[Badd Dadd]

As recently posted, I had a Pirelli P1 RF go flat. Luckily I was just coming in off of a state highway into a gas station when the TPMS started to show I was losing pressure. It did not act like a run flat when it was down. When the tire was changed they showed me the old tire. It appears to have dry rotted around the bead. You could flake off rubber all the way around. It was hot day 95 degrees, we were loaded for vacation 40lbs on the pak it rack, and a total of 80lbs divided among the 2 saddle bags and the trunk. I have been running 28lbs in the tire. The second operator is 150lbs with gear on. I am 230 with gear. The tire's date code says it was made the 16th week of 2017.

The question is did I overload the tire with to little pressure on a hot day or was it a bad tire? Any help or wisdom from the crowd would be appreciated. And may help someone else in the future.

 

[RedBag]

Irrespective of the tire, I think you may have overloaded the machine at 460#. Might want to check the GVWR. Good luck!

 

[El Toro]

Irrespective of the tire, I think you may have overloaded the machine at 460#. Might want to check the GVWR. Good luck!

All bets are off on the loading. It’s a car tire.

FWIW, the tire should not have already degraded due to aging, and as hot as it was, it wasn’t like Death Valley hot.

The 28 psi? Who can say. It was being used in an unintended application, so not even Pirelli would likely give you an answer on that question.

Probably the guys who think the dark side is a great idea will have opinions. Everyone’s got one ... just like, well, ... you know.

 

[Mr. Whiskey]

I'd say 40 lbs hangin' off the pak it rack put quiet a bit of extra stress on it,
(it's why we went back to a small trailer, the shock load from 40 lbs cantilevered that far behind the rear axle acts like twice the weight or more)
and low pressure will build more heat.
Think you toasted that one.
Glad y'all are safe and here to tell the tale0

 

[techdude2000]

I think it was a little under pressure for your load. If running that heavy, I would start off at 32lbs. cold.

 

[RedBag]

Here's a helpful calculator from Dunlop--not specific to their brand but is specific to MC tires: https://www.dunlopmotorcycletires.com/wp-content/uploads/2017/10/17D_LoadLimitCalculator_single.pdf


A solid discussion and chart of Load Index ratings can be found at: https://www.bikebandit.com/blog/are-your-motorcycle-tires-overloaded


If the bike exceeds its rated carrying capacity ("GVWR"), it is overloaded and has the potential to act squirrely. Car tires can't help an overloaded frame.


For instance, the 2012 Level 4 has a carrying capacity of 410#...not much when you figure in rider & passenger, fuel, oil, coolant, farkles, and a hair dryer!

 

[Zee Fifty]

You can try the same scenario with a motorcycle tire and see how that work out for you.

Why did the tire go flat initially? It sounds like your concluding the bead failed? How was this determined?

I would assume your bead took a beating riding with a flat.

 

[Badd Dadd]

The tire did not go flat until I stopped at the gas station. In 2 blocks it went from around 37lbs hot to 24. It started leaking really bad once I stopped. When we aired it up at the station. It was coming out from where the tire meets the rim. Looking at the bead after the tire was off it would crumble in your hand. There were no other holes in the tire.

Thanks to all for the input. A lot of time when you pack up for a trip the last thing you think about is how much weight it going into it. My only hope is someone sees this and does think about it.

 

[F6 rider]

Look at it this way.
My sons Mini Cooper S runs the same size run flat tire as I run on my Wing and F6B (before I traded it on the WIng). The Mini weighs 3000lbs so 750lbs per tire and the recommended PSI is 35.


I believe the 28PSI was way low for the load. I ran 35PSI in the run flat on my F6B for normal loads.


I don't believe any car that runs that tire would ever have such a low recommended PSI.

 

[jlbc212]

Who mounted the tire on the rim and what was used to lubricate the tire bead when it was mounted on the rim? If some other substance was substituted for an appropriate tire rubber lubricant, that substance may have caused the rubber at the tire bead to prematurely dry out and break down.

 

[MountainRider]

28lbs is to little for even the rider and passenger. Add everything in and on the saddle bags and trunk, and you're already stretching its capabilities. Now, with the 40lbs on the packit, which is roughly the equivalent of 80+lbs 2 feet behind the axle, it makes no difference if it's a run flat or not, she's going to wag her tail like a dog. With all that weight and the tire being underinflated, you're riding on a rolling oven. If you're going to travel that heavy, ditch the Packit, and find an inexpensive trailer, otherwise the next time you try this the end result may not be as forgiving. You dodged a bullet.

