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  1. #1
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    Front-end TUCK - Has anyone experienced it? What to do about it?

    I may be using the wrong word to describe it, but while turning a bike through a corner, the front end (bars/fork/wheel) suddenly turn more than desired until the front wheel is 90 degrees to the direction of travel... at which point the bike stops moving forward, and the rider is usually tossed over the bars.

    I've also heard it called Knifing or Oversteer.

    A friend of mine has found himself on the ground a couple of times recently after going over the handlebars -- once so quickly he still had the bars in his hands as he lay there wondering what happened.

    He suspects the front end tucked, but he's not sure.

    What causes tucking? How prevalent is it? How do you cure it?

    Thanks in advance...

  2. #2
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    Never experienced it, never heard of it, so I would say not prevalent at all. Perhaps build some upper body strength.
    Low and slack.

  3. #3
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    Quote Originally Posted by CaptDan View Post
    What causes tucking? How prevalent is it? How do you cure it?
    Broadly speaking, it happens when the steering angle, lean angle, and front/rear weight balance isn't right. It tends to happen when the bars are turned too much, the bike isn't leaned over enough, and the weight balance is too far to the front. The front wheel wheel starts catching and slowing down the bike which transfers weight to the front & compresses the fork, which does wonky things to the steering geometry of the bike and makes the front wheel dig in hard and spin sideways. The bike comes to a sudden stop and the rider gets dumped.

    How prevalent it is depends on the trail surface, bike type, and the rider. Trails with lots of soft spots in the middle of corners can cause lots of knife ins as the front tire slides out and then catches traction again. XC bikes with shorter wheelbases and steeper angles are also more prone to tucking under than a long and slack AM/Enduro bike. And finally, riding style, people who steer mostly with the bars and don't lean the bike much are more prone to having the front wheel go sideways on them in a turn.

    Prevention comes down to awareness, practice, and undoing bad habits. If you see a patch of sand in the middle of a corner you might want to be prepared to make some fast corrections or think about taking a different line to avoid it. Then there's training out bad habits. A lot of riders will turn the handlebars in more when the front tire starts sliding and they think they're going to go too wide on a turn. Problem is when the bike bleeds off enough speed and the front wheel regains traction it'll bite in hard, spin sideways, and flip the bike. More advanced riders will countersteer and lean the bike more which puts the arc of the turn where they need it while pointing the front wheel close to the direction of travel so that it can't catch wrong and start the crash sequence.

  4. #4
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    I thought I was the only one experiencing this! I have had this happen numerous times on my Tallboy. It happens mostly in tight downhill switchbacks, usually when I haven't quite judged the apex right and I have to steer a bit more...then bam! I'm on the ground. It's the one thing I don't like about my Tallboy.

    I call it a "flip" of the steering. It's like it passes over some pivot point and all of a sudden the steering acts different.

    I'm not sure if it's a 29er thing or the steeper head angle that contributes to it. I don't seem to have the issue on my Mach 6.

  5. #5
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    Happened to me just 3 days ago! Riding my rigid 29r on a very skinny section of single track with a 15' drop to my right and a bunch of large, angry-looking rocks to my left. I approached a narrow spot that looked like it was collapsing/washed out and I tried to navigate around it and…well, honestly it happened so fast I can't really explain it. I was on the ground and my front wheel/bars had turned almost completely around as the bike lay there. I landed about 4-5 feet away from the bike - pulled off a decent tuck and roll unwittingly. Luckily I landed smack in-between the rocks and the drop-off. Crazy. Barely a scratch on me. Counting my lucky stars still...

  6. #6
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    I sometimes have that problem, more on my older bike. Which is a 26" hardtail, so I don't see it as a 29er problem.

    The worst time for me is in a compression. I think that implies that rolling something too big is a bad idea too. If I don't think I can get off something in the right attitude for landing, I just walk it.

    If you think about a bike's steering geometry, it makes a lot of sense. Having some angle in the top tube puts the front tire's contact patch behind the steering axis. So the force that turns the wheel makes it "want" to stay straight and if the wheel's turned a bit relative to the bike's direction of travel, there's going to be some force restoring it to being in line.

    With a super steep angle or if something else moves that contact patch forward of the steering axis, it's going to want to slam around the rest of the way. So if you combine a steep head angle, a compressed fork making it even steeper, and maybe the ground at an upward angle, like in a g-out or coming out of a compression, that's a pretty toxic situation.

