Tires! Hot vs Cold

[Lord_Bragle]

I never found any real difference comparing them... (maybe just some extra confidence on hot tarmac .  Whats the diff in real terms though? what % more Brake, Lean and Throttle can I apply ?

[Spidey]

% brake, lean, throttle of cold v. hot depends on your riding style, the tires, road conditions, your bike and a million other factors.  There's no good answer.  The verifiable difference between cold and hot?  Generally a few psi. 

Unless it's a really warm day out and/or you're riding like an idiot, you'd be hard pressed to get your tires up to a temp that I'd consider hot.  Most street tires get warm, but not track-like hot.  Then again, if you live in a hot climate, the tarmac temp is often enough to get them to track temp.  I know a few people who runs slicks on the street, but they're outliers and they ride like morons.  Fast morons, but morons nonetheless.

The difference re tire temm is noticeable not when they're warm (when you'll have more confidence) as much as when they're cold.  When you ride aggressively with a cold tire, it'll slide more often and more easily.  Not a good thing.

[somegirl]

I can tell you that when I leave home and it's 35F out, I take that first uphill hairpin turn extra carefully.

[EvilSteve]

Hey Spidey, what would you say is a good pressure & warm up time on the track? 28/28 and a couple of laps?

I'm talking Diablo Rossos here, not track tires.

[Spidey]

The standard answer--if you don't have any tire-specific info--is to run 30/30.  If you ran 30 front/28 rear I'm sure that'd be fine too.  As a general rule, the track is opposite of the street, i.e. your front tire runs a bit higher pressure.  Measure them cold unless they're specific track tires that you only measure hot and then run like 21 psi in the rear -- 21 psi hot --WTF?.

One or two laps is fine.  Depends on the weather of course and the length of the course.   If it's cold out and your don't run warmers, you might not be able to get full heat into 'em even after a lot of laps.

If I'm not running warmers, I warm up the tires in the hot pits by hard accelerating and hard braking for a few minutes and then do a warm-up lap with ever increasing lean angles.  If it's a trackday and not a race, I warm up tires for either 1.5 or 2 laps depending on the number of turns in a track and the overall length.  Remember that just because you've warmed up one side doesn't mean that you can rail through a turn with the other side of the tire.  If it's a primarily a right-hand track, take it even easier on the left handers until you've completed two laps. 

The quoted post below outlines a good approach.  I don't think he's right about only the part of the tire that's been in contact being warm, but the general approach of gradually leaning more and more is right on.   

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      TRACKDAY TIRE WARM-UP PROCEDURE/CONSIDERATIONS

The problem of "cold tire crashes" at trackdays is one that seems to show up time and time again, regardless of whether the outside temperatures are in the 60's, or in the 90's+.    From the observations that I've seen of trackday/track school crashes over the last 10 years, I'd conservatively estimate that at least 50% of these crashes are in some way related to tires not being fully up to temperature.    In hoping that a little sharing of a bit of personal experience on this topic might potentially cut down on this statistic at future trackdays, I'm posting the following.


                            TRACKDAY WARM-UP SCENARIO #1
                                      (NOT to do version)

Lap 1 of a trackday session (afternoon session):

Rider circulates the track at a moderate and gradually building pace, leaning the tires over off center by the following incremental amounts:

1st right turn:  20%
2nd right turn: 25%
1st left turn:  20%
2nd left turn: 25%
3rd left turn: 30%
4th left turn: 35%
3rd right turn: 30%
etc ..... etc. ...... etc. .......
last left turn for lap 1:  50%
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Lap 2 of session: (rider assumes after completing one full lap tires are warm)

1st left turn:  60%
1st right turn (Turn 3): 80% ................ (CRASH!!!!)

