Brakes

[Anderson]

Looking for experience/opinions on DirecLink trailer brake system? Supposedly ties vehicle ABS to Trailer via tow vehicle computer.

[Ron in BC]

Originally Posted by Anderson

Looking for experience/opinions on DirecLink trailer brake system? Supposedly ties vehicle ABS to Trailer via tow vehicle computer.

I'd be interested in hearing user's opinions of that system also.

It's not something that I'd ever thought about until very recently when I-5 turned into a skating rink. My truck ABS was chattering away and I was wondering about the effect of an active ABS on the tug and the trailer brakes not acting in the same way. As it turned out, there were no incidents but I may have just been lucky.

Ron

[Brian B-P]

Tuson RV Brakes, LLC: DirecLink Brake Controller

Originally Posted by Anderson

Supposedly ties vehicle ABS to Trailer via tow vehicle computer.

It certainly connects to the vehicle through the On-Board Diagnostics port, but I don't see much value in that connection, or any evidence that the tow vehicle's ABS is involved in any way. The brochure lists these items being monitored by OBD:

• Trailer Connection
• Tow Vehicle Battery Voltage
• OBDII Network Connection Integrity
• Brake Controller Ground Connection
• Brake Controller Power Connection
• Brake Switch Voltage
• Blue Wire Voltage Output
• Blue Wire Current Output
• Blue Wire Short
• Engine RPM
• Low Speed Brake Adjustment
• Transmission Temperature (Ford & GM)

None of those items indicate the amount of braking required, so that list makes this statement look like a bunch of bull:

Stop relying on brake controllers that use devices to sense what’s happening. DirecLink gets its information direct from the source - your tow vehicle

The wiring even includes a connector for the classic 4-wire (blue, white, red, black) controller connection. It needs that for power (black and white) and the output to the trailer brakes (blue and white), but why the red wire... the installation manual confirms it is for the the brake pedal switch, an input which should be coming over the OBD connection. Perhaps it is used as an output to turn the vehicle's brake lights on during manual trailer brake application, but that's not very impressive integration with the tow vehicle.

The installation manual describes use of the vehicle speed (presumably from OBD), even though it is not listed as a monitored parameter (in the brochure of features chart). This could be used to calculate deceleration, instead of using an accelerometer. That might be an interesting input for proportional braking, but it is not integration with the tow vehicle's braking system.

For context, I'll note that OBD and OBD-II were created by U.S. Federal government decree to facilitate the management of emission control systems, so any information (such as ABS operation) beyond what is relevant to exhaust emissions may or may not be available. Some vehicles segregate control network traffic so that even information which may be useful and is on a network may not be accessible via the diagnostics port.

I would be interested in the manufacturer's response, but I'm not buying one anyway so I'm not asking.


My general impression is that one of these controllers doesn't make a lot of sense unless it is to be used with their electro-hydraulic actuator, preferably with ABS and sway control.

[Anderson]

Thank you Brian B-P very helpful. Will post what manufacture response is.

[AllanEdie]

I agree with Brian's comments - I am very skeptical that this system adds anything useful. It sounds like marketing bs to me.

Bottom line not yet mentioned is that, as far as I am aware, abs systems are absolutely dependent on some sort of rpm sensor on the involved wheels, and there are no such sensors on the trailer, so there is no bloody way this system could actually integrate with the tug's abs. Further, the abs computer in the tug would have to actually be programmed to deal with 8 wheels (if the trailer has 4), and I very much doubt that it is, or that it can be modified by an add-on device.

As to the interaction between tug abs and the trailer, it can at least hypothetically cause a serious problem on winter roads, and maybe even gravel ones. If the abs on the tug is successful in generating more braking force than the trailer wheels are, the arrow is flying feathers first - this is not stable, the trailer will "want" to pass the tug, thereby causing a jackknife. Whether an actual jackknife will occur will depend on lots of details, but on icy roads with good winter tires on the tug, an aggressive stop is in my opinion highly likely to cause a jackknife, even, horrifying thought, at highway speeds.

