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Posted

Hello everyone. I've been somewhat of a lurker here and first came across this forum when I purchased a 2010 RX350 for my wife. The color (Cerulean Blue) and price were perfect for the age and condition of the car and overall it's been quite fantastic and crazy reliable with it nearing 180k miles now. We did a fairly quick test drive and loved it. But after purchasing was where this story begins. For TL;DR, skip to the end.

Around November 2023 was when we made the purchase. The test drive went well and had a pre-purchase inspection with my local/trusted mechanic I've had for years, and everything checked out well with no immediate issues or concerns. After we completed the purchase and we started driving it over the next few days, we pretty quickly noticed that many of our commonly traveled roads seemed to be SIGNIFICANTLY more harsh than we were used to feeling in other cars, such as our 2007 Camry. The ride overall was very composed, but the COMFORT of the ride was nothing like we were hoping for or expected, and seemed to be compromised in a major way. Going over rough road meant we would be thrown side-to-side in our seats, feeling every crack in the pavement as if there was someone punching our seat bottoms from the underside, and worst of all larger cracks and potholes (which there are plenty of) were extremely unpleasant, so incredibly jarring and very loud when rolling over them, it felt as if the RX was body-slamming the road with us in it and seemed to be no "plushness" or "give" to the ride. All we wanted to do after hitting bad sections of road were get out and take a break, it was exhausting. After a few months of this, I started looking more seriously into what the issue could be: did we have some mechanical problem or failure, or is this how it's expected and designed? We were baffled as our 2007 Camry rides far better than this SUV. We also used to own a 1st Gen RX300 (1999) and I think due to the wheel/tire size and suspension setup of that 1st gen (225/70 R16), it was infinitely more plush than this 2010 seemed to be. 

One thing I found right at the very beginning was that the previous owner had the tire pressures set to 40 PSI, which is much higher than I would generally run any tire. Turning those down to 32 PSI increased ride comfort considerably and wasn't quite as sharp, stiff and crashy over roads and every little imperfection. If I had to talk in terms of percent improvement, I'd guess this was approximately a 15-20% improvement over our initial experience of the ride comfort. However, this was not fully solved in my opinion and there still definitely seemed to be improvements to be had as overall the ride was still not what I'd consider a "good". Because we were losing our sanity, I later lowered this a bit more to 29 PSI which made a smaller difference, noticeable but minor, maybe about 5% more improvement.

Searching beyond that...according to what I could find on the original brochure document (linked below, page 49), I found that our 2010 model was likely equipped with the Premium, Comfort and Navigation packages. We don't seem to have the Luxury or Sport Package, although "Sport" does include the 19" 7-spoke wheels, sport-tuned suspension and "Vehicle Dynamics Integrated Management" (VDIM). While our model did have the 19" 7 spoke wheels on it, it seems those could be added as a single option, which seems likely to be the case here as we didn't have the other features listed in the Sport package.

Lexus_US RX_2010-1.pdf

Upon finding some other forum posts discussing this, I got curious if we may actually have the "sport tuned suspension" listed in the "Sport Package" and if that could be contributing to the ride harshness. I also saw on Lexus part listings there definitely are separate part numbers for both Front & Rear shocks for "sport" tuned suspensions and that seemed to be the primary change versus the regular suspension, and presumably that is more firm than the "regular" suspension. I was a bit confused how to confirm if our model definitively did or didn't have this, until I decided to call a local dealer and provided my VIN number and they confirmed it did NOT have the sport suspension configured from factory. (I called at two completely different weeks & times to verify this same info in case there were any discrepancies from the first time I was told this). While I've not gone under the car and confirmed the part numbers on the shock or anything, but I think I can safely say we do NOT have the sport shocks, meaning that was one less leaver to turn to try and better the ride.

