Electric brakes, braking force?

[maproy99]

I just got to wondering, what is the braking force difference between 7 inch electric brakes and 10 inch electric brakes. I had to go with 7 inches brakes on my trailer (only drum I could find to fit my rims and didn't want to replace 5 rims) however even with the boat off the trailer I am unable to lock the wheels with the brakes as I typically see done. So, how much braking force am I losing out on by having the 7 inch brakes? I am 90% sure I have my brakes adjusted right and it is a improvement over what used to be the not working surge brakes.

 

[UncleWillie]

Re: Electric brakes, braking force?

If they originally had 10 inch drums, why wouldn't replacement 10in. drums fit???

Given a 70% diameter and assuming 70% narrower, you are looking at a 50% loss in braking. (0.70 x 0.70 = 0.49)

They will still stop you but will get twice as hot.
Once they overheat your braking effect will become Nil.
If you have never experienced overheated brakes, Do Not underestimate how sudden and extreme the loss is.
It is like trying to brake on ice except it is warm and sunny!

 

[maproy99]

Re: Electric brakes, braking force?

They had 7 inch surge brakes originally. The only way I could have ended up with 10 inch brakes would be to buy 5 new rims and remount the tires and balance them. I didn't feel like investing that much $.

 

[UncleWillie]

Re: Electric brakes, braking force?

It sounded like you were downgrading.
I understand now; You were only asking what you would be missing by not upgrading.

The original 7 inch brakes should be fine if the trailer was originally designed for them.
10 inch drums are rated for 3500lb axles.
Can I safely assume this is for a lightweight trailer? (<2000lb axle?)

You should be able to lock up the brakes hard enough to drag the wheels in a skid.
The Braking action may improve as the new surfaces wear in.

EDIT:
Free Backing Electric Brakes will NOT lock up in reverse even with the brakes full ON!

 

[maproy99]

Re: Electric brakes, braking force?

It is a tandem trailer with 2, 2200lb axles. The trailer is older, as in era 1964, but still in great shape. I have put over 1,000 miles on the trailer this season, I was waiting for the new surface wear in period, but it never came as far as I can tell.
My normal route to the lake is on back country roads for 25 minutes, so not many fast stops. Just had a close call on the St. Louis bypass when going on vacation so it got me thinking about more braking power.

I guess I might as well tell that story, Driving there, I saw there was a line of nasty clouds coming my way. I was convoying with someone I know and we decided to pull off when we got out of the urban sprawl to put the boat cover on. Before we got to a good spot the sky opened up and it just poured. The interstate went from moving about 70 down to about 25 mph in the matter of a few seconds. Let's just say I came very close to rear ending the guy in front of me. It's not a good feeling when you are feeling the anti lock brakes working and you are still not slowing down fast enough.

 

[UncleWillie]

Re: Electric brakes, braking force?

I would think you should still be able to lock up the single axle with full brake power.
If the brake wiring is marginal you will not get full current to the brakes.
Can you measure the actual voltage at the brake drum with the controller maxed out.

I think it should be at least 9 volts at the wheel, someone with direct experience may correct me.
I have never owned electric brakes, But I have driven with them, Repaired them for a friend, and stayed at a Holiday Inn.

 

[maproy99]

Re: Electric brakes, braking force?

Yea I was thinking the same about locking the wheels up. I measured the voltage to be 4 volts at one assembly the other day with the brakes on full power. Sometime this winter I am going to rewire the power for the brakes and run a ground up to the harness. It will shorten the distance and will allow double the current to flow. Hopefully this fixes it or at least improves it.

 

[Bondo]

Re: Electric brakes, braking force?

Yea I was thinking the same about locking the wheels up. I measured the voltage to be 4 volts at one assembly the other day with the brakes on full power. Sometime this winter I am going to rewire the power for the brakes and run a ground up to the harness. It will shorten the distance and will allow double the current to flow. Hopefully this fixes it or at least improves it.

Ayuh,.... I pull a tandem tool wagon everyday,......

I once screwed up, 'n hooked the back-up lights to the brake circuit,..... :facepalm:

In 4x4, ya couldn't back it up....
At 12v, it wouldn't move,.. at all...

 

[maproy99]

Re: Electric brakes, braking force?

Well, I just undid all my previous brake wiring, planning to run a separate wire to each brake from the tongue. I got power to the 1st brake and I tested it. With the wheel jacked up, it was A LOT harder to spin the wheel then before with full power applied from the manual switch on the brake controller. Looks like I just didn't use a low enough gauge wire. Also the fact I wrapped the wire around the old brake line instead of using zip ties would have added possibly quite a bit of resistance.......... :facepalm:

 

[UncleWillie]

Re: Electric brakes, braking force?