    It's certainly something that can be reduced with good technique. If I'm centered over my pedals, lightening my front end over stuff, floating it and doing push manuals over doubles, etc, it's not a huge issue. If I've set up my bike with a lot of drop, I've got my head down, and I'm leaning on my bars, I'm putting myself at major risk for some weird front wheel behavior.
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  7. #7
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    I happens when you turn your handle bars into the turn while leaning the bike over, instead of counter steering. If you stand next to your bike, lean it over then turn the handle bars into the lean, what happens if you turn them to far... the front wheel rolls backwards

  8. #8
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    Been riding since the late 80s and never had that happen. In fact, I've never heard anyone else tell me that happens until today.

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    Quote Originally Posted by AndrwSwitch View Post
    With a super steep angle or if something else moves that contact patch forward of the steering axis, it's going to want to slam around the rest of the way. So if you combine a steep head angle, a compressed fork making it even steeper, and maybe the ground at an upward angle, like in a g-out or coming out of a compression, that's a pretty toxic situation.
    Interesting about the upward angle--I was actually on a slight upward incline when it happened the other day--hitting it fast with a lot of momentum, but nonetheless, going up…
    At the end of the day though, in my case, I chalk it up to operator error

  10. #10
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    Can also happen if your front fork is a bit soft.

  11. #11
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    Only happened to me once, which was a month or so ago. Tight lower speed downhill turn over roots and some rocks, I wasn't back far enough on the bike and I didn't pick a good line through the turn. Got into a bad position on the trail, tried to hard over the bar to salvage the turn, and over I went. At the time, I thought it was totally the result of me daydreaming or something. Never happened besides that one time, but like you said, it's all over in a hurry. I think this is 100% rider error when it happens.

  12. #12
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    I only know tuck in from street motorcycle riding which is a form of front end slide out.
    Flying over the handle bars is normally considered a high side but I also heard that term only in relations with motorbikes but who knows.
    Quote Originally Posted by Mr Pig View Post
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  13. #13
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    If you do it right, you almost feel like you are catapulted into the ground!
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  14. #14
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    Quote Originally Posted by elcaro1101 View Post
    If you do it right, you almost feel like you are catapulted into the ground!
    I wonder if they teach that in riding clinics, if I would try to lean that I would wear one of those german army spike helmets, that would add some fun factor for sure.
    Quote Originally Posted by Mr Pig View Post
    Avid is spelled wrong, there should be an 'O' in there.

  15. #15
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    It happens when you turn rather than lean. You should have pressure on your inside grip (i.e. left grip to turn left). If you have pressure on your outside grip you'll end up with your front wheel pointing inside the curve of your corner.

    In my experience slacker bikes are more likely to push the front wheel in this situation resulting in nothing or maybe a lowside crash whereas steeper bikes are more likely to end up with the front wheel at 90 degrees to your direction of travel resulting in a huge OTB.

  16. #16
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    I've ridden from 72 deg head tube to 67 degree, all kinds of variable speed AZ chunk, hard, soft, soft over hard, up, down, stiff fork or cush fork, fs, ht, SS, can't say as I've ever experienced anything even close to this.
    The question isn't who's going to let me, it's who's going to stop me.

  17. #17
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    ALL THE TIME here. I never had it on my Y33, nor my old '08 Fuel that I can think of. However, when I went to a 29er, I started getting it a lot.

    Now, I believe it is from not weighting the front wheel enough. I saw someone earlier thought it was having the front weighted too much, but I thoroughly disagree with that. The front loses traction, and begins to knife (or tuck) in.
    One way I have begun to compensate, is to change my cornering style to a more forward style as opposed to my old school "over the back" style.
    I have also started to use more front brake in corners, which is extremely difficult in loose situations, but biases the weight more towards the front wheel, and compresses the fork, and unloads the rear slightly. This should add traction to the front tire.
    Now, if the tire is locking up, due to too much front brake, it will immediately turn as far as it can. This would happen to me all the time on the MX bike. Hammering into a corner, slam the brakes, and I would start to knife the front end. That's actually one reason I wanted to go moto style brakes. My right hand is far more sensitive to the braking forces, and I can respond to a front wheel locking up. Nevertheless, if the front locking up is causing your knifing, then obviously backing off the front and biasing more rear brake is what you need.

