1200 to 1500 rear end swap 15 inch to 16 inch tire swap

[Stonbo the great]

This could be a long one so bare with me. I got the bright idea to swap a 16 inch wheel into my gl1200. I gathered the following supplies. 88/89 tire and wheel (6 rubber bumpers in the wheel vs 5, no particular reason, just what I found.) 1500 axle, washer and spacer. 1500 brake caliper bracket. 1500 drive pumpkin, I assume from an 88/89 but can't be sure. Also Monroe air shocks that fit Corvette 65 to 1980? So we tore the ass end off and started with the build. First the pumpkin went in without drilling out the 4 holes? Slid right in, we kept the 1200 drive shaft. Next slid the wheel in, again no problems. Now for the bracket. My buddy is somewhat of a machinist so this is where it got fun. If I recall correctly he machined .2 off the park of the bracket where the axle went through so you would have room for the washer, then bracket, then spacer then wheel. The end that bolted to the original 1200 brake bracket I think he took .6 off. It took many fittings to make sure the brake pads were lined up on the rotor.

[Stonbo the great]

At this point the wheel looked good and the brakes seemed to work fine. I used the original 1200 caliper but routed the hose outside of the air shocks. Next came the shocks. These sweet hearts need machined at the lower end and they had be be cut down a fair amount being careful to make sure they set straight in the mounts provided for the old shocks. After much cursing and shaving we got those on. We routed the air lines to the back of the bike and drilled a hole under the top box to mount the air line end. The directions say the shocks can run from 10 lbs to 150 lbs. We put everything back together and this was when the fun started. I took the bike off the center stand and she dropped so far that it cought me off guard and I almost dropped it. We put 50 psi into the shocks and the bike looked good.

[Stonbo the great]

Now for test ride. I'm 250 and didn't have the top box on. I went about 1 block and it sounded like the drive shaft was gonna explode, so back to the garage I went. Buddy rode it and same thing. I had a guess and I added air up to 75 PSI to the shocks. At this point the bike looked like it may fall over on the kickstand side as the ass end was way high in the air. Next test ride the bike didn't make a sound and I test drove it a various speed and under different loads and it sounded good. I have declared this experiment a success. At this point I got about 200 miles on and this is my observation. I dropped the air to 70psi as it gives a little softer ride. RPMs at speed went down atleast 300. Braking distance/feel stayed the same to me, some guys said it got better, I felt no difference. I should have measured the rear before the 16 inch tire but it definitely rides higher. If I could have gotten measurements to machine the brake bracket down this probably could have been done in 2 hours or less. I noticed no lack of torque with the bigger when pulling out or passing. Finally, I'm going to recommend it.

[Stonbo the great]

Sorry, I forgot that I'm riding a 87 interstate.

[Andy Cote]

Great effort. Seen similar posts in the past but nice to have a recent example.

Maybe add to How-To sub-forum?