Tire Air Pressure for Kona

Triathlon Forum
1

Hello All,

A friend of mine won the F50-54 AG in Louisville and is going to Kona for the first time. The stories of tires “blowing up” because of the heat is a concern. Can some please let me know their thoughts on these questions. She weighs 120 lbs., rides 650cc 404 clinchers:

Which tires and tubes do your recommend? (for tubes what do you think of Qtubes with 80mm valve stems)?

What air pressure would be best? She has been using 120psi for several years.

If she pumps her times to the recommend psi at 5:30 AM is there any chance her tubes could “burst” because of the sun and heat, if she started the bike leg at approximately 8:30 AM at the latest (give a 7am or little later start time)?

Thank you for your help with these questions. Please let me know of any other suggestions you might have for some one going to Kona for the first time. Race strategies, or simply fun things to do would be good to know. I will pass them a long to her, because I definitely did not earn a slot myself.

2

Hello All,

A friend of mine won the F50-54 AG in Louisville and is going to Kona for the first time. The stories of tires “blowing up” because of the heat is a concern. Can some please let me know their thoughts on these questions. She weighs 120 lbs., rides 650cc 404 clinchers:

Which tires and tubes do your recommend? (for tubes what do you think of Qtubes with 80mm valve stems)?

What air pressure would be best? She has been using 120psi for several years.

If she pumps her times to the recommend psi at 5:30 AM is there any chance her tubes could “burst” because of the sun and heat, if she started the bike leg at approximately 8:30 AM at the latest (give a 7am or little later start time)?

Thank you for your help with these questions. Please let me know of any other suggestions you might have for some one going to Kona for the first time. Race strategies, or simply fun things to do would be good to know. I will pass them a long to her, because I definitely did not earn a slot myself.
The tires blowing up is well old wifes tails type stuff its not true. urban legend , bs pick your phrase.
usually just about every race you hear a tire blow its not because they pumped it up to normal preasure and the heat of the day or the asphalt expanded it and boom.
Its because that tire or tube had a problem to begin with and would have blown anyway either in the transition or on the road.
I’ve always pumped my tires up day before when putting in the transition done hawaii 7 times,28 ironman races 23 half ironman never ever ever had one blow be it tubular or clincher.
I’ve left my wheel in the back of my car with the windows up fully inflated never blown.
tell her not to worry about it instead do what you should do
make sure your tires and tubes are all in good shape well before you get there inspect it that day you check in the bike make sure you haven’t picked up a wire or piece of glass from the road.
look for nicks or cuts pump it up night before you check bike in. Then check the preasure then next day to see if any small leaks.
Pretty much it but don’t worry about them blowing… I think I read somewhere conti tires have a burst preasure of 800psi and I only pump mine to 120 or so have pumped them to 180 back in the day and setout in the sun no problem…

Enjoy the race don’t worry about this old wifes tale… Funny used to when you checked bike in they checked it for safety and the bike mechanics would tell everyone be sure to let some air out so your ties to blow. I NEVER did … trust me its not a problem.

3

120# for 120 woman INCREASES her rolling resistance. I would say 100-110 depending the the tire.
At the recommendation of Damon Rinard, who posted this here on ST, I have been using the Bontrager Aero TT lite clincher 19mm front and 23 rear, with Latex tubes. I’m very happy. She will need valve extensions and, I think it was rroof or cdw who recommended the Topeak extensions. Again, I’m happy. She can get butyl tubes with 80mm valves, which is what my spare is. This is on 404 clinchers. These tires are tough to put on the first time, but I can install them without the levers now. I weigh around 170 and I’m using 105mm pressure.

4

There is NO reason to be over 105 psi EXCEPT on a track. As stated, 120 psi Increases her rolling resistance. 105 tops for Kona as it is a very smooth surface. 95 psi for rougher surfaces. As a test, have her pump tires to 95 psi at 6am a few days before the race and then go for a short ride about 11am and then check pressure. I say this as a former 130psi rider, weighing 148lbs.

5

Hello All,

A friend of mine won the F50-54 AG in Louisville and is going to Kona for the first time. The stories of tires “blowing up” because of the heat is a concern. Can some please let me know their thoughts on these questions. She weighs 120 lbs., rides 650cc 404 clinchers:

Which tires and tubes do your recommend? (for tubes what do you think of Qtubes with 80mm valve stems)?

What air pressure would be best? She has been using 120psi for several years.

If she pumps her times to the recommend psi at 5:30 AM is there any chance her tubes could “burst” because of the sun and heat, if she started the bike leg at approximately 8:30 AM at the latest (give a 7am or little later start time)?

Thank you for your help with these questions. Please let me know of any other suggestions you might have for some one going to Kona for the first time. Race strategies, or simply fun things to do would be good to know. I will pass them a long to her, because I definitely did not earn a slot myself.
The tires blowing up is well old wifes tails type stuff its not true. urban legend , bs pick your phrase.
usually just about every race you hear a tire blow its not because they pumped it up to normal preasure and the heat of the day or the asphalt expanded it and boom.
Its because that tire or tube had a problem to begin with and would have blown anyway either in the transition or on the road.
I’ve always pumped my tires up day before when putting in the transition done hawaii 7 times,28 ironman races 23 half ironman never ever ever had one blow be it tubular or clincher.
I’ve left my wheel in the back of my car with the windows up fully inflated never blown.
tell her not to worry about it instead do what you should do
make sure your tires and tubes are all in good shape well before you get there inspect it that day you check in the bike make sure you haven’t picked up a wire or piece of glass from the road.
look for nicks or cuts pump it up night before you check bike in. Then check the preasure then next day to see if any small leaks.
Pretty much it but don’t worry about them blowing… I think I read somewhere conti tires have a burst preasure of 800psi and I only pump mine to 120 or so have pumped them to 180 back in the day and setout in the sun no problem…

Enjoy the race don’t worry about this old wifes tale… Funny used to when you checked bike in they checked it for safety and the bike mechanics would tell everyone be sure to let some air out so your ties to blow. I NEVER did … trust me its not a problem.

