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Old 05-25-2009, 09:30 PM   #1 (permalink)
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Tire Pressure Question

Brought home a new 09 Dyna Low Rider and after everything cooled off I was going over the owner's manual and checking things out. I checked tire pressures and the front tire had 36 psi. The manual called for 30 psi front and 36 psi rear for solo rider. I lowered the front to 30. Took the bike in for 1K service and when I got home I noticed the work order showed front was back at 36 psi. The owner's manual shows 36 for the FXDF but not the FXDL. Does the service tech/department know something that I don't or is there a reason they have twice set the tire to 36 psi?
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Old 05-25-2009, 10:35 PM   #2 (permalink)
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My guess is that they are wrong and inadvertently overinflating them. If you are going to get the dealer to do the servicing, I would just ask them about it next time.

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Old 05-26-2009, 07:38 AM   #3 (permalink)
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i don't go by what the book says, i put the air pressure at what it says it should be on the side of the tire.
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Old 05-26-2009, 09:00 AM   #4 (permalink)
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Quote:
Originally Posted by bagga View Post
i don't go by what the book says, i put the air pressure at what it says it should be on the side of the tire.
Tire pressure is determined by the weight of the vehicle, not by what is on the side of the tire.

Tires are designed to fit multiple vehicles of differing weights. What is on the side of the tire is the maximum safe pressure for that tire - typically this is much higher than what is required for the vehicle on which it is installed.

By running a pressure which is too high, you lose ride quality, increase your braking distance, and shorten your tire life. You also increase your risk of losing traction on wet roads. You may gain a marginal increase in fuel mileage, but not enough to to offset the risks above. The vehicle may appear to handle better as it sometimes responds more rapidly to steering input, but in reality, as the tire contact patch is smaller than it should be, its actually handling worse.

With all that being said, it is not uncommon for an OE tire to be stamped with a "max" tire pressure which corresponds to the proper pressure for the vehicle. Do not rely upon this though.

In short, the tire load information sticker on the vehicle is the final authority on what is proper for any given tire size and load. When you change from stock sizes things change, but there are charts to calculate this.

Ok - education mode off...
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Old 05-26-2009, 09:32 AM   #5 (permalink)
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Exclamation

Quote:
Originally Posted by Dipsy View Post
Brought home a new 09 Dyna Low Rider and after everything cooled off I was going over the owner's manual and checking things out. I checked tire pressures and the front tire had 36 psi. The manual called for 30 psi front and 36 psi rear for solo rider. I lowered the front to 30. Took the bike in for 1K service and when I got home I noticed the work order showed front was back at 36 psi. The owner's manual shows 36 for the FXDF but not the FXDL. Does the service tech/department know something that I don't or is there a reason they have twice set the tire to 36 psi?

You didn't mention whose tires are on the bike.


Unless they are OE-spec Dunlops, it is best to check with the tire manufacturer and see what their actual recommendations are. Quite often they are higher than the stock Dunlops.

All tire pressure specs are based upon a COLD reading, meaning the tire is at rest and has been so for at least two to three hours. The best (and easiest) time to check is in the morning before starting to ride, when the tires have been at rest overnight.

The primary consideration for motorcycle tire inflation is LOAD.

Overinflation and underinflation can have various negative side effects on either/or the tire(s), the motorcycle, or YOU...some of which have already been mentioned.


Cheers
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Old 05-26-2009, 09:35 AM   #6 (permalink)
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Numbers on the side of the tire are MAXIMUM pressure.

But I have to admit, 30lb sounds awfully low to me and 36 sounds more sensible.

Also, whatever number you settle on, should be check while the tire is cold, not after a ride on a hot day.
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Old 05-26-2009, 10:20 AM   #7 (permalink)
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The good thing is you were checking it
I run 36+ front and rear on the Low Rider and the Road King and the Sportster. Found the tires were all down {22-25} from sitting over the winter.
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Old 05-26-2009, 01:26 PM   #8 (permalink)
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My '08 Street Bob manual says 30/36 front back. Don't even know what the tires say. Hopefully my tire gauge is accurate when I check them and adjust the pressure.

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Old 05-26-2009, 06:40 PM   #9 (permalink)
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Thanks for the input everyone. Tires are the OEM Dunlop D401F. When I put new tires on my Z car the tire shop recommended a higher pressure than the sticker on the car. I wondered if maybe the techs at the Harley dealer had raised the front tire pressure based on their experience working on bikes. I'll ask when I take the bike in to get the forks checked next week. I normally check tire pressure at least once a week in the morning or before heading out for a ride.
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Old 05-26-2009, 08:23 PM   #10 (permalink)
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If you know someone with nitrogen, fill your tire with it because it dosen't expand when heated and you'll get a better ride, a better handling bike and longer tire life and when ever you check tire pressure hot or cold it will be the same reading.
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Old 05-26-2009, 09:27 PM   #11 (permalink)
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N2 will expand, just not as much as regular air. Any difference will be negligible in a motorcycle tire. Some racers use it but unless there is significant heat generated in the tire such as in high performance racing where the tires are constantly breaking traction and generating heat through friction, if you're using N2, you're just wasting money.
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Old 05-26-2009, 09:51 PM   #12 (permalink)
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Filling your tires with nitrogen is just a money making scam..... Unfortunately
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Old 05-27-2009, 12:02 AM   #13 (permalink)
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My 01 came with 30psi as stock,also. 36 is way high.Try 32psi,good compromise between ride/handling
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Old 05-27-2009, 12:12 AM   #14 (permalink)
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Quote:
Originally Posted by fafcpa View Post
My '08 Street Bob manual says 30/36 front back. Don't even know what the tires say. Hopefully my tire gauge is accurate when I check them and adjust the pressure.

Fred
You might wanna look at this: www.mcnews.com/mcn/technical/200511gauges.pdf
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Old 05-27-2009, 05:39 PM   #15 (permalink)
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Check the Metzler site

I have Metzler ME880's on my 2005 Wide Glide, and Metzler reccomends 36/40. Higher than the manual's reccomendation.
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