Tires...

[Cobie Fair]

The Schools at the early and later part of the year, when it's cooler have the most issues with tire management.  There seems to be a lack of good information regarding tires.  Before we launch into that, is this a subject the forum readers are interested in more information? 

Potential points of discussion: 

• How do they work (general info).
• How to warm?
• How to tell when warm/hot?
• How long to scrub in a new tire? 
• Difference between street tires and slicks?
• When should one run slicks?

Let us know if this is of interest to any of the readers/lurkers on the forum.

Best,

Cobie

[CoffeeFirst]

Always up for more discussion and knowledge about tires and tire management.  

Worth mentioning CSS has shared some great information on this in the past. I found Keith's  "Traction Science" post and Dylan's comments in the "Contact Patch vs Grip" thread very helpful.

[Jaybird180]

I’d be interested in knowing how to tell if the tire is ready to perform. When I was on Michelin there was a discernible feel to the tire, but not so (to me) on Dunlop.

[Cobie Fair]

Let's start broadly, then narrow this down, and see about 1 piece at a time.

First issue will be getting the tire up to temperature.  What is the correct temperature?  That will depend on the type of tire, say street tire vs slick (only meant for track).

A street tire like the Q3+ will work at a lower temp, and broader temp than a slick.  I'm  not an engineer, and so this will be approx numbers.  Q3 would be 120-180, front, a little  more for the rear.  A slick will be a higher and narrow band.  I wasn't able to find much data on this, but maybe 180-200?

The engineers test with a probe, to get the carcass temp, not the surface temp.  Surface temp is not as reliable to measure (tire could get spun, be hotter on the surface).

All good on this so far?

[CoffeeFirst]

Yup, good with the general concept … street tires = lower / broader and slicks = higher / tighter temp ranges.  Plus full carcass temp is what matters.

Worth noting Dunlop website recommends tire warmers be set to the same temperature range (158-176 F/70-80 C) for Q3+ / Q4 and KR448 / KR451 / KR151 slicks.  Think this simply means for track riding all of these tires optimize their performance in the same general high temp range.  You'll find the recommendations in the footnotes in the tire specifications section.

[Jaybird180]

36 minutes ago, CoffeeFirst said:

Yup, good with the general concept … street tires = lower / broader and slicks = higher / tighter temp ranges.  Plus full carcass temp is what matters.

Worth noting Dunlop website recommends tire warmers be set to the same temperature range (158-176 F/70-80 C) for Q3+ / Q4 and KR448 / KR451 / KR151 slicks.  Think this simply means for track riding all of these tires optimize their performance in the same general high temp range.  You'll find the recommendations in the footnotes in the tire specifications section.

In my industry, before a publication is released to the public every word has been “refined” by different internal interests. Sometimes the end product bears only a vague similarity to the original. In the case of a tire manufacturer, I’m willing to bet that any temperature recommendation discussion starts in Engineering and ends with Public Affairs.

A prior Dunlop release came dangerously close to “debunking” heat cycles as a myth by excluding Dunlop from the phenomenon as a concern for the tire consumer. That discussion can be found on this forum.

I take note that no tire manufacturer makes warmers. I also take note that motorcycling being a niche market has little in-fighting among product manufacturers, presumably because every dollar spent in the industry benefits everyone.

The Q series tires are marketed to performance oriented riders and retains an ability to operate in dual environments , street and track. It would have been nice if MotoAmerica would have retained a 600/1000 stock class, running the Q tires and leave the slicks to Superbike only.

All that said, I scratch my head at the warmer recommendation. A street rider wouldn’t use them and although I’ve read reports that they do fine at A-level trackday pace, I haven’t personally seen many riders continue to use them, instead opting for more expensive rubber.

[Cobie Fair]

Jaybird,

Let's touch on your last point.  The Q's (3+, 4) are very good tires and as you said do fine at A group pace, but they aren't quite as good as slicks.  For example, all my coaches will opt for the slicks on a warm enough day.  Even w/out tire warmers.  The Q tires are for street and track day as you say, but the full pace of racing is that bit more, and the Q's aren't made for that.

We good on this point?  I'm thinking the next part of this would be an earlier point made, about how can you tell when they are working?

 

[Cobie Fair]

On 11/3/2022 at 11:02 AM, Jaybird180 said:

I’d be interested in knowing how to tell if the tire is ready to perform. When I was on Michelin there was a discernible feel to the tire, but not so (to me) on Dunlop.

This is a question we get often, and as Jaybird mentions above, a part is how does it feel?  First, lets refer to one aspect of a tire's grip, contact patch.  To somewhat over-simplify, the surface looked at closely is quite rough, with small ridges and dips.  A cold tire "skates" over the top of the ridges, and doesn't push into the dips.  

