What's the rationale of the "Inverted Forks" design?

I've recently attempted to find a clear and easily understood online answer and explanation for the above stated question, but so far the explanations are over my head. For those of us who are not mechanically inclined, please explain and demystify the rationale behind the design concept of 'inverted' front forks.

Thanks!

 

being inverted helps force the air down, there for creating downward pressure on the upperfafir.................... hell I don't know....but it looks cool...........

 

I think it has something to do with the strength factor of the inverted fork layout,the inverted forks are a stronger,less flex, unit.When I rode motorcross, MX bikes started having
inverted forks around the late 70's or early 80's(DONT HOLD ME TO THAT EXACT TIME
FRAME) eddie

 

less unsprung weight.
on a conventional fork all the internals and weight of the internals are what has to move up and down.
on an inverted fork the "guts" remain stationary and it is only the lower most part which moves up and down.
i cant really put it into words, but lessening the unsprung weight is very good for handling. i think the suspension has better control of the rebound and dampening with less weight to control...
also it looks better lol.

 

So why does everyone not do it?

 

Hey Candy, Now that I think of it, I believe you are correct. However as I stated, I
think the set up has less flex in it. eddie

 

What is 'unsprung' weight, how do inverted forks reduce this, and what are the advantages therein?

OK-- With conventional forks the bike has a certain weight by itself without a rider, and this weight compresses the front and rear suspension to some minor degree. Then there's the added weight of a rider as well as any additional weight such as luggage and a co-rider. Then there are the road forces while riding such as bumps and low spots that compress and decompress the forks from moment-to-moment, as well as lateral forces when leaning/turning, as well as additional forces to the suspension when accelerating and braking, etc. So, what are the advantages of inverted forks over conventional forks? Please forgive my naivete, and please keep the answers coming along!

 

unsprung v. sprung

Sprung weight is everything on top of the springs.
Unsprung is everhthing below the springs and basically attached to the wheel.
The rider, the gear, the motor... has to bounce up and down and be in control and damped
The stuff that is unsprung and attached to the wheels is under control and doesn't produce forces that are variable.

 

Also, there is less flex

The inversion, and some adaptations, do change where and how much it will flex. For the better.
Why don't they all have. Economies of scale. Just because something is better, doesn't mean everyone adopts it.They have tooling, and jobs, and physical plants, and parts supplies that reach into the 100 of millions invested in the old system. You can't just junk all that. Besides the fact that they are marginally better, and who really notices? Fuel injection is better than carbeuration, but it has been 30 years and you can still get a carb in a new model. Why? Because they are cheap, do the job, and most daily drivers don't know the difference

 

RedMenace hit it on the head in his last post. Inverted forks are better for the reasons he listed; torsional rigidity, unsprung weight, and better damping control. Why don't all bikes have them? Costs! New Ducati's have traction control, Ninja 250's don't. If you throw 18,000 large at a bike you get cool stuff (including inverted forks).

Redrover - Think of unsprung weight like this. If you hold a spinning bicycle wheel and turn it you can feel its inertia. Now imagine doing the same with a motorcycle wheel. More weight equals more inertia. Same with weight on the end of the forks.

Action

 

The Storm

I almost chimed in early....but....knew this was to be a shit storm.This thread may kill the tiger.

 

Google is your friend: http://www.yamaha-motor.ca/technology/technology.php?group=M&tech=IF

 

There's a couple disadvantages, too.

With a regular fork with drain plugs, you can change your fork oil without removing the forks. Just lift the front end, and pull the drain plugs and cap.

With an inverted fork, once the seals start leaking, they will likely crap out faster.

The other bad thing is the effects of a frontal collision. A regular fork tube bends at the lower triple tree. The fork tube gets toasted, but it takes up some of the impact forces in the process. With an inverted fork, the fork tube bends, but since the tube is at the end near the tire, it bends at more of an extreme angle and transmits more shock to the frame/tire. It is also much more likely for the fork tubes to snap right off. This is very rare to occur with standard forks. Either way, the rider has already been thrown off the bike, but in the latter scenario, there's a greater chance for more collateral damage to the bike... torn brake/clutch hoses, tire, wheel, rotor, and frame damage.

 

reading through this thread and seeing all thank you freebies and lack of one thank you, and your mods it becomes pretty obvious what you want to hear... upside down forks are over rated. ooooooo do i get a thank you now....ound:

 

A civil thread with helpful information....

RC46 is left behind:frown:

 

i know right... i never tried to be helpful...