[Big Kahuna]

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I'm curious about the warm tire pressure readings I have after riding an hours or so.

I've been checking my pressures at least once a week, cold, and making sure that they are the recommended amounts for 2008 GL 1800, 36 psi front and 41 psi rear. I was curious how hi the pressure was hot, after riding a while and a got readings of about 42-43 psi on the front and about 50 psi on the rear.

Does anybody know if that is about right? For these readings I was riding one up and about 70 MPH for 40 minutes out of an hour.

 

[Dancinbear]

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Thats a good question Big...... am gonna see how much my tires go up on my 1200 too. When I saw your topic, I thought, "couldn't be but a few pounds" ... I was suprised to see how much your tires increase. I think the pressures listed on the tire are cold psi's.

Would a person be inclined to start out with tire pressures maybe a few lbs less inanticipationof increase after reaching operating temps?

 

[Dubswing]

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I think you will find that the "hot" air pressure will fluctuate with the ambient air temp, tep of the asphalt, how heavy you are, the size of the tires and how curvy the road is. Motorcycle tires work harder than auto tires for several reasons and they run hotter as a result. And don't wear as long either. I haven't checked hot tire pressures in a long time but yours sounds normal to me.

Bernie

 

[Red Ron]

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I think you'll find that most keep more in the front. Like 39 or 40. Remember Firestone problems? I not saying that you will have a blowout but I believe the tire and bike will preform better with a couple extra lbs. in front.

 

[AZgl1800]

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I am in the camp of your front tire pressure is too low.

If you run it in the 40-41 psi range, the variables you mention won't be as large.

The softer tire pressures allow for more sidewall and tread flexing. That increases the friction and heat build up.

Even at the higher tire pressures, you will see differences between cold and hot. Definitely wait until your tires are cold to the touch before you make adjustments.

I've seen too many blowouts occur when someone let the tire pressures down to the "recommended value" while it was still hot.

 

[Dubswing]

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Even though we see higher pressures with hot tires, it isn't a good idea to set the cold pressure lower to compensate for higher pressures when hot. We all have seen reports of tires wearing fast and cupping when air pressure was maintained properly. I believe the tire people base their cold pressures knowing they will increase as the get hot.

Bernie

 

[Big Kahuna]

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I agree with all of you mostly. I usually sent my tire pressures on all my vehicles by the manufacter's suggestion.

And I understand about the heat and air pressure and the relationship to temperature and road conditions. The levels just seemed a little high and I was wondering if anybody else had checked their's in the past.

I had a leak, turned outto be a nail,on my 83 Aspy. Luckily it was the rear and the backend just got "mushy" andI stopped to check it out. I definitely don't want a blow out, that would be a little to exciting for me.

I have aobut 6100 miles on the stock tires and they look good so far.

 

[D-Rod]

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Hi, the place I got this information is at http://www.michelinmotorcycle.com.
It is on the right hand side under downloads. 2008 Michelin Motorcycle tire fitment guide. It is a 7.59 meg pdf. The bottom of page 27. Here is a direct link, but it will still download the whole pdf first. If you plan to reference it multiple times, I recommend you download it and save it to your hard disk or print it out.
http://www.michelinmotorcycle.com/pubs/fitment2008.pdf

Michelin recommends adjusting the pressure when cold and once set do not let any air out when the tire is ridden and warmed up. You should not even set it for less when it is cold to compensate. They know the pressure will go up as you ride and if you start with less the tire will flex more and actually heat up more.

Page 31 from the link posted:
4. Check inflation pressures on both tires at least once a month, before riding, when tires
are cold (at ambient temperature). Riding even for a short distance causes tires to heat
up and air pressure to increase. DO NOT BLEED AIR FROM HOT TIRES.
Failure to maintain the correct inflation pressure may result in improper motorcycle
handling, rapid and irregular tire wear, or sudden tire destruction.
5. For sustained high‑speed riding, front and rear tire pressures should be increased to the
maximum pressure recommended by the motorcycle manufacturer for high speed riding.
Do not exceed the maximum pressure indicated on the tire sidewall.
6. Increase the pressure of the rear tire to that recommended by the motorcycle manufacturer
when the motorcycle is used with a passenger or a substantial amount of luggage.
7. The proper inflation pressures for your motorcycle tires are shown in your motorcycle
owners manual. Unless otherwise stated, these pressures are for motorcycles ridden at normal highway speeds without passengers. Exceeding the safe, legal speed limit is neither recommended nor endorsed.
Inflation pressure measurements are only as accurate as your gauge. IT IS VERY
IMPORTANT TO MAKE SURE THAT THE TIRE PRESSURE GAUGE YOU ARE USING
IS ACCURATE.

 

[oharaLTD]

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Most all tires will tell you to check pressure when cold. The recommended pressure is the cold tire pressure. The manufacturers have probably already done the math that is why the cold pressure check and amount is what it is. I run my 1200 at 37frt and 40 rr.

That being said, I sometimes run my car tires higher than recommended because the manufacturer is more concerned about ride comfort than tire wear. so they may soften the tire to provide softer ride. My F150 2X recommends 29 psi front and rear. I found out that that pressure will wear out the outer edges of the tires, but gives a really good ride.

Always check your tires cold, when spring comes and the ambiant temp rises and stays up you may have to let air out. during the summer or warm months check them before you ride to get the cold tire temp. When there are big ambiant temp differences from day to day, check your tires daily.

