I have a 05 G35 Sedan with Eibach Pro-Kit springs and stock OEM (non-sport) shocks. I have had this setup with 20" Maya STM's for about 10,000 miles and total miles of 23,000 miles with these original OEM shocks.

How do I know when my shocks need replacing? I feel like the ride is alright, but pretty bad on a few rough roads. Can a shop test shocks?

What is the benefit of replacing the OEM shocks with Tokico D-Specs when lowered on springs? I originally was going to get new shocks when I got the wheels installed, but the shop said I didn't need them with the Eibach kit.


Thank you so much for your help!

 

If your shocks are starting to top and bottom out, then it's time to get new shocks.

 

Hi Curtis. Are you sure you don't mean MacPherson struts and not shocks?

In either case, the ride height will not be a determining factor in the continued servicability of the struts/shocks. The ride height is controlled by the springs and at 23,000 miles, the struts/shocks should be in fine shape. You wont need to take your vehicle to an auto center to have them checked, as you can do this yourself. With the very narrow sidewall tires being used with your vehicle though, this will greatly negatively impact the ride of the vehicle, so this will be a contributing factor.

To test the Macpherson struts, there are two things you can do. One is to actually look at the tube of the MacPherson strut, (near the top and on the side of the MacPhersn strut tube), and using a bright light, see if you can spot liquid seaping down the tube of the MacPherson strut. This is indicating a blown seal at the top of the strut with the internal oil seaping out down the tube. Typically, this oil will collect road grime and dust, appearing like it is damp and dark in color. The other test is the bounce test and what you do here is to go to each corner of your car and push up and down on the car, hard, until you really get the car bouncing up and down, a lot. To do this correctly, you have to use all your strength and maybe even break a sweat. When you have the car really bouncing, let it go and observe how many times, or cycles, it continues to bounce up and down on its own. If it continues to bounce up and down three or more times, this indicates that the MacPherson struts are worn out internally.

Voila! You have just checked your own MacPherson struts!

Steve
Monroe Ride Certified Specialist
CEO of Hi-Tech Oil Co.
Distributing industry leading AMSOIL synthetic lubricants for 19 years

 

Shocks begin to lose rebound stiffness from the first mile, however historically it doesn't get noticeable until ~~30k and we recommend replacement around 60k [for the average insensitive driver].

If you keep a car it is usually cost effective to buy expensive dual adjustable versions which can then be tweeked periodically to regain as new stiffness for 150-200k.

The only accurate way to test shocks is with a shock dynometer to measure the real numbers compared to brand new.

Shocks always show reduced stiffness as the temperature rises [worse in summer than winter by 10-30%].

 

http://www.roehrigengineering.com/techpgdynos.htm

Shock dyno explaination.

 

Come on fella's, of course an expensive dyno test is accurate, but at the millions of auto centers all across the U.S.A. every day, the visual and bounce test are used to check struts/shocks for the suitability of continued use. These methods have worked for years. There's no need to over-tech this. If the struts are leaking and/or fail a bounce test, that is all one really needs to know in the real world.


Steve
Monroe Certified Ride Expert
CEO of Hi-Tech Oil Co.
Distributing industry leading AMSOIL synthetic lubricants for 19 years

 

If you take turn on rough road, does car "skips" on bumps and almost slides out? That's a sure sign!
If car is rock solid in bumpy turns, you are OK.

 

Thank you for all of your help everyone. Turns on bumpy roads seem OK besides feeling a little rough, the tires don't seem to skip.

I think its just a few rough roads and my low profile tires making it seem bad.

Does the ride feel different on the tokico D-Spec's?

 

Ride is different with D-Specs, but it really comes down to how well spring and shock work together. I am very happy with my set up, just replaced front springs with 350Z, because I wanted to even F/R out a bit.

 

on d specs is it true the more stiff the more bumpier? or ???

 

yes. I think it is true with any adjustable shock?

 

Unfortunately rear rebound [resistance to shock expansion-- rate slowing of spring expansion after a bump] weakens first and this is the toughest to test on the car. Finding enough people to pull the rear up 3.0 inches in ONE SECOND smoothly?

Simple front compression test show nothing until way too late because you are pushing down against the stiff spring.

After 35,000 miles almost every one can tell the difference in a rear replacement.