7. Measuring Up

Next to measure spacers.

I found that there is not really much space to work with on the
left hand side.
The left side axle spacer is recessed onto the left wheel bearing.
The spacer rests on the internal swingarm swivel mount.

I needed to move the ZZR600 wheel centreline over by a total
of 3.5mm to the left.

I checked the available space on my ZZR1100 so I could leave a
reasonable space within the swingarm to the spacer/sprocket side.
You need to have some clearance but it can be minimised from
the ample space the original GPz900R wheel spacer has.

ZZR1100 has only 2.5mm space.

ZZR1100 Left side clearance is 2.5mm.

My ZZR1100 has almost 2.5mm space on the left hand side.
(hard to measure without removing the wheel, but accurate
enough for a tolerance estimate)
This relieved me as I didn't want to go that close on the
GPz900R at first, but after I measured the ZZR1100 clearance
I allowed myself to use at least the same tolerance.

Reference:
The midpoint of each wheel, as manufactured, is right at the
midpoint of the swingarm, and of the axle and spacers.
After careful measurements:-
 - the GPz900R wheel has a midpoint of 119.5mm
  (ie: half the measured 239mm total)
 - the ZZR600  wheel has a midpoint of 124.5mm
  (ie: half the measured 249mm total)

I also had to measure the outer surface of the wheel sprocket
to make sure it would correctly align with the drive sprocket.
There is a difference.
The ZZR600 sprocket is 3mm further left than my GPz900R
sprocket outer surface.
This is a difference that needs to be addressed.
It might not sound like much, but it may cause wear issues
if the misalignment is too large.
It may only be premature wearing out of the chain and
sprockets, but it may also result in a potential chain break,
as components will be stressed during uneven wear.
I may need to find an offset sprocket or shim down 1mm off
the bolted mating surfaces.
The sprockets are both 10mm thick.
The chain is a 530.
My GPz900R 'aftermarket' sprocket is a 48T.
The sprocket I have on the ZZR600 wheel is a ZZR-45.
(same as on my ZZR1100)

So, to move the centreline over to the left by the required
offset, there are several options.

If I took 3.5mm/3.5mm off each side, the wheel centreline
would be where the original GPz900R wheel was, however the
sprocket would be 3mm to the left of original sprocket,
and I would only have 1.5mm tolerance for the wheel spacer
on the left side swingarm.

Therefore based on the left side spacer tolerance I require,
and considering the sprocket alignment, I have decided to
only mill 2.5mm off the left side of the ZZR600 spacer,
and 4.5mm off the right side sleeve-spacer.
 - Remember I need to reduce the overall axle spacers by 7mm.
 - I need to keep a tolerance of 2.5mm on the left hand side.
   (same as ZZR1100)
 - I need to consider the sprocket alignment.

So, in choosing 2.5mm/4.5mm L#side/R#side, the centreline
will be 1mm right of original, and the sprocket is only 2mm
left of original, and I have the 2.5mm tolerance on the left side
swingarm.
The wheel is now centred at 122mm. (from the left)
Remember the measured swing arm 'uncompressed' is 242mm
so to be centred it needs to be 121mm.
But over the length of the chasis that is only a 1mm wheel offset.
I can live with that.
Please note that I may resolve this issue in future and perfect
the centreline with further machining or shimming.

This also means that the sprocket comes back to 2mm to the
left of original now.
That is within a satisfactory tolerance for the chain alignment,
considering the length of the chain.
No further action required here.

And this means I have a left side clearance of 2.5mm, just like I
measured on my ZZR1100.

Now to shim/mill it all, and fit it up.

Then do the brake bracket.