Hot wheel bearings

On Monday, June 17, 2013 6:26:47 AM UTC-7, JJ Sinclair wrote:


I usually touch the Cobra wheel bearing caps and check the tires when gassing up. They have always been just warm, (maybe 150 degrees), but yesterday they were too hot to leave my finger on both bearings (maybe 200 degrees). After slowing down from 60 to town traffic speed of 35, they both felt cool again. Is this normal? I remember Cobra having problems with their sealed wheel bearings. Should I replace both bearings? The trailer is 1999 vintage with 10,000 + miles on it.
JJ

At 13:42 17 June 2013, JJ Sinclair wrote:
On Monday, June 17, 2013 6:26:47 AM UTC-7, JJ Sinclair wrote:
=20

I usually touch the Cobra wheel bearing caps and check the tires when
gassi=
ng up. They have always been just warm, (maybe 150 degrees), but
yesterday
=
they were too hot to leave my finger on both bearings (maybe 200
degrees).
=
After slowing down from 60 to town traffic speed of 35, they both felt
cool=
again. Is this normal? I remember Cobra having problems with their
sealed
=
wheel bearings. Should I replace both bearings? The trailer is 1999
vintage=
with 10,000 + miles on it.
JJ

More likely to be a problem with binding brakes. Unfortunately once you
cook the bearings it is often wise to replace them!

I always check that the brake housing is cool after driving for a mile or
so. You have to be careful slowing down though, otherwise they will heat
normally coming to a stop. I would think 150 degrees is much too hot any
way. I would expect more like ambient + 30 or so.

Yeah, it's braking on the downhill and wheel gets incredibly hot and takes a while to cool down because its a significant thermal mass. Anyways, whenever I am going to drive in hot conditions on significantly hilly terrain, I'll disable the surge brake. I have a special piece of wood that I can insert in the tongue to prevent the damper from moving and subsequently engaging the brake. Obviously, do this only if your tow capacity is greater than the weight of the trailer.

On Monday, June 17, 2013 6:26:47 AM UTC-7, JJ Sinclair wrote:


The surge brake has been lubricated and I can feel the brakes come on and then release as I apply tow vehicle braking. Trailer rolls easily when pushing it around by hand. Don't believe the brakes are causing overheating as the hot condition was noted after 3 hours of straight towing at freeway speeds with little or no breaking action, but the fact that both hubs were hotter than normal would seen to eliminate the chance of both bearings failing at the same time. I did notice the hot condition right after a rather steep descent into Susanville, Ca, so maybe the trailer brakes did heat things up during this descent. I'll check it again after some level ground towing.
Thanks for your input, I think we may have just figured it out.
JJ

So how hot does the assembly need to get before the lubrication is destroyed in a sealed wheel bearing?

Maybe something like this would be a useful accessory?

http://www.amazon.com/Taylor-Digital...on+thermometer

I always downshift and use the engine to brake the trailer, but the surge brake is probably kicking in on the steep grades.

I live near the bottom of Kingsbury Grade at Minden. A friend brought his glider over to my house, coming down the grade (about 8.5 miles of 8% grade or so). The brakes on his new Cobra trailer were really hot, with a strong odor of burning brakes.

Not good, but I'd say normal.

bumper

At 06:24 18 June 2013, bumper wrote:
I live near the bottom of Kingsbury Grade at Minden. A friend brought his
glider over to my house, coming down the grade (about 8.5 miles of 8%
grade
or so). The brakes on his new Cobra trailer were really hot, with a
strong
odor of burning brakes.

Not good, but I'd say normal.

bumper

Interestingly the Alko manual suggests that if the brakes are coming on
when going downhill or decelerating then the overrun damper is faulty.
Excerpt from manual:

BRAKES APPLY DURING
DECELERATION OR
DOWNHILL TRAVEL
Overrun damper is defective. Replace the overrun damper.

On 18/06/2013 18:39, Jim White wrote:

Interestingly the Alko manual suggests that if the brakes are coming on
when going downhill or decelerating then the overrun damper is faulty.
Excerpt from manual:

BRAKES APPLY DURING
DECELERATION OR
DOWNHILL TRAVEL
Overrun damper is defective. Replace the overrun damper.

That makes no sense at all.

When under way, the ONLY time my Cobra's brakes apply is during
deceleration or downhill travel and if they didn't, THAT would be a defect.

That's why the whole expensive and tricky sliding tow hitch is fitted.

GC

How does it do that? How know the difference between overrun caused by car deceleration, and that due to gravity?

(Not disputing, just interested in the engineering.)

Chris N