any idea why car shudder when towing?

[shockwave20]

I went to myrtle beach last memorial weekend. I was towing my motorcycle with my 08 m35x. I notice around 65 70 mph the car would shudder at the rear. Next week I am taking another trip down to myrtle beach and I am trying to eliminate possibilities.

First I must mention that before the trip I hit a pot hole and bent both rims on the left side. I straighten the rims and put them on the rear. I felt the shop did a good job straightening them. With a full tank of gas I could go 72mIph until I could feel the shudder at the rear. When the fuel tank reach 3/4 tank the shudder starts at 65mph.

I took the bike off the trailer and rode behind the car pulling the empty trailer. The car pulled the empty trailer over 80mph smoothly with no shuddering. The trailer was also stable. I could take the car over a 100mph (no trailer) with now shuddering.

I did recently replaced one of the previously bent rim that was at the rear. I checked and grease trailer bearings. I replaced some pins on the trailer with nuts and bolts to make it more rigid. I have a single motorcycle trailer that can loose up and fit in the car. I am also thinking about replacing the two 8" tires even though they look ok.

Anyone have any ideas what could cause this situation or what I should check?

[nissangirl74]

Slow down. There's a reason there are speed limits for vehicles that tow. Replace the other bent rim. Get an alignment? Also, how much does the trailer + bike weigh?

[Bubba1]

Dumb question, but I gotta ask. After straightening the rims, and remounting the tires, were they spin balanced again? Another thing to investigate is the balance/tire pressure of the trailer tires as well and tire pressures on the M.

Another thought is the weight of the trailer + load. I don't believe those infiniti's are rated to tow much weight. If you're using a steel trailer, you might be pretty close to max, especially at the tongue, perhaps putting more stress on the rear of the car was designed to handle. That could also magnify small issues with your rear, like tire overinflation, for example.

[PapaSmurf2k3]

Another thought is the weight of the trailer + load. I don't believe those infiniti's are rated to tow much weight.

This. As you load the rear of the vehicle, it will change your alignment and accentuate any balance or roundness issues you have.

When the wheels were fixed, did you put new tires on them, or the same ones from when you hit the pot hole?

[shockwave20]

Slow down. There's a reason there are speed limits for vehicles that tow. Replace the other bent rim. Get an alignment? Also, how much does the trailer + bike weigh?

ok I will slow down. The trailer weighs less than 300lb. I don't have the exact number right now.

[shockwave20]

Dumb question, but I gotta ask. After straightening the rims, and remounting the tires, were they spin balanced again? Another thing to investigate is the balance/tire pressure of the trailer tires as well and tire pressures on the M.

Another thought is the weight of the trailer + load. I don't believe those infiniti's are rated to tow much weight. If you're using a steel trailer, you might be pretty close to max, especially at the tongue, perhaps putting more stress on the rear of the car was designed to handle. That could also magnify small issues with your rear, like tire overinflation, for example.

the wheels were balance with the same tires before I put them on the rear. the trailer tires are only 8" and I check all my air pressure before I started my journey. keep in mind it drove smooth once the bike was off the trailer. I will post a pic later of the trailer. it is so difficult to post pic on this site.
The trailer is a lightweight trailer and Im just pulling a bike. luggage wise I try to travel light. My girl had a big duffle bag. I told her she cant take all of that because its a car. She removed a pair of flipflop and bathing suit and said everything else she NEED. I decide to put our clothes in trash bags so I could fit everything in the car.

I wasn't too sure if the rims that was previously bent are the culprit so I suspend the car on jack stand and watch to see which rear wheel wasn't true. Both rear wheel looks pretty good so I replaced one rim a month ago in preparation for my trip next week.

[shockwave20]

Another thought is the weight of the trailer + load. I don't believe those infiniti's are rated to tow much weight.

This. As you load the rear of the vehicle, it will change your alignment and accentuate any balance or roundness issues you have.

When the wheels were fixed, did you put new tires on them, or the same ones from when you hit the pot hole?[/quote

I visually inspected the two tires before putting them on the rear. Tires had like 80% thread life but you might be on to something. I replace one rim saturday april 19 and I put the same tire on the new rim. I put the brand new rim with the old tire up front (LF). The next day which was easter sunday I went for a drive and notice the front end wasn't as smooth as couple days ago. Since monday april 21 was a holiday I decide to drive the infiniti. That day I hit another pothole an busted the tire on the new rim. I decide to replace the two front with bridgestone g-force comp 2. Now the front end feels smooth again. That tire was probably the culprit in the first place.

