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Discussion Starter · #1 ·
Has anyone been able to figure out how trailer stability assist works exactly? I can't seem to find it in either the eyesight or regular owner's manual. Not that I can say trailer sway has ever been much of an issue pulling our popup camper with our forester, but I am curious how it interacts with a brake controller, if at all, on the Ascent. It if it doesn't, I don't really see how it would work other than accelerating the car to pull a trailer out of sway. I much prefer the method of using the manual brake arm of the controller (on prodigy models at least) to brake the trailer and end the sway by applying the trailer brakes independent of the car brakes. But it would definitely be good to have some sensor to do that instead of having to rely on the driver to notice trailer sway in the rear or side view mirrors.
 

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Its just logic in the vehicle stability system thats tied to the variable braking capability which can apply brakes at each corner or front or back to straighten the car out.

Its not a fix for trailer sway caused by a poorly balanced trailer. What will do is help correct any type of skid caused by trailer load pushing on the back of the car during an emergency swerve or say poor traction in a turn. Its essentially just normal vehicle stability systems possibly with smarter logic to handle the added dynamics a trailer can contribute.
 

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Regarding trailer sway. The responsibility of a driver towing a trailer is making sure the trailer is loaded correctly. Trailers don’t just sway. They sway due to poor trailer design or incorrect loading.

When sway happens you don’t need the car to tell you!! The fix is reducing speed ASAP!!! Then pulling off in a safe place and typically repacking the trailer so more weight is on the tongue of the trailer.

Also with the high hitch location on the Ascent all owners should understand that you never ever tow a trailer when the hitch / tongue height is higher than the trailer axle!! Simple layman’s terms the trailer should never ever be tipped/tilted back this induces instability in all trailers. A level or nose down angle is the correct way to do it. Slight nose down can even add trailer stability.

This is set up by the amount of drop hitch or riser you need with your particular trailer. This why a hitch generically given to you with the car may or may not be correct for your needs. Each trailer can be a different setup regarding hitch height.
 

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Also with the high hitch location on the Ascent all owners should understand that you never ever tow a trailer when the hitch / tongue height is higher than the trailer axle!! Simple layman’s terms the trailer should never ever be tipped/tilted back this induces instability in all trailers. A level or nose down angle is the correct way to do it. Slight nose down can even add trailer stability.

This is set up by the amount of drop hitch or riser you need with your particular trailer. This why a hitch generically given to you with the car may or may not be correct for your needs. Each trailer can be a different setup regarding hitch height.
With regard to what was mentioned by @Subiesailor in the quote, a one size fits all hitch is not a good approach as it will not allow different trailers to be set up properly. Years ago, I carried several different hitches - drop, raise, straight. Then I found the Andersen quick hitch. I find that this has been the best hitch for our vehicles. It allows plenty and easy adjustment. I pull 3 different trailers on a regular basis with my vehicle. Each of them are adjusted to a different level for proper set up. I know carry 1 hitch and have had little issue. I originally had a 6" for my Flex (may work for the Ascent since it sits higher with a higher hitch point), but I kept hitting it when leaving driveway approaches on the ground when in the drop position. I bought a 4" drop body and changed it out and still have enough adjustment for my needs.

I know this is somewhat off topic regarding the trailer sway control, but felt it may have value for proper trailer set up to minimize sway. Full Disclosure: I am not an employee or have no interest in Andersen Products

https://andersenhitches.com/Catalog/rapid-hitch.aspx
 

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Everyone must know about sway

#1 Its speed related if you get sway. The only fix is speed reduction!!!! If you maintain speed or increase speed the sway will build momentum and eventually wipe you clean off the road!

#2 Know that sway can be started by a change in wind load ie passing a semi once ssay starts? How do fix it? SLOW DOWN!!!! Even if it means a failed pass and pissing off drivers behind you!!! If you speed up or continue the drivers behind you will be helping you pickup your wrecked mess and or assisting in life saving efforts on you or your family!!!

#3 Sway can be caused by a loss of tire pressure in a trailer tire!! Your trailer can be rock solid at 70-80mph across Nevada then get a really bad case of sway at 65mph in Utah!! Slow down find a safe place to pull clear of the highway and check tires!!!

NEVER SPEED UP TO PULL sway out of s trailer!!! EVER!!!


#4 Braking induced sway. Trailers want to travel in a straight line. When you go through a turn while towing the trailer pushes the back of your vehicle as if it wants to continue in a straight line. Even trailers that are no sway in a straight line at higher speeds can sway when you brake through a turn. This sway during a turn while braking is one of the biggest reasons light trailers and small tow vehicles are safer with trailer brakes. Even light braking ability on the trailer will reduce/eliminate the braking induced sway in a turn.

Experienced drivers towing or not rarely ever brake in a turn!!! Especially with a trailer!!!

If you must brake in a turn and see sway start the fix is simple stop braking in the turn the sway will stop instantly. Experienced towing drivers will brake if they have to but will get off the brake as quickly as they can. If your ever following a experienced driver towing on a challenging twisty road you will find they brake hard before turn and accelerate through/ out of the turn.

Nothing is worse than towing a trailer and being behind a car that brakes through turns in front of you especially when they have no one ahead of them and your going down hill.
 

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Discussion Starter · #6 ·
Regarding trailer sway. The responsibility of a driver towing a trailer is making sure the trailer is loaded correctly. Trailers don’t just sway. They sway due to poor trailer design or incorrect loading.

When sway happens you don’t need the car to tell you!! The fix is reducing speed ASAP!!! Then pulling off in a safe place and typically repacking the trailer so more weight is on the tongue of the trailer.

