How strong should brakes be?

[ericw]

I have a 13' scamp. I thought the brakes were not that strong so I tore everything apart and ended up replacing the entire brake mechanism. It improved notably but left me with the question of how strong should I expect the brakes to be with 7" brakes.

It does not lock up the tires. If I coast on a level residential road at 25mph and hit the manual override I feel a distinct tug on my minivan, but nothing profound, just a distinct drag on the vehicle. I can feel the difference between 25%/50%/100% power so it isn't a tiny drag, but it doesn't feel about ready to lock up the wheels. If I had to count on the trailer pulling the vehicle to a stop, we are going to need a lot of room (many 100's of feet).

I have a prodigy P3 and set everything to full power. I did the brake job with someone who has done non FGRV's 100's of times. I checked all the wiring and double checked the ground differential from tow vehicle to brakes with the brakes powered on and it was small.

How much braking power should I expect?

[Byron Kinnaman]

7" brakes that are 13' Scamps will never lock up the tires. The distinct tug is the best you can get.

[Cathi]

Hi, ericw,
I can tell you our situation. It may be impossible to translate to yours but you might get something from it. We are towing a 19' loaded to 3500 lbs. with a 4Runner. I would say that our stopping distance with the P3 on manual is easily less than 100 feet but then I never measured it.

The brakes were extremely grabby in the 6.0 plus range and wheels never locked up. Took it to an RV place and they said that the setting we had at 5.8 or so when we went in was way way too high. They put it on 2.5, said the brakes work great but said that it may need to be lower. Brakes no longer grabby.

I was told that a trailer that weighed many thousands of pounds more than ours had the (proper) setting in the 5.0 plus range. I also understand that for a small trailer such as ours, no boost is needed.

By the way, if you get the guy I did at Tekonsha, he did not have a clue on a small trailer. Their directions are for much heavier trailers.

[Roger C H]

Here is how I test my brakes:

When stopped at a stop light nose down a small incline, I release the foot brake and when the rig starts to roll forward, I manually apply the trailer brakes. This usually stops the roll, which proves that they are working. I don't think doing this rolling backwards would be a good idea.

[gmw photos]

Originally Posted by Byron Kinnaman

7" brakes that are 13' Scamps will never lock up the tires. The distinct tug is the best you can get.

In the old days, the brakes on our motorcycles were like that. They were essentially "poor man's anti-lock braking system"

[Carol H]

It may be that the new brakes need adjustment. I am pretty sure the manual that came with the new brake assembly I put on mine, also suggested they be adjusted after ex so many miles.

I have a P3 as well and it normally does not need to be set above the 3 range before it also starts to get to grabby on my16'. If set above 4 or higher the trailer would jumping like a bunny and I feel a lot more than a light tug.

[Byron Kinnaman]

Originally Posted by Carol H

It may be that the new brakes need adjustment. I am pretty sure the manual that came with the new brake assembly I put on mine, also suggested they be adjusted after ex so many miles.

I have a P3 as well and it normally does not need to be set above the 3 range before it also starts to get to grabby on my16'. If set above 4 or higher the trailer would jumping like a bunny and I feel a lot more than a light tug.

FYI Your 16' has 10" brakes, the 13' has 7" brakes. That's a big difference. What you report is what I would expect for a 16' 2500 lb trailer. But, a whole different thing for a 13' 1300 lb trailer with 7" brakes.

[john warren]

as a general rule,,,you should always have more whoa, then you have go.

[Jim Bennett]

Originally Posted by john warren

as a general rule,,,you should always have more whoa, then you have go.

Nat a bad way to look at it, really.

The trailer brakes should theoretically be able to stop the trailer at the same rate your vehicle brakes stop it. This way the trailer does not rely at all on the vehicle brakes. Worst case scenario is that if you are doing emergency braking to avoid something potentially perilous, you want those trailer brakes to lock up.

