Just changed brakes and bearings -- why are the hubs so hot?

[Mr. Adventure]

Originally Posted by Bill

I don't use a Prodigy, so this is an honestly ignorant question. The posts above make it sound like the boost setting applies some small voltage to the brakes even when the brake pedal is not depressed. Can this be true? Say it ain't so, Joe!

Bill

It ain't so.

"Boost" just makes the braking a bit more aggressive in the stop. There are "off" and 3 boost positions, with higher settings recommended for heavier trailer weights relative to the tow vehicle.

[Mr. Adventure]

Originally Posted by rtcassel

If I use a boost setting of b1 on the Prodigy, the hubs get too hot.
Reference post http://trailmanorowners.com/forum/sh...0275#post40275
Does anyone out there use boost without getting hot hubs?

I use the b2 setting, and my brakes don't get hot at all in normal driving. grakin, I think, posted that he observed weak trailer braking until he adjusted the brakes (this thread was the best I could find in a quick search: http://www.trailmanorowners.com/foru...ake+adjustment).

Hypothesis: if the brakes are adjusted real tight, the controller needs so be set on the softer side and vice versa. (But I'm just guessing, here)

[rtcassel]

Originally Posted by ShrimpBurrito

What power setting (1 to 12) is your P3 set to?

I have an older Prodigy, not the P3. It is currently set to 9.

Originally Posted by ShrimpBurrito

I think if you have good braking and cool hubs, all is good in the world. I'm going to remove the boost as you suggest and go from there. What power setting (1 to 12) is your P3 set to? The Prodigy instructions say to start at 6 before adjusting......

Dave

Dave:
Will you share your final Prodegy power and Boost settings that result in moderate temperatures?

If I were to start a thread on this subject, it would be worded exactly as yours. All my circumstances are the same. I would describe my hub temperatures as hot enough to blister your hand if you gripped the hub. In industrual situations anything above 140F requires some sort of personnel protection, so I had guessed at 130F also.

Thanks, Don

[ShrimpBurrito]

Hi Don,

I'm not able to tell for sure what my Power setting is as the trailer isn't connected, but I seem to recall it's around 10 or so (I have the Prodigy P3). We're going on a trip next weekend, so I can check then. But I'm also not 100% pleased with the braking power. I need to adjust the adjustment screw on each of the wheels again so the pads are just barely not dragging -- I had backed them way off earlier in an attempt to determine the source of the heat.

The Boost setting is set to zero. That seemed to have ultimately corrected the problem, as with the boost setting set at 1 and all the other settings as they currently are, they hubs were getting hot. Turn boost to zero, and all is good. So you might give that a shot first.

Dave

[Wavery]

When the brakes are new and working at their most efficient level, they will (By law of physics) create more heat at the same setting on the brake controller. The more work that the brakes do, the more heat they will create (work=heat). By having the setting too high (the original setting), you are essentially stopping the TV (or at least a portion of it) with the trailer brakes. This will create a lot more heat.

As the brakes age and become smoother, they become less efficient and will require a higher setting on the brake controller to do the same job. So, it makes a lot of sense that the brakes would be just as efficient at a lower setting on the brake controller for the first part of the brakes life.

You should never be able to feel the trailer brakes slowing the TV. If you can feel that, they are set too high. The danger in that is, when going down a grade, the trailer brakes will fade very quickly. You may not even notice it until the TV brakes start to fade. The TV brakes will then fade faster because the trailer brakes are already useless. Not a good situation to be in.

Carole & Wayne:
I like your logic. There is a lot of merit to your approach.

Dave:
Following is a copy of an email I sent to Dexter concerning high hub temperatures and the response from their Product Manager, Rick Kapsa. I was surprised by his answer. I guess we are okay as long as we don't exceed 185F hub temperature. Read below:


-----ORIGINAL MESSAGE TO DEXTER AXLE-----From: don white
Posted At: Monday, October 20, 2008 10:05 PM
Subject: Feedback

All my life I have paid close attention to axle hub temperatures when towing a trailer. However, I am not familiar with trailers using breaking systems. My current trailer seems to be running a little warm, but I need an expert opinion before I start delving into it. I own a Trailmanor 2720SL with a single axle and axle weight of approx. 3000# with Dexter running gear, including electric brakes. The trailer has about 5000 miles on it. I just adjusted the brakes, they are on the light side.
I replaced the lube with Penzoil 707L wheel bearing grease. There is no wobble and there is no hub-to-axle looseness.

When I pull off the highway in 80F ambient air temperature, the hubs are hot enough that you don't want to press and hold your index finger around it. I believe it could almost blister you if you did. My best judgement says that is around 130F, maybe slightly higher.