  18. #18
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    Quote Originally Posted by acer66 View Post
    I only know tuck in from street motorcycle riding which is a form of front end slide out.
    Flying over the handle bars is normally considered a high side but I also heard that term only in relations with motorbikes but who knows.
    I also know this as a "high side" back from my motocross days back in the mid to late 80's. I had this happen to me last year, I dove into a corner and ran out of talent and next thing I know I'm over the bars and my bike landed on me. Hurts a lot more when you get older.

  19. #19
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    A "high side" as has been mentioned, is when the bike (front or rear, but usually rear) is skidding out. You feel like the bike will keep laying over until you hit the ground, but instead of doing so, (which is a "low side") the tires bite again. Unfortunately, usually you are now probably getting closer to perpendicular to your travel direction, and so you get launched over the bike.

    If that rear was breaking loose, the WORST thing you could do is chop the throttle. Stay on it, even if it means you are laying the bike over. It's far better to slide out than to high side!
    If the fornt is washing out, the best thing you can do as well, is to crack that throttle as hard as you can.
    Of course, that's impossible on a mountain bike.

  20. #20
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    Quote Originally Posted by DethWshBkr View Post
    Of course, that's impossible on a mountain bike.
    What about e-bikes?
    Quote Originally Posted by Mr Pig View Post
    Avid is spelled wrong, there should be an 'O' in there.

  21. #21
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    Wow, some excellent responses from those of you who have experienced "tuck".

    My friend had been trying different stem heights. Could this be contributing to his dilemma?
    His bike is a DeVinci Wooky -- new to him this year -- so he's still sorting-out his 'fit' on it.

    Many thanks to all contributors.

  22. #22
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    I'm not sure if I've ever experienced what you're talking about, but is this just wheel flop, perhaps exacerbated by the terrain?

  23. #23
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    Yes! Very similar, Geralt. The concept is the same; the front end starts turning more than the rider desires or is expecting.

    The difference is Flop can be recognized and corrected-for early and easily, whereas Tuck sneaks up on you, generally when there is a lot of steering angle on the front end, rider's body weight is forward, and the forks are compressed.

    Think tight, low speed, downhill switchback. (Thank you, Ladmo.)

    In that sort of specific, critical situation, some degree of unhappiness from the front end is pretty much understandable, but when it happens in somewhat moderate situations it's an indicator that something is not quite right in the geometry or setup of the bike.

    There is a myriad of possible contributing factors, so I'm hoping someone here has dealt with Tuck successfully and offers some possible cures.

  24. #24
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    Happens when I want to take the inside line with more speed than I'm comfortable with and give it a bit too much angle. I don't "only lean" or "only countersteer" when I turn; I try and swing my weight around, when I have momentum I need to carry around a bend in the trail. My "swinging" movement incorporates a countersteer, lean, weight shift/body position, AND a handlebar turn, to theoretically offer the max ability to carry myself around turns that are practically 90 degrees or sharper.

    When the highside/tuck happens, I basically end up either cartwheeling, outside hip first, over the bars, or the front just bogs down enough, maybe even to a stop where it digs in, and the rear overtakes it and swings around to the front.

    I figure I just need to tweak my lean angle, and tweak my positioning a bit to be more centered between the wheels and have even pressure on the front. Just need to be on the front long enough to get past this critical point, then I can shift weight more to the rear to follow through on the corner.

    Processing a couple videos in which I caught it happening, so I can post them here as examples:





    Both are Specialized bikes (top SJ FSR Evo 26, bottom Enduro 29), both are running Pikes with higher offset (27.5/44mm on the SJ, and 51mm on the 29er), both are on 2.4 Maxxis tires up front and relatively low profile rear tires.

    (Click the 2nd pic if you want to see the source for the higher speed example. It happens at around 6:05. Seems like the sudden "jolt" from the "tuck/highside" was enough to tweak my GoPro's aim)

  25. #25
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    Less brakes and lean the bike into the turn while you, the rider stays in a more vertical position. Or, put a foot down when needs at slow speeds.

    Another possibility is a poor match of tread design over a given terrain.

