Tire warm-up procedure for trackdays: "Food for thought"

[theSteveCo]

Wow - great discussion. I've often wondered if you can/should adjust tire pressures once they're heated up. Sounds like the difference is only a few pounds of pressure.

I think I'll start checking pressures after sessions and keep a log of the results throughout the year. I'm sure it's been done, but could be interesting, especially combined with notes on how the bike felt on each day.

 

[Trackho]

T-ho,

using a very rough approximation (using ideal gas law)...

going from 40F to 65F will yield ~5% change in pressure -- assuming that there is no change in volume.

so if your initial pressure was 30psi at 40F, your looking at closer to 31.5psi at 65F ambient.

of course, it's been a long time...and I'm too lazy to verify my numbers and approach

If you are thinking PV=nRT---I think the result would be a tad higher---I have observed closer to a 2-3 psi diff(much more on R1s). In believe this can make a difference on post lunch warm up laps----check my math--but its something I have noticed/suspected

 

[NSR250SP]

This "Hot-Pit" area is really intended (by the AFM) to be used for riders to go slowly while assessing little functional details of their bike (if the brakes feel OK, the steering OK, the tires and wheels OK, everything flows and nothing is coming loose on the bike). The act of "weaving from side to side" is NOT a prescribed behavior in this area to be encouraged by the AFM officials, for riders. Granted you'll still see some racers doing this from time to time ....... but it's usually the less experienced ones.


Gary J

Gary,

What about the quick couple runs up and down the hot pits to slightly "scrub" in a new tire before entering the track? Do you feel that doing this gets some of the "slime" off the carcass of the tire, reducing the new tire crash?

Thanks,

Charles

 

[Gary J]

I'm at around 80% for the rest of that first lap, taking care to still be cautious on whichever side is colder for the next half lap.

I have no doubt that if the combination is running a brand/model of tires that have quick warm-up characteristics (like Dunlops D208GP's, which are known to produce some of the best "quick warm-up" for DOT race tires), and having the extensive riding/racing experience and skill level that you do Mike, an 80% lean level during the later portion of the first lap of a session (on an average weather day) would work fine.

At AFM race weekend practice sessions I enjoy the challenge of coming out on track and getting close to full speeds in a fairly short period of time (by the end of the first lap) ...... running the DOT Dunlops in which I have full confidence for their quick warm-up. With the quick warm-up Dunlop DOT race compound tires on my bike, passing folks left and right on the first lap, that are out there on harder compound slicks, and need to creep around at a much more conservative pace to keep from losing grip, adds a little spark of fun to the practice sessions.

However I would be a bit concerned if the average track day BARFer that reads your post Mike, were to assume that this same 80% level on the 1st lap would also be a safe margin for them. I feel that in most cases, this level of lean would likely not be a good decision for the majority of trackday riders.

I don't believe that a trackday/track school rider can be "too cautious" when it comes to warming up their tires, as there's no trophies at stake and lots of time to gradually work up to speed. Nothing lost by taking a very incremental approach to warm-up and adding in addtional degrees of bike lean angle ........ but LOTS ($$$$ and pain) to lose if one pushes the lean angle/speed equation too quickly.

There are a lot of variables that come into play when determining how much lean angle, and how much speed should be applied as the "maximum" used for each corner ..... over the course of the first to second lap around the track during each session.

------------------------------------------------------------------------

Key variables that come to mind are:

1. Brand/model of tire (rubber compound characteristics)

2. Rider experience/skill level (ability to "feel" for traction)

3. Ambient / track surface temperatures (cold = longer warmup)

4. Motorcycle size, weight, horsepower

------------------------------------------------------------------------------

Certain brands and models of tires have a very well earned reputation for taking a LONG time for the rubber to soften up and develop heat/grip, during the warm-up cycle. I can't count the number of riders/racers that I've seen have their bike disappear out from under them on the first lap (or even second lap), while running a particular DOT race compound tire that was introduced a few years back. The same bike, with a different brand/model of tires, would have had no problem keeping grip through that same turn, at the same speed. Definitely something to factor in when determining the rate of incremental lean for your warm-up strategy.

