Dropping to flat

supersonic

Lets keep it amicable! Has been quite constructive to the most, and a good read for nerds like me!

albo

The main question of whether real wheel landings are better is dependant on far too many different things, speed, bike type, surface, height of drop and so on... I am a logical thinker, but, I fear we have over complicated the matter somewhat.

n.battison

i'm fairly sure rear wheel landings feel smoother just because it slows down the decelleration as you hit the ground. If you landed flat with both wheels level you would stop in the vertical plane almost instantly, whereas landing read wheel first your body and the rest of the bike slow down before coming to a stop.

_Ferret_

Hang on.
This is all about rear wheel landings!?
I thought the reason trials riders do it was obvious. Landing on 2 wheels gives you a "jolt" as both wheels hit the ground at the same time. Landing with the rear wheel first and then allowing the front to follow transfers some of this impact into a rotational effect on the bike. The rear wheel hits the ground first, rider absorbs this impact and then using the rest of his (or her) body controls the front wheels as it rotates around the first point of impact to the ground.
I don't want to get all physics influenced here because many of the principles discussed so far on this thread are either completely irrelavant or so primary that they have little use (i.e. they negate so many factors they are not worth considering).
Still makes for funny reading though...

Anonymous

Northwind wrote:

No. Because the argument you've put forward isn't exclusive to rear wheel landings, it works exactly the same for front wheel and 2-wheel landings! The physics is correct but the logic is false, the example works but it doesn't prove what you say it does.

It isn't exclusive, but it is much more pronounced for rear wheel landings.
You can extend your legs much more than you can extend your arms. Pushing the rear end down until it is nearly vertical makes a much bigger difference than pushing the bike down level, with your arms and legs.
Seriously though, try it, and find out for yourself, I guarantee you will find it makes one hell of a difference, then maybe you can stop being a di*k (your words...)

_Ferret_

it's going to get complicated now - because now you're talking about rider technique. That's one of the many factors you can't easily calculate.
Please do try though - vector "a" could be your arms, vector "b" your bum, "c" your legs and then we could talk about the deviating angles of projection and lets not forget the air resistance of the baggy shorts...

Anonymous

How could dropping to flat, rear wheel first NOT involve rider technique. I thought the whole discussion was about which technique gives the softest landing?

MacAndCheese

Crikey, I think I'm regressing painfully back to A'level math mechanics lessons, but in this case it's interesting because it's something I'm actually interested in!

Just out of interest - I can't watch the video with sound at work - is there a large cracking sound when the rear wheel hits the ground? looks like quite a severe bottom out to me!

_Ferret_

I joined in when we were talking about trajectory and slopes remember.

when froward motion is involved I'd imagine a 2 wheel landing would be better. Think about the rotating energy of the bike. If you are stationary this is an advantage because at slow speeds you can control it using your upper body. At higher speeds you don't have that kind of control - the bike hits the ground rear wheel first and due to your forward motion the rotating energy on the front wheel will be increased making it harder to control the front wheel before impact.
Don't forget - it's harder to control a landing at speed when you only have one wheel on the ground. Both wheels hitting the ground at the same time increases your surface area of impact, stabilises your landing for the rider to absorb the impact - hence a softer landing.

(I'm going to try this when I get home now...hope it's not raining.)

joshtp

OK, from GCSE phisics, the way i understand it is than the longer the time period that the impact spans the less the force will be, so, if you land flat on both wheels you are putting all the energy from the fall directly through you and the bike, but by landing with arms and legs extended, and back wheel firdt you lengthen the time the impact takes, meaning the force is far less making it easyer for both body and bike to absorbe the impact. so, in theory the smoothest way should be back wheel first with arms and legs extended to act like sus on landing. energy cannot be lost, it can only be converted, so by losing as little kinetic enery as posible you aviod turningh the rest or the energy into soud(not cool) and elasic (painfull) and a few other things like pain.

_Ferret_

for a drop to flat from a static position I would agree with that - more or less.
But what about at speed?

Stuey01

_Ferret_ wrote:

for a drop to flat from a static position I would agree with that - more or less.
But what about at speed?

It's been discussed at length on this thread. A drop to flat is a drop to flat regardless of forward velocity

_Ferret_

nah, rubbish to that.
You can't tell me that forward velocity on an aparatus with 2 distinct points of contact has no effect.
I'm sure at a certain speed the control you have over a bike landing on one wheel would be detrimental to the softness of the landing.
As said before - you have to consider rider ability.
Imagine an (unrealistic) extreme - travelling at 100mph. What do you think would happen if you land the bike standing with your weight on the back wheel? The bike would be so unstable upon landing on the back wheel you would loose control and probably hit the ground with your face first.
Imagine the same scenareo landing 2 wheels first, wouldn't be pretty, but you might survive due to a larger landing area.
The problem with the discussion so far is that all the theories thrown around don't function in the real world because they neglect about 80% of the variables.
Still, nice to see that people are thinking for a change...

supersonic

As discussed earlier, it is the ground conditions that are important at speed.

bungalistic

Try landing a drop to flat both wheels on a hardtail, it's not nice and can pretty much stop any forward momentum you have. Landing back wheel first is also none too pleasant and you have less control over where your front wheel is going.

Landing ever so slightly front wheel first you can land and push through, keeping some momentum allowing the back wheel to follow the front and keep you rolling.

This was tried at the weekend on a small drop to flat, both wheels landing together nearly stopped me dead and felt pretty crap, back wheel slightly first felt better but still wasn't as smooth as landing front wheel down first, letting the forks soak up the impact and pushing through to let the back wheel follow through.

edit: the above example is when I had some forward momentum and wished to keep it, and the drop wasn't big enough to transfer all the forward momentum into a straight up fall. I also did a drop to flat after bailing from a north shore skinny the day after, this time as I was pretty much stationary I decided to hop off and landed back wheel first (like trials riding) and used legs to absorb the impact.

supersonic

Of course, personal preference is a big thing! We all react differently when landing and in the air, weight distribution etc. With a long soft fork, landing front first witha front wheel bias - I have seen many go over the bars as the bike decellerates!

bungalistic

Yeah been close to some over the bars moments myself when landing with too much front bias, sometimes good old front suss forks are life savers.