My 03.5 G35 sedan has stock suspension with 63,000 miles on it. The onlt mod to the suspension is 18 inch coupe rims with 235/45/18 Kumho Ecsta SPT tires. The suspension feels really harsh when traveling over irrecular road surfaces like RR tracks, expansion slots, or any change in elevation, even when driving at relatively slow speeds. I can feel the feedback through the steering wheel even.

I think the shocks are about due for replacement with Tokico D-Specs. I will keep the stock springs.

I also suspect that some of the rubber suspension isolation bushings may bee worn out and in need of replacement.

My 04 coupe with Tokico D-Specs, 350Z S-Techs and 30 series 20 inch tires rides smoother over the same orad conditions.

Any help ot thoughts would be appreciated.

 

63k is about it for stock shocks, and possibly springs too. As for the bushings, yes, these certainly will wear as well, but those probably aren't as likely of a culprit as your shocks and springs. Also, replacing bushings is no easy/cheap feat, unless you have access to a good mechanic with a machine shop willing to do the work at reasonable rates - otherwise, you're looking at replacing many OEM suspension components. Have you had an alignment done recently? How close does it come to (nominal) spec?

 

Rubber bushings and isolators and bent arms and mounting points are the significant reason why a worn out 60-120k vehicle doesn't feel new.

The only way is to replace the components.

Ozone, nitric oxides, heat, and salty water destroy rubber fairly fast.

Using a quality rubber protectant from day one from dealer and every 90 days can double the life of many components.

The are ~~ 200 rubber locations that need 90 day treatment

Select a protectant designed for adherance not a Silicone or vinyl protectant.

Wurth Rubber Care is the Rolls Royce of products:
http://www.wurthusa.com/project/en/l...th=04.0170.jpg

WURTH makes 700 products for automotive maintenance and repairs.

 

I had the car aligned and it was within the outside specs.

I'm just going to get new shocks and see if that helps. I'll inspect the bushings and isolators while I'm installing the shocks and see if anything looks bad.

 

Does 303 Aerospace Protectant qualify since it is not silicone or petrochem based? And what do you do with these, just spray them on the pivot points/bushings on the suspension components?

 

When I have my car on lift while oil is draining an excellant time to start at rear and work forward.

You need to become on a first name basis with every single rubber component.
Don't forget all rubber door, window, glass seals and hinges [different special lube]............while oil is flowing in do under hood rubber same with all hoses.

Once a year use dielectric grease on all connectors to exclude moisture and corrosion.

Quality products are not cheap and rarely available at discount automotive stores.

Obviously those in states where winter salt is used or coastal areas need more care!

I've never accurately costed the amounts of products used but is is not over $100 per year. Which won't pay for any single part + labor replacement, so I'm way ahead with protective spending.

 

Actually, there is very little to do with rubber bushings used specifically in suspensions other than keep them clean of excessive dirt, oil and greases that might accumulate with time. Anything petroleum based IS harmful. And lubes like WD-40 etc, contain solvents and oils that are more harmful than good.
Any kind of non-petroleum based lubricant (TFE, silicone, etc.) does more to make the owner feel good than help the bushings.
If there was a magic elixir for such bushings dealers would be lubing them and charging you for them.
But when it comes to all the other rubber and non-rubber parts like weather-stripping, hoses, hinges, etc. good sprays available from Wurth, Meguair, etc. will help clean and make them look like new for a longer time. Using them on suspension parts will seem like the right thing to do, but have little to no effect on wear so a waste of spray IMO.
Many suspension parts mfrs. do not recommend ANY lubricants for rubber bushings other than specialized ones like P-80, Dow Corning DC 7 and RuGlide (for mounting tires) to ease installation. All these lubricants will be toast in a relatively short time following the install.
You can spray some soapy water on a bushing you suspect is squeaking to isolate a problem. No lubricant will fix it except for a very short time.

 

This link would support your conclusion:

http://www.jksmfg.com/support/instal...rms_pn7100.pdf

"RUBBER BUSHINGS MUST NEVER BE LUBRICATED, as doing so will impair performance and longevity."

Of course, they could be talking about petroleum based lubricants, but still, it's a pretty broad warning.

