frame bracing

would like to know if frame bracing is actually necessary, not to take away from anyone's opinions but honestly I don't see the reason.ex. frame brace in front of engine behind front tire when engine is secured to motor mounts is the engine not strengthening this section?I would think the engineers back in the day new what they were doing.My 74 z1 does 125 m/h in the 1/4 mile straight as an arrow but yes I change steering,wheel bearings proper fork rebuilding etc. and never have the so called speed wobble some talk about.then again I run newer style front and rear ends.I have another z1 frame I am rebuilding now and really just curious for the real need to brace the frame.. just saying.
opinions please.

the modern swing arm helps a ton!

it doesn't sound like you are much of a corner stuffer,canyon carver type.(no offense meant)

where the flex in your frame shows up will be when leaning into corners hard enough to drag stuff.

especially as right and left transitions then you get "the wiggle".

the "speed wobble" is probably more a product of the bikes that did not have the headstock straight from the factory.

i read that pops always cut the headstocks off his z1's and re-welded them so he knew that they were square.

so the bracing is really for more of a road racing style application.

for drag racing,if it launches hard and goes straight i wouldn't add any extra weight in the form of bracing unless it starts not tracking straight.

thats my .02,ymmv.

leon

I agree with Leon's estimation. If you are interested in bracing for road race applications then google Tony Foale. His website has lots of information and he has written a couple of books on the subject of motorcycle handling.

no offense taken..
corner stuffer? I stuffed a corner this summer so hard I am still picking asphalt out of my ass lol.this is why I am rebuilding,bike got trashed. You can only lean these babies over so far before "oops" there goes my pipe. gsxr-forks 17" rims= dents
thanks

sorry to hear that.

leon

Take look at a stock kz frame next to a stock gpz1100 frame some time.
Youre right,I think those engineers at Kawasaki did learn something! :laugh:
So are you running a z1 frame or a 78 kz1000 frame,theres a world of difference in the quality of the 2 in stock form.

I tore down my dad's GS1000, and the cop bike my brother gave me.

The 1987 KZ1000P frame is probably twice the weight of the 1979 GS1000 frame! Thicker-wall tubing, and lots more of it.

One reason modern sport bikes have aluminum perimeter frames is that aluminum doesn't flex like steel does. Think of it like this: How many aluminum springs have you ever seen? How many steel springs? It's a good thing aluminum weighs so much less, because it's not as strong as steel, much more of it has to be used to build a strong frame.

Like Leon said, the modern bits will help the handling a great deal, but why switch to those bits if you're just going to go in a short, straight line? Harleys are good that straight line thing...

And you probably know already, but I'll go ahead and spell it out: "Stuffing" a corner means passing someone on the inside, following a tighter line. They'd like to follow a certain line, but they learn at the last moment that the spot they'd like to occupy has been stuffed full of another rider.

Mladin stuffs Hayden



Rossi stuffs Gibernau

I am going to have my frame raked and push it to a 1075 with the right adjustments in head and carbs I will do some extra bracing even though most of my torque will see short straight lines
and only occasionally.

probably not needed but as someone once said these old things were welded together with plumbers pipe

i did extensive bracing in my two race bikes, but agree that i would consider it only for road racing. or... if it was for a known flexi flyer like the two stroke kawi triples .

guitar

"One reason modern sport bikes have aluminum perimeter frames is that aluminum doesn't flex like steel does. Think of it like this: How many aluminum springs have you ever seen? How many steel springs? It's a good thing aluminum weighs so much less, because it's not as strong as steel, much more of it has to be used to build a strong frame."

lets leave aside the metalurgy facts... if that was true, Duacti wouldnt have dominated WSBK for the last twenty five years with their flexi steel frames like they did... and even this year KTM took the moto 3 title with a steel frame...

guitargeek wrote: I tore down my dad's GS1000, and the cop bike my brother gave me.

The 1987 KZ1000P frame is probably twice the weight of the 1979 GS1000 frame! Thicker-wall tubing, and lots more of it.

One reason modern sport bikes have aluminum perimeter frames is that aluminum doesn't flex like steel does. Think of it like this: How many aluminum springs have you ever seen? How many steel springs? It's a good thing aluminum weighs so much less, because it's not as strong as steel, much more of it has to be used to build a strong frame.

Like Leon said, the modern bits will help the handling a great deal, but why switch to those bits if you're just going to go in a short, straight line? Harleys are good that straight line thing...

And you probably know already, but I'll go ahead and spell it out: "Stuffing" a corner means passing someone on the inside, following a tighter line. They'd like to follow a certain line, but they learn at the last moment that the spot they'd like to occupy has been stuffed full of another rider.

Mladin stuffs Hayden

Rossi stuffs Gibernau

Ill agree with 99% of what you just said its just the way its stated.
A piece of aluminum in the same diameter/wall thickness/shape will bend just as much if not more than a similar piece of mild steel.
The aluminum frames/swingarms get their strength from being made from a boxed or rectangular piece of material versus being just round tubing.
That's what makes the frame braces I make really strong/light is that they are straight/flat in 2 differant planes to keep them from twisting from front-back and also side-side

turboguzzi wrote: lets leave aside the metalurgy facts... if that was true, Duacti wouldnt have dominated WSBK for the last twenty five years with their flexi steel frames like they did... and even this year KTM took the moto 3 title with a steel frame...

Compare a modern Ducati trellis frame with an early KZ backbone frame. The trellis is more or less the idea of gusseting a frame, carried to it's logical conclusion. I can't say for sure, but I'd bet you a beer that the Ducati frame is made of sterner stuff, a more advanced alloy...

A lot of the theory of moto metallurgy and frame geometry I picked up from Tony Foale, Kevin Cameron, and my friend Jackie, who was a builder/racer. She swore by 4130 chromo!

guitargeek wrote:

turboguzzi wrote: lets leave aside the metalurgy facts... if that was true, Duacti wouldnt have dominated WSBK for the last twenty five years with their flexi steel frames like they did... and even this year KTM took the moto 3 title with a steel frame...

Compare a modern Ducati trellis frame with an early KZ backbone frame. The trellis is more or less the idea of gusseting a frame, carried to it's logical conclusion. I can't say for sure, but I'd bet you a beer that the Ducati frame is made of sterner stuff...

well, i was just reacting to your statement "aluminum doesn't flex like steel does" as a reason as why sport bikes use perimeters....

and NO, a trellis frame is NOT "gusseting a frame, carried to it's logical conclusion"

a trellis frame is a different concept all together of using the tubes in simple push-pull load, without bending. a gusseted cradle frame is a frame that naturally bends and that you are helping by reinforcements.

like wireman said just above, maybe its just the way you put it.

And BTW, cro-mo steel has the same young modulus as the mild steel used in our old K, it's just the ultimate strength that's different.