More trailer tire/wheel issues

I pulled my Cobra up the Sierras to Sparks, Nv and then blew the right tire (6� of tread separated and took the fender off too). Tire and wheel were Not even warm. Put on the spare and drove the final 20 miles. Next morning I jacked up one wheel and took 2 tires and rims in and got 6 ply trailer tires. After the contest, I pulled the trailer back down the western slope of the Sierras and pulled over to check things after about an hour of down hill towing. To my surprised both Hubs were too hot to keep my hand on them and the right hub was hot enough to steam as I poured a bottle of water on the inside wheel area. In downhill towing the surge brake stays on most of the time and is riding the trailer brakes............something we know to never do, right?
Are these two Instances related? I think so, I did the same trip last year and I’m thinking the overheating from downhill towing caused over pressure and weakened the 4 ply auto tires. The weakened tire blew after about 4 hours of driving on my way back up the hill, this year.
Your thoughts and experiences?
JJ

On Thursday, July 18, 2019 at 4:09:15 PM UTC-4, wrote:
I pulled my Cobra up the Sierras to Sparks, Nv and then blew the right tire (6� of tread separated and took the fender off too). Tire and wheel were Not even warm. Put on the spare and drove the final 20 miles. Next morning I jacked up one wheel and took 2 tires and rims in and got 6 ply trailer tires. After the contest, I pulled the trailer back down the western slope of the Sierras and pulled over to check things after about an hour of down hill towing. To my surprised both Hubs were too hot to keep my hand on them and the right hub was hot enough to steam as I poured a bottle of water on the inside wheel area. In downhill towing the surge brake stays on most of the time and is riding the trailer brakes............something we know to never do, right?
Are these two Instances related? I think so, I did the same trip last year and I’m thinking the overheating from downhill towing caused over pressure and weakened the 4 ply auto tires. The weakened tire blew after about 4 hours of driving on my way back up the hill, this year.
Your thoughts and experiences?
JJ

Your over-running dampler may be too weak. https://wingsandwheels.com/cobra-overruning-damper.html for replacements

From a 2002 Cobra manual:
5.2 Overrun brake
5.2.1 All braked trailers are equipped with a Rückmatik brake system and except
the lubrication of the overrun piston and the bell crank lever additional maintenance is not required.
5.2.2 Lubricate the overrun piston every 5,000 km or once per year with multi-purpose grease (see
lubrication plan point 10.1).

On Thursday, July 18, 2019 at 4:30:44 PM UTC-4, Dan Daly wrote:
On Thursday, July 18, 2019 at 4:09:15 PM UTC-4, wrote:
I pulled my Cobra up the Sierras to Sparks, Nv and then blew the right tire (6� of tread separated and took the fender off too). Tire and wheel were Not even warm. Put on the spare and drove the final 20 miles. Next morning I jacked up one wheel and took 2 tires and rims in and got 6 ply trailer tires. After the contest, I pulled the trailer back down the western slope of the Sierras and pulled over to check things after about an hour of down hill towing. To my surprised both Hubs were too hot to keep my hand on them and the right hub was hot enough to steam as I poured a bottle of water on the inside wheel area. In downhill towing the surge brake stays on most of the time and is riding the trailer brakes............something we know to never do, right?
Are these two Instances related? I think so, I did the same trip last year and I’m thinking the overheating from downhill towing caused over pressure and weakened the 4 ply auto tires. The weakened tire blew after about 4 hours of driving on my way back up the hill, this year.
Your thoughts and experiences?
JJ

Your over-running dampler may be too weak. https://wingsandwheels.com/cobra-overruning-damper.html for replacements

From a 2002 Cobra manual:
5.2 Overrun brake
5.2.1 All braked trailers are equipped with a Rückmatik brake system and except
the lubrication of the overrun piston and the bell crank lever additional maintenance is not required.
5.2.2 Lubricate the overrun piston every 5,000 km or once per year with multi-purpose grease (see
lubrication plan point 10.1).

"damper".

