beercan

Hello, everyone.
I don't like how stiff and bouncy my LS is over bumps. The roads in my city are to put simply: horrible. Lots of holes and this won't change soon.
So the soft suspension is what matters most. I don't care about how well the car corners.

By looking at my VIN specs - I discovered that I ride sport suspension (even tho I don't have any badges).
My springs are: 4813150180 front / 48231-50210 rears.
My shocks are KYB (which are also positioned as sport and stiffer than non-sport). I replaced the recently.

What I'm planning to change: I want OEM non-sport springs + OEM non-sport shocks.
48131-50170 - Front springs / 48510-59805 front shocks. 48231-50200 - rear springs / 48530-59845 non-sport shocks.

My question is: will there be a big difference in how car reacts over bumps?
Can I still keep my almost new KYB shocks and replace springs only. Sport shocks / Non sport springs combo or vice versa?

Thank you for help!

TriC

Changing out of a 45 series tire might do more to soften the ride than fooling with the suspension. Suggest you drive a regular suspension car with 16 or 17 inch wheels to compare with what you have now.

Johnhav430

haha I wish we could switch suspensions, I find the stock way too soft.

Only someone who has both cars (I think some do here on the forum), or someone who has driven both back to back, can clearly say....I personally don't believe the tires will do much, as I go -1 (to 225/55- 17") in the winter with my snows, back to the 245/45-18 45's in the summer. Not much changes with the ride, except the snow tires are very noisy.....I kind of think this car needs as much grip as it can get, so I don't really like going from 245's to 225's, but that is beneficial in the snow...

BCT

Stiff and bouncy ride can be caused by a lot of things. Some things to consider:
- Suspension: currently you have new shocks but old springs right? How many miles on that old springs? What year model is your LS?
- Tire: Some tire absorbs bumps better than others. What tire do you have? How many miles and how old? Also air pressure can cause ride to be bouncy.
- What is the size of the tire and rim? Larger rim and skinny tires can make a difference.

beercan

BCT,
My new KYB shocks have ~10-12K miles on them. Yes, springs are old + SPORT with 160K miles on them.
I ride on 235/50/18 Conti Premiumcontacts. Went from 245/45, didn't feel any difference except road noise, smoothness.
I played with air pressure, at the moment it's around 35-39 PSI. I don't go below 32-34 PSI because the ride becomes not as it has to be, handling is worse.

On good roads the car floats, rides amazingly. But it simply doesn't like potholes.
3 different mechanics checked my suspension and there are no problems at all. So it has to be spring/shock combo.

05ls430518

iTrader: (1)

A lot of the time since your thinking about it it exacerbates it making it worse than it really is talking from experience lol.

bradland

Johnhav430

Pretty sure in my grandparents' time, there was a wive's tale that the car mfgs recommended pressures lower than optimal, because they wanted you to have a soft ride. So you have to "add a few psi" to whatever the mfg. said, so your tires would last longer and you'd get better mpgs. That really isn't the case today. Just go by what the door sticker says.

There are some people who go by the tire sidewall, no lie. 44 psi, 51 psi. I got a loaner bmw and when I checked the screen all tires were at 53 psi. My wife was livid she said you have to tell the dealer....nah I didn't. Some previous customer would have done it, and I get that they don't check it before loaning it out again...

bradland

Catalina45

beercan

bradland,
By testing the ride testing different pressures.
Right now I lowered from 35-36 to 32 psi, the car is already slower, handles worse, while reacting better to potholes for sure.

Catalina45,
It's premiumcontact 5, 235/50/18 97v, it's not runflat.
I constantly change from 30 to 37 psi to test how the car reacts. I don't think that lowering the PSI is the solution to all problems.
YES, it does react better to potholes, etc. But the handling is much worse, the roll-up is worse, the car becomes less dynamic.
Still, I'm not satisfied.
But my main question is not about the tires and their pressure, it's about the dampening of the OEM non-sport shocks/springs vs sport.

Johnhav430

believe it or not, I found myself observing a wive's tale from my grandparents' era,as late as 8 yrs. ago. I was on my BMW forum and I posted how do you guys mark your tires when you do your snows, do you have chalk or a grease crayon, or what?

One guy goes why are you marking your summers? for one, they are unequal width F to R. So you don't need to know which goes on front or back obviously. Then, what difference does it make if you keep the tire on the left or right?

I was like whoa, you can't reverse the direction of the tire rotation on any tire. And the response was our tires are not directional (Bridgestone RE050A RFT), so it doesn't matter.

Here was the wives tale--I thought you cannot move ANY tire from the left side, to the right side, because it reverses the direction and the belts shift. THIS WAS A 1970'S CONCEPT!! lol funny how powerful misconceptions are.

