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Discussion Starter #1
I've got new tread on the front and rear tires. The installer maxed out the psi when he inflated the tires. Front is max 36 psi - rear is max 41 psi. (Bike mfg settings - not tire mfg settings) I didn't like the way the bike handled when cornering so I set the pressure at 34 psi front - 39 psi rear and the tires seem to be gripping better - slightly more tread on the road I suppose. Where do others set tire psi?
 

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Discussion Starter #4
Tire manufacturers don't know what you are riding. Tire pressure should always be set by the bike manufacturers guidelines. Same with cars. Never use the tire settings.
 

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Not so sure about that, Atleast avon tires ask what model, and year bike your riding and gives you recommendations based on that (or atleast seems to).
Thought I do agree the pressures are a bit high, atleast for my riding style, so mine are set about 2 psi higher than the bike says, but around 4psi lower than avon recommends.
 

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The psi noted on the sidewall is the max working pressure the tire is rated for and is not a normal recommended operating cold pressure. If anything you should go by the manufacturers recommended pressures.

The higher the pressures you use in your tires the less the chance the tire will heat up enough to reach it's optimal temperature and provide adequate traction, not to mention the ride will most likely be harsher and your suspension had better be in tip top shape to maintain tire contact with the road when going over irregularities.
 

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I lowered the pressure a four lbs from what the book says. I'll never have the bike loaded to the max, single rider no gear. It made a difference in the ride. Might even go some more.
 

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Be sure to use a quality tire pressure gauge and test it against gauges that are known to be accurate. The pencil type gauges are usually inaccurate, as much as 6 psi over/under... even the brand spanking new ones I've tested over the years.
 

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Tire manufacturers don't know what you are riding. Tire pressure should always be set by the bike manufacturers guidelines. Same with cars. Never use the tire settings.
true, but Yamaha doesn't know what tires you're putting on their bikes. different tires have different qualities and pressure recommendations.
this guy suggests what i did when i switched from the factory Dunlop tires to my current Dunlop Elite 3's - looked up my bike with their tire.





Atleast avon tires ask what model, and year bike your riding and gives you recommendations based on that (or atleast seems to).
Thought I do agree the pressures are a bit high, atleast for my riding style, so mine are set about 2 psi higher than the bike says, but around 4psi lower than avon recommends.
same here. my tire pressures are also just 2 psi higher than what the manual suggests.
and as for getting better performance from tires from different pressures, my bike always feels like it has better traction and handling when i have just filled up the tires versus any other time.




The higher the pressures you use in your tires the less the chance the tire will heat up enough to reach it's optimal temperature and provide adequate traction,
is this correct? pressure and heat are directly related. and the higher the pressure of the gas inside, the quicker the molecules are moving and thus the higher the temperature, isn't it? so doesn't the higher psi give the tire a better chance to warm up? does it even matter that much with a few psi in heating up the outside temperature of the thick rubber? wouldn't the energy of the tire making contact with the road heat it up more than the characteristics of the gas inside? drag vehicles spin out their tires before a race to heat them up to gain better traction. it's been a while since high school science classes and i'm too lazy to research this right now.


edit: i spent a few seconds to find this: Gay-Lussac's Law: The Pressure Temperature Law. This law states that the pressure of a given amount of gas held at constant volume is directly proportional to the Kelvin temperature. As the pressure goes up, the temperature also goes up, and vice-versa.
 

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Discussion Starter #11 (Edited)
As a previous poster said, the inflation numbers on the tire indicate max pressure allowable for that specific tire. It has nothing to do with recommended pressure for your bike. If you inflate your car tires by the max pressure spec on the tire - absolutely do not do that. Always fill by the placard on the car. This I know for fact.
 

