Lean angle, chicken strips and tire pressure - BMW S1000RR Forums: BMW Sportbike Forum
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post #1 of 24 (permalink) Old 08-15-2019, 02:42 PM Thread Starter
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Lean angle, chicken strips and tire pressure

My brand new 2020 RR is the first bike Iíve had with a lean angle sensor/display. Iím wondering about the relationship between the displayed (actual) max lean angle, rear chicken strips, and tire pressure. Iíve only had my bike just over a week and 400 miles, all on the street. I donít even have my first service and rev unlock yet. But with everything new, I see about a half-inch rear chicken strip (I donít take it near the limit on the street) and have a fairly symmetrical max lean angle of about 43-51 degrees most rides where I hit some good curves. Leans over 40 degrees also constitute a minuscule amount of my street riding time.

Iím running stock tire pressures (near 36/42 psi) on the street, though am tempted to lower them (especially the rear) fairly substantially so they are closer to what I would run on the track. Reducing tire pressure would expand the contact patch and help absorb bumps when leaned. I would think that at a given lean angle, a lower pressure would also eat into the chicken strip. I donít care about chicken strips except as a metric to better understand tire dynamics. I also understand there are many other variables such as tire type and body size and position (good hang off reduces lean at a given lateral acceleration).

Iím hoping to get some knowledge from those far more experienced. What can you tell me about the dynamics, tradeoffs, and anything else important here? What pressures would you recommend for fairly typical sport street riding with the stock tires?
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post #2 of 24 (permalink) Old 08-15-2019, 03:21 PM
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On my Power RS tires I run 34F and 32Rear.

Lowering the pressures on the rear will make the tire squat more increasing the contact patch causing more grip. You'll need to crank those tires over past 55 degrees to totally nuke the chicken strips. I don't advise doing this on the road re: potholes, deer, etc etc
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post #3 of 24 (permalink) Old 08-15-2019, 03:22 PM
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Originally Posted by Tom Bernhardt View Post
My brand new 2020 RR is the first bike Iíve had with a lean angle sensor/display. Iím wondering about the relationship between the displayed (actual) max lean angle, rear chicken strips, and tire pressure. Iíve only had my bike just over a week and 400 miles, all on the street. I donít even have my first service and rev unlock yet. But with everything new, I see about a half-inch rear chicken strip (I donít take it near the limit on the street) and have a fairly symmetrical max lean angle of about 43-51 degrees most rides where I hit some good curves. Leans over 40 degrees also constitute a minuscule amount of my street riding time.

Iím running stock tire pressures (near 36/42 psi) on the street, though am tempted to lower them (especially the rear) fairly substantially so they are closer to what I would run on the track. Reducing tire pressure would expand the contact patch and help absorb bumps when leaned. I would think that at a given lean angle, a lower pressure would also eat into the chicken strip. I donít care about chicken strips except as a metric to better understand tire dynamics. I also understand there are many other variables such as tire type and body size and position (good hang off reduces lean at a given lateral acceleration).

Iím hoping to get some knowledge from those far more experienced. What can you tell me about the dynamics, tradeoffs, and anything else important here? What pressures would you recommend for fairly typical sport street riding with the stock tires?
33F 33R is a good starting point
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post #4 of 24 (permalink) Old 08-15-2019, 03:43 PM Thread Starter
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Originally Posted by simes007us View Post
On my Power RS tires I run 34F and 32Rear.

Lowering the pressures on the rear will make the tire squat more increasing the contact patch causing more grip. You'll need to crank those tires over past 55 degrees to totally nuke the chicken strips. I don't advise doing this on the road re: potholes, deer, etc etc
Thanks. I need a bit of chicken strip as evidence to my disbelieving family and friends that I have a bit of remaining sanity.

I will only hit 55 degrees if I really screw up and go into a corner too hot. I'm hoping not to see 90 degrees.

I'll start by going to 34/34 and see how it feels. Should there be a significant difference?
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post #5 of 24 (permalink) Old 08-15-2019, 03:47 PM Thread Starter
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33F 33R is a good starting point
Thanks. I just set them to 34/34 to start with, but it's a Texas afternoon (100F) and won't be able to test them out until the morning. Even then I wear my airflow tour-riding gear instead of my track gear. That won't come back on until Oct.
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post #6 of 24 (permalink) Old 08-15-2019, 04:09 PM
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Also please try to understand that the lean angle you see it may not be the actual lean angle. There is always the camper of the turn to be calculated.
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post #7 of 24 (permalink) Old 08-15-2019, 04:36 PM Thread Starter
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Also please try to understand that the lean angle you see it may not be the actual lean angle. There is always the camper of the turn to be calculated.
Good point. It represents the lean angle relative to the horizon perpendicular, not the road perpendicular.
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post #8 of 24 (permalink) Old 08-15-2019, 05:01 PM
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PSIs depend on rider's weight, ambient temps and style of riding. And no one cares about chicken strips if riding on the street.

If you're over 200lbs with gear, running stock 42/36 is fine R/F. Can reduce it a bit if it's cold out.
I'm 180lbs with gear, run 37/33 most of the time on the street. Running track PSIs on street tires or on street is stupid and asking for trouble.

Tire profile makes a big difference on chicken strips. 180/60 VS 200/55 Vs 200/60. Focus on what keeps you safe and confident in the turns.

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post #9 of 24 (permalink) Old 08-15-2019, 05:27 PM Thread Starter
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PSIs depend on rider's weight, ambient temps and style of riding. And no one cares about chicken strips if riding on the street.
Totally agree. I was just using it as a metric, not a goal. I'm very happy having chicken strips. I focus on technique, position, lines, balance, rhythm, relaxation, etc. when on the street and generally keep it within 70%. There's way too much downside to being overly aggressive.

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If you're over 200lbs with gear, running stock 42/36 is fine R/F. Can reduce it a bit if it's cold out.
I'm 180lbs with gear, run 37/33 most of the time on the street. Running track PSIs on street tires or on street is stupid and asking for trouble.
I'm 6'2" and 210 naked, so I'm at the upper end in size.

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Tire profile makes a big difference on chicken strips. 180/60 VS 200/55 Vs 200/60. Focus on what keeps you safe and confident in the turns.
The profile makes a huge difference obviously. The front has a much larger strip due to its near straight-down section to the bead.
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post #10 of 24 (permalink) Old 08-15-2019, 05:31 PM
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Excellent post, z00.
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