Going to throw my experiences here, since this seems the penultimate GSXR fork swap thread...
This is my second iteration of the fork swap - my first was with a set of easy to fit Showas from an '06/7 GSX-R750, a temporary solution since a local junkyard was willing to let them go for around a hundred duckets (talked them out of an axle as a bonus)... Essentially, one day I threw a steering damper on my bike, and found with the damper on when leaned over it was wandering all about in the lane. Feeling the bike's front end was waaayy too soft, I took the forks off, the low end Marzocchi's, one for compression and one for rebound (least that's how I understand they're supposed to work), no adjustments, no way to rebuild, and found the compression fork completely toasted. No hint of damping, and to top it off, metal chunks were draining from it in the oil...
- used an '06/7 GSX-R750 axle (if I'm really worried about the extra half-pound it weighs over the Ducati axle, perhaps I should think about diet and exercise to shave off a few pounds of my own, maybe even get my "big-boned" @ss under 200lbs somehow... that'd save me tens of thousands worth of trick CF parts!!!).
- used 0.5mm brass sheet two shim up the 53mm lower outer tubes to fit my 54mm lower triples
- got steel tube stock from Wicks Aircraft and Organ Supply to use as axle spacers (McMaster-Carr should have the right sizes as well, just that Wicks was for 12yrs my ever-ready down-the-street walk-in metal and composite supply shop), cut them slightly oversized with a chopsaw with a fiber cutoff wheel, squared them on a bench sander. I put the forks on the bike, and sized the spacers to center the wheel between the fork lowers, just simply measured the distance between the fork lowers, subtracted the distance between the outside edges of the Ducati wheel bearings (under compression against the spacer between the bearings), halved the result and cut the right (bolt) side spacer to this. Left side spacer I cut to a long enough that the axle and axle bolt wouldn't meet, yet short enough that the larger diameter portion of the axle wouldn't stick out too far from the fork lower.
[EDIT] - forgot about the offset in the wheel bearings, left side sitting deeper in the wheel than the right (knew there was something I was missing, little rusty upstairs!). If I recall I did something complicated like measuring the bearings outer to outer, then took a depth gauge to the bearings against the outermost hub surfaces (the ones the brake rotors center around), then crunched some numbers... Easier, just measure distance between the outermost hub surfaces, subtract this from the distance between the fork lowers, divide by two, and on the right side (GSXR axle bolt side) add to the /2 number the depth to the bearing inner race from the hub surface, and cut your right side spacer to that (and again cut the other spacer to whatever it takes to disallow the bolt head and axle from meeting while keeping the axle nicely clamped in the left fork... precision's not quite as important on that side).
- did same as above to make 5mm brake caliper spacers out of 1/2"x1" 6061-T6 tube stock
- to make brake rotor spacers, took 5mm sheet 6061-T6, first cut the blank out with a 4 1/4" hole saw, then used the pilot hole in the blank to cut 2 1/2" out of the center (this was before I had a mill-lathe setup, or the space for it), then took the resulting ring and slapped it on a Monster wheel, put the brake rotor over it as a guide to drill the rotor bolt holes. Note, using a hole saw will leave lots of scarred/marred material, stress fracture is not a concern here but corrosion is - I sprayed them down with ACF-50 prior to installation to absolutely prevent corrosion, but your favorite anti-corrosion oil will work (Corrosion-X, etc.)
- calipers, R1/R6 four piston monoblocks for some 25 odd smackers from fleabay. Well worth the money, they are infinitely better than what was on the bike.
- caliper bolts, measured the ones that came with the R1 monoblocks, added 5mm, walked over to the local Fastenall store, and grabbed a set of flange-headed cad-plated grade-8/metric-10.5 hex cap bolts.
Result - Oversprung, way harshly damped... But... I never knew this bike could go this dang fast and hold such a tight line in the corners. Waaayyy better than it'd ever been, way better even than when I bought it (with 200miles on the clock). The forks are sprung and, on the compression side, damped so that an 800lb gorilla can't sue for liability in a crash due to the forks bottoming out... Fortunately, the rebound side is reasonable at speed, so with a little adjustment, no matter how rattled I was, the bike was always solid in contact with the road, and I could get thrown off of the bike and it would still hold its line - I never had to work at holding the line in the corners!
So, temporary, since I had a pair of 2008 GSX-R1000 KYB triple clickers, with their smooth-as-glass black DLC coating, sprung for my weight, etc. - only problem, they are 56mm at the lower triple. I like the idea of HS compression adjustment since the Santa Cruz Mountain region offers a wide variety of beautiful scenic twisty as hell roads that are totally fun to ride on.. as long as you have a suspension that can handle foot tall buckles and potholes to the infinite abyss...
Not until recently did I discover you can take the outers from an earlier model GSX-R1000 KYB forks and swap the entire stanchion/cartridge/spring/cap assembly into them, keep the triple clickers and not have to bore out your lower triple... The '07/8 forks are stiffer for more metal on the fork tubes (and I'm sure heavier as well). Alas, despite all the threads I've read of folks boring their lower triples to 56mm (think all for fitting Ohlins SBK forks), then riding totally paranoid of their lower triples cracking under the stress, I went ahead and bored my lower triples to 56mm on my newly acquired mini-mill.
couple of notes on the mini-mill, outside of the usual making sure you're centered, head angle is nill, etc..
- tighten the gibs, they're not adjusted well from the factory. and if they are, they're still not...
- low RPM and cut fast.... should be common sense if you're used to cutting soft metal, but I forgot and tried the opposite first pass, wound up with an oblong bore on my first cut.
- chamfer all of the resulting sharp edges after boring - this distributes the forces more evenly and helps prevent fatigue/stress cracks.
I've got about 1Kmi on the bored triple over the past month over the roughest roads I can find, and no sign of problems (I'm using dye penetrant inspection). Of course, though the lower triple sees more stress, if you think about it, the forks are clamped by the upper triple and the axle to the inside of the lower triple, so really it is the structure between the inside halves of the lower triple's fork clamp and its steering stem point that are subject to all of the stress, and the rest just has to keep the forks from sliding up/down, so as long as the clamp bolts aren't overtorqued, there's nothing to worry about... I think...
Thoughts so far - even better... stiction is much lower, less than 3mm, and resulting feel is precise, easier to find the "sweet spot" on rebound, etc.. they're very well machined, and well built parts, and I really have nothing to complain about them WRT where the bike started - they perform above and beyond expectations, and more importantly well above and beyond the $235 I've got in them...
But I'm still going to complain - every bump feels harsh, they soak up the huge bumps quite well, with exactly the same harsh feeling that they give going over a manhole cover or a crack in the pavement...
So far, I'm blaming this on the same avoidance of lawsuit from the 800lb gorilla... looking at the shim stacks, compression and rebound damping should be extremely digressive, regardless of bleed valve setting. which means the big bumps feel like little bumps, and the little bumps rattle your teeth.. IMO the SBK Showas are much better valved - not that they'll let you[me] go faster, just that they'll be a lot more comfy while you're going faster...
Anyway, I've got a dremel, a pile of shims, and a bottle of sake, going to tackle these forks and see if I can't bludgeon them into behaving as I'd like them to.
Cheers
