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[DesignerDan]

I noticed the tire inflation pressure that’s stated on the frame of my 2013 Zero S is as follows:
Front: 32 psi
Rear: 35 psi

However, in the owners manual it states that tire pressure for the 2013 Zero S is:
Front: 30 psi
Rear: 30 psi

Which one is the correct inflation pressure? The one stated in the owners manual or the one that’s on the frame of the bike?


I tried contacting Zero but I haven't gotten a reply yet.

[Richard230]

That may be a leftover sticker from the 2012 models.  That 32/35 psi was what the sticker said on my 2012 S.  However, the sticker on my 2014 S says to use 30/30.  That seems kind of low to me for a tubeless street tire as my BMW F650GS, which weighs about the same as my Zero but has a higher total load capacity, says to use 32/42 when carrying a full load.  However, whenever my bike visits my BMW dealer they pump the tires up to 38/42.     (The BMW's tires are 110/19 and 140/17.)

Having said all that, I set my Zero's air pressure to 32/32 and let it go down to 30/30 before adjusting it again.  As far as the ride and handling go, 30/30 appears to work well and those pressures provide a smoother ride and seem to provide better traction that the higher pressures when riding solo with no passenger or luggage.

[DesignerDan]

Thanks for the reply. I've been using 32/35 the entire time I've owned the bike. I'm content with the amount of traction the tires are providing. My main concern is the longevity of the tires. I want to get as many miles out of each tire as possible and I'm willing to sacrifice traction for that.

[CrashCash]

What do the tires say? There's usually something on the sidewall.

[Richard230]

What do the tires say? There's usually something on the sidewall.

Don't go by the tire pressure on the sidewalls.  That is the maximum safe inflation pressure for the tire.  It is also the tire pressure used to determine the maximum load as also stated by the sidewall.  Always follow the manufacturer's recommendation for inflation pressure.  Alternately, you can use the tire manufacturer's pressure recommendation for your specific bike using their specific recommended tire.  Good luck finding a tire company's recommendation for Zero motorcycles, though.   

As far as mileage goes, typically using a higher pressure in the tire will provide better mileage.  But it might also give poor handling, poor traction in the wet and a rough ride.  Using too much air pressure can also cause the rear tire to flatten out the center of the tread resulting in a tipsy feeling when the tire tread becomes worn.  In any case, do not exceed the pressure on the sidewall and if you use that pressure on the rear tire, don't use it on the front tire, as doing so will make the handling very "quick" and steering and front tire traction will be degraded.

[LiveandLetDrive]

Tire sidewall is usually a max, not a recommendation (they go on many different bikes.)  A max load inflation is also going to be excessive for a lighter loading.  The only REAL way to know is to see how the tire wears (or compare to a similar rider on a similar bike on similar tires) but anything in the vicinity of the lower 30's is going to be fine 95% of the time.  My Sprint ST says 36/42 but when I went to a track day, Pirelli told me to run 30/30.  Depends on your use.  Higher pressure will generally get you more efficiency, less grip (unless it's so low the tire isn't supported properly), and faster wear to the centerline of the tire.  The front to rear balance will affect the bike's handling balance so if a spread is recommended and you go lower or higher, you should probably scale them to maintain the same ratio.  Tl;dr:  start in the low 30's and experiment if it doesn't feel right.

Richard beat me to it but there you go.

[Richard230]

The "rule-of-thumb" for setting tire pressures is to set the pressure to a specific value when cold, ride in normal temperatures for about 10 miles then stop and check the tire pressure.  You want to see about a 10% increase in pressure.  So if you adjust your pressure to 30 psi, a reading of 33 psi immediately after riding at freeway speeds would be what you are looking for.  If you were to set the pressure to 42 psi (a typical maximum pressure for most motorcycle tires) then you would want to see 46 psi when the tire is hot.  If it is less than that, the cold pressure is too high for the load, speed and usage. 

Still, it is not going to be the end of the world if you set the pressure higher than the recommendation, but below the max pressure on the tire sidewall.  Note that if you are running tubeless tires, a higher pressure is desirable if for no other reason than the higher pressure will help protect your wheel rim from being damaged should you hit a big pothole. If you run a tube-type tire, you can typically get along with a lower pressure which will provide better traction and a soft ride, but running too low pressure at high speeds will result in the tire running very hot and result in rapid wear.