  26. #26
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    2nd video was all worth it for the spandex ninja at the end!
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  27. #27
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    Quote Originally Posted by Hawg View Post
    Less brakes and lean the bike into the turn while you, the rider stays in a more vertical position. Or, put a foot down when needs at slow speeds.

    Another possibility is a poor match of tread design over a given terrain.
    I thought about the tread issue as well but that would just cause a wash out [a slide].

    I'm thinking it may be a 26"-29" carbon frame aluminum frame dropper post non dropper post long stem short stem wide bar narrow bar issue. Any combo there of can certainly cause a front end tuck.
    Quote Originally Posted by NDD View Post
    Dude, I'm in Illinois. The only place anyone would come from that would say this area is hilly is Kansas.

  28. #28
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    Quote Originally Posted by acer66 View Post
    What about e-bikes?
    I'll stick to my original statement!


    On those things - when in doubt, gas it!

  29. #29
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    What the hell? I've never ever had this happen to me and I've never even heard of this phenomenon before. Right angle to the direction of travel? Wow that ain't good. OTB ya go!
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  30. #30
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    Quote Originally Posted by DIRTJUNKIE View Post
    I thought about the tread issue as well but that would just cause a wash out [a slide].
    That's the start of a front end tuck.


    Irrelevant to HOW it starts, the front wheel will NOT tuck under unless it loses traction.
    Whether that loss of traction is due to tire pressure (too high causing poor bite, or too low, causing sidewall flex or insufficient tire pressure pressing into the dirt), tire compound/tread, rider position, too much braking force, or poor dirt traction on it's own, the front wheel MUST lose traction to knife.

    Again, with me, I was always a "grab the saddle with my thighs and lean back" to keep the front wheel nice and light. The newer bikes just do not like this, and I have struggled to change my riding style to put more weight over the front.

  31. #31
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    In my world, the definition of "front end tuck" is when you get into an oversteer situation. Everyone I know attributes it to a too-soft suspension fork.
    When you enter the turn, braking or not, if the fork compresses too far as you load it for front traction (or just due to g-forces), the head angle changes enough that the fork trail becomes too small/short. Beyond a certain threshold, esp. with steeper headanlges, the fork trail causes an increase in oversteer even as the bike is already oversteering.
    It can be corrected most simply with an increase in fork pressure, with wider bars, or maybe a higher offset fork, or maybe a longer fork if the bike frame will tolerate it.

    I ride rigid so I NEVER have that problem.

    -F

    PS - I just got back from a weekend of riding where we reminisced about crashes at that trail system (they love to remind me how I hit most of the downhill turns too hot and ride off into the forest). One of the worst was a guy on a FS bike who oversteered through a g-out and got stuffed into the wall when his bars practically ripped out of his hands. The combination of high speed, possibly low tire pressure, really high g-forces through the turn, and narrow bars resulted in a wicked crash. Essentially, the bars crossed, the bike stopped, and he got stuffed into the turn, shoulder-first.
    It's never easier - you just go faster.

  32. #32
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    Front washes, you overcorrect, hook up, and crash, and that's called a 'tuck'?


    Learn something new every day...

  33. #33
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    Quote Originally Posted by DethWshBkr View Post
    That's the start of a front end tuck.


    Irrelevant to HOW it starts, the front wheel will NOT tuck under unless it loses traction.
    Whether that loss of traction is due to tire pressure (too high causing poor bite, or too low, causing sidewall flex or insufficient tire pressure pressing into the dirt), tire compound/tread, rider position, too much braking force, or poor dirt traction on it's own, the front wheel MUST lose traction to knife.

    Again, with me, I was always a "grab the saddle with my thighs and lean back" to keep the front wheel nice and light. The newer bikes just do not like this, and I have struggled to change my riding style to put more weight over the front.
    As you and I both know this so called "front end wheel tuck" has been given the wrong name. In the motorcycle world we call it high siding.

    "Did you see Bob high side as he was entering that berm"?

    Prior to this jump I did a front end wheel tuck [high sided] but saved it at the last second.

    Last edited by DIRTJUNKIE; 09-21-2015 at 06:00 AM.
    Quote Originally Posted by NDD View Post
    Dude, I'm in Illinois. The only place anyone would come from that would say this area is hilly is Kansas.

  34. #34
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    High Side compilation

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  35. #35
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    Autsch, I crashed quite a few times on a motor bike but fortunately never had a high side.
    Quote Originally Posted by Mr Pig View Post
    Avid is spelled wrong, there should be an 'O' in there.

