ajs

The sticker on the door of my car says the recommended cold tire pressure is 32psi. However, I checked the pressure first thing this morning and all my tires are inflated to 46psi, which did not surprise me.

Does anybody actually keep their tires to the recommended tire pressure? I have always noticed that the tire shop always inflates the tires to well above the manufacturer recommended pressure.

johnpg

46 seems crazy high. Mine were 33.5 to 34 when I got the car home and I deflated to 32. I think I had a better ride when they were higher. In fact in general I'm not very happy with the ride quality so far. It's better than other cars I've driven in, but not as nice as I'd expect or remember from the test drives. So I'm really interested in others opinions on what to do here.

Cheers,
John

rxets

46!? Wow, you should feel the difference in Day 1...

The day I picked up my car which was 32/32 in cold.



Now I use 34-35 (front), and 32 (rear). To me, I've found 32/32 makes this vehicle's handling/control "nuetral" but "FWD-like". 34/32 may help my RX move a little more nuetral.

rxets

John,

You got 19", right? Are they Michelin's? Do you remember what test-driven RX was?

johnpg

rxets,

I test drove 18" initially, but did get a chance to test the 19". The difference though was that the 19's were on an AWD, which was noticeably heavier. So I wasn't really able to judge the difference as weight may have played a factor.

I may try increasing the tire pressure back up to 34, which is how the car came. Any reason for more in the front and less in the rear? I confess to knowing next to nothing about car maintenance. :-)

Cheers,
John

rxets

I wasn't the expert, and just attempted to apply the understeer corrections of FWD into my RX. I feel my RX is a little plowing when making turns, which is similar to FWD vehicles. To raise the front tire pressure is the simplest way to do since I don't want to replace the shocks/springs/toe/camber, sway bar, tire size, etc. (High pressure may result in the rought ride but the better MPG.)

With 32/32, when entering the turns, my RX front tires were sliding out first. But when passing the middle of turns, my RX was then slightly oversteering. I'm not sure if AWD is kicking in or not during the common turns. I usually prefer to have my car with the slight understeer but very closed to the neutral.

So far I don't find the big difference with 34/32, but I do feel less understeering when entering the turns. Anyway, I may change my front tires pressure back to 32 or 33 in the end.

johnpg

Quick update, I had to get gas today so I decided to increase the tire pressure. There was no way for me to know exactly what the pressure was because the gas station unit wasn't very good, and it was late in the afternoon after 45 minutes of driving. But I set the pressure higher than it was and even on all tires. The difference was dramatic. The ride was a lot smoother. I think I must have incorrectly deflated the tires to match 32psi when I first got it and my tire pressure gauge was giving me inaccurate readings. There's absolutely NO WAY that 32psi is correct for this vehicle if my gauge was accurate. It felt like the tire pressure was too low, and now that it's higher it drives the way I'd expect it to. I have a mechanical gauge that I'll try tomorrow morning and see what the pressure actually is. Assuming THAT one is right! :-)

Having said all of that, the ride is still bouncier than I'd like. I imagine it's the suspension. The 2008 RX400h I drove was inferior in every way except that it seemed smoother over rough or uneven roads.

Cheers,
John

data2009

John,

How many miles have you driven your RX so far? For me, the bounce was annoying, but after about 1500K miles, it almost went away, and now its mostly a smooth ride. Even bumps don't feel that "bumpy".

My RX came with 18" Bridgestone HL400s. I don't think these will stay on my RX for long, as reviews on them are not good, and I feel they belong on a passenger car, not an SUV.

ajs

It appears my old tire pressure gauge is not giving me accurate readings. It seems to have an offset of +5psi. So the actual pressure in my tires was more like 41psi. I bought a new analog gauge and confirmed my suspicion. I have now reduced the tire pressure to 36psi, according to my new gauge. We'll see how the ride feels now.

rxets

Don't forget to reset your TPMS... btw, get your own tire pressure gauge...

The G Man

Stick with the good old pressure gauge that has the stick that pops out with the reading, there is nothing to braak on those things.

johnpg

I have about 500 miles so far. So you're saying you also noticed the bouncy ride at first and it went away over time? I wonder how that's even possible. I'll report back if I notice any changes as time goes on. The transmission is better for sure, it's much smoother now than it was originally.

In any case the ride is much better with the tires inflated higher. I still haven't had a chance to check with a proper gauge what the actual pressure is. I'll do that tomorrow morning if I have time before work.

Cheers,
John

The G Man

The shock and springs like everything else mechanical will wear in after some use, I would give it at least a 1000 miles or 2 before they are nice and loose.

tomd

FWIW, we are very disappointed in the ride quality of our new RX350. A lot less composed than the ML350 we traded in and worse than the 2006 RX330 before that. This will probably be our last Lexus.

rxets

John has Michelin tires, right?

Well, some of wide/low-profile Bridgestone tires used to have the flatspot problems, the belt insides causes the problems. Tires may temporarily produce the bumpy, uncomfortable, and noisy rides, but it usually goes away after a few miles or mins' road trips. I don't know how Bridgestone makes our tires. So far, I don't experience this on my RX.