Superbike forks - do I need to space my rotors?

[suzyj]

I'm doing a superbike fork conversion on my '07 695.  I've bought a pair of 998 Showas to go on there, and am currently gathering the rest of the bits I'll need to do the conversion.  I plan on sticking with my 300mm rotors and 2 pot calipers for now, but will go to 320mm rotors with 998 calipers at some stage.

In any case, I've been measuring things to death before I dive in to machining and fabrication.  So far I've measured the unloaded length (axle centre to top) is 718mm, 23mm longer than my 695 forks.  That's cool, as it means I'll be able to use no-rise clip-ons above the triple.  I've measured the diameter of the legs where they go through the triples - 52.9mm in each case.  Cool - I can shim the lower and bore the upper, as expected.

So then I moved to the bottom, to see what thickness of spacer I'd need under my rotors to make it work, as all the conversion threads talk of rotor spacers.  Trouble is, I can't find any difference between the Showa bottoms and the Marzzochi ones.  My fender will bolt straight on, which is nice, and the diameters of the axle mounts are the same (I think - I really need to pull my Marzzochi forks out to measure them properly).

The caliper bolt spacing is 65mm, and they're in the same place.  I measured from the caliper mounting point to the seam (centerline of the forks) and got 10mm for both the Marzzochi and Showa forks.  So as far as I can tell, I don't need spacers at all.

I'd appreciate some guidance though.  I've included photos of one leg of each fork, showing the measurement.

Original Marzzochi:



New Showa:

[rockaduc]

IIRC, since you are using a 998 fork, you will not need to shim.  It should be a direct bolt on.  I did the same conversion but used SBK rotors and calipers, so I don't have any FHE with a SBK fork and the stock rotors/calipers.

If you were going to use a 999/749 fork, you would need to shim. 

Others can chime in to verify/call me names.

[ducpainter]

The 998 Showa should not require any rotor spacing.

[suzyj]

Thanks for that.  With the myriad of different possibilities I was unsure exactly what needed doing.  I've been told I need to space my rotors, and was surprised to see that it doesn't appear I'll need to.

So it looks like the 998 fork swap is the easiest of the superbike fork upgrades, at least for those of us with newer Monsters (with 25mm hollow axles and 65mm caliper mounts).  All I need to do is:

• Replace fork springs with 0.85kg/mm ones (adjust to taste - in any case the 1.0kg/mm stock ones are too heavy for me) and change shock oil.
• Machine top triple to 53mm (or replace with speedymoto).
• Shim lower triple with 0.5mm shims.
• Drill holes in axle to access lower compression adjusters (or replace axle with 998 one).
• Fit clipons.
• Assemble.
• Grin like an idiot.  [moto]

[rockaduc]

Don't forget to take measurements to retain the stock geometry.  I measured from the axle center line to the bottom of the bottom triple. 

[corey]

i believe the 749/999 are the only ones that need shimming. rotor offset is 5mm verses the stock zero-offset on the monster. i just spaced my calipers in, rather than spacing the rotors out. 5mm washers are easy to make

[Paegelow]

Nice!  This is a very useful thread.  I also have an '07 695 and I'm planning a swap.

I have a pair of 748 Showa's, which should have the same dimensions (I think?) as the 998's.
And I also picked up a Cycle Cat upper triple clamp.

So all I still need are some 53mm clip-ons.  Have you found a good option for yours yet?

[Speeddog]

~SNIP~

• Drill holes in axle to access lower compression adjusters (or replace axle with 998 one).

~SNIP~

AFAIK, any 25mm axle from a Monster with adjustable forks will work.
And, I'm pretty sure that some of the bikes before '05 had the drilled axle even if they didn't have adjustables.

If you choose to drill yours, note where the holes are in relation to the change in wall thickness.
IIRC, on the large diameter end it intersects the 'butt', so it doesn't drill well.