In another thread touching on this topic, someone mentioned that several jurisdictions have rules requiring chains on at least one trailer axle during winter conditions - which would put the feathers back where they belong, on the trailing end of the arrow.

[ericw]

Originally Posted by AllanEdie

I agree with Brian's comments - I am very skeptical that this system adds anything useful. It sounds like marketing bs to me.

Bottom line not yet mentioned is that, as far as I am aware, abs systems are absolutely dependent on some sort of rpm sensor on the involved wheels, and there are no such sensors on the trailer, so there is no bloody way this system could actually integrate with the tug's abs.

I generally agree with everyone's comments.

But I have a slight clarification. I have heard from the dealer that my Ford F150's trailer brake controller does integrate with the trucks ABS. I asked what the brake controller does with this information. I was informed that if truck ABS thinks it is very slippery, the trucks brake controller decreases the braking force to the trailers brakes to prevent the tires from locking up and "the feathers passing the tip of the arrow" in your words. I think this is logical and does not necessitate having any type of wheel sensors on the trailer.

I have not researched it extensively so take it FWIW, but I thought this may add to the discussion.

[Brian B-P]

Originally Posted by ericw

I have heard from the dealer that my Ford F150's trailer brake controller does integrate with the trucks ABS. I asked what the brake controller does with this information. I was informed that if truck ABS thinks it is very slippery, the trucks brake controller decreases the braking force to the trailers brakes to prevent the tires from locking up and "the feathers passing the tip of the arrow" in your words. I think this is logical and does not necessitate having any type of wheel sensors on the trailer.

This makes sense to me for an integrated controller from the vehicle manufacturer. Unfortunately, the information required to do this probably isn't available via the OBD port, and the DirectLink documentation doesn't indicate any use of ABS status information.

[AllanEdie]

Originally Posted by ericw

I generally agree with everyone's comments.

But I have a slight clarification. I have heard from the dealer that my Ford F150's trailer brake controller does integrate with the trucks ABS. I asked what the brake controller does with this information. I was informed that if truck ABS thinks it is very slippery, the trucks brake controller decreases the braking force to the trailers brakes to prevent the tires from locking up and "the feathers passing the tip of the arrow" in your words. I think this is logical and does not necessitate having any type of wheel sensors on the trailer.

I have not researched it extensively so take it FWIW, but I thought this may add to the discussion.

Thanks for the clarification, that is an interesting potential improvement that I hadn't heard about. No doubt other manufacturers may be doing similar things. Adjusting the gain on one's add-on electronic controller to match slipperiness might accomplish the same thing.

In any case, when I hear the claim that trailer brakes are being incorporated into the abs system, that means to me that the trailer brakes are being prevented from locking up with the same effectiveness as the tug wheels are, which can't be done without having rotation sensors on the trailer wheels.

Even with the system on your Ford, which is certainly better than nothing, the brake controller is still just guessing what brake pressure is tolerable without locking up the trailer wheels. If it over-brakes the trailer, the trailer wheels will lock, and the abs on the truck will brake better, and we have the "feathers at the wrong end". If it underbrakes, we have the same problem - too much braking on the front, not enough on the back, and away we go again. Further, and considerably worse, even if it gets the maximum non-locking brake pressure to the trailer wheels perfect - even if it had wheel sensors on the trailer - that will not fix things if the tires on the tug grip better, which winter tires usually will. You would still have more braking on the front than on the back. Chains on one trailer axle, and none on the tug, fix this, which is the reason for the legal requirement where it exists, but we know how much fun that solution is.

This issue has no completely effective fix that I am aware of. Towing heavy trailers always includes risk of jackknife events, although the risk is small on dry paved roads when the grip of both tug and trailer tires is reasonably well matched, and the likelihood of a braking event violent enough to lock the trailer wheels is relatively small. As roads get slipperier, and as the comparative grip of the tug tires relative to the trailer tires goes up, the risk of jackknife goes up.

We just need to be aware of the nature of this issue, and understand that, with a trailer behind us, the task of matching our driving behaviour to road conditions is more difficult. Pretty much our only options under really slippery conditions are to slow down, likely a lot, and look a long way ahead to anticipate the need to slow down. Or safer yet, stay put until conditions improve.

