Autsch, I crashed quite a few times on a motor bike but fortunately never had a high side.

 

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.

 

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!

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.

 

T

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.

 

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.

 

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.

 

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.

 

Curious if any of you guys experiencing this are running Ardent tyres on the front??

 

Yes, but only with the 2.25 on 26". It doesn't hook up and washes out.... not to be confused with tucking. The solution was to fit a 2.4 which is a totally different beast with proper edge blocks.
Got it on video too. Caught me completely by surprise and I wasn't even pushing it.

How not to ride Corners, Rotorua. Video - Pinkbike

I used to tuck the front on my Amp B4 with 90mm stem and somewhere in the neighborhood of a 70 degree head angle. I would turn into a high speed corner and the ground would reach out and grab the wheel and twist it inwards, throwing me over the bars. Part of it was bad technique on my part. Standing too upright on the bike and steering it too much instead of leaning it. The long stem and poor geometry just made it worse.

By the way, talking about high-siding a motorbike is not helpful. Tucking the front on a road-race bike is when you go into a corner too hot on the front brake and it loses traction, tucking in in the process. Mortals like me then low-side it and chuck it down the road. Legends like Colin Edwards can save it with their knee.

Tucking the front on a mountain bike is a different beast and what I used to call jack-knifing.

 

Huh, I'm running Ardents--2.4 in the front. Well, in my case I think it's still 99.9% operator error!

 

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.

 

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.

 

Nose wheelies.

 

Deathwishbiker, I would seriously not recommend the technique you were espousing to turn your mountain bike. Don't reach for the front brake to put more weight on it in a corner.

Watch some videos, like this:

One thing that will help:
Heavy feet, light hands.... Stand on your outside pedal, drop your heel, and allow your knee to bend slightly, preferably in toward the frame. Physically lift your outside elbow, push down on your inside grip to create lean angle, and twist your hips to stick your ass outwards and your upper body in.
Do NOT lean on the outside grip! This mucks up your front tire's ability to track the terrain and loses you a lot of traction. Your weight should be centered on the bike, not leaning on the front.
And braking in a turn adds an extra axis of force on your front tire when it is already fighting for grip. Don't do it.

 

This is similar to the turning technique I read about (I forget where) but it has improved my descending greatly - especially on smooth gravel / dirt where grip is really hard to find.

Basically you always have the inside pedal at 12 o'clock, outside at 6 o'clock, light hands, heavy feet (centre your weight on the bike), push down more on the outside foot than the inside, lean the bike into the turn, turn your hips into the turn too and let the bars find their natural attitude (don't lean on or turn the bars more than they want to).

This should allow you to use your entire bike and body to steer and harminise between the lean angle and the angle of the bars, rather than just relying overly on any one component to turn.

When I first tried it, I was cornering at my usual pace and felt that I was in danger of toppling over into the turn - apparently a sign that you can take the turn faster.

Oh, and never NEVER use the brakes once you are committed to turning. Always adjust our speed beforehand. A light drag on both brakes are fine to scrub off some speed but if you try to grab a hand full of brakes (front, back of both) in a turn you are asking to eat dirt.

 

One way to look at it is trail: normally trail is positive and indicates the distance between where the steerer axis is pointing (forward) and tire contact patch (rear).

A slacker head tube angle means the steerer axis is pointing further forward -> fork offset is increased to prevent trail from increasing. When suspension compresses, the head tube angle steepens, and trail is reduced. Effectively if your bike was handling quickly at sag height, it will steer even more quickly when compressed. Even if the rear suspension compresses as well, trail is still reduced because head tube height is lower (steerer axis can't point that far forward).

When you run into a bump, the tire has a new contact patch much further forward than normally. The contact patch could be in front of the point where the steerer axis is pointing, and you get effectively negative trail. If the front wheel is straight, no problem. If it was turned to either side, it will try to turn further.

Again, leaning helps against this movement and having a solid grip on the bars will stop any surprises. Leaning a lot means you must counter-steer, and counter-steering helps against tucking.

 

One way to look at it is trail: normally trail is positive and indicates the distance between where the steerer axis is pointing (forward) and tire contact patch (rear).

A slacker head tube angle means the steerer axis is pointing further forward -> fork offset is increased to prevent trail from increasing. When suspension compresses, the head tube angle steepens, and trail is reduced. Effectively if your bike was handling quickly at sag height, it will steer even more quickly when compressed. Even if the rear suspension compresses as well, trail is still reduced because head tube height is lower (steerer axis can't point that far forward).

When you run into a bump, the tire has a new contact patch much further forward than normally. The contact patch could be in front of the point where the steerer axis is pointing, and you get effectively negative trail. If the front wheel is straight, no problem. If it was turned to either side, it will try to turn further.

Again, leaning helps against this movement and having a solid grip on the bars will stop any surprises. Leaning a lot means you must counter-steer, and counter-steering helps against tucking.

That's what I said... :yesnod:

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 headangles, 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. :thumbsup:

-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.

This is similar to the turning technique I read about (I forget where) but it has improved my descending greatly - especially on smooth gravel / dirt where grip is really hard to find.

Basically you always have the inside pedal at 12 o'clock, outside at 6 o'clock, light hands, heavy feet (centre your weight on the bike), push down more on the outside foot than the inside, lean the bike into the turn, turn your hips into the turn too and let the bars find their natural attitude (don't lean on or turn the bars more than they want to).

