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my thoughts on braking and turning

Posted March 12th, 2014 at 07:12 PM by alex.s

on these bikes, the actual amount of gas or brakes doesn't really matter (unless you have terrible suspension or tires). it's how you get to that point that matters, and how you get out of that point. you can go full brakes while you are all the way down on a well tuned fork and good tires... IF you do it smooth enough. not that you would ever want to do that unless you were trying to avoid someone crashing in front of you while you were already trailing it in. even then it's questionable. but to know that the limits in your mind and even the actual limits of the bike aren't really hard limits and that you can glide around beyond those limits if you're careful... it is something that's hard to be comfortable with. but if you can push aside being scared of crashing and just focus on being smooth and correct, you can do some terrifying things. i know you know that sliding isn't a real issue, reacting poorly to a slide is the issue. continuing to be smooth with everything and continuing to correctly drive the bike usually ends with you setting up for the next turn. only when you doubt yourself and make mistakes and do incorrect things do incorrect results occur.

if you do things smooth enough and slow enough at first, you can feel as you increase things the feedback from the bars and the seat. for straight up and down braking, as you increase the brake pressure, you will feel the front of the bike go down. how fast you go determines how quickly it goes down right? so it's important to know how quickly you can bring it down. too fast and you bottom out and/or overload the front tire before it has good grip. too slow, and you're just wasting time. as you increase the brake pressure smoothly, the bars go down further and further, which feels like your butt is getting higher right? i personally find it hard to tell when i'm bottoming out so i use a zip tie on the forks to tell if i ever bottom out. usually when you bottom out, the front starts skipping. but it can skip without bottoming out.

there's kinda like two zones of sliding... skipping, and full sliding.. skipping the front straight up and down has a very unique feeling to it. the front gets very vague and vibrates slowly- think 10hz, or how it felt on the steering wheel when you had warped rotors and hit the brakes hard. that ****ed up vibration grinding undulating vagueness. sometimes the rear will start to skip around too which feels like the bars are doing a really tiny miniature tank slapper at around 1-3hz. its hard to feel the rear sliding through the seat when its a small slide but easy to feel it when it turns your bars. in the seat it feels a bit like the seat just dropped half an inch, which is much easier to feel if you are nice and relaxed. when you are straight up and down and the front is skipping you can simply smoothly decrease the braking pressure and the front hooks back up but do it slowly otherwise the front pogos up and its rough and can send the front off to the side unexpectedly. a full slide is a bit scarier and basically the bars go completely loose and the bars actually kinda feel like they move up toward your face. turning them to the side either direction makes the front shoot off in that direction and has usually results in a crash for me. if you keep the brakes on through the skips it will turn into a full slide eventually (a few seconds) . my reaction (not sure if its right) on a full slide is to dump the brakes in the hope that the pogo pushes the front back down and the loose tire catches again. its violent though when it does and the front typically snaps to one side or the other. but when its a full slide and the wheel is locked, maintaining any brakes will simply keep the front wheel locked. so if the front wheel is truly locked and you're in a full slide, just dump the brakes and hope for the best and expect the front end to snap back. (as loose as possible on the bars, good grip on the bike with your legs)

skipping the front while you are braking leaned over is the same, but happens quicker, and the bike feels like it's falling away from you which can cause you to make unwanted steering inputs if you don't have buffer space (bent elbows) having your chest against the tank helps a lot for keeping yourself from making mistake steering inputs when things start sliding. same with resting an elbow on the tank. remember to stay loose.

fully sliding the front while you are leaned over is actually really strange. it doesn't really do much and typically you don't feel it except for vagueness in the bars until you have been sliding for a few meters. the bike feels like its falling away from you but it's oddly stable until it starts falling (takes half a second or so). sliding the front without skipping first usually is a short event from a small spot of low grip and doesn't last long, or if its a lot of bad grip for a long time, (more than a couple seconds worth) than you can loose the front in a tuck.

if you let the skipping turn into sliding while you are leaned over, the bars turn in, the front tucks, the bike falls on your knee and you go sliding/rolling away.

okay. so that's the braking part. what about the turning part, right?

so what does turning actually do to the bike? we counter steer, the front of the bike goes in one direction, causing a rotational torque, sending the top of the bike leaning the opposite direction right? what happens to the tire when it has to change the direction of a 400lb rider and bike? it has to work more right? so turning the bars takes a bit of that classic pie, or a few cents of your dollar. does turning compress the forks? depending on the rake, yes and no. sport bikes do a little bit, but street bikes and cruisers and dirtbikes basically don't. how much traction can a dollar buy you? i think this is the real question. how do you determine "how much" traction the tire has anyway? you can take a tire and put it on the road, and push on it. you can feel how if you slowly apply pressure, the rubber deforms a bit, the contact patch becomes bigger... more force on the rubber means that it is being pushed into the ground harder... when you push a tire into the ground harder, it becomes harder to push it to the side. you can do the same thing and hit it instead of pushing smoothly and see how it skips and jumps over the pavement instead of gripping. likewise, even if its pushed in, if you hit it, it skips. so it seems like (perhaps obviously) the key to grip lies in the contact patch... the only thing that is actually touching the ground. when we smoothly push that contact patch into the ground, it gets nice and fat and grippy and you can do a whole lot more pushing on it. we've all heard it right? smooth smooth smooth, everything about smooth in smooth out smooth this smooth that. but this is the reason. it is because rubber has a damping rate and if you exceed the damping rate it bounces -> skips. but if you are smooth, you can put tons of force into it.

it all fits together into trail braking because being on the brakes is like a traction-sale. it buys you more front-wheel traction for your dollar because it is forcing the front wheel into the ground smoothly. traction you can spend on turning the bike slow and steadily while on the brakes. once you are over, you are no longer spending traction on changing lean angle; just corning and braking if you still need to brake. so from there you can either continue until you are ready to smoothly trail off the brakes or if emergency arises, you can smoothly go to full brakes trying to avoid the guy rolling down the track in front of you. a lot of people increase lean while decreasing brake (most people are finished trailing off by about 80% lean, past there you have to be extremely smooth changing the amounts) but as long as you are smooth you can increase lean without decreasing brakes. you just need to make sure you don't overload the front. 100% brakes means you don't have any left for turning, but 90% brakes means you can still turn slowly. 80% means you can be more aggressive. make sure that you don't increase your lean angle while you add brakes or gas. add the brakes or gas, then add the lean angle. you can add brakes or gas while decreasing lean angle as long as you don't overload it. remember past 80% lean angle or brakes needs to be extremely smooth. you can go full brakes but it has to be a smooth transition. its hard to quantify how smooth or at what speed the transition needs to be, but as smooth as possible while being only as quick as you need to be is all i can really say. if you do it smooth enough and you have good brakes and tires, you will endo before you wash the front out. which isn't a real endo anyway. still a lowside, just a weird backwards one. so don't worry about washing the front turning in or trailing. the hard part is getting back on the gas from there. transition needs to be smooth. coasting while leaned over is dangerous, you're basically braking with only the rear tire which isn't great for front tire grip. so it's best to get back on the gas once you are finished slowing down. just like the front, the rear has to be eased into with a smooth roll on.

gas is also a traction-sale when you are leaned over, but that's another topic. wot wot gets the pot.

just remember this is just one persons interpretation of a horribly complex dark art. get lots of perspectives and lots of interpretations. your individual riding style will be unique because we all have different bodies and styles. but learning how one person does it can help you identify problems in your own style.
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