I am running Michelin PR2 front and PR3 rear at Homestead with a outside temperature of 78. What setting should I set my digital tire warmer to? What should the tire pressures be when they are checked warm? Thanks again fellas!
Juan
any chance of getting rid of that PR2 for a PRC? Is this a race or a track day? that PR3 is gonna go off fast...
I run 135 in the PRC front, 175 in the PR5's... ran 33psi cold on the C, 22 cold on the 5, never checked hot pressures...
IIRC Tommy said Michelin doesn't really have a "recommended" warm pressure, only cold.
Exactly. Michelin's you use just cold pressures. Someone might have put a pressure guage on it warm, but it's not of specific consequence for them at this time in their construction like other manufacturers.
I do admit that I have ran higher than 33psi cold in the PR2. It helped it feel better. Yes, get the PR C. It's available through race distribution.
Thanks for the info! It's to late to get the PRC's. I just need them to last for one short practice session, 1 9-lap sprint, and 2 6-lap sprint races. I will use the temperature settings that tstruyk recommended, unless some of you have better suggestions. Going by what some of the comments are saying, do you guys only check your tire pressures at the begining of the day?
Tim's temperaturs are good.
I check my tire pressure in the morning before I put on my warmers.
Later, I will check and adjust my cold pressure. If it's 55 in the morning, and later it's 77, your cold tire pressure will increase. You'll want to adjust that.
Look for an opening in the schedule to do it. Sometimes, I'll have a race in the middle of the day, so I can check my tires after lunch or a little later after they've completely cooled down from practice.
Dave, in your opinion, will the PR 2 & 3 last for what I am using it for? Thanks!
Well, yeah, you should be good.... depending upon how fast you are. The PR3 has a shorter life than a PR5 or a commercial Med/Soft. The PR2 is just a completely different construction compared to the PRC that we're all talking about. The PR1/2's are kind of mushy feeling, and they lack some feed back that previous Michelin tires had, and they restored that in the PRC. That's one reason why I liked running more than 33 PSI in the PR2.
Now, when you do change to the PRC compared to the PR2, they are different heights when compared to each other. So, it will change the way the chassis reacts to your inputs and how you feel things. I might be inclinded to just say try it when you make the change. Just take your time.
Dave, this is my first amateur race. So, it's safe to safe that I will not be pushing the tires to their full potential. I will do some more research regarding the tire pressures and it all depends on what the temperature is like at Homestead that weekend. These will be the last set of PR# that I will purchase.
Have any of you heard that Michelin is coming out with a whole new race version for 08?
Oh, yeah. I've ridden on the PRC rear's off and on since June. I sampled a front tire that wasn't a production version DOT tire, but I liked it. I had that in May. I liked it.
Melka might have some ideas on what the new stuff will be like to. He should be there...might be lurking too...
is it just me or is it retarded to have cold pressure recommendations and no hot? What defines cold? 40f, 70f, 90f ?
Yes, the outside temperature would define it. But a hot pressure could be indicated by a temperature change of 110, 75, or 40 degrees from the outside temperature, which would originally be the temperature of the air inside the tire.
Just a little information. Homestead taking place in December can be in the upper 50's range to sometimes 80's. Go with the recommend pressures given by Frank Kinsey or speak to Greg Melka. He is always helpful with stuff like that.
As far as tire life goes, plan to do up to 7 practice session on Saturday before racing your three races on Sunday.
I smile at the remark that you "won't be using all the available traction" - I beg to differ. It seems that Amateurs tend to crash more than experts all the while experts are turning faster times. I believe that Amateurs will use all the available traction right up to the point that they crash. The difference is the expert can maintian a higher level of speed(use of traction) and do it more consistently than the Amateur.
Mark
My point with the temp is........cold is never consistent.......while hot can be.
I am going to swap tires out at the end of Satrurday. This way, I have a fresh set going into the first practice on Sunday.
Sig, I see your point about what defines checking your tires "cold." What temperature defines that? My original question was in reference to checking the tires while the tires are warm with the tire warmers. After reading all these posts, it seems as though no one does that. I just thought I would ask. I like this forum because I am getting some great advice from all the veterans of racing.
I'll state this again. Someone will have to tell me if I didn't say this, but...
Different manufacturers do different things.
Pirelli specifically states their hot tire pressures. That is how you check them. You'll have to have a basis of the heat in your tires from loading them up under traction to have any kind of basis for setting the tire pressure before you go out to ride. Example, if a particular Pirelli tire requires 29psi hot, you're going to assume an increase in your tire pressure from cold. Might be 3psi, might be 5psi.
Michelin specifically states their cold tire pressures. That is how you check them. You'll check them cold, then you'll use the tire.
Methodology for checking tire pressures is derived from what the manufacturers find is effective for their carcass and compound.
I believe you said it right the first time. I just wish there was less science behind checking tire pressures. There are so many factors that come into play. The temperature, the track, and the bike set-up all factor into what the tire pressure should be. I guess it is cut and dry for street, but racing is a whole different ball game.
nitrogen is an option...
here' s a decent read, most of it is covered but as I read it I found some interesting info...
http://nationalprivateer.com/Racetirepressure.html
There's a lot of myths about nitrogen out there and the one in that thread is completely untrue. ANY gas will heat and expand resulting in a higher warm pressure and nitrogen is a gas just like any other. Nitrogen is used in tires and suspension components because it is a DRY air (the result of careful processing, ordinary compressed air can be filtered and dried as well). It has no moisture or oxygen in it like the air around you or from you air compressor. This can help to reduce deterioration of the rubber but we change tires so often that this is really not a concern. BTW the air you are breating right now is about 75% nitrogen.
does nitrogen expand less than air? This is above my pay grade...
