towing vibrations

Submitted: Tuesday, Jun 23, 2009 at 11:17
ThreadID: 70078 Views:5692 Replies:9 FollowUps:9
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Looking for help. I was wondering with the members experience they may have come across the following.

Recently I purchased a Forester XT and when towing a small two berth dog trailer the car has intermittent vibrations. I have towed the trailer with two other vehicles a Hyundai Elantra lift back and with my previous car a Subaru Liberty wagon with out any issues.

The vibration comes and goes, very inconsistent but can be quite violent at times. I find if you vary your speed when the vibration occurs, the vibration disappears for a period then reappears. When my wife first brought it to my attention I thought little of it till I test drove the car.

Initially the vibration came in around the 80klm mark and got progressively worst as the speeds increased. I have completed the following checks

Removed the springs & axel to ensure no damage
Fitted new bearings to both wheels (one bearing was slightly worn)
Tyres checked and re balanced, ran at different pressures 24 to 30 psi
Car has been checked by Subaru, no faults
At 500klm the car was re aligned, out 4 deg rear & 2 deg front (no change to trailer behaviour)
Rotated the hitch (turned upside down to lower ball height) & changed ball to a ball from my previous car (no noticeable vibration until reaching highway speeds)
Replaced coupling with a new coupling with an adjuster (slightly better, not as violent vibration)
Recently fitted a roof pod from my car on top of the Trailer for aerodynamics (no change)


Not sure where to go next, I am wondering if this is a turbulence issue. The difference between the Forester and Liberty are



Forester Liberty

Length 4560 4720

Width 1795 1730

Height 1700 1470

Ground clearance 225 150

Weight 1510 1395



The Forester has a small rear wing as did the Liberty, another family had a similar issue when they bought a Nissan Xtrail but chose to sell the trailer and replace it with a larger trailer. An expense I 'm not comfortable with. I have spoken to the manufacturer of the trailer and they have not heard of the above, we went thru a range of solutions which are mentioned above.



Trailer specs

2 Bays @ 1167mm x 900mm
length: 3.30M x Width: 1.70M x Height: 1.50M
Empty weight: 280kgs approx


Is there any one who may be able to shed some light on the subject?
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Reply By: Member - Troll 81 (QLD) - Tuesday, Jun 23, 2009 at 11:44

Tuesday, Jun 23, 2009 at 11:44
Had a issue on my Patrol some time ago and it turned out to be the swivel hub bearings needed to be redone. It started doing it again but not as bad and this time it's the tie end rods there's about a 1cm play. What happens when you turn your steering wheel 5cm does the wheels move? In my case it didn't. What we also did was jacket the front up and moved the wheel around and you could feel the play in there
AnswerID: 371470

Follow Up By: graham1 - Wednesday, Jun 24, 2009 at 07:54

Wednesday, Jun 24, 2009 at 07:54
Thank you, no issues with either trailer or car. Only when you combine the two the issue arises.
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FollowupID: 638852

Reply By: Member - Tour Boy ( Bundy QLD) - Tuesday, Jun 23, 2009 at 12:01

Tuesday, Jun 23, 2009 at 12:01
Did you check the tyres on both the car and trailer for "eggs" or out of round?
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AnswerID: 371474

Follow Up By: Travelling Pixie - Tuesday, Jun 23, 2009 at 12:39

Tuesday, Jun 23, 2009 at 12:39
this would be my suggestion - out of round tyres can still be balanced

i think tyre places call it "run out" and for some reason they don't automatically check for it when they balance the wheels/tyres
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FollowupID: 638720

Follow Up By: graham1 - Wednesday, Jun 24, 2009 at 07:57

Wednesday, Jun 24, 2009 at 07:57
Thank you, yes the out of round was checked. The problem only surfaces when you combine the two vehicles. I have towed a heavy duty box trailer with the car, no issues. I tow the dog trailer with my other car no issues.
Some say it may be the length when combining the two.

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FollowupID: 638853

Reply By: Angler - Tuesday, Jun 23, 2009 at 12:29

Tuesday, Jun 23, 2009 at 12:29
My brother has a similar problem towing a kayak trailer and it turned out to be too long a towbar on the trailer. He cut some off and now all is well. This was with a Subaru outback. He had no problems with the same trailer towing it with one of those dual cab holden utes. Great car but could not see out the back for reversing down a boat ramp.
AnswerID: 371481

Follow Up By: graham1 - Wednesday, Jun 24, 2009 at 08:01

Wednesday, Jun 24, 2009 at 08:01
Thank you, this is the next avenue. We are in the process of discussing with another couple whether their trailer was a long or short draw bar. My wife spoke with some one on the week end and they had no issues towing a similar trailer behind a similar vehicle but their trailer had a shorter draw bar.

Responses thus far seem to have a similar trend.