[shockwave20]

[shockwave20]

[PapaSmurf2k3]

Yeah, I'd hate to say it, but it sounds like you need to rule out the wheels/tires. If you know anyone with the same car (or wheel/tire size/bolt patter), you could borrow them and put them on the car to see if it fixes it. Otherwise it is sort of an expensive gamble.

[Bubba1]

By the way, that trailer is pretty cool.

[MinisterofDOOM]

Narrow trailers are really prone to rocking and weaving, especially at high speeds. That one looks like it has a very high center of gravity, too, so that will accentuate both problems. I'm sure that's contributing to the shuddering. But I also agree you need to rule out wheel and tire problems before narrowing things further.

[shockwave20]

I will replace the trailer tires with better tires capable of higher highway speed. The old tires have a mfg date of 2009 and the new tires have a mfg date of 2013 so I cant go wrong replacing them.

[shockwave20]

update. the shuddering was gone. The problem was the tires that hit the pot hole over a year ago was damage. I was able to go 80mph but I mostly set the cruise at 72mph.

While I was at myrtle beach I went out saturday morning for breakfast. I took the bike and left the trailer attach to the car. The waffle house was 3 blocks away from the hotel. After breakfast I told my girl lets go for a ride. She decide she wants to walk back to the hotel to get something. I said i'm going to go too so I could check on the car.

We pulled in the hotel parking lot and it felt like my heart stop. I said to my girl "WHERE IS MY CAR?" I ran to the front desk and told the manager my car is gone. The manager calmly ask if I had my parking permit displayed. Then he said to call the # at the side of the building.

I called the towing company and they said that they have the car. Which was a relief for me to hear that they have the car. I put the address in the gps and proceeded to the towing yard. 20miles and over 30mins later I reached to a location that have no storage yard. I called back and they said there in south myrtle beach not north myrtle beach. This location was only couple blocks away from the hotel.

I reached the storage yard and they won't even let me look at the car until I pay. I had to sign the receipt saying that they are not responsible for any damage to the vehicle during towing. I didn't even see the vehicle but I had to sign to get the car. It cost me $160 to get the car back. I got the car back and the trailer was still attach.

The car got towed because the parking tag was not displayed. First thing I did when I got up saturday morning was to drive around to look for a car wash. I took my parking permit off of my rear view mirror and put it in my center console because it was blocking my view while driving. I got the car washed then I return to the hotel parking lot. I then went back out for breakfast with the bike. I would think the hotel would have some extra measure to prevent one of their customer from getting towed.

[PapaSmurf2k3]

That sucks dude. I hate towing companies like that.

[AZhitman]

I visually inspected the two tires before putting them on the rear.

I was going to hit this, but it looks like you figured it out... unless you've got x-ray vision, a visual inspection is useless. You probably broke some of the internal cords - pretty typical, and should have been replaced before you went out hauling a$$.

Also, an 8" tire spinning at 80mph is just waiting to disintegrate. Centrifugal force (centripetal?) is enough to shred it. There's a reason none of them are rated for high speeds.

A unibody vehicle isn't as stable for towing as a full-frame vehicle... you're always going to be severely compromised with something hanging on that hitch - I'm not sure I'd exceed 65, in fact. No biggie if you bust up the bike, but keep in mind when the s*** hits the fan, that bike is an out-of-control projectile.

As a side note, if you WERE to get in an accident with that setup, your insurance company will tell you to go pound sand - you'll be on the hook for your damages and maybe someone else's as well.

Gorgeous M, by the way.

[shockwave20]

I replaced the tires on the trailer with bigger circumference tires that was rated for high speed. These I bought in a trailer store. I felt much more confident with these than the cheaper tires that came with the trailer. The tire that came with the trailer were manufactured I 2009.

If stability was suppose to be one of my issues with the trailer then I'm lucky because the trailer is stable. The trailer have some weak points because it's so light. I could lift the entire trailer off the ground when assemble. I always inspect the trailer for wear and tear. Right now I notice the pin holes for the front wheel chock are getting big. I will have to weld a piece of metal over them to reinforce them.

The trailer is not something I made up with my spare time. It was bought and register just like a typical trailer. I can't see why I would have insurance issue with this and not with another trailer. My trailer have safety chain attach just like a regular trailer. I don't know why you are making it look like I'm a big disaster waiting to happen on the public highways. Last year while I was driving from myrtle to Georgia I saw three trailers at the side of the road. Two of them had a wheel missing and the third the driver and passengers were standing at the right rear of the trailer steering at it.