Tire Temps - whats okay?

[Dale777]

Using the SmarTire system with display on the Silverleaf system, I recorded the following temps and pressures today in the rolling hills of Eastern Tennessee on I40 with an ambient temp of 103 degrees. The cruise control was set at 66 mph , dropping to 62 mph on the uphills and increasing to 70 mph on the downhills.

When the Goodyear G670 tires were cold (75 degrees) in Greensboro, NC at the start of the trip, the pressures were:
LF 120psi
RF 120psi
LR outside 110psi
LR inside 110psi
RR inside 110psi
RR outside 110psi
2006 Jeep toad (Goodyear Wrangler SR-A):
LF 33psi
RF 33psi
LR 33psi
RR 33psi

In Eastern Tennessee at 103 ambient temp, the tire pressures and temps were:
LF 134psi and 147 degrees
RF 132psi and 147 degrees
LR outside dual 127 psi and 163 degrees
LR inside dual 126 psi and 145 degrees
RR inside dual 125 psi and 153 degrees
RR outside dual 124 psi and 147 degrees
Jeep toad:
LF 37psi 138 degrees
RF 38psi 149 degrees
LR 36psi 129 degrees
RR 37psi 135 degrees

Are these temps okay?

[Dale777]

Using the SmarTire system with display on the Silverleaf system, I recorded the following temps and pressures today in the rolling hills of Eastern Tennessee on I40 with an ambient temp of 103 degrees. The cruise control was set at 66 mph , dropping to 62 mph on the uphills and increasing to 70 mph on the downhills.

When the Goodyear G670 tires were cold (75 degrees) in Greensboro, NC at the start of the trip, the pressures were:
LF 120psi
RF 120psi
LR outside 110psi
LR inside 110psi
RR inside 110psi
RR outside 110psi
2006 Jeep toad (Goodyear Wrangler SR-A):
LF 33psi
RF 33psi
LR 33psi
RR 33psi

In Eastern Tennessee at 103 ambient temp, the tire pressures and temps were:
LF 134psi and 147 degrees
RF 132psi and 147 degrees
LR outside dual 127 psi and 163 degrees
LR inside dual 126 psi and 145 degrees
RR inside dual 125 psi and 153 degrees
RR outside dual 124 psi and 147 degrees
Jeep toad:
LF 37psi 138 degrees
RF 38psi 149 degrees
LR 36psi 129 degrees
RR 37psi 135 degrees

Are these temps okay?

[Cruzer]

Your numbers are fine. Tires that are running hard can climb 60 degrees over the ambient temperature. The danger threshold is around 200 degrees. You're within the 60 degree figure and far away from the 200 degree figure so you're in great shape. Those numbers are typically to what my SmarTire system reports as well. Note that your R-R inside dual generally is the hotest of the rear axle tires. That's because it bears more weight than the others due to the crown of the road.

I am a bit surprised that the L-R outer was hotter but it's not a significant amount so it's meaningless. Maybe the sun was on that side or the HydroHot exhaust was hitting it. Either way, it's nothing to worry about. If you ever see one tire heat up drastically over another it's time to check for a dragging brake or hot wheel bearing. That's the beauty of the SmarTire system. None of the others have temperature readouts nor temperature compensated pressure readings. It really is the best system out there.

[Tom and Patty]

Here is an answer I recieved from Bridgestone a year or so ago, posted July 2005.

Cruzer is right on

Hot tires! I got my answer from Bridgestone. Sounds like everyone is on the right track.

Here is my question and their answer.



quote:
With air pressure and tire temp sensors installed in aluminum wheels, what kind of temperatures should be observed while driving in 90 to 100 degree temperatures?

What air temperature reading would be too high? We are using the Smart Tire system.



Thank you,

Tom Dietrich

Am-Pac Tire Dist., a BFS distributor in California.



Dear Tom,



Thank you for the opportunity to be of assistance.



The answer to your question depends on a number of factors, and quite frankly, there is not a hard and fast rule.



There are basically (3) types of tire temperature measurement

Probes inserted into the tire

Contained air temperature (which your system uses)

Tread (surface) temperature



A probe inserted into the tire – into either the belt edge or the bead area – the hottest points of the tire – is the most accurate method; however, it can only be performed under controlled conditions.



The contained air temperature method is the next most accurate, however, it is affected by the mounting system of the sensor – if the sensor is attached to the wheel, it will pick up heat from the wheel (which is picking up heat from the brake drum); and if it is attached to the tire interior, it will pick up heat from the casing.



Tread (surface) temperature is the least accurate, since measurement is normally performed by a hand held unit, thus hampering repeatability, plus the question of where do you measure? The ribs will be cooler than the grooves, and the center will be cooler than the shoulders, etc.



So, while all this has so far done little to answer your question, hopefully it has shed some light as to why I am being a bit reserved in my answer.



Now, what can I say to try to address your question?



While this is not set in stone: A very general rule of thumb is that a properly inflated/loaded tire, when up to operating temperature – one hour+ operation - will typically run about 60 degrees F. hotter than the ambient temperature. Anything above 200 degrees F. could lead to tire degradation and you need to investigate for a problem.



I hope this has answered your question to your satisfaction; if not, or if you have any other questions, please feel free to contact me.

[OldForester]

Dale Dowdy,

I had the same questions about temperature as you. I have had SmartTire for the life of the coach - now 20,000 miles, and always wondered on max temperature.

Today we were driving in North Central Texas (near Abilene), and had our highest temperatures. Ambient was 95 degrees, and inside RR dual was 150 degrees at 125 psi. Other rear tires were around 130-135 degrees at 120-122 psi. Fron tires were 135 psi with temps at 128 on LF and 135 on RF. We keep our Toyos at 120 psi front and 110 psi rear when cold.

We had not seen 150 degrees on any tire until this day. I found reducing speed from 65 mph to 62 mph dropped the temp to 146 degrees at same ambient temperature.

Our toad tires are very similar in pressure and temp to yours.

I also heard from some experienced tire people that 200 degrees was a point of concern, so even though 150 degrees was a new high for me, I have decided it's not enough to get worried about, as long as pressure is where it should be.

So, we're running similar pressures but your temps look a little higher - 5 to 10 degrees -- but that may be related to the weight of the coach as well as the heat.

I'll take Cruzer's and other's advice, including the Bridgestone quote on 200 degrees. Any my next tires will probably be Bridestones when my Toyos approach 40,000 mile.s