Is250 Suspension Harshness

[rollex]

Hi, I'm brand new to the forum, with a bit of a dilemma, so thought I would throw this out for comment. About three months ago I purchased a pre-driven '06 IS250 AWD. I test drove the car several miles and really liked everything about it. I felt the ride was firm, but this was part of what made the car feel so good. The test drive was on pretty smooth roads with three people in the car on a nice warm day. After owning the car for a few weeks I noticed how the car could be quite harsh on certain roads shaking me up pretty good. This was with stock 17" tires, 36psi and suspension that is stock and perfect (I had Lexus check it out). As time wore on and winter came the roads got bumpier, the suspension might have gotten stiffer with the cold, and my neck was having a hard time taking it all. Not wanting to give-in a decided to put on "winter" tires and wheels, but move to 16" tires and buy very good smooth riding Michelin all season tires, I figured this would smooth things out. Well it did improve the ride for the most part, but mostly with the small bumps, the mid size waves/bumps in the pavement still come through loud and clear. Others who drive or ride in the car, like my wife, agree the ride can get to be quite choppy at times, but they don't feel the pain in the neck I have developed. So I have a sensitive neck! I've tried different driving positions to no avail, and if I stay out of the car a few days (driving our SUV which is sort of bumpy) I am fine. I've even talked to my Dr. and he basically said if it hurts when you do this, don't do this.

So here is my real question(s), I really like this car and would like to keep it, but what do I do? I actually found a place willing to make custom coil springs that would be softer than stock. They believe going to a rate about 25% softer would help considerably. We would keep the stock height, and stock shocks/struts. Has anyone modified their suspension harder/softer/lower, that could give me an idea how much effort it is to have the new springs installed? Does anyone have a feel for the stiffness of the stock shocks/struts to get an idea of how well they would work with softer springs? It would be great if I could get this thing a few notches closer to an ES like ride. Other thoughts, suggestions, besides buy an ES. Thanks for any help.

[smooth1]

Welcome to the LOC.

I have a feeling you may be at the last 10-25% life of the tires you have on the car also. I'm not sure what tires you have, but alot of them lose their ride quality toward the latter half of thier useful treadwear.

So here is my real question(s), I really like this car and would like to keep it, but what do I do? I actually found a place willing to make custom coil springs that would be softer than stock. They believe going to a rate about 25% softer would help considerably. We would keep the stock height, and stock shocks/struts. Has anyone modified their suspension harder/softer/lower, that could give me an idea how much effort it is to have the new springs installed? Does anyone have a feel for the stiffness of the stock shocks/struts to get an idea of how well they would work with softer springs? It would be great if I could get this thing a few notches closer to an ES like ride. Other thoughts, suggestions, besides buy an ES. Thanks for any help.

I think you may be making a big mistake here. The spring rate and the shock are designed to work together. A softer spring, especially a significantly softer spring, is going to put alot of load and strains on the stock shocks. You'll probably have to change those also. And if your going to go thru all that trouble, then I suggest you get a set of adjustable coilovers. They aren't just designed to adjust hieght, but they also have dampener adjustements. For example, I have the Tenabe Sustec Pro 5 coilovers with the NF 210 springs. I lowered my car about an inch, and set the dampeners to 9 (1-16 are available. 1 is softest and 16 being firmest.) to soften the ride up a bit as lowering the car made it firmer. I also have the TEAS system. It's an electronic suspension adjuster that can be controlled/programmed from inside the car. So when the car is travelling at low speeds, the suspension is nice and soft, but as the car starts to speed up, the suspension progressevly gets firmer as I have programmed. ( A super nice feature). But not as soft as an ES. I don't think that's a realistic goal for this car. But the car does have a significantly better ride now. Especially over the smaller bumps. I barely even feel those now.

[rollex]

Thanks for the response, I agree just going at it with softer springs is taking some risk. I feel the stock spring rates are quite high just by the fact that if I sit on the trunk lip, when open, the car barely moves. With a lower spring rate the car would show more movement. But the shocks are also critical, if they are resisting motion moving more for only large jounces, they will transmit the force through without the spring even having a chance to compress. Your reference to active suspension makes me believe the shock is most important in ride stiffness/quality since this is all that is being adjusted with the TEAS system. When the shock valves are wide open the ride is smooth, when closed down the ride is very firm, your springs never changed their behavior/rate. Softer springs on the higher rate stock shock might also encorage them to pump the car down over bumps since a softer spring would not push back up as hard. Something like the TEAS system and new springs may be worth looking into, however I would prefer not to lower the ride height, and this is an is250 AWD which does not seem to be listed for any aftermarket springs. Out of curiosity, what would you reccommend as a good all weather tire replacement for the stock RE92s?

[bartkat]

Continental Extreme Contacts give a good ride and long mileage at a good price. I tried mine in some freezing rain this week and they did really well. I like them much better than the OE tires on my IS350

[smooth1]

Thanks for the response, I agree just going at it with softer springs is taking some risk. I feel the stock spring rates are quite high just by the fact that if I sit on the trunk lip, when open, the car barely moves. With a lower spring rate the car would show more movement. But the shocks are also critical, if they are resisting motion moving more for only large jounces, they will transmit the force through without the spring even having a chance to compress. Your reference to active suspension makes me believe the shock is most important in ride stiffness/quality since this is all that is being adjusted with the TEAS system. When the shock valves are wide open the ride is smooth, when closed down the ride is very firm, your springs never changed their behavior/rate. Softer springs on the higher rate stock shock might also encorage them to pump the car down over bumps since a softer spring would not push back up as hard. Something like the TEAS system and new springs may be worth looking into, however I would prefer not to lower the ride height, and this is an is250 AWD which does not seem to be listed for any aftermarket springs. Out of curiosity, what would you reccommend as a good all weather tire replacement for the stock RE92s?

Both Tenabe and Tien make springs for the IS250 awd. Tien makes a Comfort Sport sreies called the CS. You may want to take a close look at those. As for tires, I live in Florida and I have an IS350. So it's strictly summer performance tires here. I've heard alot of good things about the Conti's Bartkat listed and the Goodyear F1's a/s plus. But I would suggest going to Tire Rack.com and looking at the comparison charts and reading thier tests and so on to decide which tire is best for you.

* My bad. no coilovers for awd yet.

[sktn77a]

If you're not happy with the 17" wheel/tire combo and, especially, the 16" wheel/tire combo, then I think the car is just not for you. Messing with the spring rates and/or shocks will likely be a disaster (braking performance is also linked to the suspension chracteristics).

Maybe you should just bite the bullet and trade it in on an ES350.

:(