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The instructor is right. I run 31 front and 29 rear for track use on my FZ1. I don't run those pressures on the street because of pot holes, bricks, etc. Low pressures will result in bent rims on the street.
 

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Hmmm....35 yrs of this and first time I've ever heard such a thing.



I don't buy it. Not at all.



My "Fat Lady" would wallow like the hog she ain't. In fact, a couple of years ago I had a local dealer mount a set of nice, fresh, tasty Metzlers on the old girl. My wife dropped me at the dealer...I paid (and paid then paid again)...then I pulled out onto HWY 41 (of Allman Bro fame) and dang. Felt ALL wrong. I went direct back to dealer, got service mgr. Ft and rear about 12-15 psi down from ST11 spec of 36/42.



Nope...10 below spec ain't right. And that "dealer" is off the list and I went running back to the arms of my fav independent...
 

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Thats a tip that wont work for a Kawasaki KLR 650 where recommended pressures with 215 lbs or less is 21.8 psi front and rear. I increased my rear tire to 28 because I'm just over the 215 limit with all my gear on. NFL linebacker type.
 

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I have ridden for about 20 years. First I heard of it. My VFR800 feels like it is falling over in corners if my pressure is as low as 32. I run 38 front and 36 rear normally.



Not only would I not run lower but you can increase control in the rain by running 5 or 6 lbs. above normal. This increases the speed at which your tires will hydroplane. Motorcycle police do it and so do airplane pilots.
 

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Doesn't sound like a good idea to me.



In general, lowering tire pressure will increase traction, but also increase heat and wear while decreasing steering response. This is good for the track, but not for the street. Also, even on the track a 10psi drop is a bit much.
 

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Track day pressure

I only have one day at the track, but they suggested I start out much lower then my street riding pressure. I ended up running something like 29 - 30 psi front and 32 psi rear.

The manufacturers recommended tire pressure is probally what you would need on the street as you are riding in a much rougher enviroment then a track. Like was said above, there are pot holes to consider, longer tire wear life, heavier loads etc etc etc etc.
 

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Reducing tire pressures is standard fare for track days. Get track-specific advice for your bike from one of the tire reps at the track or an instructor that doesn’t limp too badly.



As noted earlier, you definitely don’t want to run these low pressures on the street. But that begs the question, what pressure SHOULD you use on the street?



For bias-ply tires, a good rule of thumb is that a properly inflated tire should gain about 10 percent pressure when warmed up to operating temperature. For example, if you start with 40 psi cold and end up with 44 psi hot, you were right on target. If it only got to 42, your starting pressure was too high. If it got to 46, your starting pressure was too low. With a little trial and error, you can get the ideal starting (cold) pressure for any condition of ambient temperature and loading. With this kind of info you can head out of the garage with the smug satisfaction that you have exactly the right tire pressure, whether you intended to blast down the freeway two-up with luggage on a hot summer day or carve the twisties solo on a cool autumn morning.



Now that I’ve said all that, I can’t find anyone that recommends using a similar rule of thumb for radial tires. Dealers, manufacturers, answer-guys at motorcycle magazines all say, "follow the owner’s manual" for street use. My VTR 1000 calls for 36 front, 42 rear. I find it hard to believe that this is the best pressure for all ambient temperatures and all vehicle loadings. Somebody in this forum has got to have the right answer for this one.

 

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A lower pressure would yield a larger contact patch. At the track, this is good. Also, at race pace, tires get much hotter, and the internal pressure difference between cold and hot temps. is greater. Thus, if you start with reccomended cold pressure, once you reach operating temperature of the tire, it could be WAY over-pressured, making you more prone to blowout. Also important is the converse thinking...that a lower tire pressure, ceteris paribus (all things being equal), allows more flex, and thus greature temperature, which is, to a certain extent, good for a race tire, it being designed to stick better at higher temps.
 

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I run the the front tire at 32-36 psi and the rear at 34-38psi on track days. These pressures are too low for the street, but when the tires are warm on the track, My ZX-12r will stay behind the 600's, but coming out of the turns and getting on the throttle-wow.. you know right away that the tires are set right. 600's seeing taillights until the next turn.
 

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If manufacturers were intentional advising cyclists to run at overinflated pressures, they would be exposing themselves to liability resulting from irregular tread wear at the edge of the contact patch, fatigue cracking, overstressing and eventual failure of the tire carcass. Likewise for underinflated tires, which can result in imprecise cornering, higher running temperatures, irregular tread wear at the edge of the contact patch, fatigue cracking, and overstressing and eventual failure of the tire carcass. Quite simply, correct inflation values are directly related to easily verified tire wear patterns and, though somewhat subjective, perceived performance by the rider. What other bizarre advise were you given by this character?
 

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Let's use some common sense. If your on a cruiser or dual sport does it really matter that you maximize the contact patch/sidewall flex for maximum cornering? I'd say no. If you're not on the track go with what's comfortable and recommended. If you have a bike for the track then let's hope you make an attempt to understand the setup and tire pressures a little beyond the instruction manual. If it feels like it's squirming under you then add a couple of pounds at a time until it goes away. Heat the tires up and check the hot pressure etc...
 

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Yeah...what he said...which is what I just said, though more verbosely, which is why he's the former journo and II still aspire to that lofty state.
 

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Are you confusing tire manufacturers recommended maximum pressures vs bike manufacturers recommended tire pressures?

They are very different.

The only time you need to lower tire pressures 10lbs from pressures recommended by manufacturer is if you are going to ride the bike at it's maximum braking, acceleration and cornering potential for a long period of time. The heat generated will result in dangerous over pressuring of the tire which can lead to failure. This is hard to do on the road!

Main thing is to check pressures weekly and keep the pressures within a couple of pounds of recommendations either way front and rear as you get the feel of the bike, then stick with what you like.

This action alone results in longer tire life and a safer bike.
 

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Over 25 years here. And yes, I've heard that. Track days on my NT650 I've found that 30-30 suits me perfect. My RC51 is maintained at 29-31, My ST1300 gets the 34-36, while my DRZ400SM sits on 25-25.
 

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Let's see. 10lbs off a maximum tire pressure of 42psi puts you right at the pressure your classmates agreed should be used. Hmmmm.



Why wouldn't warranty or insurance reasons be the same as safety and performance reasons?



Anyway, it might be that dropping the tire pressure 10psi from the maximum allows the extra heat of riding hard on a track to prevent the pressure from exceeding the tires maximum recommended tire pressure.
 
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