Now it has always been said, that a Corvette has 4 distinct part numbers for its tires, and yes each tire must remain in its original position. i.e. you need to know if it's front left, front right, etc. They are directional, staggered, and asymmetrical. Directional and asymmetrical is the key....

p.s. the all seasons that came with my used LS are in fact directional and asymmetrical...(but not what came with my BMW--they were NOT directional)

Catalina45

From my understanding and that of a friend who had a new Ul plus and a '04 Sport identical to mine, the smoothest ride is a UL. The second smoothest would be the standard suspension and the least smooth is the Sport. The Sport has the best handling with the UL on the low setting the second best (which could be argued). The Sport has about 10% higher spring and shock (strut) rates and a larger rear sway bar. Your KYB units are just slightly firmer than the Sport struts. As previously posted, you could have lost some spring rate over time. Search for threads on how to measure to see if your springs have sagged. If they haven't sagged and have just lost some spring rate, chances are they are very close to new Non-Sport springs. You could also send your springs out to be tested and then work with the suspension engineers to tweak the specs of a stock or sport spring(s) Contact me offline and I can provide a vendor who I have used to design springs to my specs (Classic GM vehicle). If you are concerned about handling then examine or replace the front and rear sway bar bushings and control arm bushings. I wish there was an answer but a Sport model with the OEM tires type (not Grand Touring) will handle better but be about 15% less comfortable on broken pavement than a standard suspension.That's the trade-off we make by going to Grand Touring tires (on Sport models) is to increase comfort but decrease handling. On this platform having absolute comfort and sharp handling isn't possible with the suspension. Had Lexus elected to choose magnetic ride from Delphi or a similar system that can adjust the firmness of the shocks/struts this would have provided your answer. Another point of reference, having driven '17 Lexus LS460 and '17 BMW 740 models both handled better than my sport but were harsher riding (about 15% in each category) even with those companies suspensions on the softest settings. The larger tire size and type accounted for some of it but the trade-off they made was for better handling. I would love to have had MR integrated into this chassis so we could have the smoothest ride and best handling but it isn't to be. Having road and open road raced I would not even think of taking any variety of LS430 and enter it into a 120-125 average mph open road race. I may be licensed to drive on course at 168 mph but this platform isn't designed to handle as a true Sport Sedan (BMW M5, Cadillac CTS-V). Handling and ride-comfort are very subjective so before you make changes examine your springs and bushings and see if other 430 owners in the area will let you test drive their vehicles.

StanVanDam

To have the smoothest ride in an LS430:

1) Tires: change to LS430 Type A tires and wheels, which is P225/60R16 tires and 16x7 JJ wheels. The 60 sidewall ratio absorbs bumps better than the 55 (R17). Use a quality tire that absorbs bumps well and rides smooth (e.g. Michelin Premier A/S, Primacy MXV4), and select the lowest speed rating available (e.g. use a H-rated version of the same tire instead of the W or V, since higher speed ratings ride rougher). Inflate to owner's manual spec, which is 30psi for the Type A configuration. For reference, Type B is 225/55/17 95H 32psi (35psi if regularly driving over 200km/h = 124mph), Type C is 225/55/17 97W 35psi (36psi if regularly driving over 200km/h = 124mph). The psi rating in the owner's manual, in the glovebox, and on the driver door sticker is what you need to inflate to. Never inflate any car to the sidewall max capacity - the owner's manual and/or door jamb sticker is what you need to follow. If your tires are directional, there will be an obvious arrow built into the tire markings on the sidewall showing the rotation direction. If there is no arrow, feel free to rotate across the axle.

2) Agree with your proposal to replace the sport shocks and springs with the standard non-sport shocks and springs. When you install the shocks, turn the adjuster so that they are set to the softest setting, instead of using the default middle position. Search the forums to ensure you have all of the part numbers required to do this job, several air suspension replacement threads discuss the required OEM parts.

3) Replacing the sport front and rear stabilizer (sway) bars with the non-sport versions, or remove them altogether to reduce your cross-axis bounce on potholes and rough roads. You'll have a more bouncy but softer ride and much worse cornering, but since you said you don't care about cornering, you should evaluate your need for the stabilizer bars, or at least try out the non-sport bars.

4) Consider getting an LS430 with the air suspension. The shock stiffness dials are then electronically-controlled by a motor on all 4 shocks, varying through a range of 10 stiffness settings depending on whether the console switch is set to Norm (0-4 soft) or Sport (5-9 hard), and automatically adjusting based on multiple speed, angle, and suspension sensors (there is even a sensor/flag you can see in Techstream called something like Bumpy Road Detected or Bumpy Road Sensor). The rubber air bags of the air suspension are great at absorbing road imperfections.

Not relating to smoothing out your ride, but based on your driving conditions of being on bumpy roads very often, you'll want to check your engine mounts, transmission mount, radiator mounts, and other such shock-absorbing components, and replace as needed to prevent more expensive repairs down the road.

Hipatchy

How did you find out that you have sport springs?
I have a similar situation the roads in Toronto are terrible and I refreshed the suspension but still very stiff.
Totally unknown history on my car.