Cause of Shimmy while trailering
 

All,

On the ride home from the Glen yesterday, I was experiencing some shimmying at higher speeds. To help me diagnose it:

When trailering will a shimmy be more pronounced than when just driving the tow vehicle on the street? I would think so, but since the tow vehicle drives nice and smooth without the trailer am wondering if it is that one of the trailer tires got out of balance.

BTW - thanks for an awesome event and I now have a new 'favorite track'.

Thanks,
-Skip

I found that with my setup, trailer sway was caused by aft CG on the trailer. Move the car forward a bit more.

Also, getting a sway control can help as will use of a weight distributing hitch.

ed

x2 that its probably a weight balance issue.

Depending upon the trailer, sometimes 911's need to be backed on in order to get the weight balance correct. Trailer axle location can make a big difference. Some here have tongue scales that can be used to validate how much is transferring to the trailer hitch.

This is a pretty nice resource, from Sherline, who also sells a trailer scale:

http://www.sherline.com/lmbook.htm

what do you mean by shimmy?

ed

but from his sentence above, i thought he meant the truck is the one shimmying...? so i would think that means CG too far fwd/tongue weight too high.

Hopefully he'll clarify...but it's hard to see how that would happen with a 911 on the trailer (assuming a normal single car trailer).

ed

To clarify. The setup is a Trailex with a 964. I've used the same weight distribution with my previous Jeep Grand Cherokee without issue for the last 4 years or so. I've now picked up a newer Grand Cherokee and was experiencing some shimmying (feels like tires out of balance). It is not a trailer swaying issue nor a weight distribution problem as it is the same that I've used for a while.

I'm wondering if the cheap Goodyear Fortera tires on 20" rims is part of the issue. The previous Jeep used 17" wheels and I had General Grabber tires on it and was very happy with the feel. Anyone else have experience with the tires?

**I just read a post on the Internet and maybe it was a driveline issue. I'll keep you all posted**

Thanks,
-Skip

yep, that's what i was thinking too until i remembered my econotrailer was built with axles set back 18" to compensate for rear engine. even tho i havent had issues yet with weight distrib, i wonder if it's possible given that kind of setback.

oh well, skip seems to be narrowing down on a cause so my point is moot anyway! :p

It could very well be the Jeep's tires. Maybe the added weight when the trailer is attached helps to exaggerate the feel in the vehicle. I've tried a wide range of truck tires over many years, and have found that Michelin LTX's are the only ones that consistently balanced to my satisfaction. Another possibility is the lower sidewalls associated with 20" rims versus the 17"; might be making for an overall stiffer ride, that gets worse/moreso with the trailer load.