Bottom line - on icy roads, no built in or added brake controller will keep us safe if we try to stop too quickly with a heavy trailer, so we better be able to anticipate every need to slow down a long way ahead. Not too difficult as long as there are no other drivers out there.

As always, just my two cents.

[Iowa Dave]

I’m not much on this electronic stuff. I was in the smokies in the late fall with the 19.
It snowed up in the mountains the way we
were leaving. I turned the controller voltage lower and had no problem even on black
Ice. Easy does it
Iowa Dave

[AllanEdie]

Originally Posted by Iowa Dave

I’m not much on this electronic stuff. I was in the smokies in the late fall with the 19.
It snowed up in the mountains the way we
were leaving. I turned the controller voltage lower and had no problem even on black
Ice. Easy does it
Iowa Dave

Good on you Dave, turning down the controller to accommodate slippery conditions is a really good idea - combined with care and attention of course, which you seemed to have exhibited nicely.

Cheers,

Allan

[Brian B-P]

Originally Posted by AllanEdie

In any case, when I hear the claim that trailer brakes are being incorporated into the abs system, that means to me that the trailer brakes are being prevented from locking up with the same effectiveness as the tug wheels are, which can't be done without having rotation sensors on the trailer wheels.

I agree.

Originally Posted by AllanEdie

This issue has no completely effective fix that I am aware of.

There is one effective solution which is relatively obvious, and commercially available: ABS on the trailer. The vast majority of trailer owners are not willing to pay for it, so it is very rare on recreational trailers and on light commercial trailers in North America; however, it is now becoming routine on heavy commercial trailers (with their air brake systems of course, not electric drums).

Tuson does offer ABS and stability control, and the DirectLink controller would be suitable for use with those systems, but the DirectLink controller by itself - regardless of the tow vehicle - has no ABS or stability control functionality. In Tuson's product line, the ABS is available only with hydraulic trailer brakes (disk or drum); however, the stability (sway) control is for electric brakes.

[AllanEdie]

Originally Posted by Brian B-P

I agree.


There is one effective solution which is relatively obvious, and commercially available: ABS on the trailer. The vast majority of trailer owners are not willing to pay for it, so it is very rare on recreational trailers and on light commercial trailers in North America; however, it is now becoming routine on heavy commercial trailers (with their air brake systems of course, not electric drums).

Tuson does offer ABS and stability control, and the DirectLink controller would be suitable for use with those systems, but the DirectLink controller by itself - regardless of the tow vehicle - has no ABS or stability control functionality. In Tuson's product line, the ABS is available only with hydraulic trailer brakes (disk or drum); however, the stability (sway) control is for electric brakes.

I agree that abs on the trailer would be an improvement, especially if combined with effective stability control specifically for the trailer wheels, and even better if the computer control of the trailer brakes could be really integrated with stability control for the tug wheels. That one should keep the programmers busy for a while.

That said, stability control and ABS on the trailer cannot fix the problem of significantly greater grip on the tug tires (say dedicated winters with new studs) than on the tug tires (normally dedicated summers, and stiff ones at that). ABS on the trailer or no, in an aggressive braking event on slippery roads, the arrow feathers will still be up front.

Perhaps someone should invent a mechanically locking WDH which in emergency braking events locks up the hitch and prevents the trailer from swinging into an jackknife. Should be doable, the forces don't really get boogying until the angle increases.

[Brian B-P]

Originally Posted by AllanEdie

Perhaps someone should invent a mechanically locking WDH which in emergency braking events locks up the hitch and prevents the trailer from swinging into an jackknife. Should be doable, the forces don't really get boogying until the angle increases.

Since the WDH mechanism has no idea what the angle should be, I don't see any way to determine what coupling rotation it should resist, other than to generally damp sway by providing some resistance to any motio (which is what existing systems do). Locking in any position risks preventing the combined vehicles from going the intended direction.