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... is this correct? pressure and heat are directly related. and the higher the pressure of the gas inside, the quicker the molecules are moving and thus the higher the temperature, isn't it? so doesn't the higher psi give the tire a better chance to warm up? does it even matter that much with a few psi in heating up the outside temperature of the thick rubber? wouldn't the energy of the tire making contact with the road heat it up more than the characteristics of the gas inside? drag vehicles spin out their tires before a race to heat them up to gain better traction. it's been a while since high school science classes and i'm too lazy to research this right now...
  1. the higher the tire pressure, the less the air molecules within are able to move. Don't confuse increasing pressure, which inhibits air molecule movement within a confined space with the act of increasing temperature of the air, which certainly increases molecular movement but since it's within a confined space it's movement is limited and therefore creates higher pressure within that confined space.
  2. heat in the tires is built up via the tire's deflection... the more you stress the contact patch and/or the sidewalls (during cornering) as a result of lower pressures (respectively), the more heat can build up in the actual carcass of the tire which eventually will affect the air within and heat it up causing a slight increase in pressure.
What I and fellow racers did to find the optimum pressures is to keep a log of ambient temperatures, track temperatures, tire pressures, tire make/model and bike as a guide for determining tire pressures given particular conditions. We would run a tire with higher pressures than what we think would be best (via experience), run a few hard laps (so called 'practice laps') and measure tire pressures and log the tire's feel. If the tires would slide a little mid-turn and then hook up then the tire wasn't at it's optimum pressure and/or temperature. Then we would lowball it slightly and run the same number of laps and again take pressure readings and note the tire's characteristics. If the tire felt sure and retained grip lap after lap then the pressure was close to optimum... if they felt greasy (sliding from turn to turn) that means they were heating up a little too much and you would increase the pressure slightly and accordingly (one to two psi in many cases), trying to find a happy medium between the two sessions and taking the rise in ambient and track temperatures into account as the day wore on and your heats came up during various times in the afternoon (many of us raced four heats... two of which were above our class with superior machines but hey, it's time on the track :grin:) was one of the concerns in road racing.

If you got your machine dialed in, you were on your game and the planets aligned for you (win = rider + bike + luck) then you were rewarded with a rubber trophy, the one that matters. To me the awards were overshadowed by the rewards of racing.

 

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edit: i spent a few seconds to find this: Gay-Lussac's Law: The Pressure Temperature Law. This law states that the pressure of a given amount of gas held at constant volume is directly proportional to the Kelvin temperature. As the pressure goes up, the temperature also goes up, and vice-versa.
You have discovered HVAC, how heatpumps and AC units work. decrease the pressure, and make it cold, then increase the pressure and dispose of the heat.

This is why you do not fill your tires with air when they have been driven a few miles or more, cause they are now hot, and will be 5psi or maybe more higher than when you should be checking them, cold. If you are on a track, you would be able to consistently heat the tires to the same tempature using the warmers, so you could check them hot then, but on the road, the tempature of the tires could be anywhere, throwing off your psi numbers to check and adjust against.
 

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Discussion Starter #14
I'm looking for an accurate tire pressure gauge. I've got 5 and they all read different by several psi. I've got a couple with big round faces that are far apart. I've got a Husky inflator with a big round gauge, a digital gauge and a stick gauge. It's driving me nuts! I don't have a compressor to test off of. Anyone?
 

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I'm looking for an accurate tire pressure gauge. I've got 5 and they all read different by several psi. I've got a couple with big round faces that are far apart. I've got a Husky inflator with a big round gauge, a digital gauge and a stick gauge. It's driving me nuts! I don't have a compressor to test off of. Anysone?[/QUOTE. Tire gauges are like most things, you get what you pay for, I found a nice one, made by Lyle I think, when you do get a good one use that one and only that one. If you get a cheap gauge don't expect it to be accurate even if it is it won't be for long
 

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Hmmm, I never really thought about this before... I have always just kept them at the amount stamped on the tires, which if I am recalling correctly is 36 psi front and rear. That has always felt right to me. Now I think I need to experiment a little.

Glen
Focus On Newfoundland
 

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Setting the tire pressure to the max rating stamped on the tire is almost always wrong. That would be the pressure to use if the bike puts the tire's max rated weight on it. I dont think any motorcycle is designed using tires at their maximum rated weight capacity.

Check your owners manual, or there should be a sticker somewhere on the bike if you have not scraped it off.

The 650 is 32 front and 34 rear (off the top of my head). I dont have the manual PDF on this laptop to look it up right now.
 

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When I first got the SVTC the to was always at 40/41 F/R wether riding or first thing am. A few days ago I went to ride and I checked it cold it’s 34/34. I pump it up, ride and the next day riding the TPM says 38 ?‍♂?
 

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Part of the problem here is that it's hard to know what gauge is accurate. If you cannot find out, then just use the same gauge all the time and adjust your pressure based on (1) mfr's recommended for the bike, (2) same cold location during check, (3) how the tires are wearing (4) how the ride feels.

This will change some with different tires on different bikes. Example: For my Road Star I only need 30# in my rear car tire to make the ride feel right, be comfortable, corner well, and wear straight across. I need to keep 38-40# in the front to avoid cupping.

Some things I have discovered include finding the best guess on gauge accuracy by comparing it to 4 tire dealers in town who have gauges they think are perfect. Of course, none of them were the same--go figure. Also, to keep track of the wear periodically from new, use a tire depth gauge and write down the measurements. Your eyeballing it is never accurate.

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