Have you ever gone out on a cold tire, cold day and the bike felt like it was skating on the surface?  Well, it was!  When steered into a corner of any kind, it also didn't turn and hold the line well at all.  

Have you noticed this?

[Jaybird180]

Is the skating sensation more pronounced based on speed? Probably.

And that's the rub: not going so fast as to make unnecessary risky, yet fast enough to feel the tire skate. How does one sneak-up on the sensation? Of course, ignore all of this if skating isn't speed induced.

[Cobie Fair]

This next part is to see how to tell what it feels like, and some simple guides:

No, not necessary to be going fast, this can be felt at slow speeds.  This is before sliding of course, the tire just doesn't feel like it's tracking exactly as it should, it doesn't feel positive and planted, it's not turning and holding a line well.  One might think, "I'm just being a wuss" but in fact the tire isn't working, the rubber is not filling into the those little dips.  Tires do not work below temp, full stop.

A way to check the tire is simply when you pull over, pull your glove off and feel the tires (both front and rear).  If it feels cool to your touch, that's stone cold.  If it feels tepid/lukewarm, that's cool.  If it's for sure warm, you are getting there.  If the rear is hot, then you are there.  This is just a rule of thumb of course.  But the idea is to start to get a feel for what the tire is like as it warms, and when it's finally hot.

When hot, it turns in, and holds the line (sometimes going even tighter than you'd expect).

So a question to all reading: have you experienced this?

 

[Jaybird180]

Since a tire will never reach similar temperatures, I would imagine the skating sensation would be ever present?

I recall a conversation I had with a buddy about waiting until the tire is warmed. We were on the same size and model Michelin 2CT. He was believer in the magic of the tires and wouldn’t heed any warnings. Next time I saw him, he had low sided and then had become more skeptical of cold tires.

Although I could feel the change in those tires on track I am not sensitive enough on the street.

I recall a session where you @Cobie Fair yelled out to me that I needed to get the tire working, that I was too timid; it was still early in the session. I’m glad you did that- I am still working on finding that good pace to work the tire up to temperature but even  when I get up to my full pace, I still don’t have a trust in the tire.

I still forget to do the hand check on the temperature of the tires. I do agree that it’s a valuable tool to get a sense of how it’s working. I’ve previously been looking at the surface tearing to get an idea of how I’m working the tires.

[Cobie Fair]

Honestly, on the street, I don't know that I ever get tires to full temp.  It would have to be very warm day.  I just don't ride that fast on the street.

At the track (or street too) one thing that can help is in a straight line, accelerate hard, and brake hard-ish too.  This will help flex the tire and get some heat.  Still have to make sure you increase the pace gradiently at the edges of the tire though, no sudden increases in lean angle, just gradual ones.

See if it helps to be aware of that feeling of a cold tire, and then notice the opposite, how does it feel when it is hot.  Might have to wait till you get a warm day for that :).

[CoffeeFirst]

Quote

On 11/10/2022 at 2:44 PM, Cobie Fair said:

To somewhat over-simplify, the surface looked at closely is quite rough, with small ridges and dips.  A cold tire "skates" over the top of the ridges, and doesn't push into the dips.  

As described by Cobie above, this process of a tire's rubber meshing into the surface texture of the pavement is referred to as "micro-mechanical grip".  Tires also have "molecular grip" which exist within the chemical makeup of the rubber. Even on perfectly smooth driving surfaces, a tire's vulcanized rubber can still produce grip by being chemically "sticky".  Both concepts are important physics to how our motorcycle tires perform on track. 

[Jaybird180]

Not sure we we are in the discussion, but I'd like to address my perceived inability to feel the tire's traction.

 

 

[Cobie Fair]

JB,

Regarding being able to feel the traction: earlier in the thread we'd talked about the feeling of a cold tire and it feeling like it was not holding a line well, feeling like it was not positive and planted, skating even?  Have you ever noticed that when you have started on a ride, with cold tires?  

[Jaybird180]

Sorry if I'm rehashing, wasn't my intention. I should have had some coffee this morning, but I didn't.

No, I can't say that I have experienced that. Only time I felt a tire skate was riding in the wet at NJMP few years ago when they had sealer all over the place- I got discernible perturbations in the front end.  I might have shared the video of that highside with you and in retrospect I shouldn't have been on the track, there was standing water and streams in some places. Otherwise, I'm blank on the sensation of a skating tire, cold or wet. I don't ride below 60F and even then, I start off slow with gentle lean angles and work my way up. I don't generally have any prohibitions about riding in the wet, approaching it similarly to a cold day/surface. I think about 3 years ago, my last session at the school was after a thunderstorm at ViR and I pretty much had an empty track and it was great! I slowed my overall pace accordingly because I don't really have a sense for how fast can I go in the conditions.

