Bob Broussard has a 90 GSXR 750
swingarm on his GS. He had a 93 gsxr swingarm on it before. The linkage from the 90 works with the shock for '96-'99
750. The shock was turned out to be way too long, but with the '90 linkage it works great.
The swingarm needs to be
narrowed to fit the frame. The bearings are the same as the GS, just use the stock spacer and bolt. He also had to grind
the frame inside behind the pegs so the swingarm wouldn't rub. The most difficult part is the shock linkage. The 90 gsxr pivot
piece is wider where it connects to the frame. It has 2 bearings while the GS has 1 wider bearing. Except for the width, they
are the same. He milled the piece down to fit the frame and used the GS bearing and spacer.
His extra long shock fits with
the correct ride height. A different shock would cause the rear to be too low unless it can be lengthened enough with the
ride height adjuster like Fox shocks have. Or you can find a 96-99 gsxr shock.
The GSXR swingarm is lighter and stiffer than
the GS one. It has much larger sized tubes, and are made from aluminum. The GSXR swingarm also would allow the use of
the wider GSXR wheel and wider race rubber. The later GSXR also uses a very large diameter hollow aluminum axle, which weighs
about 1/2 the solid steel GS one, and is also stiffer. Very small deflections in the rear axle would allow considerable
movement at the rear contact patch, which steers the bike in response to bumps and power application. The rider doesn't want
that kind of steering input on a racetrack!
Lighter and stiffer is always better
for a race bike. The GSXR has lots of great technology in it - the 750 GSXR weighs the same as the GS500, makes 3 times
the HP, and controls all that power at very high speeds. They've really worked at making it light and stiff, so transferring
that technology to the GS where possible can only help.