Tire Stiffness & trailer swaying [long]
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Tire Stiffness & trailer swaying [long]
Several people have had good luck towing a trailer with previous model Subaru Foresters. I do not know why mine is different.
I just bought a 2004 Forester tried to tow with it. Mine is a
nightmare. It is unstable above 50mph. It has a lot of side to side sway above 50mph if there is any steering input. It is almost
harmonic in nature - it does not dampen out quickly. If feels like
you are driving on Jello. It feels like the problem is much more the
tires than the suspension. Though that is hard to prove.
Even when parked if you push on the hitch with your foot the Forester will sway side to side [right and left] a lot. You can watch the rim move right and left in and out of the tire. I think the sidewalls are just really weak. The tread is probably relatively soft also.
The Forester's tires are
Yokohama Geolander G900 P215/60 R16 94H.
Even in normal driving the steering response and cornering are poor.
[Other Foresters may be equipped with 15" tires, and other models of
Geolander tires - rather than the G900].
My Mazda MX-6 [much lower car] has Pirelli P4000 P205/55 R15 87H - it
is stable, and if you push sideways it does not sway side to side
anywhere near the degree that the Forester does. Steering response
and cornering are good.
The Geolander G900 has a tall soft sidewall, it is 4.500" above the
rim rather than 3.625" for the P4000 [24%higher].
My best idea right now is to change to a shorter and stiffer sidewall tire.
I am considering changing from P215/60 R16 94H
- an "H" rate tire with 60% width/height ratio, to
Bridgestone Turanza LS-V 225/50R16 92V - this is a V rate tire so the
sidewall is stiffer and at a 50 or 55 ratio it is shorter.
This is the V rated version of the tire that some other Forester
owners have [LS-H]. The tread should also be a harder sports car like
compound.
Some of these tires are rated and discussed on www.tirerack.com. It seems that Steering response and cornering stability are good expressions of my issue.
On tirerack there are a mass of good comments on the Turanza tire -
though I doubt anyone is towing. As far as I can tell everyone on
"tirerack" hates the geolander 900 like on mine.
Does anyone else have any Experience changing to a shorter V rated tire for better stability?
My trailer does great and stable to 85+mph behind my Mazda MX-6, so I do not think it is the trailer. The trailer weighs ~1800lbs [816kg]. The tongue weight is 153lbs [69kg]. The Forester's manual says to keep the tongue weight between
8-11% of the trailer. 8%=144lbs [65kg] 11%=198lbs [90kg].
[the max allowed is 200lbs on the tongue] The manual transmission version of the Forester is rated for 2400lbs [1088kg] towing capacity.
I have already tried raising the tire pressure on the rear tires to
41psi [2.8bar] as recommended by the manual. The trailer tires are about 40psi.
------
Since my original write up I have learned the following:
The dealer told me that the 2004 model is the first to be equipped with the Geolander G900 tires, previous years had a different model tire. This is the only change to the suspension that he is aware of between the 2003 and 2004 model.
The Maximum tire pressure on the tires is 44psi, so I upped the rear pressure to 44psi and the fronts to 41. [for towing the manual says 29psi front, 41psi rear]. I also changed the hitch from a straight one to a "drop hitch" it is now 1.5" lower than the straight one. The drop hitch is about 4.0" shorter than the "lift hitch" [bent receiver hitch] that I originally tried. The hitch ball is on a short receiver.
A test drive showed that the lower hitch/ball placement and the higher tire pressures are an improvement. However still not acceptable. I think the higher pressure stiffened the tires but not enough and the tread is still too soft.
I have heard another Forester owner has had good luck with 75-100lbs of tongue weight. An additional test drive was done after I moved several items out of the front of the trailer to the back of the Forester. This reduced the tongue weight to 118lbs [down 35lbs from 153]. The swaying seemed worse with the lower tongue weight. [This follows the logic I have heard many times].
I would like to hear some other ideas.
Chris
I just bought a 2004 Forester tried to tow with it. Mine is a
nightmare. It is unstable above 50mph. It has a lot of side to side sway above 50mph if there is any steering input. It is almost
harmonic in nature - it does not dampen out quickly. If feels like
you are driving on Jello. It feels like the problem is much more the
tires than the suspension. Though that is hard to prove.
Even when parked if you push on the hitch with your foot the Forester will sway side to side [right and left] a lot. You can watch the rim move right and left in and out of the tire. I think the sidewalls are just really weak. The tread is probably relatively soft also.