 

[dalemcg]

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Being in the tire business we typically see a 10% pressure increase hot. The best way to reduce the hot pressure is to raise the cold pressure, less tire flex, less heat build up.

 

[Wolfman]

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Your rear tire, being the drive tire, will heat up much more. So you will see a bigger pressure jump in the rear. So what you are describing is normal.

I carried a IR thermometer on a long trip I did last summer. My trailer tires and the front tire all ran about 95-110 degrees and the rear tire was running about 150-165 degrees.

There's a lot of force/energy transferred in that rear tire. The other ones were just rolling along.


And the above answer about the engineers already doing the math is exactly right on. The tire pressures that you set are based on cold, and the tire is designed to run at a higher pressure. They plan on the pressure going when you are driving/riding to get the tire up to actual operating temperature/pressure.



That's also one of the reasons that using nitrogen in tires isn't all that it is cracked up to be... it doesn't build up the necessary pressure like straight air does.

 

[3rdwing]

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After having problems with a tire cupping on me I keep the front at 40psi and the rear at 44psi - cold.I run Metzlers.

 

[Kit Carson]

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I would like to second what Wolfman said about using nitrogen in your tires. It is not a good idea in motorcycle tires.

As a tire under stress, such as speeds of 75 mph for hours on end, riding two up, pulling a trailer and so on heats up, you need added pressure in the tire to support the tire.

The tire is basically designed to support the load. The air supports the tire and allows it to function as intended by the manufacturer. So if you take away the engineered expectation of higher pressure under stress, then you have created a safety situation.

You can get away with nitrogen in automobile tires as normally pressures in them never increase a whole lot, maybe 4 to 6 pounds at most. So just normal differences and inaccuracies in tire gauges create that much variance , so not a concern.

Motorcycle tires though under stress do heat up a lot, and sometimes air pressure of the rear tire can reach 65/68 psi . It is supposed to, the higher pressure supports the tire and the load and is as realized by the tire design.

So it you use pure nitrogen(it still expands a bit) then you do run the risk of actually creating the very same situation as letting air out of a hot tire to bring the pressure down to what you think is the right pressure, there by creating a unsafe condition by actually running on underinflated tires, that now will create even more heat

Very good Wolfman, I have argued with some of the guys locally that are using nitrogen in their tires. You can watch them absorb this thought and the light bulb come on. It is just something no one thinks about when they do it. Seems to be a totally innocent thing, till you put it into perspective.

Now for those of you who will tell me air is mostly nitrogen anyway, I agree, but in its pure form it does not expand as does the mix we all breath, I have already had this discussion with some of these guys, some of them are doctors, attornneys , well educated people and love to debate any issue. I do not dis-agree, just making a statement that pure nitrogen in a motorcycle tire, defeats the design intent of the tire.

Kit

 

[Longboater]

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On the 07 1800 I pump them up to 42 frt and 47 rear cold. This setting has been maintained for 19000 miles on the set of Stones that came new with the bike.



Plugged a hole in the rear at about 10,000 miles and it is inspected every Sunday.



Getting near the wear points and will change out in late spring. Stand by for a review on the set at that time.



Note: This is not for everyone and I do not recommend this course of action. These are just a bunch of facts that will be passed along at the end of this test.



Longboater,

 

[Whiskerfish]

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Ross Davis has an interesting write up on the subject of tire pressures and hot verses cold on his web site. Look in the tips section http://www.retrorideinfo.com/index.html


Ross is a retired Motorcycle Technician Instructor, and pretty much knows "a bit" about what he speaks

 

[AZgl1800]

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Longboater,

I'm with you. I tend to stay on the high side of the recommendations as per the advice of my local m/c dealership maintenance mechanic.

And I always seemed to get more mileage out of the tires than has been considered average for a tire.

 

[96aspencade]

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Also being in the tire business (go through a set a week on my skid pad)I agree & live by MAX pressure " Max pressure 100% of the time". I can supply many pic's of tires worn to the cords at max pressure & are all worn perfectly even from side to side. Less heat build up, better "tread" contact, better mileage, cornering, braking & handling. Lower recommended pressure might give a softer ride but you give up the better handling characteristics. Max pressure also prepares for overloading the tires in aggressive emergency situations. ie. panic stops. Ride Safe :action::action:

 

[Whiskerfish]

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Just Curious but has anyone ever seen a breakdown of the differences in the contact patch between min and max pressure?? Probably not much I would think?

 

[Longboater]

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Whiskerfish wrote:

Just Curious but has anyone ever seen a breakdown of the differences in the contact patch between min and max pressure?? Probably not much I would think?

Interesting comment.



I think about this most often while riding through the summer rains here in FL. There is a difference to be sure but it's unknown to me.

The more air pressure the more the tire resembles a steel ball.



While up in Cedar Key last summer (west side of FL near the bend) the water was deep enough to track through for mayby close to 30 min. Some cagers were pulled off to the side. The Stone's gripping was right on the money. This was a good test for braking and trying the ABS function. It works. Great training too.:cheeky1::cheeky1::cheeky1:

Longboater,

 

[Biker John]

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When I bought my 1800 new, I ran 41 front and rear in the D-250's and got 16,000 good miles out of them.
I could have run them longer, but I was going on a long trip and didn't want any tire trouble, so I had them replaced.