Shortening the frame

[oohsam]

Hi Guys.
Am going through the cafe racer build of my GS1100G.
One thing that stood out like a sore thumb to me was the length of the frame that houses the seat. It really comes out really far and I wanted to chop it just after the rear shocks.

I did notice however, that the springs/shocks don't attach to the frame, but some fabricated steel that is welded to the frame, and that steel runs down almost the full length of the frame. This is the area I'm talking about (not my bike in the pic, i shamelessly stole it from another thread!)

Im a bit worried now to cut it, and lose stability/rigidity etc.
Can anyone advise here what I should do.

I was thinking of cutting it and re-enforcing a cross bar that will join the ends, kind of square it off, or put a hoop. Only problem is height. i dont want that reinforced bar to hit the tyre on bumps. So it might have to weld it above to the top...
but again. i have no idea how much support i will be removing from the bike....

 

[Hammered]

From a structural stand point, that portion of the frame will not effectt he strength of the shock mounts. You will want to connect the 2 sides of the seat rails to add a bit rigidity to that area. Especially if youre using a fiberglass or alloy seat pan assembly. Stiffening it up will lessen the effect of cracking there. Ive completely removed that portion of the frame for a slight drop seat design. Though Im adding over and under bracing so I can use an airbag suspension. You can weld a cross member in or create a bolt on option. Either will be just as good for what youre doing. Now if you plan to put this through the rigors of racing or stunting, you may want to go a different route.

 

[oohsam]

Ok that is great info....

I will weld a cross member across the area to join the 2 sides. I was just worried when looking at it, that the part the shockers are bolted into are not the actual frame, but a welded piece that tapers off towards the rear. you can see it in the pic. I dont want to weaken that and when i hit a bump, it breaks the weld...

It hasn't been welded all the way across, just in 3 sections. i might continue the weld along the entire length of the tapered piece, to create that extra bit of strength.

looks like the grinder is coming out tonight!

 

[Loose Seal]

That's exactly what I did on mine. Chopped off the rear 4-5" after the rear shocks and welded a piece of steel across the frame.

I have bottomed out a couple times on nasty potholes but it wasn't a big deal.

 

[oohsam]

Thanks guys!
see you later back end!

 

[hillsy]

Looking at the pic you posted there is a cross brace already on the frame seat rails about 3 inches in front of the shock mounts.

I can't see you losing much lateral rigidity (if any) seeing that brace is already there.