  36. #36
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    I know the phenomena, but it has never made me fall.

    Everyone knows wheel flop, right?
    And everyone knows that there's only so far the wheel will turn when it flops?
    This "tuck" thing happens past that point, when the wheel is turned further than it would flop. It feels like the head tube wants to head straight and past the contact patch of the front tire.

    "Tucking" can be initiated on almost any bike by turning the bars with the bike upright. It can be avoided by leaning the bike more (a good feeling to look for is to push the grip down on the inside turn) and keeping a solid control to the bar.

  37. #37
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    Sounds like we may actually be talking about two different things.

    Here's MX video of two of my front end knifes that I actually got on video!

    https://www.youtube.com/watch?v=RufTGiEH_bI

    First video, my first time on the bike. Bought it used, and it had a crap front tire on it. Came into the corner, was not quite familiar with the bike, and locked up the front. You can see the "jerk" when the front end knifes in, and I end up low-siding it. Ooops.

    Second video, entering turn two, someone starts to crash right in front of me (also a front end knife). As soon as I grab my front brake, you can see my front wheel lock up, and knife under. Both instances, low sides. I only went over the bars because of impacting his bike.
    I ran it slow motion too.

    The street video above is indeed high sides. Rear wheel usually breaks loose, you so sideways, and down you go. Street bikes usually high side MUCH quicker than an MX bike.

  38. #38
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    DethWsh, those dirtbike vids indeed look like classic front end slides, AKA Low Side. The front end starts to push, it never hooks up again, and the bike (and rider) slide to the ground on the inside of the turn.

    A Tuck is when the front tire hooks up, slams the fork to the stops (on a motorcycle), and pitches the bike & rider to the outside of the turn.
    The lower speeds of a bike usually (just?!) has a rider going over the bars, but the higher speeds on a motorcycle wind up sending the rider into the air -- a classic High Side.

    Some great discussion here, and the videos are a bonus!

  39. #39
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    I did this years ago while trying a friend's bike. Later realised that it was because his bike has a much longer stem than mine. Personally I feel that shorter stems give you much more stability in corners.

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    If you put your bars in neutral position, in 95% of cases, if you are turning them past about +/- 30 degrees, you are likely to be oversteering and at risk for an endo.

    The usual argument here is super narrow trails at low speed and then switch backs on top. The problem is when someone is in a negative angle, they are likely front loading their suspension, likely on their front brake, and then they wrongly twist their bars to steer through the turn. The result is a nice endo.

    In this situation, should either A) Lean the bike into the turn and counter-steer, or B) lock both brakes into a track stand and hop the bike into a better position.

    Problem is many people don't know how to perform option B, and option A scares a lot of people. The result is people struggle their way though it and hope not to endo.

  41. #41
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    Quote Originally Posted by Hawg View Post
    Less brakes and lean the bike into the turn while you, the rider stays in a more vertical position. Or, put a foot down when needs at slow speeds.
    I agree with this. More bike lean, less brake

  42. #42
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    Quote Originally Posted by CaptDan View Post
    DethWsh, those dirtbike vids indeed look like classic front end slides, AKA Low Side. The front end starts to push, it never hooks up again, and the bike (and rider) slide to the ground on the inside of the turn.

    A Tuck is when the front tire hooks up, slams the fork to the stops (on a motorcycle), and pitches the bike & rider to the outside of the turn.
    The lower speeds of a bike usually (just?!) has a rider going over the bars, but the higher speeds on a motorcycle wind up sending the rider into the air -- a classic High Side.

    Some great discussion here, and the videos are a bonus!


    OK, so it sounds like I am interpreting things differently. Both of those clips of me, the front end started to slide, which then makes the bars go to the stops. (Or in the case of a bicycle, just push out. )
    Yeah, if you're not ready on the bars, they will turn to a point which the front wheel will not roll anymore, but instead "stuffs" and pretty much could make you go OTB, since you are really "slamming on the brakes" to the front wheel.

    Still should be a lack of traction to the front wheel. I have gotten a lot here (again, since going to the newer bike) where I'm just cruising a corner, and the front end DOES start to turn a lot more than I'm expecting. Usually I am able to just clip out and stab the ground with my foot. One time I couldn't save it, and went down (it was a slightly slippery day).

