!@#$%^& Hot In Phoenix Today !!!!

[Bob_Roller]

Left for work at 0445, 96 F, 36 C , left work at 1630, 117 F, 47 C in the shade .
131 F, 55 C on the expressway in traffic .

Road surface temp on the expressway, 197 F, 92 C .

Even I have to admit it was  hot today on the bike !!!!!!

Tires sure ' stick ' real good at these temps !!!!!

[montmil]

How did you determine the road's surface temp? You carry one of those Harbor Freight non-contact temp readers? Careful, Bob. They look like a Taser.  

[Bob_Roller]

When unusually high temps are forecast, I take the non-contact infared thermometer with me to work .

Road surface temp at 0445 this morning, 106 F, 41 C .

[Barry]

Tires sure ' stick ' real good at these temps !!!!!  

Bob,

Are you at risk of a tire blowout with those temperatures or if not at what road temperature would you draw the line.

[Bob_Roller]

I've never heard of a motorcycle failure due to high temps, if you keep the pressures at the proper level .

But, if you let the tires get more than 4-5 psi low, then the chances are greatly increased of some tire issue .

I keep the oilhead and Guzzi at 40 psi cold and the R65's at 38 psi .

This time of year, the highways are littered with failed tire debris, a majority are heavy trucks, but you see passenger vehicle, light truck tires that the tread has separated from the carcass of the tire .

An on road auto service here in the US, AAA, just had a short video on the local news a few days ago, they are getting about 900 calls a day in the Phoenix area during this latest abnormally hot spell, for failed tires on passenger cars and light trucks, they mentioned that most have complete tread separation, usually caused by under inflation .

This is a few years old, but even it mentions road surface temps exceeding 200 F., 98 C. here in the Phoenix when air temps exceed 110 F ., 43 C .


https://www.az.aaa.com/news/automotive/aaa-dont-end-tire-straits-summer

I've also learned from friends and co-workers, that the in vehicle tire pressure monitoring systems can be very misleading .

I've heard reports that the monitoring systems are not giving an under pressure warning, until the tire is 20 psi  or more low .

[Barry]

I can see why you run relatively high pressures which minimise the heating effect over and above the ambient/road surface temperature.
Under inflation can cause blow outs any place but in Phoenix it sounds like the margin for error is much reduced.

I think you are right about the TPMS not being that accurate.  I noticed my new to me C class Merc has no actual pressure transmitters fitted. I presume it relies instead on measuring the RPM of each wheel and flagging up any difference that might be due to low inflation. To give it some chance of working accurately you are supposed to reset the system when tires are changed or pressures adjusted which I can imagine many people won't bother doing. I have been experimenting with the tire pressures by at least 10% to optimise the ride comfort and the TPMS system hasn't spotted it. Don't see how it could if they all change at the same time. Maybe I should drop one to 20 psi and see if it gets flagged up.  I've managed OK without TPMS for 40 odd years so I'm that that bothered if it doesn't work well.

[Bob_Roller]

I was on the oilhead yesterday, checked tire pressures when I got home, the pressures on front and rear were at 40 psi  'cold ', actually 101 F, 38 C. in the garage when I left for work at 0445 .

The tires pressures were 44 psi front and 45 psi rear when I got home from work at 1400, I thought they would have been higher .

Front tire temp, 170 F., 77 C., rear tire 178 F. , 81 C. .

Road surface not as hot as it was the day before, 165 F. , 74 C. .

This was two hours earlier in the day .

[Barry]

The tires pressures were 44 psi front and 45 psi rear when I got home from work at 1400, I thought they would have been higher .Front tire temp, 170 F., 77 C., rear tire 178 F. , 81 C. .

I agree I would have expected the pressure to have risen more.

A 4 PSI increase suggests the tire temperature or rather the air in the tire should have increased in temperature by only approx. 20 Deg C  and it appeared to have risen by a lot more than that.

The actual theory from the gas laws with your front pressures converted to Bars:

(-1+273)*(3.03+1)/(2.76+1)-273=18.5 Deg C.

It's usual to round up a little because the formula assumes a fixed volume where as the tire will expand very slightly. That's a bit of unknown that makes the accuracy questionable.

Maybe the air temperature inside the tire is less than the external surface temperature.

[montmil]

Today, Monday, Good Morning Murica had a feature on hot highways from Phoenix AZ. TV stations are warning of tire blowouts. Local WX Chic had her non-contact thermometer scanning concrete. Came up with a balmy 148 F degrees.

Bob knows!  [smiley=clap.gif]

Awaiting Barry's latest graphs and charts re: Tires n' Temps.  

[Barry]

That formula might look fancy but all it says is that pressure is proportional to temperature.  It only looks complicated because temperature and pressure have to be expressed in absolute terms which is where the 273's and the 1's come in.  The graph would just be a straight line which would show that if we took Bob's 40 PSI cold pressure  measured at a 47 C ambient and brought the wheel t to England with an ambient of 20 C the pressure would fall to 35 PSI.  

[Bob_Roller]

After 22 years here, I can tell the temperature by the tire shards on the sides of  the road !!!!!!

[thrang]

Based on my limited experience of the USA, even when its pissing down with rain its to bloody hot! Cracking country though, just hot, or to quote our guide for the last few weeks. "In summer, if its over 90 its hot, over 100 a very hot, and over 110 fucking hot!"

[clonmore1]

Hey Tony,

Is there upcoming video's of the trip to the States?