An experienced roadracer is very familiar with the "sliding" of a bike's tires on track, and as such, is much better equipped to feel for traction during the intital warm-up process. The occasional trackday rider will usually not have that same level of sensitivity to feedback from the tires, and what would be a minor "twitch and correction" for the experienced roadracer, would potentially develop into a full fledged crash for the novice trackday rider. I've learned over the years that it's always important to consider the rider's experience level, before providing any specific riding or bike setup advice. There's no "one formula for all" ..... other than adopting a plan that is a good fit based on the rider's experience and equipment.

I believe that the incremental lean formula that I described as the original post for this thread, is a sound one ....... and though perhaps a bit conservative for the more experienced riders/racers, is a plan that I feel ........ if followed religiously by all trackday/track school riders ...... would seriously reduce the crash statistics at future events. One prevented crash ..... is all it takes to have been a worthwhile transfer of knoweldge.

Gary J

 

[MrCrash]

I thought about it, and you're right - I was about to edit my numbers before you pointed it out. Not that it's something easy to quantify. I'd hate for someone to lob their bike attempting to follow my numbers, telling me afterwards "But you said..."

As riders become more familiar with their bikes, they are able to feel how much of a load is placed on their tires. I like to think I minimize that load by being a smooth as possible, generating load by picking up the pace in faster turns where the same lean angle isn't required. The whole time, I'm trying to feel how much heat is getting into the tire by feeling how much the carcass is flexing.

I tend to skim a knee much sooner on a warm up lap than most riders, but I also ride bikes with a lower seat height than most do.

I think the technique I was trying to share was that riders should make sure and use those faster turns - the ones that don't require as much lean angle - and build a little speed through them (not hammering it, but not just coasting as many do) to generate load, flexing the carcass and creating heat in their tires, in addition to your techique of incrementally adding lean angle through each turn.

I agree though, your technique of playing it on the conservative side with the lean angle numbers is only smart, given the different temperatures, tire characteristics, and experiences levels.

 

[nine]

If you are thinking PV=nRT---I think the result would be a tad higher---I have observed closer to a 2-3 psi diff(much more on R1s). In believe this can make a difference on post lunch warm up laps----check my math--but its something I have noticed/suspected

yeah.
I didn't want to take into account gas mixture and non-ideal behavior.

keep in mind that you can't just take the ratio of temperatures in Fahrenheit. I believe that the unit for T is in kelvins (0 C ~= 273k~=32F). Since all the constants divide out, the ratio would be Tf=65F=291.3k and Ts=40F=277.4k. Where Ts is the start ambient temp. and Tf is the final ambient temp.

Tf/Ts = 1.0501 ~= 5% increase

30psi + 5%*30psi = 31.5psi

NOTE: Black is a nice color for a heat sink...so, the tire will absorb energy from radiation.



EDIT: one last note...

pressure rise from Heating effects of friction/flex >>> than heating effects of change in ambient and radiation

^
|
|

qualitive explanation: final temp of the tire and thus, change in pressure, will be determined by how hard you are running and the track temp. This temp will asymptote well above ambient + heat due to radiation.


Sooo....set it and forget it.. What you need to do though, is account for your initial pressure set up. i.e.

*all things being equal* if you are used to setting up your pressure at 29/30psi on a 65F day, to get an equivalent mass of air in the tire on a 40F day, the pressures would be ~28/29psi

 

[Gary J]

Gary,

What about the quick couple runs up and down the hot pits to slightly "scrub" in a new tire before entering the track? Do you feel that doing this gets some of the "slime" off the carcass of the tire, reducing the new tire crash?

Here's a few thoughts on your question Charles.

