Question about tires..smell? Temp?

[cbigham]

Hi all,
Have a question about tires..Tires are hot at 80, 82 psi returning from cold mountain trip thru local desert, traffic and home. Rear tires noticably hotter than fronts and had a smell like hot rubber.
Posted are the weights on the axels for my 23u thor. I notice I'm about 700lbs below the limit of the rear axle. Usually that axle is loaded about 600 lbs lighter. No smell, not so hot.

Is there a danger? Factory michelin tires, 2016 date. Don't recall smelling this. Tires not painful hot but hot. Touched the rims, axle shafts..not the source of heat. It's tire flex. This is the most I've loaded this. E450 chassis, 2017 model 14,000 gvwr. Usually carry a 300 lbs motorcycle on back never a worry. This time a 470 lbs bike and about another 50lbs lbs for the more stout rack tying into frame.

Any thoughts?


Thanks

Cb

[hujarine]

I feel it's normal for tire to be hot after a long distance journey. Though most times the front tire is always hotter than the rear tire especially if it's a motorhome. But I guess the reason the rear is hotter than front in your case may be due to overload. I don't think it should be anything serious.

[cbigham]

DrewE-
That's what I figured. Using K for units P1v1/t1=p2v2/t2 assuming minimal or no tire volume expansion. It's the smell.. I cannot find any bulges, delam as I normally see on tires about to lose it. (No need for n, R in formula to compare temp to temp)

thanks

[DrewE]

The 5 psi gain suggests that the air temperature in your tire increased by very roughly 17C or 30F -- perfectly reasonable.

(That's based on the ideal gas law: PV=nRT, or pressure * volume = quantity of gas * ideal gas constant * absolute temperature. In the case of a tire, the volume and quantity of gas don't change appreciably, and of course the ideal gas constant is also constant. Hence, the change in (absolute) pressure is directly proportional to the change in (absolute) temperature.)

[cbigham]

No, thanks.
I did the calcs before putting the bike on. Scale reading is with bike, rack on. The 82 degrees is hot, just in from the road. Readings were 77 prior to.

[4x4van]

2 quick thoughts; based on your weight ticket, you have only 660 lbs available on the rear axle; if you added the bike after that ticket, then your axle IS overloaded. Also, is that 80-82 psi that you referred to the cold pressure (before driving), or is that the pressure after driving and when the tires were hot?

[cbigham]

A lighter bike, sure, we do on occasion carry son's bike there. Then you have issues of blocking radiator if bike big, and headlights. I calculated the 790r with rack puts about 1100 on the hitch when accounting for the center of gravity is about 3 ft or so further from the hitch. The rear is reinforced with 3 receivers, 2bon the frame rail, and the center hitch. It's all very heavy duty and reinforced.
Front, no.

[Holiday27]

Maybe placing the bike up front might help? I've had smaller bikes up front but a big bike could block some of the view so not sure.

[cbigham]

phillyg wrote:
Nothing to be concerned about IMHO, but you should invest in an infrared temp gauge. My rears will always show higher temps when pulling my fiver.

Your number, ratio is about what I calculated. I'm still under the 9600 lbs rear axle weight. That's the factor, tho this is the most weight I've had on the rear axle which likely is.

[noteven]

c'mon up to west Canada and Alaska for the next 6.5 months.

Tire heat will cure its own self.

I know, not helpful.

[phillyg]

Nothing to be concerned about IMHO, but you should invest in an infrared temp gauge. My rears will always show higher temps when pulling my fiver.

[whemme]

cbigham wrote:


Hi all,
Have a question about tires..Tires are hot at 80, 82 psi returning from cold mountain trip thru local desert, traffic and home. Rear tires noticably hotter than fronts and had a smell like hot rubber.
Posted are the weights on the axels for my 23u thor. I notice I'm about 700lbs below the limit of the rear axle. Usually that axle is loaded about 600 lbs lighter. No smell, not so hot.

Is there a danger? Factory michelin tires, 2016 date. Don't recall smelling this. Tires not painful hot but hot. Touched the rims, axle shafts..not the source of heat. It's tire flex. This is the most I've loaded this. E450 chassis, 2017 model 14,000 gvwr. Usually carry a 300 lbs motorcycle on back never a worry. This time a 470 lbs bike and about another 50lbs lbs for the more stout rack tying into frame.

Any thoughts?


Thanks

Cb

Please be aware that adding 520 lbs behind the rear bumper has an amplifying effect of increasing the weight on the rear axle of about 780 lbs.

[cbigham]

Big fingers, small phone?? 76. Came un looked like 82. Fully loaded, bike in back, fuel, water propane 12240.

I noticed no bubbles, delamination I seen on other tires going bad. Just smell and heat.

[CA_Traveler]

cbigham wrote:
I've already done the math. I set off at 86 lbs, came in at 82, 83 lbs??

What math? All things being equal psi goes down with elevation. All things being equal psi goes up with tempeature.

[rjstractor]

cbigham wrote:
I've already done the math. I set off at 86 lbs, came in at 82, 83 lbs??

Meaning your cold tire pressure was 86? When I had a C I ran rear tires at 80 psi cold, and they would routinely read 95 psi when hot, which is normal.

On these rigs in particular there are factors at play that contribute to hot tires and premature failure (learned this the hard way). When fully loaded, the tires are very close to their maximum load ratings. Also, the wheelwells are quite small, so there is not much airflow to help cool the tires. Another thing that I experienced was two tread separations on the passenger side inside dual, which was quite close to the exhaust. I think that the extra exhaust heat may have contributed to the tire failure.