Relevant Info: (1988 VN750, 31K miles). Two weeks ago, bought, balanced, installed ME880 Marathon's, (I weigh 160lbs), I put 36psi front, 42 rear, and nearly killed myself! Bounced all over the place. Tweaked (cold) a pound or two and still bumpy. After the 100 mile break-in, I put in my "Ride-On" Tire balancer/Sealant (5oz/front, 8oz/rear) and though it got a lil better, I still wasn't confident at high speeds; the bike was not handling. I re-read the post, manuals, Metz's recommendations, BMW's flex theory of 3 pound hot/cold difference, then our verses hit me with very important insight that made sense: My suspension? (I bought my bike with black elect. tape covering my front fork seals; you go figure). My bike seems to handle/grip and feel better with a lower psi at ALL speeds, then the Metz. recommendation. I Presently have 28-29 front, 31 rear (cold). After about 40mins highway speed (hot), they're 34psi rear (perfect), but still only 28 front; which means that the front tire is NOT flexing as it should/suppose to be? But god forbid if I should go below 28psi, right? (Hoss?) I do know that the rear tire now gives me everything I ask for (and some) for all around/all weather performance; top notch! Wow! And the front tire goes over any and everything as if it were all flat road (even paralleled hi/low areas). These are amazing tires but getting the proper psi is still an on-going process because at 60-70mph, the front sort of...bounces? bumps? I do know that the handling is...shaky and I let off the throttle. My old front tire only held 22 psi and was nice to ride (no bumps)! Ride safe..
OK, I`m no tire specialist, I was only passing on the 3 psi difference in cold/hot inflation recommendation that I remembered. But I think you are probably right not to go below 28 psi in the front tire.
I wonder about the black electrical tape wrapped around the fork seals. Are the fork tubes free to slide in and out of the lower section without sticking?
If not, could that be contributing to bumpy, bouncy, shakey front end?
Have you serviced the fork tubes? Do they have the proper level and viscosity of oil installed?
See lances fork rebuild thread:
If your shocks are not set up properly, or if something is broken inside, it is conceivable that a too soft tire could make a stiff suspension feel better to you.
I think your `88 model still had provision for air adjustment/preload in the fork tubes.
Any possibility they are pumped up too hard?