+1.

Every time I’ve done Timberman, hanging in TA, you hear BOOM!!! Uh oh, somebody’s day just went to shit.
It certainly wasn’t the “heat” of the NH am. It was a poorly mounted clincher, where the tube got pinched, and then after they inflated it a bit that am, it went ka-blooey!

Mounting your race tubes/tires PROPERLY (and checking to make sure no tube pinchage has happened) a few days prior to the race, and getting in at least 1-2 shakedown rides in the days before the race can prevent this issue from ever occurring.

As to the OP, Kona does not have some magical properties whereby all the normal laws of physics are somehow rendered moot.
Proper PSI is proper PSI. 120 for a Womens is ridiculously overkill - she is going SLOWER and having a harsher ride doing that.

I’m ~155 or so, and I run 105-110 psi. YMMV.

6

fwiw - i’m only 128lbs… ride my 650’s my conti tubulars between 100 -110 psi on most courses and in addition post not so shabby bike splits. also, never had issues w/ tires blowing in transition in 5yrs of racing or while resting in the car during the hot florida summer heat heat.

7

I agree with all of the posters that you should be at 105 to 110PSI for your body weight and then you will not have to worry about the “heat” of Kona.

I do want to assert that the “urban legend” is true. I have worked pro bike row Kona Transition for 7 years and most years have witnessed tubulars (and clinchers) blow while the athletes were in the swim. Many of these occur because of pumping the tires to very high (150+PSI) and once the sun rises and the temps begin to rise “poof”. Our job as athlete assistant no longer allows us to pump the tires like the old days because athletes would request a very high PSI and then if the tire blew, they would get upset with the volunteer. We now just hold the bike, provide pumps and light (remember we are on the pier at 4:30am). While the athletes are in the water, we police the racks checking tires to see if any have blown and then alert the tire changers who fix the problem before the athlete finishes the swim (but in the case of an athlete with tubulars, if that is there only spare then they cannot have another flat or their day is done.) In 2008 I was standing next to Mathias Hech’s Kuota when the tire blew and the panic mechanic/tire changers were there in a minute to change out his tubular and he raced to a Top 10 finish.

GolferChrisL

8

For a woman that small she should even consider going under 100 PSI.

Check out the recommended tire pressure chart from Michelin.

http://www.michelinbicycletire.com/michelinbicycle/index.cfm?event=airpressure.view

more is not always more…

9

I agree with all of the posters that you should be at 105 to 110PSI for your body weight and then you will not have to worry about the “heat” of Kona.

I do want to assert that the “urban legend” is true. I have worked pro bike row Kona Transition for 7 years and most years have witnessed tubulars (and clinchers) blow while the athletes were in the swim. Many of these occur because of pumping the tires to very high (150+PSI) and once the sun rises and the temps begin to rise “poof”. Our job as athlete assistant no longer allows us to pump the tires like the old days because athletes would request a very high PSI and then if the tire blew, they would get upset with the volunteer. We now just hold the bike, provide pumps and light (remember we are on the pier at 4:30am). While the athletes are in the water, we police the racks checking tires to see if any have blown and then alert the tire changers who fix the problem before the athlete finishes the swim (but in the case of an athlete with tubulars, if that is there only spare then they cannot have another flat or their day is done.) In 2008 I was standing next to Mathias Hech’s Kuota when the tire blew and the panic mechanic/tire changers were there in a minute to change out his tubular and he raced to a Top 10 finish.

GolferChrisL
WRong its simple thermodynamics although its been a long time since I’ve done the math so any of you brainiacs out there can pull the ole math out and show that.
I believe charles law comes into play.
Now we can argue what the preasure should be for less resistance and better ride and so on but the sun and heat is not an issue unless you pump you tires way over the max rating.
I think most tires have much higher burst preasures than the max on the side so it would take a lot of heat.
Your talking about what 70 degrees to 100 or lets say 120 increase in temperature thats only 50 degrees F not very much.

I’ve worked the pro bike row at kona transiation a few times my self.
Now yes tires blow during the swim sometimes but its not because of the sun heating them up which is the point. In fact probably lucky for the athlete it happened in the transition area
because it was going to blow anyway at some point and better there than out on the course.

During the swim the temps don’t go up much from 7:00 to 8:00 or even 9:00 even in kona and they don’t even get direct sunlight.
On the pier that early in the morning its just not that hot what maybe 80 degrees at the most and its not direct sunlight either.

The tires burst because they were weak had a defect or hole the tube finally went through or clincher bead didn’t hold weren’t mounted right who knows
but has very little to do with the heat unless you pumped them up really high(200’s). I’ve been in transitions when it was 60 degrees and cloudy and heard tires blow.

With 1500-2000 bikes in the transition its almost ineveitable one or two are going to have a problem just the odds.
HAS nothing to do with the sun increasing the preasure.
Most sewups burst preasure is way above what anyone pumps them up to.
I believe I read once conti’s had 800 pound burst preasure theres no way setting in the sun will make them burst.
I’ve raced kona more than a few times as well as work the transition area. I’ve(back in the day) pumped tubulars up to 170 pounds out in the sun all day and Have never had a tubular or a clincher blow in transition or for that matter during a race and I’ve been doing tris since 1986 28 of them ironman.