[Miklos]

Just went from a 200 to a 190 rear. With the 190 being a smaller diameter, I needed to shim the rear shock to retain the original suspension geometry. I could'nt find any shimming info on a search of this site, so I decided to post up my findings. Shimming was done on a '02. To raise up the rear .25, use a .125 thick shim, to raise the rear .375, use a .188 thick shim. The lift from the shim is just slightly more than double the thickness of the shim.

Remember that to retain original goemetry, you are raising the rear of the bike the difference between the original tire radius and the new tire radius. NOT diameter, but radius.

 

[Miklos]

Wouldnt it be true that if you put a shim on top of the shock that is 1/2 inch, you would have raised the rear end by about 1/2 inch?

If your rear shock attached to the frame directly above the rear axle, then the shim/raised height would be at a 1:1 ratio. If the shock mount was exactly halfway between the rear axle and the swingarm pivot, then the ratio would be 1:2.

I tested with several different thicknesses of shims, measuring them with dial calipers, and using a tape measure from the rear axle to the subframe along a vertical axis.

 

[Miklos]

Yup, my "12" was well hung on Saturday.

I made "C" shaped shims. That eliminated the need to un-bolt any other suspension parts than the nut on the shock mount.

 

[Miklos]

Gunner- you are correct on the 180 and 200 diameters being very close to the same. It is the 190/50 that is shorter, and thus requires the shimming.

And, yes, short peeps could lower the front instead of raising the rear.

 

[Miklos]

OK Mr Pissy :wink:
Here is some light reading for you.
How to
Trail Tweak
Motorcycle Stability
Steering Geometry

 

[Miklos]

Wait a min here guys.....ok..now..call me stupid but the dia of a 190 tire SHOULD be the same as a 200...right ?? I thought the 190 is the width of the tire in mm....it is still a 190/55 "17" right ??

Depends on the manufacturer.

Bridgestone BT014, same height

Dunlop 208ZR, different heights

Also notice that the same listed diameters are not the same between manufacturers. Note that the actual tire installed on your bike can easily be .1" or more different than what is listed. They also shrink in diameter as they wear. :wink: :lol:

 

[Miklos]

How tall are you guys? I am 5'7" and I can not get my feet flat on the ground.
I have just ordered a lowering link to lower the rear 1.25 inches and was planning on raising the fork tubes up about .5 inch. That should quicken the steering nicely. Raising the bike for me is not an option since I get hungry a couple times a day and need to STOP.

Doood- if you lower the rear 1.25" and the front 1/2", you have just made the steering slower, not quicker. Also, lowering links change the effective ratio of the rear shock including spring rates and damping rates.