[borzwazie]

So, note this picture:

I see a lot of people cutting the tail off the frame (everything behind the shock mounts). It does look cleaner, but I have to think it affects the handling somehow.

Anybody got any hard numbers on what this does to your handling? Does it make that much of a difference?

 

[Geeto67]

as long as you put in a cross brace above the shock mounts it should not make a difference.

 

[mudmonkey]

yep, what geeto said.

 

[craig641]

Make sure the hunk of metal you put above the shock mounts won't rub on the tire when the shocks are completly compressed.

Craig

 

[ROSKO]

quote:...Anybody got any hard numbers on what this does to your handling? Does it make that much of a difference?

YES, it does a number "3" to the handling.

 

[KeninIowa]

I don't think that's the weak point even if you don't put anything back in. I have a theory, but it's too convoluted to type.

I would like to see some pics of the infamous braced CB350 frames running around and hear the opionions of guys that have ran them both ways.

 

[FR]

quote:Originally posted by ROSKO

quote:...Anybody got any hard numbers on what this does to your handling? Does it make that much of a difference?

YES, it does a number "3" to the handling.

NFW dude, it does a number "2", worst case a "2.5".

Oh wait, were you factoring the stock rim width in that calculation, 'cause if you were then you're right...

FR

 

[UngaWunga]

Ok, #1 & #2 are only really there to hold the rear fender on the bike. The horizontal brace right before the shock mounts is structural, and should be enough if you decide to remove the rear loop. That rear loop also holds up the back of the stock seat. Even with a fiberglass seat its nice to have that back there to give support.

The green lines are where the frame braces normally go. And put 18" wheels on it and don't lower it if you want it to handle well.

 

[ROSKO]

maybe you are right, 2.5

made of 4130 but you get the idea...

 

[chrisf]

I did this to my CL350 with no rubbing problems at all:

This is what i did on the CB360. I didn't use the DOM tube because, as others suggested, there would have likely been rubbing issues. Also of note is the welded plate under the seat. Together, I think this adds significant stiffness over stock.

Just chopping off the end--in my opinion--introduces a lot of flex. How could it not?

--Chris

 

[UngaWunga]

Well, its not really a structural part in the first place. Think of where most of the flex occurs on those bikes. Its the twisting of the swingarm plane in relation to the plane of the headstock. The best way to get the bike to handle is to minimize the flex between those two. The green lines in the picture above is how you do that.

Now, check this out. From the Eurospares site, a custom frame for a Laverda racebike:

Look at how the frame is structured to keep the swingarm and headstock from flexing.

 

[UngaWunga]

And the flat plate you added might help, but where its located it most likely just adds weight more than it braces the frame.

But I'm blabbering on two large cups of coffee. Read the real stuff here: http://www.tonyfoale.com/Articles/Frame.mod/KawaMods.htm

 

[HackAsaw]

I made a reasonably substantial passenger support and frame brace for my feather bed

shown here not ground, sanded, polished, or swiss cheesed

glass seat was bedded to fit it

overkill I guess but a Fbed will wiggle around in the rear with the flimsy stock metal

and it wouldn't support a passenger

 

[FR]

quote:Originally posted by UngaWunga

Ok, #1 & #2 are only really there to hold the rear fender on the bike. The horizontal brace right before the shock mounts is structural, and should be enough if you decide to remove the rear loop. That rear loop also holds up the back of the stock seat. Even with a fiberglass seat its nice to have that back there to give support.

The green lines are where the frame braces normally go. And put 18" wheels on it and don't lower it if you want it to handle well.

In a timely post, bcr took this photo this weekend, and it does show Unga's frame braces (w/K&N sticker applied);

The thing that bugs me about some of the rear/seat frame mods that I've seen is that often times people will cut away the seat support and throw their 'glass racing seat on, but have no support for the 'glass seat. Then when they need a push start, you're pushing the weight of the rider and the bike on unsupported fiberglass. My racebikes have a loop that supports the seat and makes the seat frame continous. It may not add much torsional rigidity, though it will contribute some, but it definitely adds structural rigidity, and gives your pit buddy something solid to push on.


FR

 

[catboy]

i'm no structural expert, but i don't think that arch is very significant.

couldn't you just cut off and reposition that arched brace forward once you hack off the rear loop, keeping both a seat support and what little strength or stiffness it might offer the frame?

 

[ROSKO]

quote:Originally posted by chrisf

I did this to my CL350 with no rubbing problems at all:

Just chopping off the end--in my opinion--introduces a lot of flex. How could it not?

--Chris

Chris,
That's weird. I had a brace in the very same place and it did rub. Are you getting full suspension travel? Maybe your spring is too heavy. You should get about 1/3 static sag with rider... that's a whole 'nother can o worms...

I have ridden behind tex into the carosel at summit point and I can tell you that the stock frame WITH the loop does flex A LOT, anything that can help is worth doing.