That was a good link for tire info. Dave pretty much explained all of that in a short paragraph.
Different gases do expand differently but for the sake of tire pressure the difference is almost unmeasureable. It has been way too many years since I took physics but remember that air is 75% nitrogen anyway so the difference is going to be minimal as long as you aren't using an air source that has a lot of condensation in it (water vapor will have some effect).
doesnt compressed air contain a high amount of moisture in it? I thought that was the main point. I really dont have a stake in this, just looking for accurate info. I've got bigger issues than TP LOL
Quote from: Hawk on November 21, 2007, 02:36:34 PM
Different gases do expand differently but for the sake of tire pressure the difference is almost unmeasureable. It has been way too many years since I took physics but remember that air is 75% nitrogen anyway so the difference is going to be minimal as long as you aren't using an air source that has a lot of condensation in it (water vapor will have some effect).
Under race conditions and on tire warmers we were getting between 3 and 6 lbs of air pressure increase using standard dry pressurized and un pressurized air (i.e. bicycle pump). While we were getting .25 - 1.5 increase using nitrogen. On an extremely accurate gauge. To say the differenece is unmeasurable is incorrect. Unnecesary maybe, but not unmeasurable.
Quote from: tstruyk on November 21, 2007, 02:42:12 PM
doesnt compressed air contain a high amount of moisture in it? I thought that was the main point. I really dont have a stake in this, just looking for accurate info. I've got bigger issues than TP LOL
Compressed air will have moisture in it which will condense out as the temperature of the air goes down but line driers are very inexpensive and rather efficent and the other really big culprit is not draining the compressors tank daily.
Quote from: Super Dave on November 21, 2007, 09:20:42 AM
I'll state this again. Someone will have to tell me if I didn't say this, but...
Different manufacturers do different things.
Pirelli specifically states their hot tire pressures. That is how you check them. You'll have to have a basis of the heat in your tires from loading them up under traction to have any kind of basis for setting the tire pressure before you go out to ride. Example, if a particular Pirelli tire requires 29psi hot, you're going to assume an increase in your tire pressure from cold. Might be 3psi, might be 5psi.
Michelin specifically states their cold tire pressures. That is how you check them. You'll check them cold, then you'll use the tire.
Methodology for checking tire pressures is derived from what the manufacturers find is effective for their carcass and compound.
I know that Michelin says to use cold temps. My point is, logically this cannot be consistent. Cold temp at VIR in March is a hell of a lot different than cold temp at Barber in August. With hot temps you can turn your warmers to whatever is recommended and set pressure accordingly.
Hot temps seem to make much more logic for a race tire. Maybe I'm just biased as a pirelli customer.
I never came to grips with the PR1/2 fronts. :wtf: The rounded profile was different than typical Michelin and feed back sucked compared to the previous Michelin fronts and the PRC. The PRC is worlds better and has the steeper more typical Michelin profile. :thumb:
The PR3 is pretty short lived, but they are great one race tires. As Tom Mason says, Fresh is best! A PR5 will give "nearly" the same grip levels for much longer, its proven to be a true race all day tire. That said a new PR3 is magic when warm! I have the digital tire bakers and heat the front/rear to 140/170. 30 psi in the PRC and 22 psi in the PR3 or PR5.
Quote from: Hawk on November 21, 2007, 11:05:43 AM
There's a lot of myths about nitrogen out there and...
There are some race distribution points that use nitrogen almost exclusively. It has a purpose, and the purpose is recognized as being useful in specific applications.
Yeah, nitrogen is most of what we breath, but there's more to it than that. You'll have to contact the real tire engineering guys for the real specifics on it.
I'll cut somebody a sweet deal on 500 cubic meters of 78% nitrogen air.
I'm sorry, just can't hold back from posting on this.
I believe the Michelin cold temp pressures given to club level racers is just an easy way to answer their customers question about what pressure to run. Michelin probably has found that most of their customers can not or will not be able to consistently control Hot pressure and are more satisfied and have a more consistant tire performance when set to their recommended "cold" pressures. If you think Michelin supported AMA and Moto GP teams are setting their tires at "cold" pressures then you are naive.
One thing that no one has mentioned yet is the tire's optimal operating temperature. Air pressure is one of the things that effects the tire's operating temperature. To really have optimum tire performance for your bike and riding style takes lots of testing and data collection. Just because one combination is working for someone doesn't mean it will work for everyone. This is why you hear all the talk during broadcasts about riders and their tire selection/decisions for the race when watching AMA or Moto GP.
Some things to think about when searching for optimal tire performance:
What is the outside temp and humidity?
What was the cold pressure?
What was the tire warmer temp set at?
What was the warm pressure after the tire warmers were on right before you went out for a session?
What is the pressure when I come off the track (and I don't mean after you pull into the pits after a cool down lap)?
What is the left side, right side and middle tire temperature when I come off the track?
What is the track temp?
What compound?
Type of track surface - abrasive, green, etc...
What is the riders feedback on tire performance and traction?
Take Notes!
Taking notes will be key to finding a successful combination. You have some really good suggestions and I think I will use them to start my track notes. I didn't realize that people actually check the temperatures right after taking the tire warmers off and right after getting off the track. This is a good idea because I will always have a reference point to work off of whenever I am in doubt what my tire pressures should be. All I will need to do is refer to the notes. Thanks!