A number of years back, some brands of tires were known to come from the factory with a form of "mold release" agent that remained on the very surface of the rubber when they were brand new. There was a lot of issues with people leaving a shop after having new tires mounted, and crashing the bike at the first corner on the street.

I imagine partially as a result of potential liability issues associated with this, it appears that the molding process has been revisited since those days, and the molds have a very smooth surface material that allows the tires to be removed without the use of an actual mold release compound ending up on the tires.

As such, I don't believe that there's much value in taking your bike up and down through the short "hot-pit" area at Sears Point, with the intent of weaving side-to-side to try to de-virginize a new set of race compound tires before heading out on track. The idea of weaving side-to-side, in this narrow area, where other riders directly behind are going straight (as they bed in brakes, etc.), creates a potentially dangerous situation.

I must admit that during some AFM race weekends, I have taken my bike to the Sears Point hot-pit area in years past, with the intent of getting the "newness" off of a new set of tires before going on track ........ but with the tire manufacturing process improvements and rubber compound improvements that have come into being the last few years ...... I've long since discontinued this activity.

I believe that as long as a rider/racer follows the incremental lean angle formula I'd described earlier, any other form of pre-scrubbing of tires (like the Sears Point hot-pit) would not provide any quantitative reward.

Just one man's opinion Charles, ....... FWIW.

Gary J

 

[Trackho]

I can't count the number of riders/racers that I've seen have their bike disappear out from under them on the first lap (or even second lap), while running a particular DOT race compound tire that was introduced a few years back.

-------

Hmmmmm, I wonder if this is the same DOT race compound tire that has been earned a rather curious reputation recently---ie not Dunlop, nor Pirelli/Metz or Bridgestone, but the other guys

 

[NSR250SP]

Just one man's opinion Charles, ....... FWIW.

Gary J

Gary,

Thanks for your thoughts on this...

I do know that onces I started racing, my comfort level for new and cold tires did get better.

I know even from the Ninja 250, running the D509's that they really "grabbed" pretty good on the second lap. Something I would never had thought from simple looking at them on a street bike...

Then comes the D208GP* and man those things grabbed very nice. Of course the added weight/speed/power from a 750 over the 250 really does add to the equation of when is it safe to play at 100%... Nothing like opening the throttle up, and having the rear tire spin up on a 750. Something that is hard enough to do on a little 250, even for cold tires (I guess the 32HP they put out just doesn't mean enough sometimes).

Ah, the whole bedding in brakes... Are you going to write something up on this as well?

Thanks,

Charles

 

[mikeyjudkins]

Chuckie,

Warning level 22? hahahahahah! what did you do to get that?

MJ

 

[BigMeanTam]

Chuckie,

Warning level 22? hahahahahah! what did you do to get that?

MJ

It was a valiant sacrifice for a just cause....... LOL.

(It had something to do w/ this thread... btw: http://www.bayarearidersforum.com/forums/showthread.php?s=&threadid=20551 )

-BMT

 

[CHAMPIONR6]

sounds like great advice to me Gary - I wuold trust your advice since you have a hell of alot more time than me on a bike . I read one of your books too which had some helpful info in it for me , and saved me a time or two

 

[kimchee]

yeah what he said...
:|

yeah.
I didn't want to take into account gas mixture and non-ideal behavior.

keep in mind that you can't just take the ratio of temperatures in Fahrenheit. I believe that the unit for T is in kelvins (0 C ~= 273k~=32F). Since all the constants divide out, the ratio would be Tf=65F=291.3k and Ts=40F=277.4k. Where Ts is the start ambient temp. and Tf is the final ambient temp.

Tf/Ts = 1.0501 ~= 5% increase

30psi + 5%*30psi = 31.5psi

NOTE: Black is a nice color for a heat sink...so, the tire will absorb energy from radiation.



