What does it take to bend/break forks?

.blitz

Encouraged by my new Revs, I find myself riding off steeper drops without the skill to back it up. There have been a few flat landings, several nose-dives and a faceplant

I wondered how much of this ham-fisted riding the forks will take, and whether anyone has bent/broken a pair of forks?

Louis84

Thats the whole point mate! I look at it this way............I actually TRY to brake my bike components......Because if I break them, it means I deserve something better, stronger, and hopefully more expensive :twisted:

bomberesque

broken fork crown -> hospital though

You can break anything ofc but I've not yet seen a broken Rev

cgarossi

Any force will take the path of least resistance, so if anything is going to break it'll be your rims/wheel first and then to damage the fork it would have to bend so much that for fork takes the impact too. Very unlikely.

flowpro

This would do it!

cgarossi

Tis but a step!

joshtp

in that situation i would pull an endo front flip, then finish with a tailwhip into the transition at the bottom.

cgarossi

That would be difficult if the transition turned out to be solid granite at 90 degrees to your descent!

Thewaylander

A fair bit but it.s more to with the type of impact.

nose diving to a stop is more likely to dmg them as the force is at 90degree to the fork. most up and down force is going to break much unless you excessivle bottom out(trashed a few this way when riding street many many many years back).

So go bonkers will be fine mate, but still get learning your technique, the smoother the better hehe

joshtp

cgarossi wrote:

That would be difficult if the transition turned out to be solid granite at 90 degrees to your descent!

in that situation, i would pyll a table so as to max my surface area and slow my decent, then at the last second i would pull out of it and land on my back wheel, lowering my front slowly to absorb the impact.....

joshtp

and on a seious geology-agraphic note, as a gneeral rule, cliffs like that then to have a rather large, steep, scree slope at the bottom..... not that that would make droping of the cliff posible, but it is true....

mcj78

Never broken forks, however some moons ago I turned my old GT into a lowrider when jumping a small stream - about a 4 foot drop from one side to the other and 6-8 feet wide but with a slight incline on the landing side, (those were some nice yellow Rock Shox Quadra 21's - told you it was a while back) the forks remained in one piece but with quite a rake... think that Ian Brown video "fear"
J

bomberesque

cgarossi wrote:

Any force will take the path of least resistance.

pfft, that's lightning you're thinking of, not force I think

It's perfectly possible to break the fork crown without collapsing the front wheel or snapping the frame, normally by landing vary badly but that's what we're on about here.

ride_whenever

Front on impacts tend to kill forks pretty quickly, but anything where the suspension can compress is unlikely to cause damage.


As for that cliff, i'd do a suicide front flip then pull my parachute!

Hercule Q

i had revs and did a couple (read alot) of sketchy landings on them no problems

cgarossi

bomberesque wrote:

cgarossi wrote:

Any force will take the path of least resistance.

pfft, that's lightning you're thinking of, not force I think

It's perfectly possible to break the fork crown without collapsing the front wheel or snapping the frame, normally by landing vary badly but that's what we're on about here.

Nope.

If you apply a force to anything, it will give try to give way and will transmit the given force through the weakest points first.

I would suspect the wheels would give first.

.blitz

bomberesque wrote:

It's perfectly possible to break the fork crown without collapsing the front wheel or snapping the frame, normally by landing vary badly

That's what I was concerned about

Have you broken a crown?

dan shard

This would probably bend them too

http://www.photochopz.com/gallery/data/ ... sh_dog.jpg

Oxygen Thief

How are you supposed to land then? Noob!

bomberesque

cgarossi wrote:

Nope.

If you apply a force to anything, it will give try to give way and will transmit the given force through the weakest points first.

<strike>Bollocks</strike> sorry, that simply is not true. The fact that the weakest link will fail first is not the same as "the force travelling through the path of least resistance"

The forces applied will travel between the supports through *everything*, the exact force applied at each point will depend on the geometry, not the strength of the materials.

Just because the wheel hasn't failed yet doesn't mean there's no force on the crown (for example).

The only time this will change is is one member deflects enough (or fails) so that it "bottoms out" against another.

supersonic

Usually riding into trees is what kills forks.

cgarossi

The fact that the weakest link will fail first is not the same as "the force travelling through the path of least resistance"

Um, yes it is. The force may be applied equally everywhere, but if you inflate a balloon inside a drainpipe for example, the air will force the balloon down the pipe toward the end. Following the path of least resistance. Geometric shapes are there to channel these forces in the direction required.

In the case of a wheel and shock, the wheel should transmit the force to the shock which should absorb it using its suspension action (the weakest point in this case). If for some reason the shock cant absorb the impact the force will then its next weakest point, the wheels probably, which collapse and buckle. Theoretically.

I never said it was to do with materials, just the transmission of forces through it.

Raindrops will follow the path of least resistance down a window pane. Electricity will follow the path of least resistance through a conductor. Pressure will do the same.

supersonic

Force in a shock is cumulative - ie x newtons per y inch. It is possible to kill a wheel and not use full travel of course. Especially in a lateral impact.

cgarossi

Well yes. It would have to be a major impact (one that would put you in hospital) for the fork and wheels to fail. Wheels are obviously designed to take upward forces.

bomberesque

No, no it's not.

like I said but applied to your scenario, as the fork is compressing but has not yet bottomed out, there is still force being transferred through the fork crown (and all other components / members between it and the next point of support / momentum source) the force does not magically wait until something breaks before moving on to the next bit. if that were the case, you would feel no resistance in the handlebars, you would be completely insulated from all forces coming out of the ground until every component between you and it failed. Patently not the case.

Oxygen Thief

The simple answer is the weakest point will break first whatever it is, doesn't really matter whether that's the point of least resistance or not.

joshtp

bomberesque is right on this one.....

supersonic

The part that fails first is the one where the load or force it can handle is exceeded.

As bomber points out, this can depend on the geometry of the situation.

A sudden, very sharp hit can kill off many components, but might only use half the travel. You may fold the downtube and not use any.

Larger amounts of travel spread the transmitted force over a greater time period ie lessen peak force from an impact. Suspension cannot compress if there is no force to oppose it ie our weight.

bike-a-swan

joshtp/mbukman wrote:

bomberesque is right on this one.....

+1

mackie1

I piled into a 2 foot wide, 1 foot deep gulley at probably 25-30mph and the bike stopped dead and threw me off (no serious injuries, landed on camelbak!). That spun the stem on the steerer and buckled the wheel but the forks (2009 Reba SL) were totally undamaged.

I suspect even the light ones are over-engineered. Probably more chance of a weld failing at your head tube?