Also with the high hitch location on the Ascent all owners should understand that you never ever tow a trailer when the hitch / tongue height is higher than the trailer axle!! Simple layman’s terms the trailer should never ever be tipped/tilted back this induces instability in all trailers. A level or nose down angle is the correct way to do it. Slight nose down can even add trailer stability.

This is set up by the amount of drop hitch or riser you need with your particular trailer. This why a hitch generically given to you with the car may or may not be correct for your needs. Each trailer can be a different setup regarding hitch height.
Yes, it is a very high hitch. I needed a 10 drop to reach our camper tongue. I agree that sway shouldn't be an issue if packed and weighted properly, though conditions do sometimes change dramatically with a passing semi or very high wind in a valley. I still would like to know how it works and how it can be disabled if need be. Subaru promotional materials say there are yaw sensors that monitor the trailer and then interact with car braking systems. Just like the lane keep assist, I'd like to know where the button is to turn it on and off. But I can't find it anywhere. Perhaps it is connected to the the more general vehicle stability.
 

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Yes, it is a very high hitch. I needed a 10 drop to reach our camper tongue. I agree that sway shouldn't be an issue if packed and weighted properly, though conditions do sometimes change dramatically with a passing semi or very high wind in a valley. I still would like to know how it works and how it can be disabled if need be. Subaru promotional materials say there are yaw sensors that monitor the trailer and then interact with car braking systems. Just like the lane keep assist, I'd like to know where the button is to turn it on and off. But I can't find it anywhere. Perhaps it is connected to the the more general vehicle stability.
Its not something you shut off. I think you still don’t understand how trailer sway impacts a tow vehicle. The system is part of the Ascent stability system you don’t disable it.
 

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Discussion Starter · #8 ·
Its not something you shut off. I think you still don’t understand how trailer sway impacts a tow vehicle. The system is part of the Ascent stability system you don’t disable it.
Most of the stability and accident avoidance functions on the ascent can be disabled; there are various buttons for this. So perhaps you haven't researched the car sufficiently or read through the manual. Precollision, vehicle stability, lane assist, etc. I have found that applying only the trailer brakes with the manual lever on the P2 brake controller is the best way to address those rare instances of sway from a passing semi, etc. I am rather mixed on all these new functions. Just yesterday the precollision system applied the brakes quite hard in a situation that did not need braking (a car crossing the median that clearly had time to pass without a collision). The car's precollision system kicking in could have frankly caused a rear end collision to my car!
 

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I am pretty sure the sway control is for emergency maneuvering only, I wouldn't trust it by itself to control a trailer. We get a lot of sway when we are being passed on the interstate. Otherwise the trailer tows fine. I try to keep as far right as I can when i see a high sided vehicle coming around, it would be nice not to have to fight with eyesight and LKA to keep the vehicle where I put it though. I have experimented with shutting both off and that shuts off the constant steering correction from the system which causes its own bouts of sway. I don't like running down the road that way for too long though, maybe I am just paranoid.
 

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I always turn off LKA when towing (with the button on the steering wheel). I don't want it nudging the trailer as it makes more of a mess than it solves. You still get the lane departure warning though.
 
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Glad its not just in my head, although i still get the nudging even without a warning, so I turned off eyesight and turned LKA back on and that seemed to be ok. I thought LKA would only work with a warning first, but it seems to nudge regardless of warnings.
 

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I (Kevin) am new to this forum. I found it by searching the web for the recommended break controller with all of the technology features y'all have described (not that I'm trying to change the topic of the thread). I have only pulled a Scamp, U-Haul and other small utility trailers. I am very familiar with sway from the Scamp while driving along the Pacific. So this topic has been very helpful and a great introduction to your forum. I'll do some more searching and reading. Cheers!!!
 

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I always used an anti-sway bar on my hitches. Luckily, I asked the dealer about it. NO! NEVER use that on the Ascent. It's totally screw up the tow assist.
I pull a 4000lb, 21' travel trailer (when loaded). It pulls like a dream. First time we had 35-40mph winds up I75 to Michigan's Upper Peninsula. It was the BEST towing experience ever. ZERO sway or effect from that side wind. I was amazed.
Better than a Chevy pickup, S-10 AWD van or Chrysler van I'd pulled the trailer with in the past 20 years.
The only thing is the '19 Ascent makes you turn off the RAB every time you back up. Getting into my driveway the first time with a new vehicle was a bit stressfull (a BIG maple tree 3 ft off each side of the driveway approach, but it worked great.
 

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The only thing is the '19 Ascent makes you turn off the RAB every time you back up.
I've been towing my utility trailer a lot recently because of a move and backing it up quite a bit. My MY19 Touring seems to automagically recognize that RAB needs to be off and makes it so. I've only had one single instance where it reacted and applied the brakes.
 
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I've been towing my utility trailer a lot recently because of a move and backing it up quite a bit. My MY19 Touring seems to automagically recognize that RAB needs to be off and makes it so. I've only had one single instance where it reacted and applied the brakes.
@Jim_in_PA my 20 touring seems to do the opposite and the RAB is on every time I turn the car on. I mostly forget if I don’t see it on the screen and while I’m backing up the trailer and the slamming of brakes automatically is never far behind. Any suggestions besides holding the button of the screen for 3-5 seconds to disable this?
Second question about trailer loading. I just installed my Eibach lift kit (about 1.25-1.5”) and new 18” wheels. I did a test run with my same ball drop of 3.75” while towing my Mantis. It felt great, no sway….yet and the squat is greatly improved. Anyone object to the ever so slight nose high stance? Or should I go buy another ball that would drop the same amount of the lift? I think previously I was to nose heavy.
12405
 

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I'd drop the ball more. Tail heavy isn't good for towing as it can introduce sway. Nose up/tail down means the tail will effectively weigh more than when riding flat. This will be amplified as vehicle and trailer suspension make the nose/tail dip up and down.
 
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