A truly integrated trailer and tug system could include measurement of the coupling angle and active response to it with individual wheel braking, but the chance of any manufacturer trying to accommodate any possible trailer of unknown dynamic characteristics seems low. It would even be possible for this sort of integrated system to actively control the coupling, but to me that seems like a step to follow much later behind integrated braking and brake-based stability control. At this point, trailer owners are not even willing to pay for decent hydraulic sway damping, and use some really crude friction-based systems. Commercial truck systems include ABS and stability control, but no mechanical control of the coupling.

I think differential application of the trailer brakes should be lots of control action... but we'll have to use it.

[AllanEdie]

Originally Posted by Brian B-P

A truly integrated trailer and tug system could include measurement of the coupling angle and active response to it with individual wheel braking,

Beat me to it! I was thinking the same after my last post. Hitch angle data should permit considerably more effective programming of ABS response in the trailer, and maybe even both the tug and trailer.

OTOH, this is all hypothetical stuff - entertaining to puzzle about, but, as you point out, it ain't likely to happen any time soon. I wonder how many cars and trucks would have ABS if customers had a choice of whether to pay for the option. A lot fewer than the law requires, I'll bet.

[Brian B-P]

Originally Posted by AllanEdie

I wonder how many cars and trucks would have ABS if customers had a choice of whether to pay for the option. A lot fewer than the law requires, I'll bet.

I agree. Safety does sell to some extent, so features such as ABS and ESC (when they were optional) helped sell higher trim levels and more expensive models, but not many people would individually check them on the option list (with associated price tag). That's even on the vehicle in which they are driving; on a trailer, they would be a very difficult sell.

[Defenestrator]

Originally Posted by Brian B-P

Since the WDH mechanism has no idea what the angle should be, I don't see any way to determine what coupling rotation it should resist, other than to generally damp sway by providing some resistance to any motio (which is what existing systems do). Locking in any position risks preventing the combined vehicles from going the intended direction.

A truly integrated trailer and tug system could include measurement of the coupling angle and active response to it with individual wheel braking, but the chance of any manufacturer trying to accommodate any possible trailer of unknown dynamic characteristics seems low. It would even be possible for this sort of integrated system to actively control the coupling, but to me that seems like a step to follow much later behind integrated braking and brake-based stability control. At this point, trailer owners are not even willing to pay for decent hydraulic sway damping, and use some really crude friction-based systems. Commercial truck systems include ABS and stability control, but no mechanical control of the coupling.

I think differential application of the trailer brakes should be lots of control action... but we'll have to use it.

I definitely think you'd be better off with a stability control system that selectively brakes one side of the trailer wheels rather than trying to dampen the sway by clamping the angle relative to the tow vehicle. Detecting the sway would be a bit tricky - cars use a steering angle sensor to detect a skid, but that doesn't really apply to a travel trailer. It would need a wheelspeed sensor either way. That plus a yaw sensor and some good electronics/software might be enough, or it might need a pivot angle sensor on the hitch.

This thing claims to do sway control with a GPS speed sensor and a gyroscope. I have some doubts as to whether the GPS speed sensor is fast and precise enough, but it probably does the job most of the time. It also looks like it brakes all wheels instead of selective braking, which isn't as good but is still a lot better than nothing. $300 is cheaper than I expected, too - I'm actually a bit tempted.

[Duer]

Originally Posted by Iowa Dave

I’m not much on this electronic stuff. I was in the smokies in the late fall with the 19.
It snowed up in the mountains the way we
were leaving. I turned the controller voltage lower and had no problem even on black
Ice. Easy does it
Iowa Dave

Perhaps a tad bit controversial, it is always a good idea to practise a little from time to time to have an understanding or idea of how a system will function in a controlled situation.
I've wish to share some experience with emergency braking situations that when combined in a controlled situation reveals some enlightenment perhaps. Again this is only my experience!

Every spring when I get my motorcycle out for the season, I do some practice with the ABS system as a type of check out or proficiency if you will. Since I 'think' I know what I'm doing. ABS braking systems function very well, but they only work as engineered which when over simplified greatly reduces that amount of braking applied in an emergency braking situation on slippery roads. The distance to stop can be 'greatly increased' sometimes so much so that the vehicle will continue to travel a long distance in some resemblance of a controlled braking event. It is good to practise and experience how much wheel brake slip is applied to attempt keep the vehicle straight as guided by directional stability functioning.

