GSX wheel upgrade

I recently had the chance to try a set of 18' re-spoked (Australian)
Katana wheels 2.75 front & 3.00 rear on my '81 GSX1100EX.
It made it into a new bike. Not only did it help with quicker turn in,
as expected, but it also stopped the top end weave (180 kph/110mph+).

I'd like to find cast wheel alternatives (to the original 19"/17"
combo)in 18" sizes & believe that an 1986 GSXR1100 front 18xMT2.75 (with
15 mm axle diameter/310 mm discs) will fit.
But the closest rear I can find is a 85-87 GSXR750 18xMT3.50 (5 bolt/220
mm discs).
Does anyone know if this 3.5 rear wheel will fit (it looks like it will)
and whether the whole rear GSXR axle spacers, sprocket carrier etc will
fit?
Or any other ideas/alternatives that could work?

Bernie

 

I saw a GS-1100 with the swing arm and rear suspension from a GSXR-1100
surgically implanted. It was a very nice machine, but it begs the
question, "Why bother? Why not just buy a better later model machine,
used, for a low price and cosmetically improve it?

I inherited a set of wire spoked wheels with wider rims that had once
been on a GT-750 endurance racer. I installed them on my 1982
GS-1100EZ.

Suzuki axles were the same diameter from 1972 through 1983, so the
GT-750 hubs would fit, the GS-1100 brakes would bolt right up.

But the 3-inch wide front rims did NOT stop the GS-1100 from doing
*terrifying* speed weaves any time the front end got light on the race
track.

My solution was to pull the front fork stanchion tubes up through the
triple clamps as far as they would go. That worked.

Another solution that superbike racers employed back in the early
1980's was to cut the frame and re-angle the steering head.

You might also want to study up on how the triple clamps on early model
GS-1100's
interacted with the leading axle forks. My friend who owned an early
model with leading axle forks was bragging to me about how he used to
do feet up low speed powerslides
on Griffith Park's famous "Backside" road.

So he rode my 1982 GS-1100 and I rode his XV-920 Eurosport Yamaha. He
thought he'd show me a thing or two, but I just ran away from him on
his own machine and he arrived at Griffith Observatory about 2 minutes
later, telling me that the new GS-1100's
chassis geometry was all wrong and that the front tire just wanted to
"skate away".

Well, the 1982 GS-1100 did come with the infamous hard-as-a-rock Mag
Mopus tires, and the Helmut Muth restyling had set the rider 3 or 4
inches further back and made him sit about 2 inches higher.

But, I tried various front tires and pressures and changed the wheels
and front springs and fork oil and still had the terrible speed weave
problem until I pulled the fork tubes up in the triple clamps as far as
they would go.

 

Hans Muth.

Look, you couldn't even get the Bridgestone tyre names right in your
other diatribe. try and get your facts right, eh?

 

Hmmm.......I might look into that.

but it begs the

I find the GSX has the seat/pegs/handlebar combination that is great
for comfortable long trips - ie 1000km days. And a motor that is simple
to maintain. Its got enough grunt & handles well enough to keep up with
most of the sportsbike crowd in the twisties.

I'm tying to avoid spoked wheels, again, for ease of maintenance & cleaning.

Were they 18" rims tho? - That's what really STOPPED my speed weaves.
any time the front end got light on the race

I'm not racing it & haven't had that problem on track days. It's pretty
much a stock motor.

I don't have any problems on dirt roads. (Well, I didn't with the
19"/17" wheels!)

You mean the 1st Katana?

Tried all that.
until I pulled the fork tubes up in the triple clamps as far as

Then it starts scraping exhaust collector & alternator cover in the
twisties. (It does already when pushing.)

 

No, I was using a 19-inch front rim, but the problem really isn't with
wheel diameter.
It has more to do with weight distribution to the front, rubber
compounds, and very much to do with the trie's profile.

Back around 1983, Motorcyclist magazine bored out a GS-1100EZ to 1260cc
and put an 18-inch front wheel on it. The motorcycle was called "The
Beast" and the outspoken John Cordona of Fours 'N' More wound up buying
it. I saw him riding on the Angeles Crest Highway with a nitrous oxide
bottle strapped to the side.

But the problem with the 18-inch wheel then was that it lowered the
front end so much riders would drag the alternator cover on the ground.
That was nothing new, my friend who raced a GS-1000 on Willow Springs
was dragging his alternator cover, so he just removed the alternator
entirely and installed a special aluminum plate that had a cylinder
piece to cover the crankshaft stub end that still stuck out.

Then, there is the present day problem of getting 18-inch tires in race
compound. Avon was about the only manufacturer who still made soft
compound 18-inchers a few years ago when I was looking for such tires.

There are plenty of 17-inch tires, they are standard now, but that
would really drop the
front end of your machine too low. And having a 17-inch tire doesn't
guarantee that it will have a suitable tread profile. I bought a set of
Bridgestone BT-020's on the advice of Usenet users and discovered that
the 17-inch front BT-020 felt just like a 19-inch tire!

The old Spitfire tread pattern used on the BT-020 made the tire wiggle
and squirm on SoCal freeway rain grooves and the pointy profile made
the steering vague. Many sport touring riders had already observed this
vagueness.

Anytime I wanted to countersteer the machine to lean in the direction I
wanted to go, the damned tire would out-track the other way far more
than I was used to.

But, there are other ways to get more weight on the front tire and make
the machine steer properly with an 18 or 19 inch tire. You could cut
the frame and reposition the steering head, you could pull the forks up
through the triple clamps, or you could do what the guys with 1988
GSXR-750's did to avoid dragging their dual canister exhaust system
during hard cornering.

They raised the *rear end* of the machine to redistribute the weight to
the front.

No, the 1982 GS1100EZ was not a Katana. The first Katanas had 1000cc
engines. And, they came with the infamous Bridgestone Mag Mopus tires
that were hard as a rock. I removed the Mag Dopus and stored it in my
garage until a broke biker buddy came around begging for any kind of
tire he could put on the front of his Honda CB-750.

I was a broke racer, so I sold him the Mag Dopus for $10 and he was
still using it 2 or 3 years later.

I thought that the Muth styling of the original Katanas was extreme and
bizarre, I didn't like the rear sets and the seating position, but, by
the time I was racing my GS1100EZ, I had experimented with clubman
bars, and finally selected short superbike bars to reduce the amount of
leverage I could input to the steering, which was far too light at
speed.

I had a hard time getting decent tires, too. I started out with the
original Michelin hard-as-a-rock Hi-Sports. They were low profile and
wide, but the tread compound was so damned hard I couldn't get the
needed front end traction when the front end got light.

If I had never raced dirtbikes in the desert, I think I would have shit
my pants the first time the GS-1100EZ started speed weaving at 100+ MPH
after cresting Monroe Ridge at Willow Springs. The Ridge sets up speed
weaves for unwary riders because they are turning while cresting the
ridge.

Fortunately, I was able to find discontinued Dunlop K-291R's cheaply. I
was getting them for only $49.00 each. They were soft compound race
tires and pulling the forks up through the triple trees eliminated the
frightening speed weave.