Under the hood: If your car wobbles, check suspension
Before modifying your suspension perhaps its best to perform an inspection of front and rear suspension parts, especially both stabilizer bars and their attaching links. This part specifically reduces side-toside sway and leaning during turns. It's possible a link may have come loose, rendering your front or rear stabilizer bar ineffective.
You might also try upgrading your existing struts (a structural shock absorber that is surrounded by a coil spring) with possibly a premium product such as the KYB Excel-G, which should help restore handling to same or better than when new. At 76,000 miles you're certainly ready for new struts.
Tire type, inflation pressure, and condition can also
BRAD BERGHOLDT
result in a noticeable decrease in stability if not correct. A shorter (low aspect ratio) tire typically handles better than a taller one. If your Highlander is the base model, the 245-65-17 tires do a good job, while the Limited model's 24555-19 tires are even better. Rotating your tires on schedule to promote even wear can help, along with keeping inflation pressure perhaps a couple of pounds higher than the vehicle manufacturer's recommended setting (no higher). Premium tires such as the Michelin Premier LTX, if you have deep pockets, sit at the top of Tire Rack's steering response and cornering stability ratings.
The SumoSprings you mentioned sound like they could be worth a try on your Highlander's strut-type suspension as the micro-cellular urethane part — sort of a cushion — slides between your existing spring coils, wrapping around in a complete circle, gently stiffening that portion of the spring without significantly raising vehicle height. These seem vastly superior to oldschool rubber or metal coil spring booster wedges, which tended to slip out of position or fall out. Perhaps start with a pair of SumoSprings for the rear first; they are easy to install. If you don't see the desired improvement, add them to the front.
Adding traditional top-ofthe-spring spacer rings or pads would simply elevate the vehicle body, possibly restoring it to its original height by compensating for spring sag, but do nothing to enhance spring rate. I'm thinking this could actually work against you, especially if they squish out or come loose. This isn't a huge problem, but it needs fixing... or better yet, removal.