zigmeister

I asked because I read a recent article about tire pressure and a formula, it used the bike weight also, which as I mentioned, could change the pressure by nearly 7-8% at my weight personally.

I run Zipp FC tubies, which means around 120psi I run my tires at 170lbs, 16lbs full ride time bike weight/water bottles/shoes/clothes etc..

Plus, I've read several articles and quotes from Pro mechanics and tire pressures they run for guys about my weight on similar equipment, and come to my tire pressure number.

Of course, bumpy brick crit course, the pressure drops 20psi sometimes, but average nice road racing back to normal 120psi range. But, everybody has their ideas/theories.

Vlaam4ever

You'd think you'd have a happier photo i your avitar.

Psimet2001 

That was a happy avatar. I was about 8 beers in at that point.

JohnnyCyclist

I haven't read all 275+ posts in this thread, so if my question was addressed in post #xxx, forgive me.

On my two road bikes, I run different tires (poseur decision to color-coordinate, nothing more). One says "inflate 90psi to ...", the other says "inflate 100psi to ...". Both are 700x23.

The formula gives me (rounded) values of 115/105.

Could the stated inflation values on the tires be taken into account? On the "inflate 90psi to ..." tire, I could drop 10psi from the formula-calculated values, run 105/95, and still be within the range specified by the tire manufacturer. There are some rough roads in my area, so a slightly lower tire pressure would be welcome. Would this 10psi drop increase rolling resistance that much and/or make the tires more prone to flats?

Thanks.

Psimet2001 

Ignore the sidewall. Inflate as you like. Adjust to suit.

This is like a recipie - follow it to the T and you'll get a result. Add some flavor on your own and get something that tastes a lot better.

Youngin

Hey Psimet, sorry to hijack the thread. Just wondering how long a quote takes, about to pull the trigger on a set of wheels but wanted to give you a chance first.

rubic

Wow, this is an old thread. So Psimet, here is a question for you concerning the air pressure formulas that you posted. In the last couple of years, some rims have gotten wider such as the Velocity A23 at 23mm. I am told that these wider rims can run a lower air pressures. How can this formula be adjusted for 23mm rims?

CyLowe97

This post made my day.

Your avatar moment was a marked improvement over your "gimme the ****ing keys!" moment at the day's first rest stop.

Good times, man, good times.

Back on topic: What's more optimal: washing the bike every three months or every five? I always forget.

Psimet2001 

2-3 year bump. As some of you know (the ones who are still around) a lot has happened. Social media drew away the vast majority of heavy content posters on forums like this. My business took off like a rocket, etc.

It's a slow Friday and I am literally waiting for some glue to dry so...

In the hiatus I have done a lot: worked with tire manufacturers, glued thousands of tubulars, built thousands of wheels by hand, developed and run neutral race support services, sponsored and pitted for UCI ranked pro road and cyclocross racers, Fielded pro women's teams at NRC level events, etc.

Pretty sure I have a few new tips to offer and most likely would be able to contradict some previous tips. I learn more everyday and have no problem looking at something I may have done before and admit it was wrong if it truly was.

Since I obviously don't come out here much anymore there isn't much of a point in saving tips I can think of now so I will just share what comes to mind.

Athens80

Nice.

I am interested in the question of whether wider rims like the A23 change the air pressure recommendation for a 25 tire, all else being equal.

vwchad

I believe the answer is yes, but I'm curious to hear his thoughts as well as I'm not sure how much.

Psimet2001 

I worked neutral race support for a multi day stage race a few weeks back. Race consisted of a circuit race for the pro men/women on a friday, TT early saturday morning, Road race saturday afternoon, crit on Sunday.

I gotta be honest - I felt like I wouldn't be needed much at all until the crit. Boy was I wrong. 6am on the morning of the TT I had a line by my tent that didn't slow down until noon.

1. Racers (I include myself in there) are idiots...errr....I mean have a lot of opportunities to learn new things.
2. If you are coming to a TT and bringing special TT specific equipment - ride it BEFORE driving 5 hours to the event. That way you'll realize what is out of order since the last time you rode it. Remember that tire you needed to re-glue? well you do now and that's a better time to realize it rather than 30 minutes before the start of your TT.
3. If you are "switching" to carbon wheels....bring carbon pads. Keep extra sets in the car at all times.
4. If you want to make money at a race: bring carbon pads and sell them.
5. Gearing....really guys - this isn't hard. Make sure it works....oh and taking it to a shop is nearly meaningless. It's only as good as the person who worked on it and an unfortunate side-effect of an ever changing industry that has tiny profit margins is that even the good shops really can't pay enough to keep the good ones...so you got the bad one.

....and with that I got a business call and need to go work on something. I'll see if I can pop back to this.

Psimet2001 

It does. Roughly start with 5 psi less and adjust to suit. I plan on doing some studies with different tires and draw some new curves using basic deflection measurements and the current models that are common in the market. Knowing some of the tire guys now will help as well.

Wanderer

Another age bump....... Thanks a lot - now I gotta get bigger tires!

gios

If you're going to wear take-a-look mirrors on your glasses during morning after sunrise rides, learn to ride one eyed as you close the mirror'd eye to block out the sun on your 90 deg or u-turns.