New General Grabber AT-X's flat-spotting and the Toyota shimmy

As I've already posted, finally got my wheels/tires.

The tires are super. To date, no road noise, great traction and handling. But they flat-spot overnight. Not the end of the world, as it only takes a couple minutes of driving to get rid of the flat-spotting, but weird nevertheless.

Then there's the infamous Toyota steering-wheel shimmy. When I chose the tires in 305/50R20, I was worried because the same size caused an intermittent steering wheel shimmy from 40-60mph on my FJ. Well, guess what? Same thing on the 4Runner. The steering wheel usually shimmies when first driving off. Then it'll disappear magically, usually after braking lightly. Strangest thing...

 

ODD EH!. Last week the Hankook All Terrain were removed from the V8 2008 as the shimmy is apparent at 110KM/Hr and Only at this speed when first rolling onto the highway. Cold or hot tires. Not a good feeling as WTF is going on? Replaced with the michelin M&S and no vibration. Drove 700 miles in two days going to and returning from destination. Back roads allowing sustained speeds of 160 - 170 for. No issues and these michelins are five year old rubber with approx. 6/32nds of rubber. The Hankook AT had the vehicle sitting on them during the winter BUT I believe it is a poor balance job as the passenger rear was acting out of balance. Removed and balanced. The hop stopped. Will balance the Front tires and remount in the fall. Flat spots shouldn't occur with good rubber.

 

I’m guessing it isn’t a flat spot, but a balance issue. Sometimes it takes a lot of care to balance a big tire like that. Those poor guys doing it, unfortunately are not highly motivated to take care unless they need to. Just my experience. Also, sometimes tires can be out of round from the manufacturer. I’ve had it happen.

 

Nope. Flat-spotting and the infamous Toyota steering wheel shimmy are completely unrelated.

The flat-spotting, I can live with, even though the fat that a single overnite parking causes it is ridiculous. Our X6 in Florida would flat-spot, but that was due to it sitting in the garage for 3 months at a time. Race-Ramps Flatstoppers took care of that. They don't give them away, but I've heard that some tires never recover from the flat-spotting. At $400/tire, $180 is a small price to pay. And they work!

But the shimmy is a weird, Toyota-only beast. Many discussions about it on the FJ site for years. Tires don't unbalance/re-balance themselves every day. This is a Toy issue. Was hoping that it's only with the FJ, but I'm obviously wrong.

 

Ok, I believe you! But I’ve driven a lot of 4x4 Toyota pickups and 4 Runners and never heard of it. Granted, I’ve never driven or owned an FJ. Hear about it on Jeeps, though, aka death wobble. Good luck.

 

Neither flat-spotting, not shimmy today. Damndest thing

 

Any big outside air temp change? Not sure if that would matter??

 

None, but thx for the thought. Freakiest thing...

 

Maybe it was a stone stuck in your wheel. It doesn’t take much with big tires.

 

Interesting, I just got a set of Cooper AT3 4S and noticed a steering wheel shake at 60 going to work this am. Went away after about 5 minutes. At least these seem to balance well, I gave up on Falken Wildpeaks.

 

My Tacoma did it and my 4Runner does it too.

 

I just had the 265 ATXs put on the stock wheels yesterday. No issues with flat spotting overnight or "shimmy" even up to 80MPH on the highway, so it could just be the size of yours that makes the difference. They're as quiet and smooth as the stock Duelers on the highway, but handle/grip noticeably better.

The only issue I have is that they rub.

 

Garage was at 90*F this am. Went to work, had the flat-spotting for the first 3-4 miles. Also had the shimmy for the same amount of miles.
On the drive home, slight flatspot for 1 mile or so, but the shimmy kept me company the whole drive home. Starts at around 45 mph and disappears at 60.
Yesterday, nothing at all.

I'm wondering; Remember how with solid-axle front ends, we'd have to install a steering stabilizer when installing bigger tires? Would/could that work?

And again, running the same size tires 305/50R-20 (but not brand) on the FJ produced the same shimmy, but no flatspotting

 

Honestly no idea, but it sounds like a possible solution.

From past experience, I just assume that changing anything about the physics or dimensions of the vehicle from stock is going to have some sort of repercussions, unless you do something to correct it. Like bigger, taller tires not only mess with your speedo and aerodynamics, but also your suspension. They're heavier so they add a lot more rotational mass to each axle... I know the panhard bar can become misaligned with a lift and bigger tires, which sounds like it results in stability/handle issues, so maybe that's something to consider as well?

 

i have KO2's and dont think I have ever experienced flatspotting. i got them aligned after they were installed and it drove like a dream up until i got them rotated last week and now the shimmy is showing up intermittently :/