Properly setup brakes are paramount to good performance, and as Carol eluded to, you definitely want to check the adjustment on newer brakes as they do get a bunch of slack quickly as they set in.,

I too have a P3 brake controller, and I set it up as per instructions, and for my setup I find it is usually set just over 5 somewhere. The level it is set at will differ from tow, to trailer, to brake setup though. If I apply the trailer brakes fully manually, the wheels will lock up, but under normal driving I only notice the brakes if I am stopping quicker than normal for some reason. These brake controllers these days are quite smart, and can sense how hard you are braking, and adjust the level of braking to the trailer accordingly.

I know LOTS of people, some good friends, that back the brakes off way too much in my opinion, just because they don't like that grabby feeling every once in a while. I much prefer to go the safe route.I have even met so called professional shop guys that advise backing off more than what the manufacturer recommends.

[ericw]

Thanks for all the feedback everyone. It sounds like 7" brakes are not going to lock it up. Let me know if anyone has a different experience.

Per the suggestion above, we did adjust the brakes (3x in fact to make sure we got it as close as possible). Sorry I didn't mention that.

I do agree that the trailer should stop the trailer and the tow vehicle the tow vehicle. I agree most people set their brakes too low.

Ideally, I don't think you want your brakes to actually lock up. Static friction between the wheels and the ground (wheels rolling) is greater than kinetic friction (wheels locked up) so you lose "stopping power" if your wheels are locked up. Maximum deceleration comes with maximum braking applied, but without wheels locked up. It is one of the reasons ABS brakes are a good idea for most drivers. It is the same reason you try not to just spin tires on ice if you want maximum grip. Let me know if I have always thought incorrectly about this. I would like to know why and learn something new.

[Carol H]

Originally Posted by Byron Kinnaman

FYI Your 16' has 10" brakes, the 13' has 7" brakes. That's a big difference. What you report is what I would expect for a 16' 2500 lb trailer. But, a whole different thing for a 13' 1300 lb trailer with 7" brakes.

Thanks for pointing that out Byron, but if the brakes are not adjusted correctly they are not going to do much regardless of the size of the brakes or the trailer. I would also think that as the 13' is that much lighter than a 16' its all relevant - isn't it? I just think it odd that his 13' trailer is taking 100' or more to stop at 25mph with the controller set on high & good brakes on the trailer - just doesnt sound right somehow.

All I know for sure is that the old set of brakes that where on my trailer did not do much even when set to high until they were correctly adjusted. When I had the new brakes installed I honestly could not tell the difference between the new and old ones until they were adjusted correctly.

There is something else that I thought of last night that I have noticed using my controller. I always check and fine tune my brake settings in the first couple of miles of my trip through my neighborhood -slow speed & little traffic so no one to upset by doing a fast stop in the middle of a road. After that once the brakes are really warmed up they may need a little fine tuning but not much. If the controller has somehow had the setting moved up much higher than where I normally have it while the trailer was not connected and I connect the trailer I have on occasion had a situation where even if I move the controller to max the brakes do not have the braking power that they should. If I stop and disconnect the trailer and reset the controller down to low and reconnect the trailer and then adjust the controller back up to the 3 range its all good. Its only happened a couple of times and I have no idea as to why that happens. There is probable a way of achieving the same reset of the controller while the trailer is still connected but that would involve reading the controller manual again

[Cathi]

Eric, that is correct according to the instructions that you do not want the brakes to lock up. You run them until they lock up and then back down so they don't. Ours, however, did not lock up at all even through the 6.s and yours apparently do not either. Tekonsha did say that they may not lock up at all as it is often difficult to get them to do that. As you say, you should get maximum braking without lock up.

Ours were ridiculously grabby and now at 2.2 there is just a little grabbiness and they are greatly improved. Had an emergency stopping situation today but didn't come to a complete stop as I wasn't sure how safe it was to do so. Will have to stomp on the brakes in a parking lot somewhere to see the effect. A good thing for us to test, I am sure. I only used the manual in the test runs, trying to get the right setting. Never could get it. Close now.