Here are some of the previous forum posts I found regarding this overall ride harshness topics, which is where I started my research journey (in no particular order):

Horrible Ride - What Can I Do ? - 10 - 15 Lexus RX350 / RX450h - Lexus Owners Club of North America

Supension Lexus Rx 350 Model 2010 - 10 - 15 Lexus RX350 / RX450h - Lexus Owners Club of North America

2010 RX350 very rough ride - suggestions - 10 - 15 Lexus RX350 / RX450h - Lexus Owners Club of North America

265/50r19 possible on a 2013 RX 350? - 10 - 15 Lexus RX350 / RX450h - Lexus Owners Club of North America

2015 Rx350 19 Inch Tires - 10 - 15 Lexus RX350 / RX450h - Lexus Owners Club of North America

Rough Rider - 10 - 15 Lexus RX350 / RX450h - Lexus Owners Club of North America

 

The one major area left to address was the wheel and tire sizes. For reference the original wheels/tires on our model at the time we purchased were: 

Installed wheel/tire sizes: 19" 7-spoke OEM wheels with 235/55 R19 Goodyear Assurance MaxLife tires (UTQG rating: 820-A-B). I'd estimate there was about 30-40% life left on the tread, although it did have some dry rot and smaller cracking showing. The tires were dated from 2021.

Goodyear Assurance MaxLife | 245/60R18 | Tire Rack

I decided that we should downsize to the 18" wheel + tire set as that seemed to be our biggest lever to pull for improving ride comfort as it could provide the most tire sidewall possible. Ideally, I also wanted to increase tire size over stock by at least 1 level to gain even more sidewall. I did hours of research to see what the best possible tire for comfort is that would also be well performing in other areas like lifespan, dry/wet traction etc. I researched for an extensive amount of time, reading reviews, tests, videos and consumer feedback, other forums etc. over weeks. I also researched a bit on the original Goodyear tire as I've not had that one specifically before, and concluded it only seemed "average" performance except for rating highly for long life and has an 85k mile warranty, and the model itself is slightly older, so I decided I would then start looking for the "best" tires, basically at any cost.

I settled on the Pirelli Scorpion AS Plus 3 tires (UTQG rating: 800-A-A) as the model to go with. These are rated very high in comfort and noise, which I prioritized, and in the top of the pack for dry/wet performance and long life with a 70k mileage warranty, so it seemed to be a really good above average, even segment topping tire. I'd also used Pirelli on our RX300 and liked them, but was just a coincidence now as I happened upon Pirelli again after prioritizing comfort and performance, no matter the cost, not specifically going for Pirelli here. However, I wanted to get these tires in 18" size and also increase the size slightly to provide that extra bit of side wall. I spent some time searching on best 18" tire sizes for 18" wheels, but couldn't find much in the way of specific "oversized" tires which are actually confirmed to fit on stock 18" wheels and not cause any amount of rubbing or issues. So I decided I would go one level over stock size to keep it conservative and minimize any fitment issues.

Pirelli Scorpion AS Plus 3 | 245/60R18 | Tire Rack

Problem now was that I had to source some OEM 18" wheels before getting tires. I spent some time on Facebook Marketplace, where I did have 2 potential listings to choose from. One listing was about 4-5 hours away from me and the wheels looked brand new for a great price ($360 all in) and owner confirmed they were removed from their car just a few miles after getting the car. Sad part was that logistically I couldn't make that exchange happen, so I had to say bye to that. Really unfortunate as that was my top pick and also one of the cheapest listings I found. The 2nd option (and only real "local" option) seemed ok, but after reviewing more detailed pictures the set was in kinda rough shape with multiple wheels having curb rash, scratching etc. and didn't seem in the best condition for the price (about $400). My next spot to look was on eBay and I found several options here, mostly from various wreckers across the country, but also found some "remanufactured" wheels for a bit higher price.

