8" tires shake and vibrate at higher speeds?

[road kill]

I just replaced the dry rot cracked tires under my 12' boat. It's on a small bunk trailer with 4.80x8 tires. The original tires were getting so cracked they leaked so I shopped around and found three new tires at a large local tire dealer. The tires are Goodyear brand, and came with new galvanized rims. The problem is that if I go over about 45mph the trailer now shakes violently. Up to that point it's perfect, over 45 it feels like one of the tires is egg shaped or something. I swapped in the new spare, on either side but no change. Putting the old wheels back on fixes the problem.
I then went to another dealer, bought two cheap painted wheels and two Chinese tires and I still get a bad shake at higher speeds. The Goodyear tires are inflated to 80psi as on the sidewall, lowering the pressure to 50psi allows me to go to 48mph without any shake.
With the old tires, I could go 65mph+ with no shake.
I asked about having the new tires balanced or at least checked and was told that they can't balance such a small tire?

At this point I've got 5 new wheels and tires, and no combination of any of these work without a bad shake. Since the old wheels don't shake, I know it's not the trailer. The shake is so bad that it moves the boat around on the trailer and I can see air under the wheel in my mirror as it hops up and down. Its as if the new tires are growing a high spot at speed?

The trailer is very light, only a few hundred pounds and the boat is 300lbs tops.
I did use the two painted wheels and Chinese tires on another trailer and they did fine on that trailer, but that trailer weighs a lot more.

I could go slower but I'd most likely get run over on the turnpike if I try to go 40mph.

 

[Bifflefan]

Re: 8" tires shake and vibrate at higher speeds?

My only guess is, the newer wheels dont fit the hubs correctly for some reason.
Try putting the new tires on the old rims and I bet you be fine.

 

[Bass Tracker TX17]

Re: 8" tires shake and vibrate at higher speeds?

My only guess is, the newer wheels dont fit the hubs correctly for some reason.
Try putting the new tires on the old rims and I bet you be fine.

Agreed..
Also make sure the hub surfaces are clean.
you CAN balance those tires. It's a little tricky. You need to fool the machine that there is a bigger tire on there than it is. I also had a small trailer with same tires. Also had problems. Took a couple of times to rotate the tires on the rim and then balance to be ok. Not positive if a different machine from what i use can be fooled but mine could.

After 38 years in the business you learn a few tricks.

 

[fisherguy123]

Re: 8" tires shake and vibrate at higher speeds?

Those small tires wear out fast, once they get worn you can replace them with 5.70 x 8 which fit the rims but add a lot of outside diameter and ride better and don`t spin nearly so fast.

 

[Silvertip]

Re: 8" tires shake and vibrate at higher speeds?

8-inch tires at 80 PSI??????? Are you certain that number is correct? Check the sidewall carefully as 50 or 60# is rather normal for that size tire. By inflating to 80# you may have popped some cords and now have a ballooned tire. Jack up each wheel and spin the wheel. If there is an obvious out of round or wobble it would be noticed. Check for wheel bearing play by grasping the wheel at 6 and 12 o'clock and trying to rock it in and out (push in at 12 and pull out at 6). Repeat at 3 and 9 o'clock. As was mentioned, ensure you have the correct wheel for the hub.

 

[smallboatlover]

Re: 8" tires shake and vibrate at higher speeds?

i would suggest if you have room put a 12" tire on there. IF you have too take out the fenders. if you don't want to do that try filling 5 gallon buckets and putting lids on them and put them in the boat. if you put in a coulp 3 or 4 that might help you might need more or you might need less depends.

 

[texasabil]

Re: 8" tires shake and vibrate at higher speeds?

Those small tires wear out fast, once they get worn you can replace them with 5.70 x 8 which fit the rims but add a lot of outside diameter and ride better and don`t spin nearly so fast.

They do wear out fast I have got to put a set on my small trailer every year!!! say you can also use your old wheels. I mount my own take the old one off put on the new one .and to get it to take air I put a ratchet strap around it .get it pretty tight put a small bit of air just enough so it will air up completely. UN do ratchet strap and air up to recommended psi. don't over fill tire with the strap on it it can break lose and do some damage Oh make sure and put a small amount of grease on the new tire!!!!

 

[rallyart]

Re: 8" tires shake and vibrate at higher speeds?

How come nobody suggested you balance your tires? It's far more likely that they need to be balanced than that 5 tires are out of round or all the rims are bent. 40 is about the speed where the harmonics of a small tire would start oscillating.
You can balance an 8" wheel. Just call a different tire shop. Even find someone with a bubble balancer if you need to.

 

[texasabil]

Re: 8" tires shake and vibrate at higher speeds?

How come nobody suggested you balance your tires? It's far more likely that they need to be balanced than that 5 tires are out of round or all the rims are bent. 40 is about the speed where the harmonics of a small tire would start oscillating.
You can balance an 8" wheel. Just call a different tire shop. Even find someone with a bubble balancer if you need to.

I tried that here went to 6 or 7 tire stores and they told me they cant balance such a small tire. wish they could I have blown out so many of these tires its not funny. so I retired the boat to the lake house where i don't need to pull it anymore!!!

 

[wbc1957]

Re: 8" tires shake and vibrate at higher speeds?

You can perform your own balance to some degree. Just jack up the trailer, verify that the tire and wheel assembly move freely. Then move the tire a quarter of a turn and watch it move the heavy end to the bottom. Add weight to the top section equally on both sides of the rim and try again. Either add more if it shows the weight back on top, or take some off if the weights are at the bottom, until it no longer spins and settles on its own randomly. This is known as a static balance, and is like a bubble balance. The real fix is moving up in wheel and tire size, because the amount of revolutions you are running those small tires is too much for high speed. BUT, for the purposes of proving you can balance your tires, i have offered you something to improve your situation and putting the trailer back into operation. Good luck.

 

[Bondo]

Re: 8" tires shake and vibrate at higher speeds?

At this point I've got 5 new wheels and tires, and no combination of any of these work without a bad shake. Since the old wheels don't shake, I know it's not the trailer. The shake is so bad that it moves the boat around on the trailer and I can see air under the wheel in my mirror as it hops up and down. Its as if the new tires are growing a high spot at speed?

Ayuh,.... 2 Questions,.....

#1,... Why didn't you just go back to the 1st Tire Shop, 'n see if they could make things Right, instead of just buyin' another set, from somewhere Else,..??

#2,.... Have you measured to see if the trailer is misaligned,..??

Both yerself, 'n texasabil wearing off a pair a year need to see what's not right...

 

[DJ]

Re: 8" tires shake and vibrate at higher speeds?

Tire pressure, etc. cannot address an inbalance issue.

Take them to a tire store and get them balanced.....

They won't get 8" wheels/tires perfect but close. You'll see a marked difference.

 

[jeeperman]

Re: 8" tires shake and vibrate at higher speeds?

Are your wheels mounted to the hub via lug bolts?
Could it be the rim is different enough that the lugbolt is bottoming out before it tightens the rim to the hub?
Check the lug holes on the new rims, is there any evidence of the holes getting banged up or chewed up?
Or that the new rims have a different stamping shape between the center hole and the bead that is interferring with the hub?
Also make sure the tire bead is seated all around, both sides. Easy to over look and not always obvious at a casual glance. They will still hold air and run smooth until speeds increase.