Tires, weight, and air pressure

[Addiction]

Are the tire pressure recommendations on the Kat's swingarm specific to the expected, stock Macadam meats (which are actually still on my bike)?

That is to say, if/when I change the tires to something more realistic like PR3s... do those pressures still apply? If not... ?

The big ol' Kat has a gross weight of 900+ lbs. As I understand it, this is because it is a sports-touring bike meant to actually accomodate a passenger. My CBR's gross is much lighter and passenger weight limit is quite low.

But the Michelins on my CBR are run at a higher pressure than even the fat-boy (ha, 2-up) pressures recommended on the swingarm. I'd expect more weight = more tire pressure.

So, will the tire pressure requirement change with a different tire, and how will I know what that should be?

[Addiction]

Interesting. From Dunlop:

"Overinflating tires does not increase load-carrying capacity, but will result in a hard ride and accelerated tire wear in the center of the contact patch."

http://www.dunlopmotorcycle.com/info-center/care-and-maintenance/

Air just disipates heat. A heavier load makes more heat, needing more air, or so'ins I figure.

Now to find the Load Index rating of a Macadam...

[Addiction]

Deflection

Also interesting:

Because of the weight they bear, pneumatic tires' sidewalls bulge and their treads flatten as they roll into contact with the road. This results in dimensional difference between the tire's "unloaded" radius (i.e., between the center of the axle and the top of the tire) and its "loaded" radius (between the center of the axle and the road). The engineer's call the difference between the two radii "deflection." Increasing vehicle speed will cause the tires to deflect quicker and increasing vehicle load will cause the tires to deflect farther (if tire pressure isn't increased).

from: http://www.tirerack.com/tires/tirete....jsp?techid=72

The article goes on to explain that deflection is countered by custom inflation, but while the speed allowed increases, the load capacity is decremented. Which, on the CBR600RR, kind of makes sense. Light bike, can do 170mph, W-rated tire allows max 168. Higher inlfation scrubs heat and limits deflection while decrementing the load capacity that isn't needed. Sounds good.

Which does nothing to tell me why the Kat's recommended inflation seems low. Comfort ride? It's not as fast; deflection may not be a real concern.

This is so complicated I forgot what my original question was.

http://www.motorcycleanchor.com/Katana/kat_tires.html

That link is probably posted here all over the place. I just didn't find it.

"Double-check with the manufacturer's site on recommended tire pressures on your bike with a specific tire. Not all tires are supposed to run at the same pressures as the OEM Macadams or Dunlops that originally came with your Katana (the Metzlers and Pirelli's for example run 34 - 36 PSI front, 37 - 39 PSI rear rather than the 32/36 recommended by Suzuki for the OEM Macadams & OEM Dunlops). "

I haven't seen these bike-to-tire tables yet... must be out there somewhere.

[mammut89]

some tires react more to pressure than others. ive noticed very little difference on the pr3 tried high and low, rain or dry trackday. roughly 36front 38rear is what I have found out is good for milage on them without being sloppy, not that its a whole lot of difference as I said. Dont spend too much time on this

[Addiction]

Heh, thanks. I've spent all the time on it that I'm going to, but it's funny... once I start looking stuff up I find so much more stuff I want to look up. Soon I'm talking to myself in my own thread.

[hardlydangerous]

bias tires require less air pressure because they heat up faster and higher then a radial tire.

33/36 is set for Bias ply tires, what the bikes came with from the factory.
with a cooler radial tire you can bump up the pressure a bit more with no ill effects.
36/39

I ride pretty aggressive compared to most Kat owners. I run supersport or hypersport radial tires like the Pilot power 2ct, Or perelli super corsa low 30's front and rear. Tire life s a little less but grip is outstanding

[Addiction]

bias tires require less air pressure because they heat up faster and higher then a radial tire.

I think that's backwards. Air helps dissipate heat. A bias-ply is softer; a radial is known to hold its shape better in a catastrophic air-loss event. The deflection of the tire - the tire changing shape as it does its job - contributes to heat.

I don't think a softer tire that makes more heat would do well with less air.

Probably depends tire to tire.


Thanks for your reply; forgive the lateness of my attention to this thread.

[moodylane]

Anybody else notice that WhiteNora appears to be a spambot?

[92xjunker]

we've been spammed alot lately, mods are most likely on the look out for spammers, so he will be gone soon

[steves]

Hit the report post button. We'll get to it.