Inverted Forks

[bwringer]

Back to the topic at hand, are there any handling problems created by lashing super-stiff "new style" inverted (or conventional) forks to the flexible "old style" GS frame? As it is now, both the frame and the fork have similar "matching" limits.

Also, it is possible to easily perform such a fork transplant on a shaftie, where you're pretty much stuck with a 130/90-17 rear tire? IOW, would you be able to retain the stock 100/90-19 front tire and rim while transplanting the newer stiffer forks?

Anything's possible with a machine shop and plenty of time, but I didn't know if anyone's found a way to do this less painfully. I know most fork/front wheel transplants also involve a swingarm/rear wheel transplant to fit wider rubber, and that isn't an option on a shaftie.

Just random thoughts...

[morthrane]

Of course there's the potential for problems. The chassis, much like an engine, is a system that is more than the sum of its parts. Changing one part of that system will invariably bring out the shortcomings in other parts, or introduce new problems (e.g., ground clearance); if you're not careful, the whole system just won't work well at all. The best analogy I've heard is that of baking a cake-- the finished product does not resemble the ingredients, and major changes to the quantity of ingredients can make an otherwise tasty cake totally unpalatable. This isn't to say you can't tweak and tune, just that its apparently very easy to reach a result that won't fit your tastes as a rider.

For example, most of the "serious" chassis upgrades made to Katanas involve bracing the frame in addition to upgraded brakes/forks/wider wheels/swingarm/shock(s).

Another point to consider is that wider tires are actually detrimental to handling. Wider tires are a method of coping with horrendous horsepower outputs; does a shaftie put out that much power to really need wider tires?

Unless you're willing to go the whole route and upgrade the entire chassis, it doesn't seem like its really worth the effort when you can spend a small sum of money to make what you have work better. Different brake pads, Racetech Emulators, different springs, some cheap shocks that aren't 20 years old...

[morthrane]

FWIW, I've had a chance to put some miles in the mountains on my 82 1100-motored Katana. It doesn't actually handle that badly for a 550+lbs bike, it just can go way too fast and overwhelm the pitiful OEM brakes.

The chassis definitely is a flexiflyer, as I found when a bad mid corner bump essentially levered the front wheel into the air momentarily, the Yoshimura 4-1 left a chunk of itself embedded into the asphalt, and a piece of the seat vanished into a black hole.

I'm looking right now at how I can make an extra 01 R1 frontend fit on the Katana....

[Dink]

FWIW, I've had a chance to put some miles in the mountains on my 82 1100-motored Katana. It doesn't actually handle that badly for a 550+lbs bike, it just can go way too fast and overwhelm the pitiful OEM brakes.

The chassis definitely is a flexiflyer, as I found when a bad mid corner bump essentially levered the front wheel into the air momentarily, the Yoshimura 4-1 left a chunk of itself embedded into the asphalt, and a piece of the seat vanished into a black hole.

I'm looking right now at how I can make an extra 01 R1 frontend fit on the Katana....

TO fix the brakes flush with Methylated spirit and refill with Castrol SRF brake fluid, it isn't cheap but it will then pull two finger stoppies. Remove anti-Dive lines if not already done.
Dink

[katman]

and remove the garden hoses and go with s/s lines

[RJ]

OK it seems that alot of us are missing the point. If the factory engineers of all 4 Jap companies went to inverted forks for their high-end bikes (and race bikes), there must be some kind of benefit to that design. It doesn't take a rocket scientist to figure that out. You can argue all day long about the virtues of outdated technology like the dyed-in-the-wool muscle car guys constantly do, but the reality of things is that improvements in suspension technology have been made since 1982. How much of that technology you do or do not adopt is up to you. But there is no way in the world yo can tell anyone that a set of forks or brakes built in 1982 can possibly compete with 1990's computer-designed tech.

[katman]

HERE HERE!!

cOULDN't OF SAID IT BETTER MYself.....

[Nerobro]

Yes, and no. I think you missed what has been said. First off, as has been discusessed, inverted forks have lighter unsprung weights, and weigh less because you can use larger diameter, and thinner metal, for more of the fork.

Yes cartridge type shock valving is a huge advantage, but that can be retrofitted to older forks. And rightside up forks can also be had with cartridge type internals.

As for braking, really there hasnt' been all "that" much development. Radial brakes? Those came about because their mounts are lighter. Multi piston brakes? Have you noticed that they went through a phase of as many as 8 piston calipers, and are now back down to 4 piston calipers.

Given a proper master cylinder, sticky tires, and a ballsey enough rider. Even a GS1100gk could endo on two fingers.

The major advances in chassis design have been with frames and tires, more than suspention and brakes.

Making the "musclecar" analogy is false. The actuall "improvements" in motorcycles have been much more incremental, and even have gone to their ultimates and come back again. (think chassis stiffness, flexable bikes make more traction than stiff ones) And the funny thing is.. Live axles are still the fastest way to go straight. Also most modern cars use a strut type suspention, which is CHEAP not good. Those old musclecars frequently had unequal length a-arms up front. And at least the chevys had pseudo 4 link setups out back. While the back end sacrifices unsprung weight for strength, the front end is still better (at least if your frame of refrence is dictated by what race machines use) than what you'll find in a modern beemer ;-)

What it comes down to is that our GS's are "relitively" modern bikes. And while "flexi fliers" they do have the building blocks of a quite quick bike. The biggest thing we can do is emulate the new bikes. :-) (In my case, reducing trail, reducing rake, swapping out my master cylinder...)

[katman]

this started with a comparison with stock 82 forks with progressive springs and heavier fork oil and modern forks and brakes.....

