry about blow off.

I would just max them and ride.If you check the rims and tires on most all road bikes,the rims would have a lower psi then the tires but most all rims can take the max tire psi.

max ing the pressure is slower due to higher rolling resistance

Thanks, everyone! My question has been answered and I learned more than I thought I might. I had no idea that rims had max pressure ratings too. :)

these ar ethe max pressure rating for Ksyrium ssc sl

TIRE SIZE MAXIMUM PRESSURE(BARS) MAXIMUM PRESSURE (PSI)

19 10.00 146.00

23 9.50 138.00

25 9.00 131.00

28 8.00 117.00

Originally posted by TimB
max ing the pressure is slower due to higher rolling resistance

maxing the pressure will add wieght to the tire, seeing as how more air is in the same area.:D

LOL So a big old flat tire rolls real nice.

Originally posted by TimB
max ing the pressure is slower due to higher rolling resistance

It's the exact opposite. That's why roadies run such high pressures-it's faster.

Originally posted by smelly
maxing the pressure will add wieght to the tire, seeing as how more air is in the same area.:D

If you've come to this stage of weight weiny-ism you need counselling.:p Of course you could put helium in your tires, oh the possibilities!:beer:

p.s. Sorry about posting twice, couldn't figure out how to quote twice in one reply!

Originally posted by chrisk
Of course you could put helium in your tires, oh the possibilities

The only way to put helium in the tires would be to go to mylar innertubes. Now there's a weight savings plan. Heck, maybe mylar would be the way to go even without helium.

Hydrogen! Now that is the ticket. Watch those cig butts. :D

Originally posted by chrisk
It's the exact opposite. That's why roadies run such high pressures-it's faster.

Only amateur roadies who thinkthey know what the pro's are doing.
Most pro's and many people around the area where I stay run their tyres at relatively low pressure ie towards the bottom end of the recommended range.
Even Lance, the north american icon of cyclesprot runs pressure around the 100psi mark and he's not a small guy.
Speak to uncle Al if you choose not to believe me. He'll put you straight.:beer:

He did'nt say anything about pro's,you are.Read his post,it says roadies.We need a poll.List you tire size,max psi and what you run.I'm 700X23,max is 120 and that what i use.

Well, as mentioned above, the tire will blow off the rim at about twice the suggested pressure. So you can put more in if you want to.

Now I had some friends who run around 150 lbs because they have heard that more pressure = less rolling resistance. That is true. But the change in rolling resistance over 100 lbs pressure is nearly zero and all more pressure does is make the tire harder and give you a rougher ride.

I am a heavy rider and I put in enough air to avoid pinch flats. I get on the bike and look at the tires. If they deform much, then I am at risk for a pinch flat and I add a bit more. I usually run between 100-110 lbs.

Originally posted by TimB
Only amateur roadies who thinkthey know what the pro's are doing.
Most pro's and many people around the area where I stay run their tyres at relatively low pressure ie towards the bottom end of the recommended range.
Even Lance, the north american icon of cyclesprot runs pressure around the 100psi mark and he's not a small guy.
Speak to uncle Al if you choose not to believe me. He'll put you straight.:beer:

Well, compared to the pressure I put in my MTB tires, even the "low" pressure of 100 psi is alot of pressure. For a seasoned roadie this may seem low, but when you compare it to every other inflatable device in this world, it's pretty high, that's what I meant by high pressure.

what about weight? That extra air has mass. We need a professor to figure this out. Any takers?

chris, we're not comparing roadie tyres to inflatable dolls now are we! We'e talking tyre pressure.

I weigh 70Kg and use around 90 psi in the front and around 100 at the back.Thats just above the recommended minimum for the Michelin Axial Pro's.
Thats considered low pressure in relation to that tyres recommended pressure ratings.

Originally posted by Xavier
Number you see listed is maximum allowed by manufacturer. You can go lower or higher at your discretion. Up to you.

You should read sheldon "inflated" browns discourse on maximum tire pressure

Most tire pressure guages on pumps aren't worth a darn. I push down on my tires with my thumb. If they're rock hard, they're good enough for me....never had a tire pressure related problem.