A year later, I'm still having the problem I've had off and on for over 20 years on my 1992 Cobra: i.e., after a moderately hard stop, the brakes occasionally jam on and stay on.

New damper strut. Disassembled and lubed the overrun tongue piston. Same for the pivot for the e-brake/hook. New brake hardware and shoes. Lubed the actuator cables. Filed out the slot in the inner tongue tube that had a very small machining discontinuity that I thought might cause the big bolt that slides in it and holds it all together to jam.

I know most owners are happy with their Al-Ko overrun brakes. But based on my experience, I'd never buy another one. I'm ready to rip out all the Al-Ko junk and go with an aftermarket axle. Apparently, if one tiny thing is wrong, you're looking at a blown tire, burned bearing, or worse. I bought a tire pressure/temp monitor last year that alerts me now when the temps start to climb but what a pain. I suspect I'll just disconnect the brake permanently.

I continue to think this is another example of European/German pilots lovingly devoting hours and hours of maintenance to their Daimlers and Cobras every year while we Americans just want to jump in our vehicles and drive 3000 miles across the country to a contest, hassle-free.

Chip Bearden

I checked the surge cylinder and it came on softly and released properly when pressure was released. I bought new 6 ply trailer tires recommended for 50 psi, which will help any overpressure caused by brake/tire heating. If the sealed bearings and brakes look OK, l’m considering a brake lock-out to fit when descending a long run, like Hwy 80, West of Reno.
JJ

I have a brand new Cobra and even towing short distances on relatively flat roads the hubs are too hot to touch. I can tell from my rear view camera that the surge brake is not engaged. My conclusion re the quality of this stuff is the same as Chip's (i.e., POS). Has anybody tried the Dexter electric with the parking brake feature? Unfortunately I have to have a PB otherwise I'd be switching ASAP. Clay

On Thursday, July 18, 2019 at 3:58:23 PM UTC-7, Clay wrote:
I have a brand new Cobra and even towing short distances on relatively flat roads the hubs are too hot to touch. I can tell from my rear view camera that the surge brake is not engaged. My conclusion re the quality of this stuff is the same as Chip's (i.e., POS). Has anybody tried the Dexter electric with the parking brake feature? Unfortunately I have to have a PB otherwise I'd be switching ASAP. Clay

I have Dexter Axle with electric brakes on my older Cobra Trailer. Works great.

Richard
www.craggyaero.com

Thanks Richard do they get hot?

Clay
You should have your bearings/ brakes checked out by a mechanic if you can't do it yourself.
Getting hot like you describe is not right.
Your not going to get very far with them heating up on a flat short drive.

On Friday, July 19, 2019 at 9:11:01 AM UTC-4, Nick Kennedy wrote:
Clay
You should have your bearings/ brakes checked out by a mechanic if you can't do it yourself.
Getting hot like you describe is not right.
Your not going to get very far with them heating up on a flat short drive..

I cannot confirm any of these described design deficiencies! My ~2012 vintage Cobra dual-axle trainer got moved across the US from SC to NM now four times - 1,600 miles each way - plus once to CO and back over some pretty punishing road surfaces. I installed a TPM system and keep an eye on the pressure and temperature of each wheel. Even during the long descent on I-70 west of Denver or while doing the 'Million Dollar Hwy' did the tire temperature not increase notably. I always check the hubs during gas stops and never burnt my finger.
The only thing I need to change now is the damper in the over-running brake, which seems to have gotten weak.
Please note that these trailers in Germany are subject to a state inspection every two years, where the brake and light system is checked, so regular maintenance is advised and generally accepted for the sake of keeping them safe.
The argument 'they don't use large pick-ups and SUVs over there, so we don't need brakes on our trailers here' is laughable! Once the towing vehicle is no longer perfectly in line with the trailer, the trailer will try to pass you - no matter what you are sitting in. The 'Auflaufbremse' or overrunning brake system is designed to keep the trailer behind the towing vehicle longer.

Uli
'AS'