[Nerobro]

*grins* Threads evolve. Though I think the root of the thread is someone thinking that you could "invert" conventional forks. Which can't be done.

[corndog67]

holy cow...sportbikes went with inverted forks because of dirtbikes? hahahahahahaahha How do you figure? Just about every manufacturer that adopted inverted forks introduced them the same year...most actually popped out dirtbikes the next year.

The development and placement of inverted forks had nothing to do with dirtbikes or streetbikes. It was entirely about structural rigidity. They're sturdier...beefier...heavier. They don't flex as much, which equates to better road handling in the curves. Also, the travelling end is shorter, reducing the amount of leverage against the road, making bending more difficult.

Oh and just for kicks:



Anyone want to tell me what dirtbike had inverted forks from the factory in 1988?

In '88, ATK came stock with White Power 4054's. I had one back then. KTM also used the 4054 that year (I still have one that I ride regularly, a 500 MX).

Now, for other matters. It is obvious that a few of you guys haven't ridden a late model Suzook or anything with USD forks, and 6-piston calipers. Besides the stiffness mentioned by others, they are absolutely PLUSH, ridewise, and jjust plain work well. The originals, even with progressive springs, emulators, flluid change and whatever else you can do to them, do not compare, not even close. As for the stiffness having to match the flexiness of the old frame, well, the stiffer the better. If you are riding hard enough on the street to really get your frame flexing that much, maybe you ought to buy a newer bike.

The 6-piston calipers, not even necessarily the radial mount ones, are also so much higher performance than, say some early 80's brakes, that it's almost unbelievable. If you use the right pads, not necessarily race pads, just some fresh stock ones, the master cylinder that came with those 6-piston calipers, the discs are in good condition, there is no way that the old brakes can compare. It's not just the power to lock the wheel. It is the FEEL that those brakes have. They are so sensitive, you can modulate them right to point of locking up the wheel, and have complete confidence while doing so.

[akreider]

Yes my original question was about if inverted forks were coverted from the older conventional style. But this thread is getting interesting, very informative.

Thanks for all of the feedback

Adam

[flyingace]

OK it seems that alot of us are missing the point. If the factory engineers of all 4 Jap companies went to inverted forks for their high-end bikes (and race bikes), there must be some kind of benefit to that design. It doesn't take a rocket scientist to figure that out. You can argue all day long about the virtues of outdated technology like the dyed-in-the-wool muscle car guys constantly do, but the reality of things is that improvements in suspension technology have been made since 1982. How much of that technology you do or do not adopt is up to you. But there is no way in the world yo can tell anyone that a set of forks or brakes built in 1982 can possibly compete with 1990's computer-designed tech.

Don't buy that for a minute. I remember when every bicycle manufacturor put oval-shaped chain rings on their new bikes one year. They said they were more efficient by some outrageous percentage. It wasn't until a couple of years later when an idependent party actually did research did they find they provided zero improvement.

My point is a bike maker will market whatever they think will sell. Only time and trial and error will tell whether it's better or not.

[corndog67]

Don't buy that for a minute. I remember when every bicycle manufacturor put oval-shaped chain rings on their new bikes one year. They said they were more efficient by some outrageous percentage. It wasn't until a couple of years later when an idependent party actually did research did they find they provided zero improvement.

My point is a bike maker will market whatever they think will sell. Only time and trial and error will tell whether it's better or not.

Go ride something with the new front ends on them. Be objective. There is no comparison between then and now as far as suspension and brakes go.

[Nerobro]

Um... LIke I said before. Modern bikes don't use 6 piston calipers. They use 4 piston calipers. Brake disks have been getting smaller (on average) since the mid 90's. However pad per piston calipers are now the rage.

What causes brakes to do what. "feel" is directly related to the stiffness of the brake lines, the stiffness of the caliper mount, master cylinder layout, and pad design. Pad per piston brake designs "decouple" the pad and allow more feel to come through the lever. Holes, waves, slots, in both the pads and rotors change the way the brakes feel on intial pull, and change the behavior when the disks and pads come up to temprature. The more leading edges your brake pads see, the more intial bite you get. Conventional master cylinders have a lot of "sliding" action on the lever, which works out the same way as a friction steering damper does. You don't want that in your brakes, so they are moving to radial master cylinders which don't have the sliding interface on the master cylinder piston. Master cylinder diameter, brake disk diameter, and brake piston aera all factor into the multiplaction of force from the brake lever to the disks. Larger disks affect handling due to gyroscopic forces, and greater unsprung weight..

These are all things that can be transfered to our older bikes. Or trimmed, tuned, and adjusted on any bike really. This actually does affect the forks eventually though. If your braking forces are high enough to cause major fork flex you'll see some handling issues under heavy braking. Sadly the forces applied under braking aren't the kind of forces that a fork brace will help with.

This years GSXR's actaully are going to SMALLER forks for reduced stiction. Larger diameter seals take more force to break loose and can hamper suspention action.

I"m not about to say that a modern fork isn't going to out preform an older fork, but I will say an older fork has a fighting chance!

That "plushness" is the result of having seperate high and low speed damping. That is something that comes from having a cartirage fork.... which you can have with either a USD or standard fork.

There are some advantages to spindily forks. And a flexy chassis. So long as neither is so flexable as to make you feel out of control. The big reason behind going to stiffer components is so they can tune back in flexability. There was a time in the early 90's where the bikes were frighteningly stiff, and now they retain the stiffness in the vertical plane, where you see advantages on acceleration and braking, but they're almost noodly in the horizontal planes!

(yes, I know this started with forks, but you can't discuss forks without discussing the rest of the chassis that goes with them... )