Street Riding Lean Angles (according to iPhone) | GTAMotorcycle.com

Street Riding Lean Angles (according to iPhone)

Sochi

Sochi

Well-known member
Forum Sponsor
I use Calimoto on iPhone and it gave me this report after last ride. It shows 41 percent lean angle - usually my max (according to this app) is in 35-40 range. I don’t hang off the bike much on street so all tire is used edge to edge (have no “unused” stripe lol).
How accurate do you think this measurement of lean angle by iPhone? What do you think a real max lean angles on the street is? Just currious, that’s it.
 
Last edited:
My track laptimer app offers a similar feature. It's calculating an approximate lean angle based on the speed and radius of the curve, but it's not highly reliable, mainly because of the GPS update rate.

Do you have a GPS booster, or are you relying on the built-in GPS from the iPhone? Most phones have a 1hz GPS update, which is very poor for stuff like this. A GPS booster will give you an update rate of 10hz or more which is a lot better. But even at 10hz with a Garmin GLO I can see that the raw data is very noisy, so any extrapolated peak lean angles are an educated guess at best.
 
Makes sense, I’ll look into GPS boosters now, I don’t have one but see if I can get one :)
 
Wouldn't a phone be able to calculate actual lean angle from accelerometer data?
 
TwistedKestrel said:
Wouldn't a phone be able to calculate actual lean angle from accelerometer data?
Click to expand...
A solid maybe? It would be simpler if phone was in a known orientation (eg parallel to ground) but that can be solved with math (either zero out when stationary or just always work with resultant and ignore components). G forces affect the accelerometer to so it would need to remove the effect of speed to get angle, it couldn't see it directly. Basically it acts like the turn coordination ball in a plane. Unless something is going wrong, the vector will be from the phone to the contact patch. It will obviously be longer as you pull more g's but there is no angle component to it. Without gps, a compression would look a lot like a turn in the accelerometer data. If the phone can see angle to the centre of the earth that means your tires are no longer resisting the cornering force and you are flying straight out of the corner.
 
Last edited:
TK4 said:
Just see how wide the chicken strips are when you're done. :cool:
Click to expand...
I'm a little surprised some tire manufacturer hasn't done this. Cut lean angles into the tread pattern. Not entirely accurate due to rim width or tire pressure and it measures bike angle not bike plus rider angle but it would cost nothing and I could see some people caring. Although the people that care are also likely the people that can't reach the limit and wouldn't want it to be so obvious that they are full of crap.
 
For what it's worth, here's turn 2 at Shannonville using a 10Hz GPS booster. The blue line (speed) is fairly stable, but you can see that the extrapolated lean angle (pink line) is all over the place. The dip in the pink line during corner entry is around 30*, and the peak at apex is around 50*. The 30* dip is absolutely not accurate, and I don't trust the 50* much either; the truth is somewhere in between.

You can see the GPS update rate (yellow) line also wavers quite a bit. Despite the booster being 10Hz, the real update rate often drops way lower than that. In this screencap it varies between 5.0Hz and 7.0Hz, and that's with the booster being mounted in my suit hump. If you're relying on a 1Hz phone that's buried in your chest pocket the data will be way less reliable. It's still fun to look at, but take it with a big grain of salt.
 

Attachments

  • lean_angle1.png
    lean_angle1.png
    979.1 KB · Views: 29
Ash said:
For what it's worth, here's turn 2 at Shannonville using a 10Hz GPS booster. The blue line (speed) is fairly stable, but you can see that the extrapolated lean angle (pink line) is all over the place. The dip in the pink line during corner entry is around 30*, and the peak at apex is around 50*. The 30* dip is absolutely not accurate, and I don't trust the 50* much either; the truth is somewhere in between.

You can see the GPS update rate (yellow) line also wavers quite a bit. Despite the booster being 10Hz, the real update rate often drops way lower than that. In this screencap it varies between 5.0Hz and 7.0Hz, and that's with the booster being mounted in my suit hump. If you're relying on a 1Hz phone that's buried in your chest pocket the data will be way less reliable. It's still fun to look at, but take it with a big grain of salt.
Click to expand...
If someone really cared, A laser dot out the bar end with a rear mounted camera facing forward and some software or a laser distance meter from somewhere similar (on the side of the triple tree?) could give accurate lean angle relative to road. Make a lookup table that converts distance from dot to bike or distance from tree to road into angle. Would be spectacularly wrong if road wasn't even (eg if sensor passed over curb) but for most riders, most of the time it should be reasonable. Obviously doesn't work at minimal lean angles as distance is too far. Seems like more trouble than it's worth. Just look at your tires and see if there is more.
 