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In this scenario, the problem is that despite the bike having completed a full lap, (or maybe even two laps, if traffic restricted speeds during that time and limited the maximum lean angle incrementally obtained), 50% of the sides of the tires have not yet made contact with the pavement.  As such, despite the middle 50% of the tire being relatively "warmed up", the part of the tire that will be called upon to provide traction when leaning the bike that added 30% into the 1st righthand turn on the 2nd lap, will still be "cold".  The outcome?   The tires let loose just like the bike was starting on its very first corner, on its very first lap ...... because in the view of this previously untouched portion of the tread surface of the tire .... that's exactly how it sees things.    Make sense?

The secret to avoid this situation is to recognize the fact that only the portion of the tire that has actually made contact with the pavement up to that point will have developed any heat (i.e "traction potential").   The rider must then make it a religious ritual to never adding in more than a couple of degrees of additional lean angle from one corner, to the next adjacent corner, regardless if it's the first lap of a session, or the second. 


                            TRACKDAY WARM-UP SCENARIO #2
                                     (RECOMMEDED version)
Lap 1 of session:
 
1st right turn:  10% lean
1st left turn: 10% lean
2nd right turn: 15% lean
2nd left turn: 15% lean
3rd right turn: 20% lean
3rd left turn:  20% lean
etc. ... etc. .... etc. ...

Lap 2:
1st left turn:  50% lean
1st right turn: 50% lean
2nd left turn: 55% lean
2nd right turn: 55% lean
etc. ... etc. ... etc. ...
Last corners of 2nd lap:
95% lean
100% lean

If for some reason (slower riders encountered, excessively cold or any dampness of conditions, etc.) I am not able to incrementally increase the lean angles in those very "baby step" increments in all corners along the way, I will simply make it a point to add another lap to the warmup process before committing to the more extreme lean angles.

Hopefully for those of you that have had the misfortune of experiencing a trackday crash where the lack of full traction being available across the entire width of the tread area of a bike's tires was a primary contributing cause, the application of the incremental lean, two-lap full warm-up procedure I've shared above might be helpful in preventing a future reoccurrence.  For those of you fortunate enough to not yet have experienced this, perhaps reading this (and religiously following it in the future) will prevent a first time get-off from this cause ...... for some track-going BARFer(s).

Gary J

[EvilSteve]

Thanks Spidey.

I have a track day coming up next week & wanted to get suggestions and I know you have experience in the area. I'd actually read somewhere (don't remember where) that braking is actually better at putting heat into the tire because it moves the carcass around.

[ScottRNelson]

One important point for street riding - if you have sport touring tires the traction doesn't change significantly between a cold tire and a warm one.  Than means that you can trust the tires a bit more during cold weather or when you first start riding after the bike has sat for a while.

I find that sport touring tires get good enough traction for all of the riding that I do, plus the last longer too.  Most of the top brands make great sport touring tires, but I currently like Pirelli best with Avon in second place.

[Lord_Bragle]

Thanx for all the advice folks, I understand now, that I have never even ridden my bike on “hot tires” because they never really get hot while street riding anyway.

ScottNelson, What you said, “Traction doesn’t change much with sport touring tires due to temperature" it makes me wonder if I wouldn’t be better of with Conti Road Attacks - as opposed to the Conti Sport Attacks I currently have?  Its time for new tires soon… I thought sport tires was hedging my bets.  I dont know what to do now? plus I just adviced a buddy to get the sports cuz their stickyer.

[Slide Panda]

Given that both tire carcass are at the same 'warm' temp, lets say 80 F for sake of argument - the sport tires will have more grip than the sport tour.  But from cold to warm, the sport tour tires traction differential will be lesser making them feel more consistent over a wider array of temp conditions.  Also the sport tours will see more miles pass under them before they need to be replaced on wear. 

I guess it comes down to what you value more - The possibility of *maximum* traction, under the right circumstances vs slightly less, but more consistent traction and longer wear life.

[Lord_Bragle]

My buddy decided on a Diablo Strada for his Multie, (Conti Road Attack was unavailable) the guy at the shop said that all road touring tires are all much the same as a class, as are the sports type tires as well.