My question: Is this normal after driving 65mph and breaking to a stop?
Or, do I need to teardown and inspect for a problem?

Thank you,
Don White

----RESPONSE FROM DEXTER AXLE------
This is normal. The brake drum surface where the brake shoes are can reach temperatures of up to 600 degrees during braking. The nose of the hub where the wheel bearings are located can go up to 185 degrees.

Rick Kapsa
Product Manager
Dexter Axle Company
Direct: 574-296-7386
Fax: 574-295-1069
[email protected]

[ShrimpBurrito]

Thanks for posting that email, Don. Very interesting. Prior to my changing the brakes, I had what I would consider decent braking, but this trailer is the first I've towed with brakes. (I changed the brakes because the magnets were almost shot, and it was about the same price to change the pads and the magnets vs. the magnets by themselves.) Whether I towed in city or highway, the hub was always warm, but comfortable to grab onto with my entire hand.

When I was experiencing 130+ F hub temperatures (which, like you, would be hot enough to make a blister), the actual wheel got very hot also....only slightly cooler than the hub. That not only doesn't seem like good practice, it seems like a contributing factor towards a blow out.

Car wheels don't get that hot during route city/highway driving, and they have the same bearing system. Most of the vehicle braking is done on the front axle, where brake systems are almost always discs these days, and the discs don't ride directly on bearings like the TM drums do. Maybe that makes a difference.

My Sequoia weighs ~6,000 lbs and has 4 wheels; the TM is ~3,000 lbs and has 2 wheels. So in both cases, all things being equal, each wheel has to stop about 1,500 lbs - but the Sequoia front wheels stop more than 1,500 pounds since most of the braking is up front. Seems like a comparable situation, but perhaps this logic is irrelevant.

I think I'm going to adjust the pads to just under the point where the drag, leave the controller settings alone, and see how that goes.

What are you planning to do?

Dave

Dave:
I plan to back off on my Prodegy voltage settings due to the fact that I can feel the TM slightly trying to stop the TV which, as Carol and Wayne mentioned in their post, is not desirable. I now have a surface temperature thermocouple which I will use to continue to monitor the hub temperature.

I would like to hear others weigh in as to whether or not they can grab and hold onto their hubs in city traffic. There is comfort in numbers.

Don

[Wavery]

Originally Posted by ShrimpBurrito

Thanks for posting that email, Don. Very interesting. Prior to my changing the brakes, I had what I would consider decent braking, but this trailer is the first I've towed with brakes. (I changed the brakes because the magnets were almost shot, and it was about the same price to change the pads and the magnets vs. the magnets by themselves.) Whether I towed in city or highway, the hub was always warm, but comfortable to grab onto with my entire hand.

When I was experiencing 130+ F hub temperatures (which, like you, would be hot enough to make a blister), the actual wheel got very hot also....only slightly cooler than the hub. That not only doesn't seem like good practice, it seems like a contributing factor towards a blow out.

Car wheels don't get that hot during route city/highway driving, and they have the same bearing system. Most of the vehicle braking is done on the front axle, where brake systems are almost always discs these days, and the discs don't ride directly on bearings like the TM drums do. Maybe that makes a difference.

My Sequoia weighs ~6,000 lbs and has 4 wheels; the TM is ~3,000 lbs and has 2 wheels. So in both cases, all things being equal, each wheel has to stop about 1,500 lbs - but the Sequoia front wheels stop more than 1,500 pounds since most of the braking is up front. Seems like a comparable situation, but perhaps this logic is irrelevant.

I think I'm going to adjust the pads to just under the point where the drag, leave the controller settings alone, and see how that goes.

What are you planning to do?

Dave

"all things being equal" ...............that's the hard part. If your trailer brakes are taking even a small part of the TV weight, it will make a big difference. You are much safer having the TV take a little of the trailer load.

Your TV brakes are MUCH MORE efficient. If you start to feel brake fade on the TV, you may be able to pull over and let the brakes cool off if you have a little reserve on the trailer. If you lose the trailer brakes to fade (which you probably won't be able to feel) and then you feel the TV brakes starting to fade, you have very little chance of stopping the whole package with fading TV brakes.

If you are going down a grade (with normal temp brakes) and feel the trailer pushing you a little bit while braking, that's not all bad. You probably have your controller set about right. If you can feel the trailer slowing the TV on a grade, you have it set too high and may be asking for real trouble.

Don't think that you won't be able to tell. That is what your brain is very good at. NASA tests have shown that the human brain is able to sense inertia better than any instrument that they can develop.