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Old September 25th, 2018, 07:40 AM   #1
dat-tomato
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Name: Phiipp
Location: Rocky Mountains
Join Date: Sep 2018

Motorcycle(s): Ninja 250R

Posts: 4
Tire Wear Help

Posted this on Reddit without much response. Need help reading the wear on my tires. This is on a big, 250CC monster of a bike at Colorado's High Plains Raceway, running at a podium contending pace in the 250 production class (there's only like 5 other bikes though...).

Done a lot of learning via suspension and tire resources (eg. Dave Moss and Life at Lean), but a lot of that deals with bikes that actually have power to work the rear tire accelerating out of turns and weight to work the front tire during braking.

2009 Ninja 250 with:
  • Front springs set to about 5-10 lbs over my current weight, sag is perfect at 30mm
  • Front damping - Racetech Emulators
  • Rear springs set to about 5-10 lbs over my current weight, sag is perfect at 30mm, no free sag though
  • Rear damping - stock oem shock

Tires:
  • Front: Pirelli SC1 - 110 / 70
  • Rear: Pirelli SC2 - 140 / 70

Front suspension related wear I'll attempt to tune during the off season (looks like I need a bit less rebound with the lip on the leading edge), can't do the rear without upgrading (but seems I need a teeny bit more rebound due to lip on trailing edge). Ignoring suspension related wear, I'm looking for help on pressure related wear.

Off warmers (180F front, 190F rear), I set my tires to 30psi front and 26psi rear which is on the low-side of the recommended Pirelli range for SCs. After a session with track temps about 110F, my tire temps drop to 130F front and 150F rear, pressures remain the same. I set pressures low because it seems like I can't keep my tires hot during a session (158-176°F is Pirelli website's displayed optimum temp range).

I'm not getting the perfect "sandy beach" wear and because my 250 doesn't have power, I can't really tell if I'm hot tearing.

Help!

https://imgur.com/a/CWybtsm
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Old September 25th, 2018, 06:08 PM   #2
csmith12
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Name: Chris (aka Reactor)
Location: Northern KY
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Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track)

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Welcome Phiipp!

My gut feeling says to put 1 more lb of pressure in em, but that is wish/wash at best.

Overall, your bike can be perfect and your throttle control can cause the tire ware you are seeing. Ride it again and see if you see the same thing. Imho, your wear looks 100% normal and well set for podium contention.

Always suspect the rider FIRST! And these tires last an entire season on a well set up bike and.... different tracks/weather conditions/rider aggressiveness will show at the end of the day.

Good luck! Go fast!

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Old September 25th, 2018, 09:05 PM   #3
dat-tomato
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Name: Phiipp
Location: Rocky Mountains
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Motorcycle(s): Ninja 250R

Posts: 4
Quote:
Originally Posted by csmith12 View Post
And these tires last an entire season on a well set up bike...
I hope to make this a reality! I like data, so I've been logging stuff religiously in hopes to use it in the future.
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Old September 25th, 2018, 10:44 PM   #4
DannoXYZ
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I say lay off the brakes!!

They do nothing but wear out your tyres and give you slower lap-times! One of my friend's front brake-lever fell off his bike at beginning of A-group session at Buttonwillow couple weekends ago. He managed to get fastest times ever! We later found brake lever in belly-pan and put it back on. Guess what? His times increased back to earlier levels!
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Old September 26th, 2018, 08:44 AM   #5
dat-tomato
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Name: Phiipp
Location: Rocky Mountains
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Motorcycle(s): Ninja 250R

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Quote:
Originally Posted by DannoXYZ View Post
I say lay off the brakes!!
Very true! I only lightly (trail)brake on the 2 slowest corners, more so to load the front and help me steer.

The 250 slows down enough purely from cornering!
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Old September 26th, 2018, 09:55 AM   #6
tgold
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Personally I don't see anything wrong with your tires. The rubber is not "tearing" at all. What you see me is simply small rolls of melted rubber. The surface of the rubber beneath that is actually pretty smooth. I'd be pretty happy with my tires looking like that.
If you want meaningful tire temperatures then they need to be done in real time. Otherwise, the cool-off lap and the rest of the time you take getting back to your pits will have a huge effect on temps causing them to be lower than they actually were on track at race pace. Think of the opposite effect: The rule of thumb for warming up cold tires is two laps of progressively stressing your tires to get them to come up to race temps so why wouldn't we expect the tires to shed a significant amount of heat as we slow down?
Just a thought.
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Old September 26th, 2018, 12:27 PM   #7
dat-tomato
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Name: Phiipp
Location: Rocky Mountains
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Motorcycle(s): Ninja 250R

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Quote:
Originally Posted by tgold View Post
Otherwise, the cool-off lap and the rest of the time you take getting back to your pits will have a huge effect on temps causing them to be lower than they actually were on track at race pace. Think of the opposite effect: The rule of thumb for warming up cold tires is two laps of progressively stressing your tires to get them to come up to race temps so why wouldn't we expect the tires to shed a significant amount of heat as we slow down?
You're probably right. I try to rush back to my pit, but of course slow speeds in the cold pits, so I probably lose a lot of heat.

Next round out, I'll have someone measure my tires from the hot pit.

Quote:
Originally Posted by csmith12 View Post
My gut feeling says to put 1 more lb of pressure in em, but that is wish/wash at best.
My gut feel is to try this out next time out. If I see some different wear, another data point for me to understand.
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