Inverted Forks

[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 You can argue all day long about the virtues of outdated technology like the dyed-in-the-wool muscle car guys constantly do, but the reality of things is that improvements in suspension technology have been made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.

 

[Guest]

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...)

 

[Guest]

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... )

 

[corndog67]

There are some advantages to spindily forks. And a flexy chassis.

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

I completely disagree with this statement. Give me some examples where flexi forks would be an advantage. Well maybe ridgid frame choppers that use tire pressure and fork flex for their suspensions. But other than that, I can't come up with any scenario where fork flex is an advantage.

As for the feel of brakes, I had an '81 GS1100E, with stainless lines, stock master cylinder, stock calipers, and some EBC high performance pads. You're right, the lever was very solid, you could lock the front wheel pretty easily. But, they did not have the feel of a late model front brake. I mean, as far as modulation at the point of lock up. In my opinion, there is no comparison. The early brakes had enough power, but not enough control.

 

[Nerobro]

There are some advantages to spindily forks. And a flexy chassis.

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

I completely disagree with this statement. Give me some examples where flexi forks would be an advantage. Well maybe ridgid frame choppers that use tire pressure and fork flex for their suspensions. But other than that, I can't come up with any scenario where fork flex is an advantage.

First off, most custom choppers are lucky they don't kill their riders. I won't even pretend to discuss those abominations.

I didn't say flexy forks were the advantage. I said spindly forks have some advantages ;-) Lighter unsprung weight mostly. Notice that 125cc motogp bikes still run quite small forks. Those bikes are entirely about corner speed and do everything they can to reduce unsprung weight. Their 425 chain is there for the same reason.

Thankfully bikes have wonderfully low forces on them. (at least while cornering) Even at 45deg of lean the suspention only has 1.4x the weight of the static weight of the bike on it. And even then the vertical loads on the tires are the same as in a straight. (in a car the tires on the outside of the corner can see as much as double their static loads, without downforce. With downforce that number can be unlimited)

Flexable chassis generate more grip, but break away more abruptly. At least if hondas engineers are to be belived.

Back to braking though. I don't think early brakes had enough power to have the "feel". You can squeeze the heck out of them, eventually locking up the front, or doing a stoppie, but if you're concentratning on squeezing hard you're not concentrating on keeping them from locking up.

That's also to say that the single disk that came with my 1980 550 were inadequate. The master cylinder and brake combination on my 83 550 isn't nearly as sharp or as powerfull as the 80 Master cylinder and 82 650 brakes on my 1980 550. The pistons on the 83 calipers are smaller than the 650's, and I'm fairly sure the master cylinder is a larger diameter as well.

This can also lead to a fork question as well. As the forks on our GS's are pretty flexable. And under heavy braking are likely to bind. Binding up in the suspention will cause the tire to skip and hop, incresing braking distance.

 

[Nerobro]

http://www.vintagebrake.com/mastercylinder.htm

That might be usefull..

 

[morthrane]

There are some advantages to spindily forks. And a flexy chassis.

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

I completely disagree with this statement. Give me some examples where flexi forks would be an advantage. Well maybe ridgid frame choppers that use tire pressure and fork flex for their suspensions. But other than that, I can't come up with any scenario where fork flex is an advantage.
[/QUOTE]

Some flex is necessary, because as the farther you lean over, the more inefficient the suspension will be. Look up the design details for the front-end on the Moto Cyzyz (sp?) prototypes-- they use fork inserts to "tune" fork flex properties.

Yamaha's made prototype/test MotoGP bikes to specifically work on chassis stiffness tuning.

Colin Edwards turned around his season in 2002, put the screws to Troy Bayliss, and won the WSBK title. Rumor has that amongst other things, an engine bolt was removed to allow the chassis greater flex.

Harley's VR1000 was a disaster for, amongst other things, having a chassis that was made as stiff as possible.

I could go on, but hopefully this gives you the idea-- yes, flex is a necessary, unavoidable, and useful thing. But like too many good things, its terrible without moderation.

 

[C7Z]

Inverted forks

Inverted forks

Not that I know anything, but I always assumed that the inverted fork was superior because it reduced some of the "unsprung weight" on the front end of the bike making it ride smoother and the suspension react quicker to changes in the road surface.

My $0.02
-D Payne

 

[xDUKEx]

ok guys ive watched this thread long enough !!! i bought my 83 E 2 years ago and rode it bone stock all year last year !!! over the winter i did the suspension mod including inverted forks, rear swing, modern rubber, brakes. HUGE DIFFERENCE !!!!!! i ride with a couple of friends that have 05/06 crotch rockets. last year i had to really slow down in the corners and catch up on the straights. this year i can hang with them anywhere. the bike is so much quicker steering and the braking is 100 times better. the antidive forks, in my book are trash. my bike used to dive down so much under heavy braking with the old forks it would allmost lift you off the seat !!! not any more !!! i am so glad that i did the mods, i love the looks and best of all the performance !!! it is a totally different machine now !!! I LOVE IT !!!!!!!!!

 

[Ogri]

I'm with the XDUKEX......

My USD forks are the berries!!!

 

[Billy Ricks]

The USD forks are superior in every way to the stock GS units. A modified GS front end can be made to work pretty good but nowhere near as well as anything newer than about '88. Even the '88 GSXR fork I have on the bike now is light years ahead of the GS stuff. Soon I'll be going through both ends again using a '95 GSXR front end with 954 triples. I'll still run the wheels I have on the bike now with a Works shock on the rear.

 

[Nerobro]

The USD forks are superior in every way to the stock GS units. A modified GS front end can be made to work pretty good but nowhere near as well as anything newer than about '88. Even the '88 GSXR fork I have on the bike now is light years ahead of the GS stuff. Soon I'll be going through both ends again using a '95 GSXR front end with 954 triples. I'll still run the wheels I have on the bike now with a Works shock on the rear.

Remember that up untill just a few years ago, they were still running normal forks in motogp. JUST LAST YEAR the R6 went to USD forks.

I don't think you're describing the difference between USD and normal forks, but the difference between cartriage forks and damper rod forks.

 

[Billy Ricks]

Remember that up untill just a few years ago, they were still running normal forks in motogp. JUST LAST YEAR the R6 went to USD forks.

I don't think you're describing the difference between USD and normal forks, but the difference between cartriage forks and damper rod forks.

You read me right. Anything after '87 on GSXRs had cartridge forks. My '88 front end is leagues ahead of the stock front end. I expect another leap in performance once I install the USD unit. It's not just about rigidity, there's plenty of other benefits of installing newer stuff.

The newer front ends don't have near the travel of the old stuff so cornering and braking benefit. The radials that get run with the shorter travel forks do a good enough job of soaking up the little stuff that you can run more agressive preloads and not get hammered on the street.

The 600's were running normal cartridge forks up until a couple of years ago. They also happen to have the same 43mm inner tubes as the USD units. I don't think you are going to find any MotoGP bike has ever run anything other than Ohlins and maybe a few one off Showa USD forks.