I just bought a 2002 sc430 40k miles with 20" rims. The car is overall great, except when it comes to bumps at speed over 20mph. It rides extremely rough and I can hear and feel the wheels/steering wheel shake. Is this because of the rims or is it a problem with the coilcovers. I own a Porsche Cayenne with 20" rims, it does not feel like this on bumps, in fact I can freely ride over them with high speed. Major difference, which leads me to believe it might be something else.

Wanted advice from someone who knows more about the sc430.

Thank you

 

Gregsc43o,
It depends...whether the tires are out of balance/bad camber, bad alignment, coilcovers are shocked, rims bend or rims are not comparable to your car. Another issue is...warp rotors etc...Any prior accident?

My Iforged Aero 20" sucks big time in wet weather. They are 3 piece and water get in them easily and cause my wheels+tires out of balance. In nice dry day, I have no issue as you have mentioned above. Are you on stock coilcover or after market?

Take care
Ned

 

on the sc430 20 inchers are supposed to decrease performance a little compared to 18s or 19s


nice choice in vehicles btw

 

your cayenne probably doesn't have low profile tires. you're not riding on much air, so the ride is going to be a little rough. if the tires are bald or nearly bald, that'll make it worse. overall, the ride should be smoother though than stock wheels with run flats.

 

To Ned: I have not checked the vehicle for any damages, but it does not seem like it went through any. The rims look like they were just put on; they seem like they are very expensive. I think It could be the alignment, but my real bet is on the coilcovers.

To Liquid SC: I don't know about the profile, maybe you are right, does that mean that changing tires can help? The tires, by the way, are brand new on the sc430.

To Sc430 guy: Thank you, but I am not too happy with the sc430 as of now, hopefully I can further diagnose this with professionals over the weekend and see if they can recommend anything.

Thank you guys,

If the problem is the coilcovers, what brand would you recommend (if after market is better) for soft, quiet, luxurious style ride?

 

if you put new wheels on you dont need an alignment. more than likely the tires are not balanced properly or hub rings are not being used.

 

The 430 is known to have a firm suspension, but it shouldn't be a really harsh ride that's like riding around in a Fred Flintstone car with square wheels.

I just traded in my '02 for an '07 and the ride in the '07 is a night and day difference. The ride is perfectly acceptable in the '07, whereas, it wasn't in the '02. In fact, the ride is one of the main reasons I traded it in.

These boards are full of information on the suspension subject of the SC 430. The problems seem to come from the earliest models and are often related to control arm/bushings problems.

One of our members recently had the lower control arms replaced and they said it made a world of difference in their overly harsh ride. They were ready to follow that up with new shocks, too, but they said the problem was corrected with just the control arms. They literally had cracks/dry rot in the rubber bushings where they mount to the body. So I would think this would be a good place to start. And of course, good tires can help, but from the way you described things, it doesn't sound like the tires are the problem.

Welcome to CL, Greg.

 

Good point made made above, there can be a difference between 20's on various cars. 19's on my SC430 were OK; decent ride and no bent rims with coilovers. 20's on my Acura RL were great as the tire ratio was taller. 20's on my AMG-7 bent rims in 4 MONTHS! With resulting horrible ride. Now back to stock wheels.

Some tires also ride better than others and the stock SC430 suspension leaves little to be desired.

 

A Porsche Cayenne is a SUV with a lot more rubber between the rim and the road. Your going to feel the bumps less with more tire rubber to cushion you from the bumps.

Try checking the air pressure. I run mine at 33-32 psi for a softer ride. The only problem is your likely to bend a rim with the lower pressure. The streets are pretty good in my area and I avoid driving in winter weather when the potholes pop up.

A 19" rim might be a better fit for ride, reliability. and style.

 

you probably can't change to a larger tire. with 20" wheels, only low profile tires will fit in the wheel well.

really, it's impossible to say if your ride is normal or not. i'd suggest you test drive an sc with runflats on it. if your ride is harsher than that, something is wrong. if it's a little better, it's normal.

one other thing, the previous owner may have lowered it with springs rather than coilovers. if so, it'll probably have a harsher ride. if that's the case, i'd look into tein comfort sport coilovers.

 

I was thinking of the Tein coilcovers...I will have to take my vehicle to a professional for examination. The point about the control arm, I will point that out to them. It will be great if that was the only problem. About the suspension, maybe I can change the current to the 07 version, I will have to talk that through with the mechanic. Thank you all!

 

Greg,
Thanks for sharing this. I have been saying this that there is a difference in the ride quality of my 2006 vs. the older models I test drove. These pre2006 (including one 2005) had much more road noise and rode "harsher" than the 2006 model. I still have RFT (7/32 tread left) and will change to conventional tires when these wear out, however I enjoy the ride thoroughly and am in no hurry.

Cheers

 

I have a FX35 with 22's and 45 series tires and it rides much smoother than my SC with 20's for the above mentioned reasons several have mentioned.

From time to time there is at least one unhappy customer with 20's on their SC...it's just something you live with...or don't and go back to stock 18".

For me, I like getting free rotate/balance at Discount Tire where I got my tires, so after they get out of balance, I just keep going back. I've learned to live with it. The aesthetic and ride compared to the stock RFT's it had are well worth the inconvenience.

I feel your pain...hang in there. There are soooooo many things to check.

I'd start with the easiest/cheapest fixes first then work your way up...psi of tires? balance/rotate? tread on tires? Any uneven wear patterns? rims are true? Then suspension...etc etc.

Also many "garage queens" suffer from dead spots in tires and typically this will yield more of an up and down hopping motion from your wheels/tires and also give you a harsher ride. Some have found luck in completely deflating the tires and re-inflating. If you have a garage queen, you may want to drive it more.

 

Yeah, I do not know whether I will find the time to do all of this, but I don't want to keep riding in the streets of NY with these conditions because I feel like they are harming my car in other ways. Overall, however, when I drive the vehicle in slow speeds and on smooth flat surfaces, the ride quality is superb! I just wish it maintained that quality, without compromising the loss of the 20" wheels that I have come to like.

 

I did not want to respond on this before, your money, your choice, your thread, but you are providing some misinformation that could cost others money.

If your 02 SC had a poor ride it was in disrepair. There are very few differences between the first SC to roll off the line and the last. Having driven an 09, the only difference I can detect from my 03 was the shifting was at different points. The performance has been unchanged, not even one more HP, which is most likely why sales died. Earlier SCs were hand built, and had some manual tuning, after 2004 they lost the human touch. Not sure if this is better or worse.

Part of the reason late models don't sell for more, is due to the high quality, and low miles, an 02 in great condition provides the same service as a car half a decade newer at far less cost. Hard to sell a car for 60K+ when you can get the same ownership experience for 20K. The owners of these cars were also much more gentle than those who drove more performance oriented cars. Also if you know where to buy it, you can get the same warranty on an 02 as a new SC. My SC has a recently purchased Lexus Platinum that will cover it for the next 5 years and 60K miles, taking my SC to 2015 and 110,000 miles.

From your posts it appears your first SC had a hard life. Very much a shame, if you had gotten a well cared for Florida car, you never would have parted with it. I have driven my 03 across country a couple of times now, and it is on par with my 06 LS in ride. Don't get me wrong, an 07 is better than an 02, more tech, better trim and lights, but for my money, if both cars had the same miles, and were in the same condition, I would go 5K more. Just too much bang for your buck with an early 430


Back on topic, I just did the 20s and the OEM wheels had a bit better ride. I am sure the engineers tuned the suspension for the OEM size wheel, and any change to the dynamics will usually have a negative effect.