I like Iowa Dave's simple explanation very similar to the old braking system when bob-tailing a 18 wheeler tractor without the trailer in slippery road conditions.
The braking function is dumbed down with a lever in the cab to detune the large braking surface of the tractors braking system..

Electronic aids are very nice to have, however, I've found it best to take them out and use them and practice to help understand how they work. Simulating an controlled emergency situation. Just like we used to do when flying and having to do a MOT ride to maintain proficiency when the 99% complacency turns very quickly in a very exciting and usually a scary situation.

Just my thoughts and rather long winded at that...

[AllanEdie]

Originally Posted by Duer

Perhaps a tad bit controversial, it is always a good idea to practise a little from time to time to have an understanding or idea of how a system will function in a controlled situation.
I've wish to share some experience with emergency braking situations that when combined in a controlled situation reveals some enlightenment perhaps. Again this is only my experience!

Every spring when I get my motorcycle out for the season, I do some practice with the ABS system as a type of check out or proficiency if you will. Since I 'think' I know what I'm doing. ABS braking systems function very well, but they only work as engineered which when over simplified greatly reduces that amount of braking applied in an emergency braking situation on slippery roads. The distance to stop can be 'greatly increased' sometimes so much so that the vehicle will continue to travel a long distance in some resemblance of a controlled braking event. It is good to practise and experience how much wheel brake slip is applied to attempt keep the vehicle straight as guided by directional stability functioning.

I like Iowa Dave's simple explanation very similar to the old braking system when bob-tailing a 18 wheeler tractor without the trailer in slippery road conditions.
The braking function is dumbed down with a lever in the cab to detune the large braking surface of the tractors braking system..

Electronic aids are very nice to have, however, I've found it best to take them out and use them and practice to help understand how they work. Simulating an controlled emergency situation. Just like we used to do when flying and having to do a MOT ride to maintain proficiency when the 99% complacency turns very quickly in a very exciting and usually a scary situation.

Just my thoughts and rather long winded at that...

Total agreement here. I will be "playing" with the braking system behaviour of the new trailer lots until I get a feel for what to expect, and not just on dry pavement.

[Brian B-P]

Originally Posted by Defenestrator

Detecting the sway would be a bit tricky - cars use a steering angle sensor to detect a skid, but that doesn't really apply to a travel trailer. It would need a wheelspeed sensor either way. That plus a yaw sensor and some good electronics/software might be enough, or it might need a pivot angle sensor on the hitch.

As far as I know, all of the existing active sway control systems for trailers use only accelerometers - no wheel speed sensors or hitch angle sensor.

Originally Posted by Defenestrator

This thing claims to do sway control with a GPS speed sensor and a gyroscope. I have some doubts as to whether the GPS speed sensor is fast and precise enough, but it probably does the job most of the time. It also looks like it brakes all wheels instead of selective braking, which isn't as good but is still a lot better than nothing. $300 is cheaper than I expected, too - I'm actually a bit tempted.

GPS-derived speed can update multiple times per second, but I don't think the speed measurement needs to be highly responsive anyway - other systems don't even measure the speed.

The flyer for the Dexter Sway Control clearly describes the use of independent left and right braking, like the DirectLink system; the Hayes system applies all brakes simultaneously, and so do the mechanical (European) and electric (Australian) ESC systems by AL-KO.

Separate application makes sense to me: sway is an oscillation in yaw, and so to actively control it the appropriate response would be to apply the brake which will create torque in the opposite direction to motion. This is not something that can be done manually by a driver, but it's no problem for an electronic systems; however, it does require re-wiring the trailer to separate the left and right brake wires.

[Defenestrator]

Huh, lots more options for active trailer sway control than I thought.

I guess for the GPS speed tracking I was thinking in terms of the trackpoint-style speed measurements, which tend to be slow and unreliable, but if it's the fancier doppler-style it could work well. Just hope you don't need it in a tunnel.