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How Far Can a Motorcycle Lean in a Turn?
- geoelectric 11y agoEasy: all the way. Coming back up again is the tricky part.
- roflchoppa 11y agonah, just use the throttle to return upright.
- function_seven 11y agoI think the joke is that "all the way" is making full contact with the ground, i.e. crashing. Kinda like falling out of a skyscraper doesn't kill you. It's the sudden stop at the end that does. (But I'm not defending the joke :)
- donjigweed 11y agoNot that tricky if you're Marc Marquez... https://www.youtube.com/watch?v=CuQVKWizmJw https://www.youtube.com/watch?v=CuQVKWizmJw
- confiscate 11y agoI think this largely depends on the tire's "side surface" as well. For instance, my motorcycle's tires are not race tires, but street tires. The bottom of the tire only goes up the "side" for a limited distance. If I lean too far the side of my tire no longer touches the ground Also, the lean angle would have to be related to the foot peg size. My current foot peg is quite long--even for mild lean angles somestimes I can feel the road scratching on my boots and the foot peg.
- agumonkey 11y agoHa foot peg. No need for a motorcycle to enjoy them. A steep downhill lane with a large roundabout. A young self not willing to brake on his mountain bike. The pegs only kissed the ground a split second, enough for me to die a little inside while my rear tire lost contact.
- jason_slack 11y agoI think this really depends upon the type of tire you have as well as the riders ability. Take Moto GP for instance, they lean a lot more (by training, lack of fear and other factors) than a street rider would. Part of this is tires. They use tires that are more rounded and don't really have a noticeable sidewall. I have Michelin Pilot 3's on my bike and I feel safer leaning more with then the stock tires that were on the bike. As a side note, my bike is more upright than most, so this has a lot to do with my ability to lean. I feel very comfortable leaning farther on a bike where I am not already leaning really far forward to begin with. Note: I have a 2012 Triumph Street Triple. My wife has a 2012 Triumph Daytona Ultra sport. Mine is more upright, hers is a significant forward lean.
- TrevorJ 11y agoIt's also a lot safer on the track: the pavement conditions are known and lowsiding doesn't put you into a guardrail that will cut you off at the knees.
- jason_slack 11y agoYou make a good point that I didn't think of. Tracks are safer, despite the higher speeds, I think. I never took my bike to the track. I always wanted to but never wanted to wreck it.
- lnanek2 11y agoI don't see anywhere in his calculations where he takes into account that the more you lean the larger the tire surface against the ground gets. Motorcycle tires are actually intentionally designed for this nowadays.
- aidenn0 11y agoThe classic coefficient of friction you learn in freshman physics is independent of surface area; the larger the surface area, the lower the pressure, so it evens out. With sticky materials though, this doesn't hold.
- lqdc13 11y agoI thought it was that the highest point of friction can occur anywhere in the contact patch. So the higher the contact area, the higher the probability of having highest friction.
- newman314 11y agoHence, area of contact patch will make a difference.
- aidenn0 11y agoBut TFA did not ever use a single model from physics where it would make a difference.
- akcreek 11y agoMany racers, including the referenced GP crowd use 16.5" wheels instead of the more standard OE 17" since you can mount a wider/taller tire. That profile allows increased lean angle due to better grip from the additional surface area of the tire contacting the track surface.
- aidenn0 11y agoThis neglects to mention aerodynamic downforce; does anyone know if that plays in at all for motorcycles (it certainly does for race cars).
- rudedogg 11y agoI know they do use the "draft" technique you see in Nascar to pass on straights, but it's used to a lesser extent. Most passes happen in the turns due to differences in how the riders brake.
- ablation 11y agoSome manufacturers are experimenting with added downforce with the addition of winglets. See Ducati's example here: http://www.bikesportnews.com/uploads/news_images/_G104079%281%29.jpg http://www.bikesportnews.com/uploads/news_images/_G104079%28...
- abakker 11y agoI'm not sure if this matters, but with the aggressive profile of motorcycle tires, I assume the effective diameter of tire changing might matter. The effective diameter at 90° is maybe 26 inches (guessing). Leaned heavily into a turn though, the diameter might be substantially less, say 18". I am not a physics person, but it would seem that the change in diameter that corresponds with the change in angle might change the effective CoG. Can anyone tell me if this is correct?
- dahart 11y agoI read hoping to see some analysis of counter-steering, for the benefit of one or two people I know who shall remain nameless and don't believe counter-steering exists, because of course, they've never actually ridden a motorcycle. Went looking just now and found better explanations online than the last time I tried, years ago, but I have yet to see a satisfactory analysis of the physics. Many of the explanations claim that counter-steering is only done temporarily to begin a lean, only for "setting up" a turn, and then switches to normal steering. After a lot of experimentation, I'm pretty convinced counter-steering is actually always happening on a bike, but relative to the turning radius of your lean, not relative to straight, which makes it a little subtle and harder to demonstrate. If anyone knows where a solid analysis of the physics is, I'd love to see it!
- function_seven 11y agoHa. I don't know why but I've recently become involved in a couple of arguments regarding counter-steering (check comment history :) ). It's the new Monty Hall puzzle. Or "does 0.999... === 1?"
