Dot5 + Brake Shoe = Hot Hub?

[SteveKuhn]

I'd appreciate any comments on the theory above and the test I ran below.

I took the truck on an 80 mile r/t run last Saturday and noted that the right rear tandem was much hotter than any other wheel. After about 20 - 25 secs, you wanted to take your hand off.

This was the 1st real run since having a wheel cylinder replaced on that one. At that time, the wheel bearing condition was good and it was packed with grease. Ergo, perhaps the brake shoes got adjusted a bit too tight in the process.

I took it back to the mechanic who did the work and he backed the brakes off a bit, making sure the shoes were loose enough. When I picked it up, he remarked that it didn't seem tight when he started but they were looser now.

My question: If it wasn't the bearing or too-tight shoes, and I know the differential oil is at the proper level, why was the hub and wheel so hot?

His answer: Dot5 got on the shoe and although they were cleaned w/ brake fluid and gas, some was still working its way out, creating heat.

Didn't sound quite right to me. So, to test the theory, I decided to try to isolate the brakes as the heat cause by driving without using them. If the temp came up again, the theory was wrong and I'd worry about the bearing.

I took the truck out for an 8 mi run w/ several miles of highway at speeds up to 40 - 45 mph I never touched the brake pedal. Ever. Speed control was with spacing and shifting, and the parking brake was used at lights. (Which in N metro NJ at a.m. rush is an experience in itself.)

The hub ended up only a noticeable tad warmer than the others by the end. Yesterday, when using the brakes, the heat was up to the uncomfortable level in less than half the distance. We're thinking that it's possible that being tightened to torque on the repair made it run a little warmer than the other 3 which are probably a bit loose and barely warm at all.

So it seems that the brakes are the heat source, and not from being too tight. Does the Dot5 marinating make sense to you? Other comments?

We're due for another 80 r/t this weekend provided I don't have to put it up for repairs.

Thanks.

Steve

 

[Flyingvan911]

The brake may have been adjusted too tight. You also might need to repack that bearing. I'd take in on the highway for a little bit at 55 mph then check the hubs.

 

[Heavysteven]

I think the bearings are to tight or the brakes. I would jack it up spin the tires by hand see if there is play and how it feels.

I set my bearings with a torque wrench per the manual. I also used feeler gauges to adjust the brakes per the manual. Check axle spring vent.

 

[cattlerepairman]

I have one hub (passenger rear rear) that runs hotter than all the others. I re-grased bearings, re-adjusted the bearing preload (was correct) and re-adjusted the brakes (were correct, perhaps a tad tight, now they are decidedly loose) and the temperature did not change. When all hubs are at 40 degrees C ("hand warm"), this one sits at 50 or 55 ("oh yea, warm..not hot..warm"). Nothing critical in any way, but no logical explanation, either.

I have read that the new seals (new star) can create more friction and heat. Perhaps that is the case.

I might add that, if you can leave your hand on the hub from 20 seconds, then the hub is not crazy hot.

You also may want to use a digital "laser" thermometer (cheap nowadays), start with the hub cold, go for a drive at speed for about ten-fifteen minutes, pull over and measure hub and brake drum temps right away.

If your hub is still cool and your drum is very warm (or vice versa) it may help narrowing down the source of the heat. Over a longer running period, heat transfers between the metal parts and all gets pretty much equally hot.

Some people say not to bother at all; unless the hub gets "too hot" i.e. beyond the lubrication capacity of the bearing grease, which is usually good up to 200 degrees C or even more, and definitely beyond anything you would want to place your hand on, no bad effects result. I am rather more timid.

 

[wsucougarx]

Did you replace the outer wheel seal?. If you did, I've found that some of the crappy Newstar seals actually put pressure on the outer wheel bearing. Thus causing it to drag and causing a hot hub. Gringeltaube has a write up on this I believe.
Highly recommend you jack the truck up, remove the axle and free spin to see if you can hear the brakes dragging. If not then replace the said seal and go from there.

 

[73m819]

We had the same problem on Jim Hendersons truck, a wheel cyl. got replaced, the axle bearing got set to tight,

 

[dmetalmiki]

Contamination of the shoes can alter the co-eficient and thus the effectiveness and heat of the drum.
Since all brakes work on the fact that ALL energy inputs (and braking output) Convert energy into heat. then Braking = heat.
A new wheel cylinder workin (now) at 99% effeciency and therefore having "better" braking = More Heat then the the (other) lesss efficient shoes.
If you were doing your own maintenance, and wished (had the time or incinination!) to "qualify" the situation. Swapping the New shoes. or a New wheel cylinder would certainly show the effect of the compnents.
Backing "off" shoes is not the ideal salution. (though a "wheel braking tester" would show the ( within) ballances.
The brake shoes should NOT have been "washed" in brake?? fluid! and petrol. There are proprietory brake pad/shoe cleaners avaliable. NON of which contain a lubricant!.