EDIT: one last note...

pressure rise from Heating effects of friction/flex >>> than heating effects of change in ambient and radiation

^
|
|

qualitive explanation: final temp of the tire and thus, change in pressure, will be determined by how hard you are running and the track temp. This temp will asymptote well above ambient + heat due to radiation.


Sooo....set it and forget it.. What you need to do though, is account for your initial pressure set up. i.e.

*all things being equal* if you are used to setting up your pressure at 29/30psi on a 65F day, to get an equivalent mass of air in the tire on a 40F day, the pressures would be ~28/29psi

 

[donoman]

Yesterday, I had Gary J talking to me inside my little big helmet as I rode around the track and warmed my tires up.

 

[ie6x]

This all sounds great, but every track day that I have been to the only one I see taking it easy for the first few laps is me. Usually the only people behind me are slower riders to begin with and never pass me so they are not warming up there tires. I feel like an ass for taking it easy, but if I didn't I know I'd be the only one to crash because of cold tires... Funny how that works. I worry about the one's that coming ripping out hitting redline before turn 1.

 

[Gary J]

This all sounds great, but every track day that I have been to the only one I see taking it easy for the first few laps is me. Usually the only people behind me are slower riders to begin with and never pass me so they are not warming up there tires. I feel like an ass for taking it easy, but if I didn't I know I'd be the only one to crash because of cold tires... Funny how that works. I worry about the one's that coming ripping out hitting redline before turn 1.

Yesterday's (Sunday, Nov 16th) 50'ish degree high temperature trackday up at Thunderhill, was a perfect opportunity for folks to religiously apply this "cold tire warm-up procedure". Unfortunately it seems by the extremely high number of crashes that happened over the course of the day, either few of them have read the original post of this thread, or have since forgotten the message.

Perhaps printing out a copy of something like this form of "heads-up reminder" about cold tire warm-up procedures, and handing it out to riders in the morning at the "Riders Meeting", might potentially reduce the probability of such high incidence of crashing as we witnessed yesterday. Just some food for thought, FWIW.

Gary J

 

[MackeyStingray]

should be a staple of every track organizer's speech. esp. important in these colder months.

 

[Harpo]

Yesterday's (Sunday, Nov 16th) 50'ish degree high temperature trackday up at Thunderhill, was a perfect opportunity for folks to religiously apply this "cold tire warm-up procedure". Unfortunately it seems by the extremely high number of crashes that happened over the course of the day, either few of them have read the original post of this thread, or have since forgotten the message.

Perhaps printing out a copy of something like this form of "heads-up reminder" about cold tire warm-up procedures, and handing it out to riders in the morning at the "Riders Meeting", might potentially reduce the probability of such high incidence of crashing as we witnessed yesterday. Just some food for thought, FWIW.

Gary J

Ditto That!! Waaaaaaaaaaayyyyy too many cold tire crashes Sunday and Monday

 

[Manu ®]

Lance did emphasized tire warming yesterday (17th) during the riders meeting. He even mentionned the previous day as a bad example because lots of crashss were due to cold tires and cold track.
But still, riders, especially in B- just seemed to have totally forgotten about it, especially after the sun came up. Looks like they thought, oh, sun is up, track is hot, all good, lets pin that throttle.

Guess what happened then...

--Manu

 

[PHAT_R1K]

Lance did emphasized tire warming yesterday (17th) during the riders meeting. He even mentionned the previous day as a bad example because lots of crashss were due to cold tires and cold track.
But still, riders, especially in B- just seemed to have totally forgotten about it, especially after the sun came up. Looks like they thought, oh, sun is up, track is hot, all good, lets pin that throttle.

Guess what happened then...

--Manu

I think part of the problem is people using tires above their capabilities, too. I mean, a B-(C) rider going out and buying DOT race tires and using them on a cold day just spells trouble. Sport and Supersport tires would be fine for most of the riders out. For the inexperience rider who doesn't know much about grip to begin with, would really have a tough time figuring out when the tires ready to go, too.