tire pressure; hot vs. cold - Sportbike Forum: Sportbike Motorcycle Forums
 
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post #1 of 9 (permalink) Old 07-16-2007, 01:57 PM Thread Starter
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tire pressure; hot vs. cold

I just got off the bike after a quick 30 mile ride. I pumped the rear tire up to 40 this morning, and the front to 36.

I just checked the pressures and both were up 4 psi. Is this typical or is that pressure (due to heat from friction) indicative of a problem?

I've been having wear issues...

Thanks.
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post #2 of 9 (permalink) Old 07-16-2007, 02:46 PM
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Yes for I always set my air pressures a bit lower, in the start of the day, & in riding the tyre pressure will be up a bit, but okay for riding.

Remember all the others on the road are crazy & out to kill you.
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post #3 of 9 (permalink) Old 07-16-2007, 05:19 PM
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Re: tire pressure; hot vs. cold

Quote:
Originally posted by iluvmacs
...I've been having wear issues...
How so?

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post #4 of 9 (permalink) Old 07-16-2007, 05:34 PM Thread Starter
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I got 3000 miles out of a set of Pirelli Diablos last year. The rear was worn to the cord in the center and the front sides were smooth.

This April I put on a set of Pirelli Diablo Stradas, which are supposed to last longer. I just bought a new set of tires today to replace the stradas, which exhibited the same wear pattern as the diablos, but at only 2000 miles.
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post #5 of 9 (permalink) Old 07-16-2007, 07:36 PM
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You're putting too much air in your tires, man. They're running only on the center because they are overinflated and that's the only thing touching the ground.

If they were wearing more on the outsides and not in the center, they would probably be under inflated, just gotta find the sweet spot.

It's normal for the pressure to increase once they're hot. A 4-5psi increase is about right. If I were you, I'd drop the front to about 32-33 and the rear to around 36. That'll put you at about the 36/40 you were going for to start with, once they're warm.
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post #6 of 9 (permalink) Old 07-17-2007, 02:40 AM Thread Starter
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I was running at the MFG recommendation of 33/36. That was until I read that the lower pressure generates more heat due to larger contact patch. So, I pumped up the pressure to reduce the heat, and reduce the wear.

Thanks for the replies guys. Hopefully I'll figure this out. I can't be spending $200 on tires every few months.
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post #7 of 9 (permalink) Old 07-17-2007, 06:35 AM
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Quote:
Originally posted by iluvmacs
I was running at the MFG recommendation of 33/36. That was until I read that the lower pressure generates more heat due to larger contact patch. So, I pumped up the pressure to reduce the heat, and reduce the wear.

Thanks for the replies guys. Hopefully I'll figure this out. I can't be spending $200 on tires every few months.
Well, those specs are for max load. It depends on how much you weigh and if you carry a passenger.

After your next ride, feel the tires. If they are pretty cool, drop the pressure. If they seem too hot, put some more air in.

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post #8 of 9 (permalink) Old 07-18-2007, 08:08 PM
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Most recommendations I've seen are to stay pretty close to the mfg recommended pressures - cold. Pressure rise from riding is factored into the cold pressures listed by the mfg.

Cold tire pressures are generally considered riding less than a mile (for a cage). I'd think it may be even less for a mc because of the generally smaller air volume in the tire.

Also, if the size of tire on the bike is not the same as original, the mfg original pressure specs no longer apply.

Have you double-checked your pressure gauge? Some of them are not very accurate and like other gauges, can get damaged, etc.

Last edited by Whoaru99; 07-19-2007 at 05:30 AM.
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post #9 of 9 (permalink) Old 07-19-2007, 12:36 PM
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Whoaru99 has two good points. First being check your pressure gauge against that of several others. Personally I just use a cheap stick gauge, but have checked it against those more expensive ones in some of the shops.

Also if you read MOM then some of the info in there is way, way out of line such as the speeds of shifting & others. I look at the 40psi for my rear & have dropped it to 36 while front setting is 36 though I use 32. My Honda 929 & 953 of '00 & 03 have done well since.

I do not make grunt (short runs around town), but ride up in the mtn roads from 5 to 8+ hrs & no problems with my tyres other then normal wear caused by riding hard. Also on the rear it came stock with 190 & first replacement & every since has been 180 while stock on the front.

I have a '97 Yamaha YZF600R & run same size as stock though again drop the tyre pressure a bit-----more or less why I use on the two Honda bikes.

Unfortunately with a sportbike they do wear out at a faster rate then a cruiser or touring bike, but then entirely different makers to numbers/names used in said cases.

Remember all the others on the road are crazy & out to kill you.
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