[gmw photos]

If using a prodigy with 'boost' settings, sometimes having the boost set ( or set too high ) can cause what I call "judder".......or grabbiness.

The prodigy controllers are really quite 'good'....but they are also probably not the 'best'. And magnet activated drum brakes are also quite 'good'....but again, they are not as linear and smooth in application as a hydraulic disc brake. So.....what we end up with is pretty darn good thank you very much.....but not necessarily as optimal as brakes could be.

Ideally, we would have electric over hydraulic disc with integrated ABS. Bring money......

[Jim Bennett]

Excellent points, George. I have used the electric over hydraulic systems, with good quality dixc brakes in larger trailers, and they sure do work much smoother.

I usually leave the boost off with a lightweight trailer, as it does help with some of the excessive grabbiness, but still provides the full braking set when in an emergency stop situation.

One thing about the grabby feeling. This is something you want to a very slight degree in many situations, it means the brakes are working. Too much though, and it means the trailer brakes are doing more than their share. It really is tough to set up our brakes and controllers for perfect all-round braking, they just aren't that perfect of a system.

[rhkirkham]

I probably have experience that not many may have. I have a 13' Boler that had 10" brakes and a Podidgy P3 controler. I have changed out the axle to a Dexter #9 which comes with 7" brakes. When I first got the axle changed the brakes were terrible. But after using them for a 1000km and adjusting them twice I find that now they are quite acceptable to stop the trailer. I can manually lock the brakes and have the trailer jump around. I now drive with the setting at 6 and boost 1. I found that I needed the boost to give a bit more on normal stopping. I think that you need to get some miles on your brakes before they give you full braking power and play with your controler settings to give you the best feel for normal stopping.

[ericw]

Rick, thanks for sharing your experiences. I would like more braking power and the guy I did it with said it would get better with time. Maybe I need to be patient. Just for reference, how tight do you adjust the brakes? What is your adjustment procedure?

[dylanear]

Yep, glad to hear that Rick. I just ordered a new Dexter 2200lb axle this morning with 8" brakes for my 13' Scamp. I was a little worried hearing that 7" brakes might not be very strong.

Has anyone heard of an ABS sensor and signal modulator for electric brakes? Seems like it would be dramatically easier to design and build something like that compared to traditional hydrolic ABS systems. An accurate sensor for a 2 wheeled trailer would be the harder part.

[gmw photos]

Originally Posted by dylanear

Yep, glad to hear that Rick. I just ordered a new Dexter 2200lb axle this morning with 8" brakes for my 13' Scamp. I was a little worried hearing that 7" brakes might not be very strong.

Has anyone heard of an ABS sensor and signal modulator for electric brakes? Seems like it would be dramatically easier to design and build something like that compared to traditional hydrolic ABS systems. An accurate sensor for a 2 wheeled trailer would be the harder part.

I have not heard of any ABS options for this type of brake. This is just a guess, but I think part of the problem is that the magnets are relatively "slow to apply and release". Even the rather basic early Bosch ABS like is fitted to my 1993 BMW motorcycle cycles at 7 hertz. I am not sure, but I don't think you could get the magnets to react that quickly.
Modern ABS cycles far faster than that even.

[ericw]

As someone said, its possible but are you willing to pay for it. What we have presently is good for the $ we pay, but ABS would add significantly to the cost. The architecture of the brakes would have to change significantly to get the inputs, speed of reaction, electronics to control it....

[rhkirkham]

The way I adjusted these - is jack up the trailer so the wheel is off the ground, the adjuster plug is on the bottom in the backing plate. Pull the plug. You will see the adjuster. Turn the adjuster to lengthen it. I adust until I feel it rub. I can still easily turn the wheel. The brakes are just touching. I drive with this and check to make sure that it is not heating up the brakes.