questions about air pressure ?

Started by Steviebee, April 10, 2003, 05:03:37 PM

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Steviebee

instead of bugging one guy, id figure id ask everyone else.

Seeing as i actually have raced now !! weee,  man how much longer till RA ??  
Iv'e got a ton of questions. but here goes the first one.

Tire pressures ??
 00' Gsxr 750  Metzeler Sportec rear (with 2 track days) and a Rennsport RS2 (or is it SC2  i forget but its a HARD compound race tire) front brand new minus the weekends practices in the cold and wet.  (yes i know, not the ideal setup but its what i had) oh. and totally stock suspension :( ..

So when i started out on Sunday morning practice it seemed ok.  I wasnt getting max lean or getting a knee down, but i was really cautious cause it was a cold track.

So i botched it in HWSB and crashed in T7 on the 2nd to last lap, but while runing i never felt like the bike was "solid" it just kinda of felt squirelly when leaned over real far.  So the next race i take it easy for a bit and then back up to the pace i was running, but the bike just didnt feel hooked up in the corners.  So i was advised to lower air pressure a bit, so i went down 1lb in the front and 1.5 in the rear.  The next race, it felt better, but still not "locked" in in the corners.  So for the last race, i went down another .75lb in the rear (dont think i touched the front).  Took it easy for the first 3 laps, and then pushed her over a bit more in the corners and it was rock solid, like on rails.  I could get my knew down in 3,4,5,6,7 no problem.  This is how my bike felt at the last track day that i was at.  now i was happy and i could hang with some of the other fast guys.

So i started out with 29 pounds in each.  Doesnt this seem like a low tire pressure to run, 28 and 27 ?  or am i just a total newbie !!.  Or is my new air pressure gage messed up ??  My last track day was about 40 and sunny and i was running 29 lbs and the bike felt great ??

One other thing is, this was the first time using tire warmers, (yes i checked the pressures before putting them on, and then just made small adjustments).  I was getting about 3-4 lbs buildup in pressure after checking them when i came back in ?

What was everyone else runing ??  Any comments

rick

#1
RS2 is the medium compound, RS3 is the hard. SC2 is the medium compound rennsport perilli style. The Sportec is a street tire that left me cold in the handling department.

As for the pressure, if 28 is working for you then use it! But that's a hair lower than I'd tend to set 'em. However, I usually just ask the metzeler/dunlop/etc guy and just do whatever he says. :)

Steviebee

ooops  green  = medium.  mybad..

I never had a chance to go talk to the metzeler guy ?  

I only say the Dunlop guy and the Michelin guy.  It was my first race weekend, I was wondering around like a frog.  You mena the Dunlop guy is really a Metzeler guy ??

rick

#3
Nah, I just meant that I ask the vendor for whatever tire I'm running what pressures they think I should run. Then I set 'em and forget 'em for the rest of the day.

...But, by all means run whatever tires/pressures you think works best for you!

EX#996

Steve:

The Michelin guy is Tom Mason, he also sells Perilli/Metzlers.

Just like Rick says, "just ask the tire guys"  They will adjust the pressure based on the conditions.

Dawn   :)
Paul and Dawn Buxton

Steviebee

yea.  my bad.  You guys know how it is .  err was your first race weekend ?  Clueless.  I guess i forgot that he was the Metzeler guy too.  Now i know.

Oh yea i forgot to say congrats on now being a moderator Dawn !!

Maybee Ill get to meet ya at RA.   Hopefully it wont be so cold so i wont have to hibernate in my trailer. !!

tcchin

Standard race pressures for Pirelli/Metzeler DOT tires are 31F/29R. On hot days, 32F/30R will keep the tires from overheating. I don't know anything about the Sportec tire, as it's not a race tire, but I've been told that the Supercorsa/Rennsport carcass is so compliant that 28psi could be low enough to peel the bead off the rim.

FYI, even the softest Pirelli front tire (SC1 blue) seems to last twice as long as a 208GP, while sacrificing nothing in terms of traction or handling. In fact, we've had them outlast the green and yellow rears nearly 3:1. I can't even imagine what the yellow (SC3) front would do...

Finally, spend $50-100 on a good tire pressure gauge. A glycerin-filled, 60psi, grade A or 1A stainless steel gauge can be found at any industrial supply house, and can even be retrofitted to many existing gauge assemblies, like QuickCar and Longacre. That's cheaper than even the smallest piece of bodywork, and about the same as an ER copayment.

EX#996

QuoteOh yea i forgot to say congrats on now being a moderator Dawn !!

Maybee Ill get to meet ya at RA.   Hopefully it wont be so cold so i wont have to hibernate in my trailer. !!

Thanks!

I try and talk to everyone at the track (hard to believe, huh?), but don't always get to meet everyone. At BHF you probably noticed a white motor home with a 16' white trailer with road rash on the driver's side, that's us.  Stop by and say hi.  

See ya there!

Dawn   :)
Paul and Dawn Buxton

Steviebee

What about tire pressure on a cold day ?  like 30 degrees ??  as opposed to a warm day ??   And how much build up should i be getting ??

I really need to know what hot tire pressure to run??

I bought a new gage thats pretty good.  Just wondering if it could be off ?

Dawn , you didnt have a dog with you guys did you ??  ohh ahh  motorhome i really was wanting one of those last weekend.  I slept in a tent ?  brrrr..

Super Dave

I guess the two things that I would have questions about what you have...

The accuracy of your gauge.  If you're not using the same ruler as the tire guy, Tom Mason, it's hard to make accurate measurments.

During the day at BFR, the temperature changed, so the cold tire pressure would change.  At what point was it best, and what was it actually?  If you started out at 29 cold but the day got warmer and the tire pressure went up cold.  You dropped it.  You might have just dropped it back to the window it should have been at.

That make sense?

As for hot pressure, we don't do that like we did back when we were racing with bias ply tires.  The radials don't heat up like they bias ones did.  How technology has changed.
Super Dave

Dawn

QuoteDawn , you didnt have a dog with you guys did you ??  ohh ahh  motorhome i really was wanting one of those last weekend.  I slept in a tent ?  brrrr..

Yes we did.  That's the little Marty dog.

Dawn   :)

MightyDuc Racing

Stevie...take it from another newbie.  Ask the tire guy at the track, check them once in the morning while the tires are cold, and then leave them alone.  You can't check or adjust them while they are still warm.  Believe me...I forgot to check them Saturday morning and had to sit out an entire session while I waited for them to cool so I could be sure.  Better safe than sorry.  (Of course they were right after all that...lol).  Nobody knows better, no matter what they tell you, than the tire guy that actually works for the manufacturer.  Hope this helps.

MightyDuc Racing
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