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FollowupID: 638855

Reply By: Nargun51 - Tuesday, Jun 23, 2009 at 12:44

Tuesday, Jun 23, 2009 at 12:44
Doubt turbulence. If onset is it is 80 Kph in still air it should be less in a head wind.

I notice you changed the ball, but have you checked all the other connections; no play in either the tow bar of the car or the draw bar of the trailer (busted welds or loose bolts)?

Is the trailer tracking true? I had a small boat trailer that had no issues when being towed by a medium car, but when towed by a small car took control (The Forester is heavier though)

Is the vibration still the same with a few more Kg in the trailer? Test it both in front or behind the centre of gravity, to see the effect of ball weight on the towing

If one or both tyres are slightly out of true, any vibration that creates may not be picked up until the “out of trueness” gets in synch (or out).

A variation to this happened to my father’s car years ago where some grit had entered into the tyre and had built up a few grams of small rubber balls which rolled around quite freely until a bump was hit, which forced them to gather in one spot. Wasn’t picked up when balancing; and remain a mystery that could not be solved until one of the tyres picked up a nail
AnswerID: 371483

Follow Up By: graham1 - Wednesday, Jun 24, 2009 at 08:04

Wednesday, Jun 24, 2009 at 08:04
Thanks, yes coupling has been changed. Suspension removed, checked and replaced. Only happening when the two vehicles are combined, not with other vehicles. The trend thus far is people seem to think it may be the over all length combination when combined.
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FollowupID: 638856

Reply By: wild dog - Tuesday, Jun 23, 2009 at 13:44

Tuesday, Jun 23, 2009 at 13:44
Had exactly the same problem with a HiLux ute and trailer.
Apparently it's resonance set up by the length of the total wheelbase of the trailer and vehicle. ( According to a vastly experienced traveller that I mentioned it to )
The idea of changing drawbar length is the one I would go with however it's a lot of trouble if the problem is not too bad.
AnswerID: 371494

Follow Up By: graham1 - Wednesday, Jun 24, 2009 at 08:06

Wednesday, Jun 24, 2009 at 08:06
Thank you, seems to be a similar trend from others. Something I am looking at.
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FollowupID: 638857

Reply By: Member -Dodger - Tuesday, Jun 23, 2009 at 16:16

Tuesday, Jun 23, 2009 at 16:16
Try towing another trailor with about the same weight and if this vibration stops then get another trailor. Cheaper than getting another tug.





















I used to have a handle on life, but it broke.

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AnswerID: 371517

Follow Up By: graham1 - Wednesday, Jun 24, 2009 at 08:09

Wednesday, Jun 24, 2009 at 08:09
Thanks, have done. Towed a heavy duty box trailer similar weight, no issues. However the two trailers are different in height. The box trailer has a shorter draw bar, there have been a few replies regarding the over all combination length.
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FollowupID: 638858

Reply By: oz doc - Tuesday, Jun 23, 2009 at 16:27

Tuesday, Jun 23, 2009 at 16:27
Hi Graham, just to clarify- you are using the term ' vibration' - so am I correct in assuming you do not mean 'yawing' or 'swaying' in any shape or form? doc.
AnswerID: 371522

Follow Up By: graham1 - Wednesday, Jun 24, 2009 at 08:12

Wednesday, Jun 24, 2009 at 08:12
Thank you, yes definitely a vibration. The trailer sits on the road perfectly under all speeds. It just seems when you combine the two the problem arises.
Towed with other cars no issues, towed other trailer with Subaru no issues.

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FollowupID: 638859

Reply By: DIO - Tuesday, Jun 23, 2009 at 17:11

Tuesday, Jun 23, 2009 at 17:11
Check the obvious, suspension, tyres, coupling etc. Consider the weight distribution of the trailer. If it is tail heavy it MAY set up a 'high frequency' (if such a thing exists - don't know how else to explain it) swerving/swaying/vibration that can be exacerbated by the movement in the springs/suspension. Try placing a little more weight forward - onto the coupling. Tow ball weight should ideally be around 10% of the gross vehicle )trailer) weight. Good luck with it.
AnswerID: 371532

Follow Up By: graham1 - Wednesday, Jun 24, 2009 at 08:13

Wednesday, Jun 24, 2009 at 08:13
Thank you, weight or draw bar length seems to be a common trend. I will be investigating both on the week end.

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FollowupID: 638860

Reply By: brushmarx - Wednesday, Jun 24, 2009 at 09:10

Wednesday, Jun 24, 2009 at 09:10
Could the vibration be looseness in the towbar tongue in to towbar itself (assuming a removable tongue Hayman Reese style bar), caused by an equalisation in towball weight at highway speed acused by aerodynamic turbulance?
We have two towing vehicles that have play between the tongue and the bar, but one bar has a tightening bolt that prevents the tongue from wobbling in the towbar, while the other towbar rattles.
Cheers
Ian
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AnswerID: 371618

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