Is it my shocks or my tires?

So I got back yesterday from a 900-mile round trip out to Rochester NY this past weekend, and the drive was uneventful except for horrendous traffic on the Mass Pike on the way out, and a somewhat uncomfortable ride in my Tacoma.

I bought the truck new in 2010 and have made plenty of long trips in it over the years, but this was the first time it's been out to western NY via the NYS Thruway. It has 94k miles and only 2k miles on the new Cooper A/T3 tires I had installed last month. The ride was noticeably bouncy, especially on a 20+ mile stretch of the Thruway west of Syracuse. At one point I thought one of my rear wheels lost a weight because it was so bouncy on that stretch of highway.

Anyway, the tire pressures were 30 PSI cold all around when I checked them before I left NH and then again before I left NY. The tires are P265/75-16 so they are not LT rated, and I wasn't carrying anything in the bed. It was just me in the driver's seat and maybe a 150-200lbs of gear in the cab (it's a double cab).

The ride was very harsh and bouncy like you get when the tires have too much air in them, which is odd because they weren't overfilled. I had the springs replaced last summer because of the most recent TSB, and the ride was actually improved over the stiffer 4-leaf springs I had after the first spring TSB in 2010.

I had a set of Cooper A/TW tires in OEM size P265/70-16 before the A/T3 tires and I didn't experience as harsh a ride on the highway, so I don't know if it's actually the new tires making a difference or if I need new shocks. Would a set of 5100's in the rear help improve the ride? Or is there something else I should investigate? Maybe the A/T3's are just bouncy.

 

1. Verify your gauge - compare to another.
2. Verify bouncing on a couple of other roads.
3. 94K miles, you may be ready for new shocks.

 

Shocks. And verify the balance on those wheels too. If they feel like they are bouncing up and down, thats a static balance issue if the shocks are still good.

Any oil coming from the shock bodies? A tell tale sign of a blown shock.

 

As for my pressure gauge I have one of these and I'm fairly confident about its accuracy. The tires have been balanced twice by my local tire shop since new (they are only a few weeks old) and they ride smooth except for a little vibration around 55 mph. I am having them road-force balanced by my Toyota dealer tomorrow morning to see if that makes any difference.

As for the shocks, I haven't notice any leaks but I also haven't looked at them under the truck in a few months.

 

Are you sure its not just the new tires?

 

Have the original tire shop check that the tires are round - some tires come from the factory out of round (even slightly) and this cannot be corrected. No amount of balancing will solve that problem. If they are out of round, they need to be sent back. I've had this happen before. Not very common, but it's possible 1 out of the 4 tires could be bad. I'm running Cooper AT3's on two trucks right now, no issues whatsoever.

 

Shocks don't have to leak to be worn out. In fact, most don't.

At 94k they are worth changing, even if it doesn't fix your problem.

I'd try lower pressure in the tires, using a tread chalk test to verify when you hit the right pressure related to wear.

 

That's my plan.

 

94k on original shocks, they are done. Replace them as they need to be replaced regardless (go 5100's all 4 corners and set the fronts at 0 if no lift is desired). Then go get your tires re-balanced.

 

I had the AT3 on my Ford Ranger and if I went by the placard on the door to inflate them it did bounce all over the road so I had to play with the air pressure for a few weeks the AT3 have a very stiff side wall so the normal tire pressure would make them even stiffer you may have to get down to a lower air pressure
TOMB

 

Shocks wear out by around 100k?

 

^^This. Had that happen to me once. Noticed the wheel bouncing a lot only at a certain higher freeway speed, and was much less (almost non existent) driving on city streets.