- dahart 11y agoYeah, he was confused and skeptical. A lot of people are, and that's okay because it is unintuitive. I don't bother trying to convince non-riders generally, but I might suggest if they want to argue with me they must first take the MSF course and attempt a few sharp turns before I will bother to engage. :)
- YZF 11y agoYou can also counter-steer a bicycle (at speed)... Also at least the gyroscopic component of it can be felt simply by trying to turn a spinning wheel held in your hands... Something I've seen in a few science museums... I guess the difference with a motorcycle is that it simply can't be steered effectively any other way at speed... So you're not going to find any biker who says this doesn't work ;)
- joeyspn 11y ago> I guess racing motorcycle tires are just awesome This is essentially the biggest factor. And more important than the surface is the material. When properly warmed (notice how they always prewarm the tires in bags before any race) that stuff is basically chewing-gum. I've worked in F1 and several circuits including the one featured in the article (Jerez) and I remember the walls in the paddock totally splattered of tire material at the end of the day. Some days I'd even go back to home with small pieces stuck in my clothing. That's the reason why engineers must wear glasses and helmets sometimes.. https://dfp2hfrf3mn0u.cloudfront.net/879/87936_1.jpg https://dfp2hfrf3mn0u.cloudfront.net/879/87936_1.jpg
- donjigweed 11y agoExactly. Tire technology is unbelievable today. With track temps reaching 50C, the tires are practically molten rubber during the race. This was Rabat's rain tire after finishing 2nd last weekend on a track that was mostly dry by the end of the race. https://pbs.twimg.com/media/CNpxNYdWIAAdD6s.jpg:large https://pbs.twimg.com/media/CNpxNYdWIAAdD6s.jpg:large
- newman314 11y agoThe surface does matter or more specifically, the suspension. If the suspension is not properly set up for compression and rebound, guess what? Materials mean nothing if the tire is not in contact with the ground. And there are some bumpy tracks out there...
- donjigweed 11y agoSuspension has seen less advancement than tires imo. And the greater the lean angle the less the suspension is actually working. If the bike could lean to 90 degrees the suspension would not work at all. This is why motorcycle handling is still something of a black art rather than pure science, because at full lean much of the "suspension" comes from frame, fork, and swingarm flex, rather than actual damping.
- 11y ago
- thecrumb 11y agoThe author also fails to mention a few things... Bikes slide while leaned over and electronic traction control. How far could you lean one of these bikes over without the computer helping? :)
- anigbrowl 11y agoI used to ride an old bike with no electronics (a Honda 400/four). It does drift but you can feel that and control it with countersteering in good weather conditions (in bad weather conditions I would cut speed significantly or just not ride). You can still lean an all-mechanical bike with ordinary tires quite a ways. When I would be turning through very long curves on freeways and so I would get back fatigue from the fake force (the one that's trying to make the bike stand up vertically again), requiring me to sit on the upper side of the bike to keep it leaned over with less effort. I have a very slim build so this is a trick that might not be familiar to most male riders.
- bigiain 11y agoThey used to lean the old 500cc two stokes over pretty much that far - and those had no computers at all on them with a carbureted 200hp screamer engine actively trying to throw the rider over the moon at every opportunity. And they certainly leaned those over: https://www.pinterest.com/pin/495607133966697834/ https://www.pinterest.com/pin/495607133966697834/
- deleted 11y ago[deleted]
- lutorm 11y agoThe calculation applies to the angle between the contact patch and the center of mass. However, since the tire has some radius to it, and the rider typically is not centered over the bike, that angle is not the same as the bike's lean angle. So that may account for some of the discrepancy between the "60 degree" mu and that coming from the radius of curvature calculation.
- bigiain 11y agoThere's two complications to that, one against our favour and one in our favour (assuming we're trying to rationalise a Cf of 1.7 being erroneously high). The rider leans off the bike to the inside of the turn, and since the rider weighs ~30-40% of the bike+rider mass, this moves the center of mass quite a long way to an even higher angle than the lean angle sensors on the bikes frame indicate - the rider moving makes the discrepancy worse not better. The left/right curvature of the tires (mostly that big fat ~200mm wide rear one) means that the location of the contact patch between the tire and the road also moves towards the inside of the curve. This means the frame lean angle sensor is over-reporting the angle somewhat. This moves the discrepancy back the other way. Another thing to consider though. Nobody assumes the rule of thumb that "the coefficient of friction is always between zero and one" applies to sticky tape (which it quite obviously doesn't), but a hot motorcycle racing slick has that same tacky stickiness to it that duct tape does. Look at any bike that runs into the gravel traps. It's tires come out _covered_ in gravel that's quite clearly stuck to them at a coefficient of friction greater than 1. It's perhaps non-obvious, but it shouldn't be too much of a surprise that tire "stick" like that to the track surface as well as the gravel on the runoff areas...
- rdc12 11y agoAnd I assume that when a rider runs off line onto the marbles [1] they stick to the tire as well, which reduces the ammount of sticky tire in contact with the track. They are also probably unstable compared to the tire. [1] Little pieces of discarded rubber
- lutorm 11y agoYeah, I've done a lot of physics and I've never heard the rule of thumb that "coefficient of friction must be between 0 and 1." There is no such requirement anywhere.
- latchkey 11y agoLove this animated gif where the guy touches his helmet on the ground around a corner on the track... http://www.gifbin.com/bin/072011/1311056598_biker_touches_ground_with_head_during_turn.gif http://www.gifbin.com/bin/072011/1311056598_biker_touches_gr...
- mirimir 11y agoBetter yet is racing on ice, with spiked tires :) It works for bicycles too!
- gpsx 11y agoI haven't thought about motorcycles or rotating bodies in a while so I am afraid to say this, but I think there is a missing force in that diagram. As the motorcycle sweeps through the turn, the angular momentum of the tires is changing directions. This tries to push the bike up, the same way counter steering tilts the bike opposite the direction you turn. If this is true, the lean needs to to compensate both the "fake" force (acceleration) and the change in angular momentum of the wheels as direction of the bike changes.