[Cobie Fair]

OK, "skate" is the wrong word, too strong.  We aren't talking about sliding at all.

The concept we're going for is what does a tire feel like that is cold, how can one tell?  What does it feel like on those cooler rides you have done, what does the tire feel like at the beginning of the ride?  Either on a cool day at the track, or on the street.  How would you describe that?

Describe that in any way that makes sense to you, put it in your words.

[Hotfoot]

Not sure if you are specifically asking Jaybird, but for me, on slicks when they are VERY cold, I notice that the bike wants to 'stand up', resisting lean into the corners. I notice it most on longer corners, I tip the bike in and it seems to fight me and requires some pressure on the bars to keep the bike leaned over. That tells me the tires are REALLY cold, they are so stiff that the contact patch won't flatten at all and they sort of bounce back. This can also show up as a weird vibration in a straight line.

When they are getting warmer but not really gripping yet, I notice that the bike doesn't quite keep the line I wanted, I miss the apex I was aiming for, the steering feels vague and not confidence-inspiring.

On Q3s or Q4s I have never had that 'resisting the lean' feeling, but I have had the steering vagueness and noticed the bike won't quite hold the line I want. There is a temptation to lean it MORE when it won't hold its line, but that is analogous to turning the wheel on your car on a slick road, getting no response and turning it MORE, it's a bad idea! That feeling that I need to lean the bike MORE in the middle of a turn is a great indicator to me that my tires aren't warm enough to grip properly. 

 

[CoffeeFirst]

Hotfoot, I have experienced the "resisting lean / wanting to stand up" dynamic so understand your comment.  Can you expand on  "vagueness" and "won't quite hold a line"?  How are you defining vagueness?  Does the tire feel like it is sliding? Or is it just not warmed up enough to provide that nice bite on turn in when you execute fast quick turns?

[Avid Motorcyclist]

I am a Pirelli guy and Pirellis are quite hard when cold. Also when cold, I get warning chatter going into NJMP Thunderbolt T3A - the left chicane and first left on the track. I usually do 2 warmups laps and then the tires are ready. You do have to be mindful of the left side of the tire in colder temps.

[Cobie Fair]

Hotfoot, nice description of what it feels like.  This subject comes up often, I'm glad we are getting more descriptions of this.

[Hotfoot]

On 11/17/2022 at 11:57 AM, CoffeeFirst said:

Hotfoot, I have experienced the "resisting lean / wanting to stand up" dynamic so understand your comment.  Can you expand on  "vagueness" and "won't quite hold a line"?  How are you defining vagueness?  Does the tire feel like it is sliding? Or is it just not warmed up enough to provide that nice bite on turn in when you execute fast quick turns?

When I say "not quite holding a line", I mean that the bike doesn't go exactly where I expected it to, which typically means I miss my intended apex by a foot or so, that the bike just goes a bit wide. It's most noticeable to me on late apex corners, when I'm off the gas entering the corner and I just don't quite get the bike on my anticipated line, don't make it to the apex I wanted.

When I say "vagueness", that is a little hard to define but it is a step below what I listed above - I make a steering input but I don't get a positive certainty that the tire is holding and that the direction change is exactly what I expected. That is what I experience when I don't have a specific reference point to check against; if I DID have a specific point on my line and MISSED it, I would know exactly how much my line was off, but if I am in an area where I don't have an exact reference then I just get the idea that the bike isn't doing quite what I want but I can't measure it, so it is more of a vague impression.

I have experienced small cold tire slides where the front tire goes suddenly sideways a foot or so and every time it happens I figure I was damn lucky not to have crashed. If you are feeling actual slides on the front you are definitely in a red zone. It is much better to notice the smaller signs and not get to that point. I haven't experienced much in the way of cold-tire rear slides, partly because I am not inclined to throttle up hard if the tire doesn't feel strongly planted, and also because the traction control on the S1000rrs will intervene to help prevent that.

[Cobie Fair]

Hotfoot, nicely described.

Here's a look at the other end of this, when the tire is really nice and hot. 

I notice that I rarely get the tires all the way hot, unless I have a fast student.  Since we are mostly on used slicks, it can often take 2-3 laps of going at a good pace to get them hot.  When they are hot, and I turn in, I notice the bike takes a tighter line than before (same lean angle and turn-in).

Anyone experienced this?

 

[CoffeeFirst]

Hotfoot, I appreciate the additional clarity. Thank you.