What am I doing wrong with my tires - BMW S1000RR Forums: BMW Sportbike Forum
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post #1 of 32 (permalink) Old 08-25-2018, 05:32 PM Thread Starter
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What am I doing wrong with my tires

Guys,

Please, help me to understand what am I doing wrong with my tires to cause the cold tear damage (see pictures below).

Tire in question is Pirelli Diablo Supercorsa SP V2 200/55-17, it has only seen 2 track days. I don't have tire warmers and run 1.5-2 laps at a slower pace to warm the tires up.

Yesterday the track (the Ridge if it makes any difference) was cold all day and it seems that I didn't warm the tire enough before going my regular speed, which is not that fast. I started at the 26 psi cold and reduced the pressure a few times during the day by a couple of pounds. By the last session of the day it felt like I didn't have any grip on the corner exits, rear would slide and step out when I rolled on the throttle.

This is the 3rd rear supercorsa I'm using this season, first 2 had also shown some signs of cold tear but it would smooth out after I reduced the psi. I was able to do 3 track days on my previous tire and it still had some life left in it, this one is a goner after only 2 days.

Any ideas on what can cause this?



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post #2 of 32 (permalink) Old 08-25-2018, 06:01 PM
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Looks like cold tear.
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post #3 of 32 (permalink) Old 08-25-2018, 06:08 PM
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Are you sure that's cold tear? It was my understanding that cold tear is from over inflation and that the "tearing" is in small fingernail size tears in the tire. Those long tears in the tire look more like what I've seen described as hot tearing from running too low pressure and over heating the tires. I know it sounds crazy that too hot or too cold can produce something so similar in the tires but the pressures you're running sound too low to me. I run my Q3 tires at 30/32 and they look like this after a track session:

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post #4 of 32 (permalink) Old 08-25-2018, 06:26 PM Thread Starter
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Originally Posted by PittsDriver View Post
Are you sure that's cold tear?

Actually I'm not, but I've asked around at the track, local WMRRA racers and the tire guy were thinking it is. Also I reduced the air pressure as per their advise. I guess I've eventually set it too low since the loss of grip at the end of the day felt pretty similar to a flat tire.
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post #5 of 32 (permalink) Old 08-25-2018, 07:25 PM
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Quote:
Originally Posted by PittsDriver View Post
Are you sure that's cold tear? It was my understanding that cold tear is from over inflation and that the "tearing" is in small fingernail size tears in the tire. Those long tears in the tire look more like what I've seen described as hot tearing from running too low pressure and over heating the tires. I know it sounds crazy that too hot or too cold can produce something so similar in the tires but the pressures you're running sound too low to me. I run my Q3 tires at 30/32 and they look like this after a track session:

You're right. I didn't look at the pressure the OP had.
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post #6 of 32 (permalink) Old 08-25-2018, 08:33 PM
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I think you're on the right track. Am I correct to think that Pirelli uses two compounds on that tire? The side of the tire looks like it was too soft for ambient temps, with the high inflation pressures centering the heat in one small area and tearing off the surface rubber. This would be great for a street application, as it would never get as hot as the track, but as you found out, not so good for cooler track temps. If you start out at a lower pressure, it would have a better chance of spreading the heat and warming the carcass.

Are you faster than you were with the first tire? That could be making a difference too.

Not to knock Pirellis, but I've always found that Dunlop Q3 (and now the Q3+) are much more tolerant of cooler temps and warm up quicker if you're not using warmers. I went back and forth between the two quite a few times. Having said that, what does Pirelli recommend for track pressures for the SPV2? Maybe start over with a fresh tire and try again.

That tire would really impress the guys at Starbucks, so don't toss it yet.
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post #7 of 32 (permalink) Old 08-25-2018, 09:15 PM
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Quote:
Originally Posted by skapan View Post
I think you're on the right track. Am I correct to think that Pirelli uses two compounds on that tire? The side of the tire looks like it was too soft for ambient temps, with the high inflation pressures centering the heat in one small area and tearing off the surface rubber. This would be great for a street application, as it would never get as hot as the track, but as you found out, not so good for cooler track temps. If you start out at a lower pressure, it would have a better chance of spreading the heat and warming the carcass.

Are you faster than you were with the first tire? That could be making a difference too.

Not to knock Pirellis, but I've always found that Dunlop Q3 (and now the Q3+) are much more tolerant of cooler temps and warm up quicker if you're not using warmers. I went back and forth between the two quite a few times. Having said that, what does Pirelli recommend for track pressures for the SPV2? Maybe start over with a fresh tire and try again.

That tire would really impress the guys at Starbucks, so don't toss it yet.
Best bet would be to use SC2 rear in cooler track surface temps—harder carcass and lower pressure allows tire to heat up correctly. SPv2 is def'ly too soft compared to the Q3/+.
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post #8 of 32 (permalink) Old 08-25-2018, 09:39 PM
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I think you're mixing them up, unless I have it totally wrong. The SPV2 is a street tire, available only in one compound, but it does look like it's softer on the sides with a harder compound down the center. For the S1000RR the Supercorsa SC2 would be a better choice when it's colder, but those tires really should have warmers. And I think there's an SPV3 out now, again a street tire but I don't know anything about those.

Last edited by skapan; 08-25-2018 at 09:43 PM.
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post #9 of 32 (permalink) Old 08-26-2018, 01:06 AM Thread Starter
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Originally Posted by skapan View Post
Am I correct to think that Pirelli uses two compounds on that tire?
Yes, SC2s are 2 compound tires, softer on the sides and are advertised as track tires that can be also used on the street. I switched to SC2s from Metzeler K3 and with K3s I never had this cold tear problem. Also I was getting K3 rears on the markers in 2 days, with SC2 I hoped I could do at least 3 days on a tire. Also K3s were 190 and SC2s are 200.

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Are you faster than you were with the first tire?
No, I'm not, my pace is more or less the same, I'm cruising at 1:55-1:56 at the Ridge, which is not that fast, but good enough to run in the fast group.

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what does Pirelli recommend for track pressures for the SPV2?
This is something I'm still trying to figure out, the charts I saw showing 21 psi cold and 25 psi off the warmers which seem too low. Also I'm not using warmers which makes this even more confusing.

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Originally Posted by skapan View Post
Maybe start over with a fresh tire and try again
yeah, I've ordered a fresh SC2 rear already. The interesting part is that the front tire can still take another track day, and this going to be the 5th one for it. With K3s fronts were on the markers in 2-3 days.
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post #10 of 32 (permalink) Old 08-26-2018, 01:47 AM
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