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Topic: Tow Dolly brake options (Read 350 times) previous topic - next topic

Tow Dolly brake options

I have a Master Tow dolly with Hydraulic surge drum brakes. It's currently acting up. The brakes are pulsing when I stop with a moderate brake application. One tire was bouncing quite violently and I found that the spindle nut was a little loose. I readjusted both sides and the bouncing stopped, but I think I have warped the drums. I think I had the brake away cable too tight recently and had the brakes dragging a bit.

So I'm looking to replace the drums and shoes. Cost for shoes vs cost for a whole new brake assembly, it's cheaper to replace the whole thing.

So my question is, would you keep the hydraulic or swap to electric. Cost is about the same either way. Am I going to keep running into trouble with the surge brakes? Are they a problem on long downhill grades, where the retarder is keeping the coach controlled, but the surge brakes are just dragging and heating up? The controllability of the electric is appealing. I have a brake controller in my pickup if I use the dolly with it. I've been meaning to add a controller to the coach in case I need to pull a different trailer. I have multiple laying around the shop, Just need to wire one in.

Just looking for some advice from those of you that have done more towing then I have. Thanks!
1991 U300 Side Aisle 6V92 Silver #3897
2004 U320 40' #6246

Re: Tow Dolly brake options

Reply #1 –
Is there any adjust ability in the surge brake system? From experience they usually require some significant braking force of the towing vehicle before they activate. You should be able to limit speed downhill without them dragging. Maybe adjusting or replacing the return spring for the cylinder coupling can get you what you need. As a test you should be able to gently back it up
Dennis Haynes
Bohemia NY
2008 Nimbus 342 SE Carlyle
Build #6475
Motorcade #19148

Re: Tow Dolly brake options

Reply #2 –
The nice thing about electric brakes is they can be set up not to work when the retarder is
activated.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Tow Dolly brake options

Reply #3 –
Quote from: Dennis H –
Is there any adjust ability in the surge brake system? From experience they usually require some significant braking force of the towing vehicle before they activate. You should be able to limit speed downhill without them dragging. Maybe adjusting or replacing the return spring for the cylinder coupling can get you what you need. As a test you should be able to gently back it up

I just got home from Florida Caverns state park. From there to Atlanta ish. No big hills, some highway, some stop lights. About 4 hour drive, mostly flat. I stopped a few times to check things and the drums on the dolly were very hot to the touch. I didn't have a temperature gun, but they shouldn't have been doing much, I wouldn't think. I don't see any adjustment on the coupler. It's a Demco. I'm going to pull the wheels off later this week and see if I can figure out what's going on. Maybe they just need to be cleaned and adjusted.

Half the problem is I can't tell what they are doing behind the coach. I'll put it behind my pickup so I can get a better feel for what's going on.
1991 U300 Side Aisle 6V92 Silver #3897
2004 U320 40' #6246

Re: Tow Dolly brake options

Reply #4 –
Turns out the brakes were just out of adjustment. I cleaned and adjusted everything and it's working fine now. I think the shoes were catching and wobbling around in there. The cylinders only act on the front shoe. That might be part of the "free backing" setup so they don't come on in reverse.

I dug into my retarder control a bit more and I have one solenoid that turns the system off or on and that provides air to a relay valve that takes the brake pressure signal and provides it to the retarder on the transmision. So mine retarder is proportional to the brake pressure. There is also a second line that comes off the solenoid and goes somewhere that I need to trace, but I'm guessing it's going to the cooling fan. Mine is direct drive with an air clutch, so I think the transmission controller can turn on that solenoid when the retarder is activated and force the fan on.
1991 U300 Side Aisle 6V92 Silver #3897
2004 U320 40' #6246

Re: Tow Dolly brake options

Reply #5 –
For one of my boats with surge brakes i found that adjusting the drop height of my ball made a huge difference. 
Mike and Loretta
Charlie our Cavapoo
1999 U320 3600 WTFE
Build 5499
Wrangler JKUR via Roadmaster and Air force One