 

[Indianawantsme]

I run a P1 also and i don't let it get below 34psi around here for sure.

Trip to Tucson, Utah , Colorado and back to Indiana : #34psi loaded with 32# on hitch rack and whatever in the saddlebags and top rack bag. Probably about the same as you had luggage wise but i am about 190# and wife about #135 with all her long sleeves and stuff on. We are lighter but i still wouldn't run below 34psi on this tire. Lots of straight line slab riding miles and thought of less air but didn't want to go lower. Wore pretty even at that pressure.

Edges took a little beating in the mountains. 36psi in the mountains would have been better but i didn't feel like changing the pressure all the time so i left it at 34psi cold at 75F setting.

 

[RonK]

--

I agree that with the overload you had with all your extra gear hanging on, you were probably overloading the tire for maximum load carrying. (As a matter of reference, on my Driveguard and carrying 450#, I am running an actual 28# with great wear evenness and 17,000 miles with no problems and perhaps 1/3 tread left.)

One difference is your overhang. A second is your air gauge may be off up to 4# so you may not have the pressure cold that you think you have. Third, your increased temp of 9# could have been from the pressure being like maybe 20# (if cold at that time) due to a nail hole and extra heat buildup. That much heat can really cook a tire--which would account for the flaky rubber around the rim.

--

 

[JoeHall]

To the OP, please elaborate on, "It did not act like a run flat when it was down."

Thanks

 

[Zee Fifty]

Who mounted the tire on the rim and what was used to lubricate the tire bead when it was mounted on the rim? If some other substance was substituted for an appropriate tire rubber lubricant, that substance may have caused the rubber at the tire bead to prematurely dry out and break down.

Agree.

Photos would help also if you have them.

 

[Badd Dadd]

To the OP, please elaborate on, "It did not act like a run flat when it was down."

Thanks

Just moving it around from the gas pump to the air hose and then from the tire store to the hotel at a crawl there was a definite thump thump. Could have been where the bead had separated.

 

[JoeHall]

Just moving it around from the gas pump to the air hose and then from the tire store to the hotel at a crawl there was a definite thump thump. Could have been where the bead had separated.

Thanks, I have read others' speculation about possible problems with sidewall rigidity on the Pirelli RFs. They are lighter in weight than most other RFs, and the weight reduction has to come from somewhere. Hopefully, they did not take it from the sidewalls, but your experience suggest maybe they did.

I agree with others though, sounds like your problems stemmed from overloading, low TP, and possibly a chemical used in mounting that eventually deteriorated the rubber where it contacts the rim. Lots of folks use WD40, and other lubricants that are not recommended, for just that reason. Perhaps the three factors combined, created a perfect storm for your tire's failure. Glad nobody was hurt though.
Thanks Again

 

[Coondaw07]

My mom ran a tire flat for a few miles without noticing it a few months ago. It was a 20” tire on a new Lincoln MKZ, but it was the same premise. When we got the tire off, it was full of disentegrated rubber; tiny little rubber pellets. The heat made the tire crumble.

Sounds like you ran it at too low PSI. A low tire will generate more heat just as a flat tire because of more rolling resistance; friction. As the tire heats up it starts to fall apart and the problem compounds. Just my thoughts, as I am in no way a professional tire guy.

 

[Micky Runey]

With my @ 260lbs, and pulling a good load in the trailer (addt'l tongue weight on the bike) I would have been running around 34-35 psi in my non-run flat General CT. Any higher, and it's sidewalls want to pogo me down the roadway at times. I drop back to 31-32psi when running with no trailer. The 3-4psi can make a yuuge difference in the way my General handles.

 

[kwthom]

I wouldn't expect a slightly over two year old tire to have age degradation...unless the bike is in the sun or some such all the time.

OP: Where was the tire mounted?

I keep my Rivco bag + rack at no more than 40 lbs...and the weight on this side of the screen is a bit more than the numbers you mentioned.

Zero issues with a Yoko running cold at 30-31 psi. Add the 8 to 9 lbs of increased pressure at temperatures at 90° or higher, and not a problem.