What I ended up with were 3 wheels from one seller and 1 from another seller, which I realize now may have been risky as I can't directly verify if a wheel is bent or beyond repair etc. I paid an overall average of $155/wheel, about $620 all-in. Here is where I have one regret. The remanufactured wheels could be had around the $200-$225 price per wheel depending on seller, which would have been an additional $45-$65 per wheel (or about $800-$900 all-in). Looking back I think I would've spent an extra $200 for "perfect" wheels and saved myself some labor on cleaning and prepping the wheels I ended up with, but not sure I'd be willing to pay more over than that. I was really hesitant at the time, not knowing if I was doing all this for no reason or no improvement, so wanted to keep costs in a reasonable check.

I've recently gotten into car detailing as a hobby, so thought I'd save myself some money and gain some experience in doing a full wheel cleaning and ceramic coating on the "used" wheels I ended up with. This took several hours to deep clean the wheels, clay and prep them, ceramic coat them and store them. They ended up looking like a 8/10 overall I think and turned out decent. There was some old tape on the wheel barrel I couldn't easily get off from old wheel weights, but other than that, they were mostly curb rash free, and only 1 or two minor scratches on the wheel faces across all wheels.

Then I moved forward with purchasing the new tires since I had success in sourcing and prepping the 18" wheels. I ended up with size 245/60 R18, whereas stock size is 235/60 R18, so about 1 level of size increase over stock to keep it conservative, but also gain just that little bit extra in sidewall. This is a tire that benefits us in multiple ways: it's in the smaller 18" size, it's wider and taller than OEM 18" and 19" size (providing more tire sidewall), the specific tire model is also rated much more favorably for comfort (priority) + performance and another benefit is it will be a brand new tire, vs the older ones we're replacing with an unknown number of miles and history. The cost came in at $232/tire + costs of install/balance + tire certificates + tax, which set the total to about $1220 for tires & install. I found a handy tire size comparison tool which could tell the exact size differences between the original 19" tire and the 18" tire. They also have a graphic which can help you see the difference in size compared to an original size, and how the size difference would affect your speedometer (approximately 1 mph difference at most with new size), which I found to be helpful.

 

Tire Size Calculator (https://tiresize.com/calculator/)

Previous installed size: 235/55 R19

Stock/OEM size for 18" wheel: 235/55 R18

New size: 245/60 R18 (+1 level over stock)

                               Previous | New

Diameter:                    29.2" | 29.6" (+1.4% increase)

Width:                           9.3" | 9.6" (+3.2% increase)

Sidewall:                          5.1" | 5.8" (+13.7% increase)

Circumference:            91.6 | 92.9" (+1.4% increase)

Revs/Mile:                    692 | 682 (-10 decrease)

 

You can see that I have gained a rather substantial ~14% in sidewall size over the previously installed 19" tire, with very minimal increase in width and height keeping fitment issues little-none.

 

I was also curious on the comparison of the OEM 18" size vs the oversized 18" size, so here are the stats for that comparison. There is sidewall size improvement here as well vs OEM, but much less substantial than going from 19" OEM size to oversized 18" size (as seen in comparison above).

 

                                     OEM | New

Diameter:                    29.1" | 29.6" (+1.7% increase)

Width:                           9.3" | 9.6" (+3.2% increase)

Sidewall:                         5.6" | 5.8" (+3.6% increase)

Circumference:            91.4 | 92.9" (+1.7% increase)

Revs/Mile:                    693 | 682 (-11 decrease)

 

 

TL:DR

Now, after having Discount Tire install the wheels and new tires this past weekend and getting everything road-force balanced, I can say I'm finally much happier with the ride now, although it's not perfect still as suspension damping still seems to be a factor in the residual firmness. I don't think we can get much better than we have it now unless we replaced every bushing and suspension component with new OEM to restore "original" ride, and even doing that, I think there would still be a firmness to it as it seemed to be designed with this characteristic and is less of a "mechanical problem" and more of a design choice on Toyota/Lexus side in my opinion.

