1986 GL1200 Aspencade

I have been attempting to make this CT thing work out without much luck so far. Finding a tire that would fit these rims was a chore to start with and then I ended up with only one real choice. Nankang CX668 Tire(s) 165/80R15 165/80-15 1658015 80R R15. Mounting ended up being a 3 hour job. I ended up having to polish down the inside lip of the rim, removing all trace of roughness from the tire bead, greasing the tire and wheel, inflating to 100psi and then sitting it in the sun till it got hot enough to bead. Ok, all well and good.

I inflate the tire to 42 psi, I had no clue as to a starting point since after reading countless post on this site the only conclusion I was able to come to was that there is no general consensus. That's fine too I never expected to have my hand held trying this. I'm running a Dunlap Elite III up front with 36psi. I take off on a short test ride of about 5 miles and hit the interstate. I feel a gentle sway in the bike, it weaves. My triple tree bearings are fine, my swing arm bearings are fine and my shock bushings are fine. I have just gone through this bike from front to back, top to bottom and it rode just fine before I decided that I needed a new rear tire and thought I would try this car tire experiment.

The next day I figured I would give it a real shake down and meet a friend 60 miles away. Having no clue about what would cause the weave I was left with only air pressure I dropped the rear tire down to 40 psi and took off. Same thing, a gentle rocking motion. I can feel nothing in the bars and I could control the bike with just a finger. This weave was constant even in the curves. Before I headed back I again lowered the air pressure to 36 psi ( I know I skipped 38) no change at all.

When I got home I noticed that my contact patch on the front was wider than I like so the next day I increased the air to 42 psi, the same as I run in my Metzlers on my other bikes, and again hit the interstate. It seemed like the weave was gone so I slowly kept increasing my speed. When I hit 80-85mph I guess the harmonics hit the tripping point and the whole bike was thrown into a violent weave! I was an RCH away from a tank slap situation! This was not a wobble but a weave. I decreased my speed until "I" was in control of the bike again and drove it on into my shop.

I'm happy with the increased air in the front tire because that did seem to make a difference so now I am left with this rear tire pressure issue. I'm not so sure about dropping the pressure below the 36 psi that I have in it now. This bike is heavy empty much less when I add a passenger, gear and my trailer so it seems as though I have but one way to go and that is up. I'm going to start again with 46 psi and work my way down. Maybe the increased air up front and an increase in air in the back will correct this problem? I may try just for the hell of it dropping below the 36 on the rear but it just seems like I would get too much roll and have it ride like I had a flat? At this point I would entertain any and all suggestions.

I am running a 175/75-16 tire on my Honda and have found that with the taller sidewall I had to run more air pressure to stop the bike from getting a high speed wobble.
No way I can run less than 38 psi on my bike. I run 40 psi and no wobbles from my tire, your bike might need more/less air pressure to stop the high speed wobble. I would put the max air in the rear tire and drop it a little bit(2 or 3 lbs) at a time till the wobble comes back and raise it back up till the wobble is gone. After 1k miles go back and check where the wobble starts and stops with the air pressure again, I have seen with the taller sidewall(75 series on up) tires that after a few miles(1k miles) the wobble comes in at a different speed and air pressure.

ROD

Welp, I'm gonna give up on my car tire on a bike thing. Got my valve stem changed, checked that tire and it was fine, inflated it to 42 psi, inflated the rear to 48 and took it for another test run. I could feel it almost immediately if ever so slight then it smoothed out until I hit 3K on the tach then it started up again. Maybe there is a sweet spot but I want more latitude than that. I don't want to have to adjust my air pressure up and down because I have a passenger or I want to ride one speed rather than another. This thing rode like a dream before so I set a high bar in that respect. Maybe the tire is bad, maybe a 15'' tire just isn't the same as a 15" bike rim, maybe it didn't bead right, maybe it needs really low pressure. Personally I don't feel comfortable putting 900lbs on a tire with low air. I'm just going to sideline that tire and rim for now and shop for a new tire and I may just use the tire that is on the other rim for the rest of the season. I know for many guys out there this works just fine but for me and this bike I can't go with it. I've spent too many hours on this project and just have no desire to keep plugging away at it, I have nothing to prove, just thought it would be cool to try. I tried it, didn't like it, oh well. Nothing ventured nothing gained.

I am on an 1800, but have found that a non run flat tire, the softer the side wall the higher the pressure needs to be. I put a walmart tire on my bike to get me home from louisiana when I picked up a couple nails. I had 55 psi in that tire and still at higher speeds I had the weave you describe. I have run non run flat tire before and found this to be a bit disconcerting. With my runflat tire on the bike I run it at about 30-32 psi.

See you out there
Smokey

If I would have had more tire choices I'm sure that I would have selected a different tire. With all the work that this was to try I can see why more GL1200 people haven't done this. Just something about some factor on this bike, tire, rim that doesn't work out or at least it didn't for me. I'm going to just sideline that tire and rim and may give it a go on a naked Wing that I'm building up. Who knows, with less weight maybe I can get good results. I may even shave the tire. For now I'm just burnt out from jacking with it and don't want to ride with the thought or fear of waiting for a weave to kick in or get comfortable with it, decide that I wanna do a 120 blast and have it pop up out of nowhere. I'll check back in and let ya'll know if I ever figure out what the problem was or if at some time I am able to make it work.