The Forester's tires are
Yokohama Geolander G900 P215/60 R16 94H.
Even in normal driving the steering response and cornering are poor.
[Other Foresters may be equipped with 15" tires, and other models of
Geolander tires - rather than the G900].
My Mazda MX-6 [much lower car] has Pirelli P4000 P205/55 R15 87H - it
is stable, and if you push sideways it does not sway side to side
anywhere near the degree that the Forester does. Steering response
and cornering are good.
The Geolander G900 has a tall soft sidewall, it is 4.500" above the
rim rather than 3.625" for the P4000 [24%higher].
My best idea right now is to change to a shorter and stiffer sidewall tire.
I am considering changing from P215/60 R16 94H
- an "H" rate tire with 60% width/height ratio, to
Bridgestone Turanza LS-V 225/50R16 92V - this is a V rate tire so the
sidewall is stiffer and at a 50 or 55 ratio it is shorter.
This is the V rated version of the tire that some other Forester
owners have [LS-H]. The tread should also be a harder sports car like
compound.
Some of these tires are rated and discussed on www.tirerack.com. It seems that Steering response and cornering stability are good expressions of my issue.
On tirerack there are a mass of good comments on the Turanza tire -
though I doubt anyone is towing. As far as I can tell everyone on
"tirerack" hates the geolander 900 like on mine.
Does anyone else have any Experience changing to a shorter V rated tire for better stability?
My trailer does great and stable to 85+mph behind my Mazda MX-6, so I do not think it is the trailer. The trailer weighs ~1800lbs [816kg]. The tongue weight is 153lbs [69kg]. The Forester's manual says to keep the tongue weight between
8-11% of the trailer. 8%=144lbs [65kg] 11%=198lbs [90kg].
[the max allowed is 200lbs on the tongue] The manual transmission version of the Forester is rated for 2400lbs [1088kg] towing capacity.
I have already tried raising the tire pressure on the rear tires to
41psi [2.8bar] as recommended by the manual. The trailer tires are about 40psi.
------
Since my original write up I have learned the following:
The dealer told me that the 2004 model is the first to be equipped with the Geolander G900 tires, previous years had a different model tire. This is the only change to the suspension that he is aware of between the 2003 and 2004 model.
The Maximum tire pressure on the tires is 44psi, so I upped the rear pressure to 44psi and the fronts to 41. [for towing the manual says 29psi front, 41psi rear]. I also changed the hitch from a straight one to a "drop hitch" it is now 1.5" lower than the straight one. The drop hitch is about 4.0" shorter than the "lift hitch" [bent receiver hitch] that I originally tried. The hitch ball is on a short receiver.
A test drive showed that the lower hitch/ball placement and the higher tire pressures are an improvement. However still not acceptable. I think the higher pressure stiffened the tires but not enough and the tread is still too soft.
I have heard another Forester owner has had good luck with 75-100lbs of tongue weight. An additional test drive was done after I moved several items out of the front of the trailer to the back of the Forester. This reduced the tongue weight to 118lbs [down 35lbs from 153]. The swaying seemed worse with the lower tongue weight. [This follows the logic I have heard many times].
I would like to hear some other ideas.
Chris
Registered User
Joined: Mar 2003
Posts: 681
From: Warsaw, Indiana
Car Info: 02 WRX Wagon White
I would suggest a tire with a stiffer sidewall. The Forester, like the Outback, Allroad, Touraeg, etc. is marketed as an SUV, so taller on/off road tires are always original equipment. They show the cars going through rivers on the commercial, so they have to equip you to do that. My only suggestion is to stick with your original size but in a V speed rated tire because of the general principle that higher speed ratings have stiffer sidewalls.
The ride may be a bit rougher, yes, but you can lower pressure back down when not towing to the Subaru recommendation and salvage the smoothest ride possible.
The ride may be a bit rougher, yes, but you can lower pressure back down when not towing to the Subaru recommendation and salvage the smoothest ride possible.
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Dexter,
Thanks for the feedback. I was thinking that a 55 series would be little change in diameter. Only about 1.5% more revs per mile. Yet a stiffer sidwall since it is shorter.
Can you recommend a 2-3 models of tires that might work well on a forester for towing?
Chris
Thanks for the feedback. I was thinking that a 55 series would be little change in diameter. Only about 1.5% more revs per mile. Yet a stiffer sidwall since it is shorter.
Can you recommend a 2-3 models of tires that might work well on a forester for towing?
Chris
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