... it was A LOT harder to spin the wheel then before with full power applied from the manual switch on the brake controller. Looks like I just didn't use a low enough gauge wire. Also the fact I wrapped the wire around the old brake line instead of using zip ties would have added possibly quite a bit of resistance.......... :facepalm:

Wrapping the wire has absolutely ZERO effect on the resistance!

The recommended wire gauge is #10 or larger. Ground wires included.
And that includes all the wire from the battery to the controller and back to the axles.
You will be pulling 6 amps per axle and can not afford to lose more than a volt along the 30 foot path.

 

[maproy99]

Re: Electric brakes, braking force?

Making the steel brake line into an electro magnet every time the brakes are powered on was probably a good chunk of my problem. It was wrapped many times around over the roughly 13 feet back. I tried about that many times wrapping around on a crow bar I had sitting around, got one strong electro magnet from that. And I didn't use 10 gauge wire, had some 12 and 14 sitting around and decided to try and get by with it, which is why I now have 2 lines running to the back. Shortened the distance by not having to cross the axle and cut the power flowing through the wire by half, allowing me to use the wires I already had.

 

[batman99]

Re: Electric brakes, braking force?

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Maproy99,

If your trailer has 2 x 2,200 lbs axles, then simply install electric brakes on both axles. re: Brake Assemblies and brake drums that fit you axle spindle - which is brakes for 2,000 lbs axle. Brakes on 1 x axle is good (better then nothing) and brakes on both axles is much better. For wiring, may I suggest STAR configuration using thick 10 guage instead of usual linear wiring that uses thinner 12 / 14 guage wires. Wires are low cost. Thus, always use 10 guage or better. With STAR design, there's less points of failure and 12v / Amp delivery to each wheel hub is balanced. For comparison, surf:
http://i178.photobucket.com/albums/w251/Spike99-Pictures/Trailer wiring/Brakewiring-Linear.jpg
http://i178.photobucket.com/albums/w251/Spike99-Pictures/Trailer wiring/Brakewiring-Star.jpg

For electric BC (Brake Controller) inside the Tow Vehicle, stay away from Timed technology models. IMO, ALL "timed" BCs must be tagged as illegal and pulled from all store shelves. Suggest installing "proportional" technology BCs. For example, Prodigy P2 or their better P3 model. For proportional, more current is sent to the trailer wheel hubs the FASTER the Tow Vehicle stops. re: Panic stops means full current to the trailer brake hubs. Slow down hill braking means low amount of braking power on the trailer hubs. Time BCs cannot deliver proper amount of current - based on Tow Vehicle's braking behavior.

If wondering, trailer brakes should only "lock up" during Tow Vehicle panic stops. If the trailer axle brake pads are adjusted properly and using a proportional technology BC, the trailer brakes will brake smoothly and should never lock up (under normal driving conditions). Each proportional brake controller has a adjustment (some have physical thumb dial and some are digital numbers). For your "loaded" attached trailer, adjust this wheel - for your unique trailer and Tow Vehicle combo. And, adjust for empty trailer as well. For my combo, my "boost" setting is 2 for empty trailer and 9 for loaded trailer. Setting for your unique combo (Tow Vehicle and Trailer) may be slightly different. Simply try different settings until the trailer braking force feels good to you. re: Both Tow Vehicle and Trailer are stopping together.

Remember that trailer brake "lock up" = "fish tailing" trailer = "very bad". Thus, trailer brakes should never lock up (under normal driving conditions).

I prefer full electric brakes (that allows stength adjusting inside the Tow Vehicle) compared to pure mechanical Surge Brakes. For me, full electric brakes for fresh water exposure. If you plan to keep your boat/trailer a long time, converting to Full Electric brakes is worth it (for fresh water conditions). For electric brakes, simply disconnect the 7-pin connector, then back into the water. After pulling out of the water, do tie-downs, circle check, then re-connect the 7-pin connector into the Tow Vehicle. Clean, simple and easy for boat ramps...

Hope this helps...

 

[maproy99]

Re: Electric brakes, braking force?

Well, I reran brake wire. Now I have 12.25 volts at each brake with the engine running. A lot better then the 3 volts I recall it being right before I tore out the old wiring. I adjusted one brake and it looks like that wheel is holding a lot better. Using all the leverage I can get I cannot get the wheel to budge at all. I still need to adjust the other one and might go for a test drive in a few weeks when I finish re wiring my junction box.