 

[SteveKuhn]

I don't want to discourage further replies but I wanted to acknowledge that this is all extremely sensible and helpful. The wheel does free spin nicely; a seal was replaced w/ the cylinder. 50 mph is the exceptional downhill for me. 40 - 45 is the norm. 55 for me is 6 years ago.

I'll revisit the bearing packing and both the brake and bearing adjustments. I found it in M35-TM-9-2320-361-24-1. Or am I in the wrong place? (I freely admit that while I have a load of PDFs, I still don't have a solid handle on which one or version to go to for what.)

I'd like to get the packing and re-adjusting done before, but I don't sense that anyone is suggesting that I cancel the weekend outing if I can't. I intend to duplicate this a.m.'s non-braking exercise. Or am I wrong?

Thanks, and keep commenting.
opcorn:
Steve

 

[SteveKuhn]

"...The brake shoes should NOT have been "washed" in brake?? fluid! and petrol..."

Typo: I meant brake cleaner not brake fluid. I actually read thru quite a few threads here and elsewhere and while I found disagreement, there were plenty of endorsements for both as Dot5 brake shoe solvents.

I like the rest of your reasoning, too. I'd do a lot more of this myself with time and space and pitch. If you've seen photos of my truck in my driveway, you get the picture. I only load up tools, jacks, and stands and escape to a level, friendly parking lot when I'm sure I can get it done in one session by myself. I do get in on it with them when I can play hooky from work.

Thanks.

Steve

 

[condor418]

when do u take it out i live in east rutherford and the only 1 i have heard about was some guy in wallinton having one .... i cant wait till i can afford one

 

[SteveKuhn]

GREAT! Another guy in the neighborhood. Today's run was down 17 to Highland Cross and back. Drop me a note so we can get in touch. It's on the road at least every couple of weeks for a joyride at least and for the next 2 months, weekly for events.

And I trust you're coming up to MTA in Augusta next weekend. You might be surprised at what you can afford.

Back to our regularly scheduled thread.

Steve

 

[condor418]

i plan on goin but i recently fell about 30 ft and shattered my heal just got the cast off on monday now i got this big ass boot im crutchin around with and 114k$ medical bill cuz i dont have insurance so its goin to be a while befor i can afford anything but still would like to see whats out there and for how much

 

[armytruck63]

^Ouch on both the physical pain and the huge bills!

 

[sandcobra164]

Could be a problem with the grease used when packing the bearing. I've had this issue on my truck. Mine like's the Lucas Heavy Truck grease. The first time I did an axle seal, I used "Disc Brake Grease" with the thought that if it can stand up to higher temps, it must be better. Well, that hub ran very hot as in move your hand within about 10 secs. After teardown, clean all grease away and repacking with the Lucas, all is well on that hub. Also, the TM calls for you to torque the spindle nut to 50 ft. lbs and then back off a 1/4 to 1/2 turn. I've been told from some folks that you may have to back off 3/4 of a turn but I've not needed to try that yet. Just food for thought but never leave it torqued to 50 ft. lbs. as that will surely cause an issue.

 

[SteveKuhn]

"...Did you replace the outer wheel seal?. If you did, I've found that some of the crappy Newstar seals actually put pressure on the outer wheel bearing. Thus causing it to drag and causing a hot hub. Gringeltaube has a write up on this I believe..." wsucougarx

I'm still going through the comments but wanted to ask if this is the thread you're referencing.

http://www.steelsoldiers.com/deuce-modification-hot-rodding/71928-3-good-questions.html#post884181

I hope to have it thought through by tonight.

Steve

 

[bsorcs]

Re: warm hub

Look for the thread titled "Axle seal quality". It's a follow on to a prior thread titled "Hot hubs". Beaucoup info therein.

 

[SteveKuhn]

"...Look for the thread titled "Axle seal quality". It's a follow on to a prior thread titled "Hot hubs..."

