winwin4all

18" OEM tires on 2008 RX350 235/55/18 and there are many posts and discussions about different sizes and compatibilities but only guessing from folks, nothing I could find legitimate to make a straight decision. My dilemma is: I want to have a nicer ride and have extra height on the rubber in case of driving on curb. If I put 235/60/18 instead of stock 235/55/18, will it affect tranny in any way? I know the speed will be different but that is not my concern, I think the height difference will be OK too and shouldn't affect neither. What I worry ,only, is that the gear ratio was intended to be for 55 height and after 60 will be installed it will be different which may bring some extra tension on internal parts or whatever, I really don't know, that is why I decided to ask people here. To summarize, will I have a softer and safer ride on 60? I'm going with Goodyear Assurance Comfort if needed. Thanks.

gt1209

Don't think so: http://www.powerdog.com/tiresize.cgi

Enter these in the right text box:

235/55/18
235/60/18

Another website:
http://ejelta.com/tiresize/index.htm...el=&maxdelta=2

winwin4all

Any pressure on transmission? Softer ride?

RX330inFL

You may find that just putting on a set of tires different from the OEM will provide the difference you are looking for without changing tire size. You can also take a pound or two of air pressure out of the tires which will also change these characteristics some, however, I would not run them below spec as found on your RX and in the Owner's Manual. I like a firmer ride, so I put a few extra pounds in my tires. This provides less flex to the sidewall and therefore a firmer ride.

Changing tire size will have no affect on the transmission parts. You can go up and down all you want. The only concern would be for the accuracy of the odometer and speedometer as you noted.

Personally, I would not make such a change. Rarely does one hear that the ride in a 2nd Generation RX to be considered rough or harsh. Remember, it is an SUV, really a tall wagon, and not a true car. It is designed to ride this way. Look for a replacement tire with the characteristics you want.

If you feel you really need a softer ride you might consider dropping down to the original 17" tire size that was available on the RX. Believe it was 225/65-17.

winwin4all

Thank you. I started thinking of it after I was making a turn on the road and had to drive up on a curb and heard that bum sound. That is when I thought that extra inch of height might help in "crossing the obstacles" I like 18" rims so will go with 60 in hope to get what I am thinking about them. Just curious why Lexus decided to go with 235/60/18 on 2010,11,12? Complains from others or bigger size?

Kendig

Looking at the specs tab on this page:
http://www.tirerack.com/tires/tires....orTred+Touring
for the two sizes, we see that the 60 profile is rated at 110 lbs higher max load. I expect that some of that difference might compensate for the greater bulk of the generation 3 RX. We also see that the *diameter* is 1 inch larger, which gives you an overall height increase of 0.5 inches...

Interestingly, if I'd looked all that up before I bought my current set of tires, I'd probably have gone to the 60's because my speedometer routinely reads 2-3 mph slow at 65-70, so the larger tires would have brought it pretty close to actually being correct.

winwin4all

Ha, I thought that my speedomEter is faulty because now it is 3-4 miles over ( when 100 on it I actually drive 95, when 70 I go 67) so it looks like I'll compensate with 60s to normal speed... or otherwise

pauljcl

My speedometer also reads some 3-4 mph 'high' compared to true speed. Not an issue for me. But I would conceptually not have a problem using 235/60-18 tires instead of 235/55-18 ones. Particularly if you lowered the ride height by the 1/2" or so that the new tire adds. I think the RX would look a lot better, and there would be less 'empty space' around the wheels. I'm really not into 'mods', but if I were, I would do it.....

kasey3881

we have the same model(2008),i use 225-60-18 x-i2 michelin snow tire.
This size is pretty close than 235-60-18.

pauljcl

I can understand the desire to have 'narrower' snow tires, but otherwise a narrower tire with a higher section = less grip with a ride that is only very slightly higher?

winwin4all

Got it today! Bought set of Bridgestone Dueller instead of Assurance ($100 savings). Don't know of how they will hold in rain (Goodyear Assurance to my opinion is best on rainy days) but so far so good.
Difference compare to 55s are: ride is smoothier, it does feel different in good way, I seat higher now not like in GX feelings but different compare to how it was before and me and my wife like it. Speed became actual, 70 is 70 80 is 80. There is also a difference in comfort or feeling bumps on the road, much better now. Over all I am happy with this size. The only thing I feel or just seems like I feel that this tires are little bit heavier compare to 55s or just Duellers are heavier then Assurance but I think I could feel difference, may be I am wrong on this.
So, if any of you thinking about same as I was thinking till today, I can tell you that I am happy that I decided to go with 60s. I would be even happier to know that I have Assurance on my car but... Duellers were my second choice anyway.

pauljcl

Congratulations!
Does the RX feel 'tippy' at all, or does it feel like it leans over a lot in corners, or does it feel like the steering is a little more 'vague'? And: what tire pressures are you using?

winwin4all

My second day driving around. Do not see anything compromising my ride to switch back to 55. Actually it seems that the car became more steady with this set. Feels more solid drive, do not feel that it became "tippy" or leaning any more then it used to be. may be it has something to do with Duelers compare to other brands, not sure but absolutely nothing I'd say became worsen than before. They put 35 in the tires this time of season, I always had 33 up front and 30 in the rear before. I do drive kinda aggressive in terms of speed so I'd notice any disadvantages if they'd appear. while cornering leaning seems to be same as before but you may be right that the steering became little more 'vague' but in good way, for me at least. While driving 75, pushing pedal all way down making car jump forward as it use to do before so no affect on accelerating neither. One more thing I noticed that I don't feel like I want to drive faster now in this car, now it feels something like driving heavier GX with it's feeling of be semi-vip Lol. But if seriously, lighter wheels and tires will make you push the throttle harder. And you know, nowadays speeding tickets almost always are not about safety but to fill the budget holes so don't let them take advantage of you.

spacecraft

How do you feel that?!?
I don't think there can be such a huge weight difference, anyway...

winwin4all

I feel the way car is driving after I fill it up from different gas stations (same 93 grade) after I wash the car myself it responding different too. There is no big weight difference in tires but I feel it. May be it has something to do with my sensitivity because I can tell difference in 1oz weight difference in my hands also. My wife loves the way car drives now but the only way for other people to know is to drive it.