Thursday Practice

[Awesome]

Colder track and colder air mean run a lower temp, a pound or two is sufficient from standard is sufficient, but all depends on the tires. Pressure rise isn't really as important as temperature.

[WebCrush]

Originally posted by Tabby
OK, how about some things that ARE important. Thursday is looking like it will be a little cool, especially in the morning. What kind of tire pressures are you more experienced fellows going to start off with? I came from the OLD bias ply days where we monitored pressure rise {10 to 15%}. I have Pilot Powers on the old gixxer.
What would be a good starting point? When I did the Penguin in Aug., they told us to set them at about 30 psi front and rear. I'm thinking a few pounds less anyways. I'm not worried about lap times, more about keeping my butt off the track. Any rules of thumb here?

Penguin bases their pressure for the Dunlop's they use.

I don't know much about Pilot Power's but I hear they use a much lower pressue, like in the 22-26 range. Give Motorace (Michelin distro for the track) and they can let you know.

fwiw, I don't intend to change my pressures from my standard 31f/29r--its not going to be THAT cold

[Kip]

Originally posted by hessogood
Colder track and colder air mean run a lower temp, a pound or two is sufficient from standard is sufficient, but all depends on the tires. Pressure rise isn't really as important as temperature.

I think you have this mixed up. Colder temp run a little higher so the tires get up to temp. If you run them lower they will not get up to temp and cold tear.

[Paul_E_D]

Kip, my understanding is that lower pressures= more carcass flex = more heat. Higher pressures= less carcass flex= less heat.

This logic would have you lowering the pressures on a cold day.

Whatever the case, giving your tires a little extra time to heat up with reduce cold tearing, as will riding smoother.

[WebCrush]

Originally posted by Kip
I think you have this mixed up. Colder temp run a little higher so the tires get up to temp. If you run them lower they will not get up to temp and cold tear.

I think you got it backwards too, at least on Dunlops

Lower pressure allows more flex which build the heat in the tire when riding.

At the same time, too much pressure causes the tire to spin which can cause over heating.

Happy medium is where its at.

[WebCrush]

Originally posted by Paul_E_D
Kip, my understanding is that lower pressures= more carcass flex = more heat. Higher pressures= less carcass flex= less heat.

This logic would have you lowering the pressures on a cold day.

Whatever the case, giving your tires a little extra time to heat up with reduce cold tearing, as will riding smoother.

doh, you posted while i was typing.

[Tabby]

Yeah, Paul, that was what I was thinking. Monitoring the pressure rise was a good round about way of watching your tire temps. Did it fall out of fashion with the radials? Why?

[s a x m a n]

i agree, with the lower pressure on colder days ... thats what I have always heard.

[legalspeed]

Gauge your preassures to your heat: measure the temp of the tire as you come off.

Want more heat? Let out some preassure to flex the carcass.

My answer: I will start with 2lbs under norm, then bring them up from there by measuring the temps with an infrared thermometer as the day progresses.

[s a x m a n]

when are people arriving ... I'll be pulling into the pits around 2-2:30am Thursday ... I am leaving after my bar shift on Wednesday.

[Paul_E_D]

Originally posted by Tabby
Yeah, Paul, that was what I was thinking. Monitoring the pressure rise was a good round about way of watching your tire temps. Did it fall out of fashion with the radials? Why?

You can still do that...

[Tabby]

Hey, I know this is being a pain, but what kind of percentage do you look for in radials? Where is Karaya 1 when you need him?

[OreoGaborio]

Originally posted by WebCrush
I don't know much about Pilot Power's but I hear they use a much lower pressue, like in the 22-26 range. Give Motorace (Michelin distro for the track) and they can let you know.

That's for the Power RACES, not pilot powers.

During trackdays when I ran Pilot Powers, Dave (Karaya One) recommended track pressures of 30/30 for your typical nice warm day. If it's chilly, drop it a LB or two at the most.

[Paul_E_D]

Originally posted by Tabby
Hey, I know this is being a pain, but what kind of percentage do you look for in radials? Where is Karaya 1 when you need him?

10-15%

[Tabby]

Thanks Paul. That might be old info to most of you folks, but for some of us, especially those who are very new to this environment, it can be a handy tool.

[Awesome]

Originally posted by Tabby
Thanks Paul. That might be old info to most of you folks, but for some of us, especially those who are very new to this environment, it can be a handy tool.

In one of the more current books on the mechanics of motorcycles i read that the hot -cold pressures was the old method. I've found with the tires that I've used the recommendations were to achieve optimal operating temperature, I don't recall seeing anything about optimal hot pressures. just a baseline to start at and adjust from.

Kip, I don't think I have anything backwards.

[Kip]

Originally posted by hessogood
In one of the more current books on the mechanics of motorcycles i read that the hot -cold pressures was the old method. I've found with the tires that I've used the recommendations were to achieve optimal operating temperature, I don't recall seeing anything about optimal hot pressures. just a baseline to start at and adjust from.

Kip, I don't think I have anything backwards.

You might be right I was just going off of what S&C told me, but we all know S&C aren't always right.

[Tabby]

I would think that having an optimum temp range is what you would shoot for, DUH! Today, infra-red temp sensors aren't that expensive and readily available, so actually measuring the temp shouldn't be a big deal. In the "old days" when IF thermometers weren't readily available, measuring the pressure rise was the simplest means of measuring the temp of the tire. Maybe it wasn't exact, but if you did it enough, you could get some consistent performance out of your tires. I don't see why today, if someone doesn't have an IF thermometer, they couldn't use the old method, if they new what percentage of pressure rise represented a certain temp range. I was just curious why it really fell out of use. I may invest in an IF thermometer in the future, but for now the old Accu-gage is all I have.

[OreoGaborio]

I know it varies from tire to tire, but what's the genearal range of temps you should you be looking for in a typical DOT race tire? 140-160?

[Awesome]

Depends on the tire, type of bike, and track temps. I run for 170 - 175 on bridgestones.

[Tabby]

This is good guys. OK, I'll show my ignorance on the subject. Is that in degrees F or C?

[OreoGaborio]

oh man, if it were C, them would be some SMOKIN TIRES!

[Tabby]

Ah jeez! Can you say "Brain Fart"? I knew you could.
Man,what a maroon I am. I was thinking about that on the way home and that tiny thing that passes for a light bulb in my head, went off. Well, I hope you all got a chuckle out of it.

[zx1012r]

This is a black art, this pressure/temperature thing! It used to be, with the bias ply's anyway, that you wanted a specific hot pressure. This was based off coming down pit road after 4 to 5 hot laps and immediately checking pressure. There was an optimal hot pressure for each brand tire. The reason being that at one specific pressure the contact patch of the tire on the pavement was at an optimum. You therefore would set your pressures hot, then check them when they cooled to get a cold reading, and on that particular day you could set your cold pressures and be relatively sure they would be the correct pressure when they heated up.

Whew! This of course changes with every degree of ambient temp change, and track temp change. We used to pull our hair out changing this stuff all day long!

Now with the radials, I don't think it is as critical as the bias because the radials don't "grow" or flex as much as the bias. I do however believe you want the hot pressure fairly consistent, and need to be careful in the cooler weather to let the tires fully heat through to the rim to minimize cold tearing.

I ought to be a politician

Mark Dages 454

[Tabby]

I know this is dragging things out. You kind of hit on what I was thinking. With radials being an inherently cooler running tire, that maybe they weren't as fussy. The old bias ply tires would self destruct lots faster with over heating. Yeah, I think I will cruise some catalogs and look for an IF thermometer. Thanks to all of you on this tire info side trip.