    Now I'm wondering however...with as tight as most trails seem to be, if this issue isn't made worse because the front wheel is breaking loose, it just goes straight. As a result you hit something at the edge of the trail (or the trail edge itself). Since the front wheel is no loner rolling along the terrain, but instead skidding, it just stops, and boom. You're flipping.

  43. #43
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    Curious if any of you guys experiencing this are running Ardent tyres on the front??
    One day your life will flash before your eyes, will it be worth watching??
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  44. #44
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    Huh, I'm running Ardents--2.4 in the front. Well, in my case I think it's still 99.9% operator error!

  45. #45
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    Quote Originally Posted by CaptDan View Post
    I may be using the wrong word to describe it, but while turning a bike through a corner, the front end (bars/fork/wheel) suddenly turn more than desired until the front wheel is 90 degrees to the direction of travel... at which point the bike stops moving forward, and the rider is usually tossed over the bars.

    I've also heard it called Knifing or Oversteer.

    A friend of mine has found himself on the ground a couple of times recently after going over the handlebars -- once so quickly he still had the bars in his hands as he lay there wondering what happened.

    He suspects the front end tucked, but he's not sure.

    What causes tucking? How prevalent is it? How do you cure it?

    Thanks in advance...
    If it keeps happening to him, then you can bet that it's user error. The dude needs to overcome whatever gut reaction he is following when he is in those situations. the cause is simple, breaking the habit may not be.

  46. #46
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    Quote Originally Posted by Flucod View Post
    Maybe, I raced Pro for 20 years and it ONLY happened with that tire (many times). IMO its the tire, lol!
    Sorry mate, this is the internet so real life experience does not count only hearsay.
    Quote Originally Posted by Mr Pig View Post
    Avid is spelled wrong, there should be an 'O' in there.

  47. #47
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    Nose wheelies.

  48. #48
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    Quote Originally Posted by DethWshBkr View Post
    Sounds like we may actually be talking about two different things.

    Here's MX video of two of my front end knifes that I actually got on video!

    https://www.youtube.com/watch?v=RufTGiEH_bI

    First video, my first time on the bike. Bought it used, and it had a crap front tire on it. Came into the corner, was not quite familiar with the bike, and locked up the front. You can see the "jerk" when the front end knifes in, and I end up low-siding it. Ooops.

    Second video, entering turn two, someone starts to crash right in front of me (also a front end knife). As soon as I grab my front brake, you can see my front wheel lock up, and knife under. Both instances, low sides. I only went over the bars because of impacting his bike.
    I ran it slow motion too.

    The street video above is indeed high sides. Rear wheel usually breaks loose, you so sideways, and down you go. Street bikes usually high side MUCH quicker than an MX bike.
    Nice vids but neither one of those were high sided crashes. When I brought up the topic of motorcycle high side crashes I meant turning and having the front end stick and the rider flys in the direction of the momentum and the bike flips. Been there done that but never on vid.

    Back to the front end tuck phenomenon.
    Quote Originally Posted by NDD View Post
    Dude, I'm in Illinois. The only place anyone would come from that would say this area is hilly is Kansas.

  49. #49
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    Quote Originally Posted by CaptDan View Post
    DethWsh, those dirtbike vids indeed look like classic front end slides, AKA Low Side. The front end starts to push, it never hooks up again, and the bike (and rider) slide to the ground on the inside of the turn.

    A Tuck is when the front tire hooks up, slams the fork to the stops (on a motorcycle), and pitches the bike & rider to the outside of the turn.
    The lower speeds of a bike usually (just?!) has a rider going over the bars, but the higher speeds on a motorcycle wind up sending the rider into the air -- a classic High Side.

    Some great discussion here, and the videos are a bonus!
    Front end tuck is when your front breaks traction, you can watch the forks unload, typically go to full lock and your face and shoulder typically go straight to the ground. Very common when trail braking hard into the corner.

    http://youtu.be/7cZKaBN-qP8 Great example at the end. Still trying to find a pic or vid from off a bike

    Next point of view of another front end tuck http://youtu.be/qCwcDMsLUpI

  50. #50
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    Quote Originally Posted by DIRTJUNKIE View Post
    T

    Nice vids but neither one of those were high sided crashes.

    Nope. I haven't high sided in 15 years!

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