Tarrant64

Hi all, I recently picked up a 2011 IS350 AWD. It's completely stock, 17" wheels, I believe Dunlop Sp 5000's. On most roads the IS rides OK but there are some where the car seems a bit bumpier than it should be. I got a chance to take it on some roads I actually test drove other 250/350's on yesterday and was disappointed to see that my car was bumpier than the others. I feel attached to the road, it's not too "floaty" or anything like that. It's just that I seem to feel the slightest dips.

My question is what can I do or specifically ask to have someone look at to ensure everything is OK with the tires/suspension? I know the ride is stiffer than what I'm used to but when I can look right and see the passenger's head bobbing on some roads it's a little disturbing. I don't want to go to the dealership and get suckered into replacing something I don't need. Hoping someone can say "suspension"/"shocks"/"tires" can improve or is specifically the problem.

I laugh about it now but I just know I test drove 250/350 RWD and AWD models before and they were not this bad. Hoping to get some suggestions here.

Thanks in advance.

Shorthand:
IS350 AWD, 17" Stock wheels on Dunlop SP 5000's - 24,000 miles
Bumpy ride, so bumpy sometimes it causes awkward moments with passenger in car.

edgeucated

iTrader: (4)

What is your tire pressure? Have you gotten an alignment recently? Has your ride always been this bumpy, or did it just start?

There's not much else to do besides changing out suspension/tires.

Tarrant64

Thanks.

I've only had it for about 3 weeks. Haven't gotten to check the tire pressure yet but will do so today.

I do plan on replacing the tires for some Michelin's this year so I'm trying to figure out if there's anything I need to have done with the suspension to try and reduce the bump.

jbone29

iTrader: (2)

the tire pressure has a lot to do with the comfort of the ride. i have had 2 sets of wheels put on my car and both times the tire place did not properly adjust the tire pressure. Once i had it fixed i felt like i was riding on air.

Tarrant64

I took a quick peek over lunch and they don't look like they are properly inflated (look low?), but I don't have a low tire pressure warning. It did go from 50 to about 8 degrees here since i got the car so I bet that's it. Sometimes it's the simple stuff. Thanks.

I will report back in a day or two if it ultimately helps.

Edit: Just checked, I'm at 30psi all around, and it should be 35front/38rear. Will fix that today.

Gville350

iTrader: (10)

Stock ride height I'd assume; so what sidewall spec are those tires? The larger the #, the more sidewall you have = usually a better ride quality feel.

Joshohoho

I noticed my ride quality to be a bit rough on some surfaces but not all the time. I was hoping it wasn't bad shocks. it doesn't sound like a loose bushing or linkage in the suspension, but I'll take out 3 Psi out of my wheels to see if ride quality smooths out on my IS. im running 18" f-sport wheels with hankook V12

Joshohoho

Cleaned my engine bay and double checked tire pressure. it was 2 psi above normal on all tires. I took 2psi off from all 4 tires and the ride is much smoother. I was thinking my shocks were bad.

Tarrant64

I was at 30 psi all around and added some air. Think I'm a little high though. Ride was pretty much the same. Will try letting out some air each time until it feels right.

Tarrant64

As I said I haven't had it that long (2-3 weeks now). I want to say that it got worse but in thinking about it it's only been since the temperature has dropped to near zero lately. I didn't get a chance to drive it a lot until it got cold either way though. Honestly I wouldn't have said anything if I didn't think there might be a problem.

The tires I have are Dunlop Sport 5000, 225/45R17 91V - http://www.tirerack.com/tires/tires....utoModClar=AWD

Reviews are pretty bad for the tires but they are OEM. Seems I will budget to replace them anyways.

I do know the various other IS250/350's I test drove were on Bridgestone or Michelin's. One used one even had Pirelli's - they all drove a little better than this. not the end of the world by any means.

surensm

This may sound outrageous but try it. Take the wheels off of a Bridgestone 250 and slap em on yours, take a spin and see how it goes.

Tarrant64

If I went to the Lexus dealership you think they would do that???

Slammer1

What size are your 17" tires and what is the recommended tire pressure for them (inside the driver's side door)? I have factory 18s and my pressure is 35 psi in the front and 37 psi in the rear. They should be at the recommended psi, btw. As for the stiff/bumpy ride, I find that my car can feel the same way in certain road conditions but I really just chalk it up to having a car with a sport suspension. It isn't irregularly stiff by any means but still isn't anything that bother me either. If you are running a very high speed rated tire, it will have a stiffer side wall which is less forgiving in regards to ride quality. Check the speed rating on your tires and compare it to what the car came with. If you own a car that comes with an "S" rated tire and switch to a "V" rated tire, the ride will be stiffer and you will feel more bumps in the road.

Noeh

iTrader: (3)

35/38 for my AWD with 17"

Tarrant64

Exact same for me.

Tire size is 225/45R17 91V.

I'm at 38psi all around I think. The tire gauge I had with me was the wife's and doesn't work well. I went a little high and will check ride quality after letting air out periodically. I used to have a digital gauge that worked well.