I have a level/protractor app on my iPhone that works off the accelerometer. I’ve checked it’s accuracy against a sine bar and it’s pretty much bang on. The only skew I could see from using it on a bike would be you’d actually be measuring compound angles, factoring in the rise of the road surface (uphill/downhill angles).
 
Some proper sport/race bikes now have built-in lean angle telemetry straight from the factory. I think they use fancy gyroscope+accelerometer systems.

For us cheapskates, an action camera mounted somewhere low and facing forwards, like on the swingarm, can be handy. Harder to use for bragging purposes though, especially if your knee is hanging out in the breeze 8 inches above the pavement. But at least it does show if you're dangerously close to running out of ground clearance.

I guess you could also just install super long hero blob bolts onto your footpegs, like the curb feeler things that they used to have on huge 1950's cars. 😛
 
FullMotoJacket said:
I have a level/protractor app on my iPhone that works off the accelerometer. I’ve checked it’s accuracy against a sine bar and it’s pretty much bang on. The only skew I could see from using it on a bike would be you’d actually be measuring compound angles, factoring in the rise of the road surface
Click to expand...
It's works fine static. Spin it in a circle and see what it says. It won't tell you the angle of the phone relative to a surface plane, angle will be relative to the arm/string holding it.
 
  • Like
Reactions: Ash
Ash said:
Some proper sport/race bikes now have built-in lean angle telemetry straight from the factory. I think they use fancy gyroscope+accelerometer systems.

For us cheapskates, an action camera mounted somewhere low and facing forwards, like on the swingarm, can be handy. Harder to use for bragging purposes though, especially if your knee is hanging out in the breeze 8 inches above the pavement. But at least it does show if you're dangerously close to running out of ground clearance.

I guess you could also just install super long hero blob bolts onto your footpegs, like the curb feeler things that they used to have on huge 1950's cars. 😛
Click to expand...
Gyroscope works too as it gives you a reasonably fixed ground plane reference. I don't know of any phones with a built in gyro though. Pretty power hungry device.
 
i thought every phone had a gyro to decide which orientation you're holding it.

OP: You say the thing says you are leaning at 41 percent.
41 percent of WHAT?
 
bitzz said:
i thought every phone had a gyro to decide which orientation you're holding it.

OP: You say the thing says you are leaning at 41 percent.
41 percent of WHAT?
Click to expand...
Accelerometer can determine orientation if phone is static. Gravity provides a constant pull down. Rotate the phone a time or two and it can figure out which way is down.
 
For fun, here's some raw accelerometer and gyroscope data from my phone. When I first starting using the laptimer app I turned all the options on to see what they did, but the raw phone data is so noisy as to be useless. A better smoothing algorithm would help, but even so, very few people are going to be interested in this sort of thing.

In this screencap, the pink line is the extrapolated lean angle. The blue line is one of the 3 gyroscope rotational channels (eg: X/Y/Z rotational axes) and the yellow line is one of the 3 accelerometer channels (eg, one of the X/Y/Z axes).
 

Attachments

  • raw_phone_data1.png
    raw_phone_data1.png
    1 MB · Views: 15
Ash said:
For fun, here's some raw accelerometer and gyroscope data from my phone. When I first starting using the laptimer app I turned all the options on to see what they did, but the raw phone data is so noisy as to be useless. A better smoothing algorithm would help, but even so, very few people are going to be interested in this sort of thing.

In this screencap, the pink line is the extrapolated lean angle. The blue line is one of the 3 gyroscope rotational channels (eg: X/Y/Z rotational axes) and the yellow line is one of the 3 accelerometer channels (eg, one of the X/Y/Z axes).
Click to expand...
As mentioned, Checking the angle to the ground would require the other forces to be zeroed out. This includes the momentum trying to keep the bike going straight (sideways from bike perspective) (red line) and brakeing /acceleration (blue line). Nice acceleration coming out of the corner.
Forum Sponsor
 
You must log in or register to reply here.

Back
Top Bottom