Anything within the range is "safe" , but might not FEEL right .

Re: Katana tire pressure question...

Suzuki doesn't buy your replacement tires, so it is my opinion that they have no vested interest in making sure your tires last as long as possible -- but they do have a liability factor on making sure the tires they originally supplied won't kill you, so do warn you with a minimum value that should prevent that. This minimum value slows handling and speeds tire wear, but tends to keep newbie riders slower than they might otherwise be (good for safety) and theoretically decreases stopping distances (at least with mediocre tires) on dry/clean surfaces (but increases the odds of hydro-planing).

Many other tire manufacturers will give you different numbers for your particular bike if you are using their tires, because they know their own products and what works. Metzeler and Pirelli for example will specifically tell you to start with a higher baseline minimum than the Suzuki-recommended 33/36.

Now for the logic part of it:

The tires deflect a certain amount at the contact patch based on how much weight is sitting on them. In the real world, that deflection amount dictates how large the contact patch is, as well as how hot the tires will run (because deforming every bit of the tire that touches the ground on each rotation is where most of the heat in a tire is generated). And how hot a tire runs dictates how well it keeps the molecules bonded together (because tire compounds are bonded by heat in the presses) -- and thus how fast it will wear away.

Common sense should tell you then that a tire set for a 140 lb load weight will deform a whole lot more if you put a 240 lb load weight on there, and thus run significantly hotter and wear much faster). How Suzuki could miss the ball on this one and just put a single value on the swingarm is debatable -- but as I mentioned above, I think it's the liability lawyers talking minimums, not the engineering staffs from the tire companies talking about ideals.

MC science tells us that the added deflection on the tires' tread will be about 1mm for every 20 to 30lbs added load placed on the bike. If we increase the tire pressure to offset that added deflection, the tires will be sharper in handling (acting as if someone of 140 lbs were on the bike) and the tires will run cooler (a very good thing, at least in warm/hot weather when most people ride -- for very short rides in 50 degree F & below weather, getting the tires up to temp may dictate a lower pressure just to get them warm).

Macadam 90X's are very old technology, and pretty crappy tires compared to virtually any other suitable radial-belted offering available in the stock Kat sizes. Figure the rubber formulation composition on a 90x is about 4 generations behind the current-generation from Pirelli, Metzeler or Conti, and 3 generations behind most of the other available suitable tires.

Meanwhile, if in doubt, consider contacting Michelin directly and see what they would specifically suggest.

Cheers,
=-= The CyberPoet

whats diffrent with the mac 100s?

Michelin's claims of differences on the 100x vs 90x, at SportRider.com

Cheers,
=-= The CyberPoet

Im running 35/38 in mine right now. Anything less and it feels sloppy..anything more and it feels to skiddish.