Read both a couple of times. Lotsa stuff. Here they are for anybody looking for them:
http://www.steelsoldiers.com/deuce/58049-axle-seal-quality.html and http://www.steelsoldiers.com/showthread.php?31749-Hot-Hub&p=341633&viewfull=1#post341633


I buy in to the idea that the axle seal could be causing this hub to run warmer, but so far it's not above operating temp. I'm more concerned about the real heat which I think is the brakes. It doesn't seem at all abrupt when coasting to a stop, so I don't think they're dragging.

DMetalmiki is pretty convincing that this might be the most efficient wheel at applying the shoes, so it stands to reason that if it's doing most of the braking it'll generate a lot of heat. If there is Dot5 working out of it, silicone as a lubricant might lessen the effective braking, requiring more pressure, making more heat, etc.

I'm gonna pick up an infrared thermometer tonight and take tomorrow's trip w/out using brakes. I'll stop about every 10 - 15 mi and measure the hub vs. brake assembly. Assuming the hub stays 'operating warm', I'll do that until the last 10 - 15 mi coming back and start using the brakes a bit. If it is the brakes, the drum should heat before the hub.

That information ought to advise any work for next week.

If I'm wrong and the whole thing heats up, I'll just beat a retreat a leg at a time.

I appreciate all the ideas. Wish I could just tear it all down and do all I've read.

Steve

 

[SteveKuhn]

Y'all nailed it. It's not the brakes. If I tapped the brake 12 times from 8 a.m. - 6 p.m., I'd be surprised.

We not only made the run out and back (40 mi each way), but I did 7 rides through the park grounds running about 10 - 15 mins each. All slow/low range, but pretty constant.

(Sidebar: Thought you might get a kick out of the part of this video that shows the robots from Picatinny Arsenal about 35 - 40 secs in. They left some of the older kids run them. Unfortunately we didn't catch the perspectives where it looked like a scene from Star Wars, trucks rumbling in vs. 'bots scurrying.)

Anyway, I took temps throughout the trip w/ my new HF Flex-Shaft closeout Thermometer but the most telling was at the end after running in I-80 at 45 mph in the afternoon (all temps are rear axle.)

Driver's side hub: 120 F (warm but not notable.)
Curb side brake ass'y (inboard, near axle): 98 F
Curb side hub: 147 F (Uuuuhhhhh, think I'll move my hand now.)

The trip out was a proportional result but about 10 - 15 degrees lower across the board. Then again, air temp was 10 - 15 degrees cooler in the a.m. as well.

BTW, the difference of 27 degrees to the touch is dramatic from 120 - 147. 147 is right where you start to not wanna stay on the metal for too long.

Back to the shop to get 'em repacked and loosened up and we'll try the same tests on the way to Sussex for the show. Now that I've read and experienced, I really think it's the inner spindle nut not being backed off far enough.

The Sussex run will include a lot more braking because of the long hills and 2 lane traffic.

 

[PsycoBob]

Ok, after reading up on the bearing work I may have to do to my truck, I have one item to add.

It seems over-packing the bearings with grease can cause issues with heat. Too much grease in there seems to make the bearing try to pump that thick snot around, causing heating. With anything as complicated as our wheel/axle assemblies are you can have more than one source of heat.

For the temps, are you checking the center hub, or the brake drum? My hubs are usually slightly warm, but the drums are almost always cool as most of my driving isn't stop/go.

 

[SteveKuhn]

That post reminded me that I owe the thread an update. The high temps were on the hub, not the brake.

In the week before the MTA Sussex show, we tore it down again, and checked bearings for lube but most importantly retightened the spindle nut to 50 lbs/back off 1/2 turn.

On the 45 mi trip up running 45 - 50 mph, neither the hub nor brake heated up at all, so my money is on the spindle nut fix.

I did rides for the public and after the 2nd/3rd run a number of guys heard screaming coming from that side, and called for a dragging shoe. I hadn't heard it over the engine and stack but did once they called it. I thought I had another problem source, but I continued the rides keeping an ear out.

Within about 3 more circuits the sound diminished and disappeared for the balance of the day and never reappeared, including on the 45 mi ride home. Again, normal temp on hub and brake assemblies. I drove the truck for 11 hours that day, block to block.

I've kicked it around with several guys since and consensus is that the spindle nut was the source of the heat problem and the 'dragging shoe' was probably something foreign that got in and worked itself out. The rides had sections of gravel road and about a third was off pavement including flattening mulch piles.

We're not gonna tear it down again at the moment but are keeping an eye on it for developments.

Steve