Greasing Hubs on 2003 2720sl

[rtcassel]

Originally Posted by rimartin58

This question really got me to thinking. When I pulled my TM home the first time, I stopped about 90 miles down the road and felt the hubs (the unit had been sitting for most of 7 years -- who knows what shape the grease is in?) and found them very warm but I could keep my hand on them. How hot is "running hot?"

Good question. I do not know the answer in terms of temperature. But if the hubs feel warmer than usual, or if one feels significantly warmer than the other, I look into it.

[rtcassel]

Originally Posted by jpcoll01

good question, i noticed that one side was hot today even after the fresh grease. I'm thinking it was from the brakes though, I need to get it out on the open road for a while and then check the hubs, The races seemed fine and the bearings were good to go.

In my experience, if the Prodigy is on boost, the hubs are warmer than without boost.

[Speckul8r]

You can buy an IR thermometer at Radio Shack for about $30. Just point it at the spindle and hold down the button for about 3 -5 seconds, release the button and take it out and rlook at the display. It's not unusual to see a temp in the 100 -110 range especially on a hot day immediately after stopping at the wayside. Bearing temps should not exceed 125 degrees. The IR thermometer is a little thing that takes up no room and the batteries in mine are 3 years old.

[Bill]

Tim wrote

if one [hub] feels significantly warmer than the other, I look into it.

FWIW, I've noticed that the tire and wheel on the sunny side of the TM always feel considerably warmer than the tire and wheel on the shady side. Not sure about the hubs, but the first time I noticed this difference, I panicked and stopped beside the road to regrease the bearings. Today I always look for the sun first.

Bill

OK I think that 125 deg temp is low. In the industrial environment the rule of thumb is that if you can hole your hand on the bearing then the temp is below 130 degrees and that temp is no problem. When it gets to 150 or so then there is cause for concern.

My tires were running over 130 deg on a long interstate run when I checked them with an ir thermometer. But the air temp was over 90 and I suspect the pavement was probably 130 or 140 degrees if not higher.

Dexter has a long list of advise on their website but they do not mention temp once:



Use using google I didn't see any obvious advise, either. My truck tires normally run well over 120 on a long highway run too.

Let me try that dexter URL again

www.dexteraxle.com/running_gear_tips

Originally Posted by agesilaus

OK I think that 125 deg temp is low. In the industrial environment the rule of thumb is that if you can hole your hand on the bearing then the temp is below 130 degrees and that temp is no problem. When it gets to 150 or so then there is cause for concern.

I think I am inclined to agree with you.

A week ago we had a Marathon blow out. I think that an outside temperature of 100+ contributed to the failure. Tires were 4 years old, from date of manufacture. They went into service March 2005.

I swapped the spare, meaning I no longer had a spare. I was unwilling to drive 200 miles home with no spare and I was unable to find an open tire shop near Truckee on the three day weekend. So we left the TM at a friend's house.

We picked it up this past Saturday. I now had a spare. I monitored the tire and bearing temps with a loaner infra-red sensor from my local shop.

The temps were only mid 90s coming home. DW had the cruise set at 55. When I got home the outside temp was 73 degrees, the temp on all six tires was 135 +- 2 and the temp on the TM hubs were 130.

If the outside temperature was 105 instead of 73 I would expect the tires and hubs to be warmer than they were.

It seems to me that the important thing is to know:

1. what your baseline temperatures are for a typical day
2. is there an unusual difference from base line
3. is there suddenly a substantial difference between one wheel versus some other wheel.

Before the blow out we had stopped for a cold drink. I visually inspected the TM tires, looking for cracks and bubbles, both inside and out. Nothing unusual. I had no way to measure the temps, but the tires and hubs did not feel unusually warm. The tires appears to be inflated properly, but I did not retest them. They had been tested at the start when cold, 1.5 hours earlier when we started out

1.5 hours later the tire blew.

To her credit, DW did an excellent job of getting the rig off the freeway onto the wide shoulder in not more than about 100 yards.

The TM was so stable that had we been unable to hear the pop because the radio was on then we probably would not have known the tire had failed.

I will be buying an infra-red thermometer soon.

I lube my TM axles once a year, via the zerk fitting, and this year, season number 4, I had the bearing removed, inspected and hand packed by someone I trust.

[Speckul8r]

The 125 degrees referred to was the outside spindle temp not the tire temp which can be higher. Also, that temp was suggested to me by the folks I get my bearings from. With over 40 yrs in the biz I find it hard to argue with them.
I'm pointing the IR thermometer at the spindle midpoint, or, if you will, parallel to the wheel (not the tire). I suppose the ambient temp will effect the heat dissipation somewhat but it should stabilize someplace unless there is more friction. The new greases are made to flow and should aid in the heat dissipation.

It's hard for me to see how you could have a tire temp of 135+ degrees and have a bearing temp much lower than that, after the system gets to the equilibrium point. You would have to have some cooling device to reduce the bearing temp below the tire temp since these are all connected from a heat transfer standpoint.

I did a lot more google searching after my post above and the only reference I could find to tire temp limits was on a Goodyear page which mentioned that one particular Goodyear tire was designed to operate between 160 and 230 degrees. However this seemed to be a race car tire so it isn't applicable to trailer tires.

There are lots of references to ir thermometer use (pyrometers) but again they mainly refer to race track use where the pyrometers are used to decide whether the tire is correctly inflated. And this is done via a multipoint temp check and some calculations. Again not much help for our interests. They mainly seemed to be interested in tread temps tho and not side wall temps.

BK

I chatted with my mechanic today, as I returned his IR thermometer.

He said that in the last heat wave, just for fun, he measuered the temperature on various surfaces inside a car that had been parked in the sun with the windows rolled up. 170 degrees in several locations.

No wonder you should never leave a pet in the car on a sunny day.

I have no explanation as to why the hub was about 15 degrees cooler than the tire surface. But that is what the meter said. I was holding it about a foot or so away from the surface and pointed the laser where I wanted to measure. I had just towed it 160 miles.