Abnormal tire wear on toad

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rankjo

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Joined
Mar 3, 2005
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337
Hi, last fall I put 4 new Cooper tires on my 2001 Jeep Cherokee Sport, got an alignment done, and then towed it to Florida. By the time I got home again I had totalled 4,500 of highway towing at 60-65 mph, plus about another 3000 regular short trip driving in Florida.
I noticed a steering shimmy when I got home and saw that the front tires were worn down and feathered on the outsides. Rotating and balancing the tires from front to back cured the shimmy.
So the question is,----is abnormal tire wear expected when towing?  I am quite sure that the steering lock was NOT engaged at any time while towing, and equally sure that the Transfer Case (it's a Jeep) was in neutral and the tranny in Park as required by the handbook. Generally, the driving was simple highway stuff, few towns and just the daily gas station manouvreing. I have knocked the alignment off once in the past, but I'm not aware that I did anything like that this time.
Thanks for your comments.
Rankjo
 
No, unusual tire wear is not to be expected, but towing does exert slightly different pressures on the front suspension and can show up problems not otherwise evident. There are a myriad of possible reasons for it, so no simple answers. The first is simply that the toad hit something and needs another alignment. Another is that the alignment you got was faulty, or at least at the border line of the specs, enough to give it a bit too much toe in. Yet another is worn steering or front suspension parts - the fact that you had a shimmy makes me think that may be at least part of it. Worn shocks is another possibility.

Does your tow bar angle up or down between toad and coach? It should be as close as level as possible and the toad end should never be higher than the coach end. Off-level angles can exert odd pressures on the toad front end, e.g. lifting it at some times and forcing it down at others.
 
We have towed Jeep Grand Cherokees since 1999 for around 100K and have never experienced tire wear as you describe.  I suspect this could be caused by improper tow in/tow out adjustment.  Might want to take it to a different alignment shop and see what they find.  Other possibilities are worn shocks or the front suspension is in need of repair.
 
Thanks for your replies. I got the answers I expected, and I'll get an alignment next week. I watched the guy do it last time and he put quite a bit of effort into checking the front suspension and steering arms etc before he did it.
The tow bar is slightly higher on the RV than on the toad, but well within the 4 inches reccommended. I might just address that too, though of course the vertical movement on the rear of the RV is much greater than that on the toad, so one wonders if it matters much so long as the toad doesn't get above the RV.
I'll report back
Thanks
Rankjo
 
rankjo said:
...The tow bar is slightly higher on the RV than on the toad, but well within the 4 inches reccommended. I might just address that too, though of course the vertical movement on the rear of the RV is much greater than that on the toad, so one wonders if it matters much so long as the toad doesn't get above the RV.
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Click to expand...

If the tow bar is not horizontal, then any up/down vertical motion of the RV's rear end also creates a push/pull horizontal motion on the front end of the toad.  The greater the vertical mis-match, the greater the horizontal jerk against the inertia of the toad.  It adds to the fatigue of the tow bar and base plate and could be a contributor to early failure if severe enough.  Works the other way too, of course, but as you say, the vertical movement of the RV's rear end is likely to be much greater than the toad's front end. 

Also, this effect doesn't matter if the RV is above or below the toad, but most cars are probably below the RV.  I did see a guy towing a 4x4 pickup once where the truck end of the towbar was more that a foot above the RV end.  It really made me cringe.  :eek:

 
OK, latest update.
I went for the alignment. The tech looked at the tire wear on the Jeep (Cherokee Sport), and opined that this was an expected effect of towing. He is a very bright guy with a lot of experience.
You will recall that I towed around 4,500 mile to Florida and back. The tech pointed out that this Cherokee has a solid front axle, and a somewhat un-refined front suspension designed for off-roading. He also opined that the front alignment is highly unlikely to go off unless some part of the very rugged front suspension or steering rod is bent or broken, which it isn't, and this in fact is my own experience. I did have a problem before and a bent track rod was found.
The tech's view is that there is a difference between driving/pushing, and towing/pulling. The normal toe-in is 1/8in, and he claims it varies towards neutral while driviing, but increases when being towed.
So there you go, believe it or believe it not. He offered to set the toe-in a bit towards neutral, but I declined, since I will not be towing much, if at all, during the summer months.
Rankjo
 
Strange.  We have towed 3 different Gran Cherokees over 100K miles and never had a problem with tire wear.  I know there are other members that tow a cherokee and have reported no similar tire wear.
 
We have known several people that tow classic Cherokees with the solid axle and tire wear was not an issue.

Your guy is correct - there are subtle differences in being pulled rather than pushed, but they normally do not result in noticeable tire wear in a relative short period (4500 miles).
 
I felt the wear on our last CRV was above normal on the outside shoulder of the front tires. I not only rotated regularly but also reversed the tires on the wheels of two of the four sets of tires we used in a combined 180,000 miles of driving and towing.

I called Honda and was given the same info as Rankjo, that the tow-in was decreased by a front wheel drive pulling the car and increased by the car being pulled by the m/h, causing the same wear as too much tow-in being set on alignment.
 
Alignment specs are always stated as a range of acceptable values, so a front end can be "in spec" and still well off dead center. I would go with an adjustment  somewhere between "dead nuts" and slight toe-out to compensate for the problem.
 
I'd sure suspect you need some adjustment in the toe in. Look at it this this way, tow in is used to center the wheels from a turn. When the towbar pulls the front in into the turn, the tow in is fighting it. Where as then you are driving, you are turning the wheels, thus no resistance from the toe in. I think your alignment guy was right in offering to reduce the tow in. If it was me, I'd take him up on the  offer.

BTW, I have towed three Jeeps and now a Dodge Dakota with no unusual tire wear.

Chet18013
 
Thank you all for that. Since all my towing is done in the 'winter' six months, I may just rotate and accomodate. Hey, that's a catchy phrase, "Rotate and Accomodate", I should copyright it.
Part of the problem, I think, is the type of tire on the Jeep, which has a 'squared-off' edge, so the problem would also be lessened if I used 'car' tires rather than 'light truck' tires.
No towing till November, so I have time to watch the wear over the summer and decide about changing the toe-in in the Fall.
 
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