I think I'll stick to just lubing the seals, hoses, etc. with 303.

 

That's what I do. If you want longer wearing bushing for sway bars, etc. you can go with various non-rubber products. Sometimes with some degradation in ride softness, but they generally stay tighter for longer.

 

WURTH is not a lubricant it is a tacky sealant to isolate/seal the rubber surface pores from ozone.

The term lubricant assumes some rotating/sliding friction something rubber hoses don't encounter...........they like bushings need protection from oxygen/ozone.

"Ozone damage can be detected by tiny parallel cracks at the stress points. Hoses damaged by ozone are likely made of oil-resistant rubber compounds"

Ozone Resistance. When tested in accordance with 4.5.8, the hose cover shall withstand an ozone concentration of 100 ± 5 parts per hundred million for 24 hours conditioning and 70 hours exposure at 104 ± 1.8 °F (40 ± 1 °C). There shall be no evidence of cracking or crazing when examined under 7 X magnification.

In smoggy ozone areas like Atlanta and LA special care of hoses and bushings MUST BE CONSIDERED!

OEM manufacturers generally skip this concern since it only applies to 10% [area of US] or less of specific locations but may represent 15-20% of car sold.
25 top OZONE LOCATIONS:
1. Los Angeles-Long Beach-Riverside, Calif.
2. Bakersfield, Calif.
3. Visalia-Porterville, Calif.
4. Fresno-Madera, Calif.
5. Houston-Baytown-Huntsville, Tex.
6. Merced, Calif.
7. Dallas-Fort Worth, Tex.
8. Sacramento--Arden-Arcade--Truckee, Calif.-Nev.
9. Baton Rouge-Pierre Part, La.
10. New York-Newark-Bridgeport, N.Y- N.J.-Conn.-Pa.
11. Washington-Baltimore-Northern Virginia, DC-Md.-Va.-W.Va.
12. Philadelphia-Camden-Vineland, Pa.-N.J.-Del.-Md.
13. Hanford-Corcoran, Calif.
13. Modesto, Calif.
15. Phoenix-Mesa-Scottsdale, Ariz.
16. Charlotte-Gastonia-Salisbury, N.C.-S.C.
17. Las Vegas-Paradise-Pahrump, Nev.
17. Milwaukee-Racine-Waukesha, Wis.
19. St. Louis-St. Charles-Farmington, Mo.-Ill.
20. El Centro, Calif.
20. Kansas City-Overland Park-Kansas City, Mo.-Kans.
20. Beaumont-Port Arthur, Tex.
20. Chicago-Naperville-Michigan City, Ill.-Ind.-Wis.
24. Grand Rapids-Muskegon-Holland, Mich.
25. Atlanta-Sandy Springs-Gainesville, GA-Ala.
25. Cleveland-Akron-Elyria, Ohio

 

Sorry to bring up an old thread Gilley but what did you end up doing. I am in the same boat I think and am not sure if it is shocks or worn bushings/ end links etc...

 

ITS THE SHOCKS.

I recently had my my original shocks on my coupe changed with OEM units at 70K miles. All I can say is that the hard slamming of the suspension is gone. All the suspension bushings were checked and found to be in excellent shape despite the fact that mine is a daily driver and I'm in Chicago were road salt is king in the winter.

In fact my second set of tires started cupping bad with 15K miles on the tires (the first set made it to 35K miles) which means that the shocks had lost much damping strength by about 50K miles.

 

I'm not sure what part of changing out the suspension (shocks, springs, sway bars, and a-arms) did the trick, but it doesn't make any noise now.

 

athens I tend to agree with you. I have a 04 Sedan in Milwaukee with 59k on it and every little imperfection in the road causes a pretty harsh response. I know the car was not like this when I bought it. My friend is convinced it has to be bushings or end links because the car is not bouncy but I am not so sure.

Anyways what shocks should I go with? I have the sport suspension and truthfully dont really care for it. I have a different sports car that rides like a go cart already. This is my daily driver and I would like it to be somewhat comfortable. I am open to changing the springs and shocks together.

 

after replcing shocks and getting an alignment... my car rides much better.