We've spent just under $2,000 to get here, but I'd say we're at a 60-70% improvement in ride quality now over when we first got this RX. And so far, I can confirm absolutely zero fitment issues with the +1 tire size over stock with no rubbing or anything even at full steering lock in either direction. I probably would've gone +2 levels over stock (or more) if I could get first-hand experience that larger sizes would still work. (anyone willing/able to confirm?) Even on one of our roughest roads we use daily, it no longer feels like you're being beaten by a hammer from the underside of the car. It definitely has more of a "glide" feeling to it and has restored some plushness to our driving and passenger experience. Sections of road that we'd brace for impact before are now much less of an event, and because it doesn't crash over pavement as much, the ride is a bit quieter as well even on rougher sections. Discount Tire sets pressure to factory setting (32 PSI) so I may even try to eek out that extra bit of comfort going back down to 29 PSI on this new setup as well, just haven't lowered pressures down yet.

 

I wanted to write this up as a sort of one-stop-shop for anyone trying to solve similar ride quality issues on their 3rd gen RX350s. To sum up my experience and research on this more concisely, seem points below:

- Verify your VIN with dealer to see if you have the "Sport Package" which includes "sport tuned suspension". (I didn't in this case, but could affect others if model was originally optioned with this. Seems it only comes in the "Sport Package" or if someone replaced shocks with the "sport" part numbers after the fact)

- Verify air pressure in tires is no higher than recommended (32 PSI). Consider running a slightly lower pressure by 1-3 PSI. I ran pressures at 29 PSI for about a year and it made a minor improvement. I don't /think/ this pressure is enough to introduce extra wear on outsides of the tires, and anecdotally, I haven't noticed any extra wear on the old tires.

- If you have 19" wheels, the best choice possible is to downsize to 18" wheels and increase tire size over OEM. I can confirm that size 245/60 R18 fit (+1 size over OEM/stock size of 235/60 R18), however, if I could have verified fitment of even larger sizes before purchasing that size, I definitely would have gone even larger to allow more sidewall on the tire for maximum comfort.

- When replacing tires, consider the ride comfort and noise ratings of the tire you're looking at. I prioritized these metrics in my search and landed on the Pirelli Scorpion AS Plus 3 as it had top marks for comfort/noise and is in the top of the pack for dry/wet performance and even tread life as well, so seems to be a well rounded performer.

- More of a reminder, ensure that wheels/tires/suspension components/bushings are mechanically sound and that there is not something worn or broken leading to an actual mechanical issue.

Posted

Wow! That has to be one of the most detailed and well-researched posting I've ever seen! Thanks for spending the time to do this.

Our older RX has 235/55/18 tires, and our ride has always been very smooth and quiet. Of course, the type of road surface material and texture can make a very noticeable difference in interior sound. It seems as if driving on darker, tar-based surfaces almost always results in a quieter ride. 

You mentioned that your vehicle now has 180,000 miles on it. How many did it have when you purchased it? Have you bought new shocks?

Worn shock absorbers and bushings can adversely affect the ride. I've had good luck with KYBs in a previous car, but you can't go wrong with OEMs, although they could be pricey.

  • Like 1
Posted

Thanks for the kind words! I tried to detail everything I thought and did during this investigation... 🤣 

I think the mileage when we got our RX was around 170k or just below, so I think we've put around 10-12k on it since our ownership up till now.

I've definitely thought about what you mentioned. The shocks/bushings and everything I can see don't appear to be leaking or feel like they are worn and mechanic agrees he doesn't see anything wrong with the suspension overall. Also the shocks are still very taught and reactive, the car doesn't continuously bounce if you tried to bounce the car (like you would traditionally see with a worn shock), it comes back to original height and stays put quickly. So to mine and mechanic eyes and experience it at least doesn't "appear" that the shocks themselves are worn or other components.

However, with that said... I do sometimes wonder how much of a difference it would make to replace all shocks/bushings and suspension components to get them back to like-new ride. I just don't think it's worth the significant time + money investment to do something like that when there may not be anything inherently wrong with the actual mechanical components we already have.

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