This should allow you to use your entire bike and body to steer and harminise between the lean angle and the angle of the bars, rather than just relying overly on any one component to turn.

When I first tried it, I was cornering at my usual pace and felt that I was in danger of toppling over into the turn - apparently a sign that you can take the turn faster.

Oh, and never NEVER use the brakes once you are committed to turning. Always adjust our speed beforehand. A light drag on both brakes are fine to scrub off some speed but if you try to grab a hand full of brakes (front, back of both) in a turn you are asking to eat dirt.

^^^That's a very understandable way of saying it. :thumbsup:

-F

 

To reiterate the "tuck" or "flop" I'm referring to is not a front end washout or really anything related to traction. It's more of a geometry thing. I think Saul's relating it to steering trail hits upon what is going on. I've thought about it that way too.

Another way to think about it is the steering reaches an inflection point where the tire wants to reverse rolling direction. I can feel it just riding on the street and doing tighter and tighter slalom turns. You'll reach a point where the steering kind of catches.

I don't think the cause is rider error necessarily, but better turning technique keeps you away from that inflection point.

I've tried to think about what I could physically change on the bike to help avoid this. It would be interesting to only change fork offset to see whether more or less offset helps.

 

I don't think the cause is rider error necessarily, but better turning technique keeps you away from that inflection point.

Everything is rider error.

Some things can be made worse, made better, improved upon, or prevented based on a gear swap, but not knowing how your bike is going to operate in different circumstances I still claim as operator error. The bike didn't cause the rider to wipe out. How the rider was riding it caused the rider to wipe out.

Just like driving a car in snowy/icy conditions. When you blow a turn and slam into a snowbank. Was the car at fault? Was the conditions at fault? I am sure you would love to say so, but it was your driving too fast, braking technique, or a combination of the two that caused the accident.

If you had a failure on your bike, such as a tire pop, catastrophic frame/fork break, etc? Ok, that is potentially out of your realm of control. If you are riding, the bike operates as intended, and you lose control of it? Sorry, but that is you.

I am not perfect either. I have wiped out. My pedal kicked a rock or stump and shot my bike sideways with me still attached to it. I was on the ground before knowing what happened. I could start investigating different cranks, different pedals, different geometries, and whatever else. That or I could watch my lines better to know what is coming and how to handle it.

 

Actually, referring to what Fleas wrote; I only ride rigid too - so compression of the front suspension is not really an issue for me either

 

Right. Unless you've got a leaky front tire, it never happens on a rigid bike. Well, maybe in a really tight turning g-out I might get a little ahead of myself once in awhile and induce it via weight transfer, but the fork is pretty constant.

-F

 

I've never experienced "front end tuck", although I'd like to. Anybody know where I could attend a front end tuck beginner training course? And are they pricey?

 

Look for a turn, sit upright, flip the bars 90deg to a side and enjoy the ride. A helmet and/or jockstrap may be desired.

While you are airborn, say "Supermannnnnnnnnnnn"

 

This is exactly how I crashed bad and took a bunch of skin out of my forearm this summer. I went into a loose corner with some lean but the front wheel started washing out, so I stood up on the bike and turn the bars and then I'm sliding on the ground as the bike flew to the opposite side of where i fell. Sounds like a lame excuse but the Fox CTD fork with crappy mid-stroke support was partly to blame for me not able to recover the initial slide. The thing brake-dove like crazy even in Trail mode and I felt I couldn't load the front tire well since it blew through travel so quickly. I ended up selling that fork after I crashed and now I have no issues (knock on wood).

 

I have your dog, mister!!

 

I experienced the tuck for the first time in a long time. Was trying to "force" a downhill switchback with lots of loose rocks and roots.

 

"Front end tuck" sounds like when you've been on a long ride & you get "turtlehead" from your crotch going numb. Like the cyclist's version of the famous George Costanza "shrinkage."

 

Similar but George had an excuse. It was cold the water was cold.

 

Stay Off The Front Brake!

 

...........

 

I almost experienced this on today's ride and this thread came to mind. Excuse me if it hasn't happened to you but trust me in saying, it will if you ride with careless abandon.

Ok DJ...Nat threw the bait...and you took it.

 

I almost experienced this on today's ride and this thread came to mind. Excuse me if it hasn't happened to you but trust me in saying, it will if you ride with careless abandon.

 

I am now on alert DEFCON 5 for the Front-end Tuck. I'm sure if I am missing something, but I can't make myself turn the bars 90*.

 

That's what bites you, you don't turn the bars, physics does.

The same phenomenon can be seen on loose and steep downhills where the rider doesn't have their weight far enough back. The front wheel breaks loose and then catches hard. This does potentially, almost certainly really, does two things, yanks the handlebars, even just slightly, in one direction and slows the bike suddenly causing the rider to put even more weight forward. Now that the bars are off center that weight shift is going to naturally put more weight on the outside bar and continue turning sharper and sharper. The wheel crosses the maximum perpendicular threshold, the end starts to lift and gravity, and momentum, do the rest.

The same thing happens in corners but gravity really isn't in play, just forward momentum. Ever heard of someone trashing a wheel in a smooth, flat corner. The same forces likely happened whether they managed to lay it down or went over the bars.

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