userdmx

One complaint I have is that the car 'hits hard' on rough surfaces...pot holes train tracks etc. I understand this is all relative as I have a 4runner as well my lexus dealer says its normal and its b/c it has a short wheel base. Anyone have any suggestions the tires are the michelen ones with about 37k miles.

thanks

xfirechief

Stay with the Michelons & try lowering the air pressure a little. I run about 34PSI on the highway trips & about 28 PSI in the city.

AM1

iTrader: (6)

its the suspension.

userdmx

tire pressures are at 30

Lil4X

Your tires are responsible for smothering sharp impacts; your suspension cannot possibly react quickly enough to absorb them. If you have Michelins mounted on the "optional" (I've never seen a 330 on anything else) 18" wheels, you have two problems:

• Michelin makes a tire with a pretty stiff sidewall and a relatively soft tread compound to maximize cornering grip - and it does an excellent job. The problem comes when you expect comfort out of this equation too. You might consider going to a tire with a more compliant sidewall. Check the reviews at www.tirerack.com.
  
  
• If you have the optional 18" wheels, those trendy narrow sidewall Michelins are really going to feel like they were made of concrete, even with reduced air pressure.

I've considered swapping someone my 18's for a set of the OEM 17's just to go back to the more compliant tire, and a little more isolation from sharp impacts. That's why your 4runner seems to take these impacts much easier - a MUCH wider sidewall to absorb those potholes, RR tracks, etc.

Before someone mentions the handling going away by going to a smaller rim and/or a more compliant tire, sure, on a sport coupe the difference might be detectable - but the RX is a mid-sized crossover SUV, it's NEVER going to handle like an autocrosser, short of torching the springs and pouring Karo in the shocks. Want to handle like a go-kart? Be prepared for a go-kart's ride. Oh, and consider buying a kidney belt.

ducks4

V rated tires have hellishly stiff sidewalls so an H rated tire might help, just don't do Bridgestone HT687's. Another thought would be Goodyear Response Edge in 255/55VR18 (UTQG 440AA). Reviews (Tire Rack) praise the ride comfort, the size upgrade gives a taller (11mm) sidewall for better impact absorption and they're less costly than Michelin. Other threads here have discussions regarding this size change.

userdmx

from the tirerack site people seem to like the bridgestone deuler....i have a version of these on the 4runner very nice tire

userdmx

I geuss what i was getting at was is there a better strut/shock that would help but you guys seem to think its the tire. I have a 2007 gs350 loaner and it absorbs potholes etc much better.

AM1

iTrader: (6)

it would seem like higher speed rated tires would be softer and stickier therefore softer riding.

Lil4X

The "softer, stickier" part is the tread, not the sidewall that needs to be fairly stiff in a high-performance tire to prevent the tread from rolling out from under the wheel when cornering. This tread "squirm" results in rather un-responsive steering as you turn the steering wheel and the rim responds, but the contact patch keeps going in the original direction for a split second before the soft sidewalls slowly bring it back into line. The result is steering that feels "mushy", and a really slow response to steering inputs.

Back in the dim dark days of my autocross career (when mods included a bigger whip for my velociraptor), we used to increase air pressure (normally 26-28 lbs) to 40-42 lbs to "stiffen" the sidewalls. It actually worked, and was considered standard procedure for those running the Michelin "X" radials. Those tires (or the similar Pirellis) were the secret to quick times at the autocross because radials tended to roll the sidewall rather than lift the inboard edge of your contact patch as would a bias-ply tire. Of course there was the considerable trade-off of reducing the size of the contact patch by over inflating your tires, but on balance, it was worth it. The alternative was to occasionally see a competitor roll a "soft" tire completely off the rim under extreme cornering loads. Tires are a WHOLE lot better now.

Lil4X

While shock/strut valving and spring rates have a lot to do with "ride quality" (if such can be empirically quantified) they are the foundation of the handling equation. The secret is that all must work in concert.

Starting with the question of how the vehicle is going to be used, we begin a series of trade-offs that relate to stability, smoothness, ultimate cornering grip, compliance with the road surface, and a dozen others. You would think that solid axles welded to the frame and soft solid rubber tires would be the answer (as in a go-kart), but it turns out that a certain amount of suspension and tire compliance actually improve handling performance at the limit.

The GS is a boulevardier with good amount of handling competence. Slung low, it takes advantage of a low CG to produce good cornering numbers - for the few to whom "numbers" matter. It is smooth, powerful, and one of the finest compromises between comfort and handling in the marketplace.

Now the RX is a sport-utility - with another set of compromises. That high profile that produces ground clearance and a modicum of off-road ability and that high sight line from the driver's seat comes with a downside - a relatively high CG. In order to tame the body roll and usually "drunken sailor" handling of a softly-sprung SUV, thanks to its tall, tippy profile, a few compromises to comfort were in order - one of which was fairly stiff tires that keep the contact patches directly under the wheel under all but the most extreme cornering loads. That's a good start, and perfectly acceptable to owners coming out of a conventional truck-based SUV where ride comfort is comparable to that of your average loaded pickup, the SUV's spiritual ancestor, if not direct parts-bin donor.

In the final analysis, the suspension of the RX is a product of the marketplace. When the crossover SUV was developed (the RX being one, if not the first to market), its target segment was the owner of the truck based SUV that was tired of the bulk, lousy performance, non-existent handling, and frighteningly absent brakes of the Suburban, Explorer, and other trucklets on the market. I for one had driven Suburbans and other SUV's for 20 years and had had enough. I was probably right in the middle of that target demographic for the crossover - needing a bit of hauling, off-road, and long-distance capability, while longing for a bit of accelerative, handling, and braking prowess. The RX, with its smaller size, considerably improved performance, and comfortable cruising was ideal for me.

Moving from a conventional SUV, the RX is a revelation. To many, moving from a passenger car to a crossover can be a disappointment. It could have been worse . . . you could be driving a truck.

The RX is never going to be a GS, no matter what the advertising would seem to say. They are slotted into entirely different markets. Unfortunately many SUV buyers purchase their new vehicle expecting a "carlike" experience, and that's not going to happen. As much as I would love a GS, it's not going to fulfill my present needs. Perhaps there is some comfort in the old adage: "There are horses for courses."

AM1

iTrader: (6)

i forgot about sidewall and overall stifness. what i find funny about the rx is that in the first gen Rx the manual even advised against going off road in it.

xfirechief

Is there anyone out there that uses their RX for off-roading?
Seems like it is not the thing to do but anyone??

Orzel

iTrader: (1)

Depends on what you mean by 'off-road'. Had ours out on logging roads, and mountain trails (Pacific NW Cascade Mountains), also driving on (very) loose beach sand on Oregon beaches. Did just fine – much to the surprise and dismay of some of the large wheeled and lifted trucks we saw at the beach. If your alluding to something like the Rubicon, the RX would probably cringe and run away itself with little or no human intervention.

AM1

iTrader: (6)

i drove my old rx300 through some huge puddles after it rained..........i stopped in the middle of a puddle and the water was midway at the door.....water everywhere...mechanic told me i was lucky i didnt mess the engine up. rod millen did some off road desert race in a almost stock rx300 a couple years ago.