I have made the 848/1198 swingarm mod to my Euro 998s. I have done it a different way to the others that have shed their blood, sweat and tears and gratiously shared their experience with us.
The 848/1098/1198 swingarms and shocks are all the same dimensions, the eccentric hub being the difference between the 848 and the 1098/1198. I will refer to this group as "848" from now on. This part of a 748/996/998 frame is all the same, I will refer to this group as "996" from now on. Save a little bit of 1 finger typing.
The 996 series axle/spindle, sprocket, drive flange, sprocket etc, all bolt up to a 848 eccentric hub in a 848 swingarm and everything lines up.
My parts list is:
1198 Ohlins shock
1198 ride height rod
848 eccentric hub
New longer chain, as swingarm is 25mm longer (1 or 2 extra links, I didn't even check coz I knew I needed a longer one).
My Euro 998s has a 50mm full system so the clearances involved in this mod are probably tighter than most others from the series that have only have 45mm pipework.
As we know from the other undertakings threaded here, the main difference between the 996 and 848 series frames is the 30mm difference between where the shock rocker mounts to the frame and the swingarm pivot point, the 996 series being 30mm further away. The 848 series rocker pivot point is ALSO 3mm rearward in relation to the swingarm pivot point than it is on the 996 series. This 3mm changes the triangulation between the rocker pivot point, swingarm pivot point and the shock pivot point on the swingarm when fitting the 848 series swingarm to the 996 series frame. Not much different, but different. There is 1 more defining difference between the frames. The 2 rockers are mounted in a different lateral position in space, the 848 series mounting point being 20mm or so toward the gearshift side of the bike.
I designed an adapter to place in the original 996 series rocker mount to carry the rocker and lower it by by 30mm and move it rearward 3mm. Thus moving the rocker pivot point to the same place in the 996 series frame as it is on the 848 series frame, allowing the 848 series suspension to function as designed in my frame.
As mentioned before, the pivot mount points on the 996 and 848 frames are in laterally different positions so the 848 rocker cannot be used as the shock and ride rod will both be skewed to the right at the top. Something like this: /
It also hits the crankcase breather box, among other clearance issues. It is impossible to create an adaptor that will correct the alignment and not foul many other things. It's not even worth considering going in that direction, promise.
IDEALLY, a custom rocker with the exact 848 measurements but with a 20mm left shift would need to be fabricated. Along with the "lowering adapter" this would allow the entire 848 suspension package to function as designed in the 996 series frame.
There a number of DP and aftermarket rockers available for the 848 series that are marketed to cure a handling deficiency in this series. All "flatter", some flatter than others. So lets have a look at that while we are here. The "cure" appears to be to take the "curve" out of the rocker enabling a more linear ratio. By the OEM rocker having a curve between the pivot point and the shock and ride-height rod attatchment points, the 2 moving attatchment points move in arcs around the rocker pivot point during suspension travel. This "arc" travel is different to if the moving pivot points were travelling in a continually uniform way. It gives progressively acting suspension as opposed to linear. So the ultimate goal is to "correct" this as well as fitting the 848 suspension system.
The ideal goal would be:
Fitting the complete 848 suspension package, giving a 25mm longer swingarm (same as the 996 Corse one), not to mention stiffer, more asthetic, newer tech and lighter.
Fitting it in the geometrically same place it was designed to be.
Correcting a talked-about flaw in handling by "flattening" the 848 rocker ratio.
Enter the 996 rocker.
It bolts to the "adapter" in the same way as it did before, the shock and ride-height rod line up like this: l Not this: /
It does not foul on the breather box
It is roughly 50% more linear (flatter) than the 848 rocker.
It is 10mm shorter on the shock to pivot point side and 5mm longer on the ride-height rod side than the 848 one is.
THE SHOCK DOES NOT FOUL on my 50mm vertical cylinder header.
(a major win as opposed to just fabricating a custom rocker and not using the "lowering adapter").
So what we have with the 996 rocker is:
A "flattening" around 50% compared to the 848 rocker, addressing the move toward a more linear setup.
A rocker ratio that will give a marginally softer ride due to the 10mm decrease on one side of the pivot and a 5mm increase on the other.
By it being "flatter", the shock compression will be more linear thus it will be a little stiffer.
One differing dimension makes it a little stiffer and another makes it a little softer. Pretty close to the 848 setup but a touch stiffer.
With some material removed from strategic places of the 996 rocker, when attached to the "adapter" it allows full movement of the suspension without fouling.
So far, so good. (in MY mind)
Everything lines up, the rocker is in the correct place for the set-up to act as designed, the suspension will act more linearly addressing a documented flaw, the shock doesn't foul the breather box or exhaust header etc.
Mods so far:
Design the "adapter"
Dremmel strategic places on the 996 rocker for clearancing
machine 5mm from the middle of the 1098/1198 ride height rod to make up for the "flattened" rocker and get the correct ride height.
Other mods needed to fit the swingarm irrelevent of which way the rocker solution is tackled.
You will either need a 848 caliper hanger or modify the 996 one as 1 of the caliper bolts wont go in because it fouls on the bottom of the swingarm.
The rear cylinder front pipe needs to be modified as it fouls the swingarm. It will need to be reshaped and squashed. Moving the bracket on the midpipe where it mounts to the frame, allowing it to move 15mm outward, will create a lot of space. You will need to space your rearsets out and slide the exhaust cans slightly forward in their straps to account for the lateral shift if the midpipe or modify as needed.
The 848 swingarm will fit in 2 ways.
Use all the spacers and bearings an 848 uses OR all the spacers from your 996 MINUS the innermost little spacer on the rear brake side.
You will not need to drop or swing the engine to remove the 996 swingarm, just pump the frame apart between the rearsets and it will fall out.
One more thing: find a way to route the rear brake line.
Pics to follow tomorrow. Maybe.
Now on to the 30mm NCR triples to complete the package.