Nissan 350Z / 370Z Tech Forums banner
1 - 19 of 19 Posts

· Registered
Joined
·
70 Posts
Discussion Starter · #1 ·
2003 350z touring.
Several years ago I replaced the struts and shocks on my Z. I bought the strut/spring combo from Rock Auto. Since then it rides very rough. I measured the spring diameter to be a little over 13 mm. I'm wondering if this is the same as stock. Does anyone know the specs on the springs?
 

· Super Moderator
Joined
·
1,925 Posts
Waited to see if anyone else would respond, but since no one has tried, here the info. OEM front springs are 13.0 mm in diameter, but that may not be why your Z rides rough. Your spring rate and ride height have a bigger effect on your ride comfort than the diameter of the spring. Do you know who built the shock/spring combo you purchased from Rockauto?
 

· Registered
Joined
·
70 Posts
Discussion Starter · #3 ·
Waited to see if anyone else would respond, but since no one has tried, here the info. OEM front springs are 13.0 mm in diameter, but that may not be why your Z rides rough. Your spring rate and ride height have a bigger effect on your ride comfort than the diameter of the spring. Do you know who built the shock/spring combo you purchased from Rockauto?
My bad. I looked up the part number on Rock Auto and found it was the strut only. No springs. KYB is the maker.
 

· Super Moderator
Joined
·
1,925 Posts
My bad. I looked up the part number on Rock Auto and found it was the strut only. No springs. KYB is the maker.
The Z33 uses a upper and lower wishbone design with the shock/spring separate from those components. So are you thinking the KYB shock is causing the rough ride? Did you reuse the OEM springs?
 

· Registered
Joined
·
70 Posts
Discussion Starter · #5 ·
The Z33 uses a upper and lower wishbone design with the shock/spring separate from those components. So are you thinking the KYB shock is causing the rough ride? Did you reuse the OEM springs?
Yes, I reused stock springs. The struts were replaced in June of 2012 with 74,000 miles. I never noticed a harsher ride at that time. The car did set higher after the install. In Aug. of 2021 I replace the lower front control arms and front compression arms. I also got 4 new Kuhmo Ecsta tires and had it all aligned. 128,000 miles. It might be worth noting that It also seems to have a lot more road noise than I remember previously. Could that be a factor?
 

· Super Moderator
Joined
·
1,925 Posts
With all the suspension changes you've done, I'd check ride height all 'round. Does the car sit squarely, or is the rear lower than the front? Also, take a close look at the Kumhos and see if there's any eccentric tire wear on the tread.
 

· Registered
Joined
·
70 Posts
Discussion Starter · #7 ·
With all the suspension changes you've done, I'd check ride height all 'round. Does the car sit squarely, or is the rear lower than the front? Also, take a close look at the Kumhos and see if there's any eccentric tire wear on the tread.
The car sits within 1/4" of factory specs at all 4 corners. I just rotated tires (side to side) and saw no wear. I have a panel I made to separate the rear section from the front that helps, but it still seems loud. I have put it in neutral while moving and backed off the throttle to see if was exhaust noise. Swerved side to side to check if wheel bearings. I'm putting about 1,000 miles on it a year since I retired, so it doesn't get used much. I would buy new tires if I could find some that are quiet.
 

· Super Moderator
Joined
·
1,925 Posts
The best way to check if wheel bearings are worn is to lift the car off the ground and manually rotate each wheel/tire in all four directions to see if there's any wooble or lockup from the bearings themselves. Have the wheel bearings ever been replaced?
 

· Registered
Joined
·
70 Posts
Discussion Starter · #9 ·
The best way to check if wheel bearings are worn is to lift the car off the ground and manually rotate each wheel/tire in all four directions to see if there's any wooble or lockup from the bearings themselves. Have the wheel bearings ever been replaced?
I've checked all the bearings in the manner you call for. All good. They have never been changed since I've owned it. It had 54,000 miles when I got it. Maybe the differential is making noise. But this thread has kind of evolved from ride stiffness to noise although they may be related. Are there suspension items that would make it ride smoother? When I put my weight on the front of the car it barely moves up and down.
 

· Super Moderator
Joined
·
1,925 Posts
I've checked all the bearings in the manner you call for. All good. They have never been changed since I've owned it. It had 54,000 miles when I got it. Maybe the differential is making noise. But this thread has kind of evolved from ride stiffness to noise although they may be related. Are there suspension items that would make it ride smoother? When I put my weight on the front of the car it barely moves up and down.
OK- ruling out wheel bearing wear is important since their failure can put you on your head! But back to the ride stiffness, KYBs are usually not considered a performance shock brand. Their bump settings are usually close to stock and I don't think they're adjustable. Were there any instructions that came with them? If installed correctly, softening the bump setting is usually one of the first things to try when trying to improve ride.
 

· Registered
Joined
·
70 Posts
Discussion Starter · #11 ·
OK- ruling out wheel bearing wear is important since their failure can put you on your head! But back to the ride stiffness, KYBs are usually not considered a performance shock brand. Their bump settings are usually close to stock and I don't think they're adjustable. Were there any instructions that came with them? If installed correctly, softening the bump setting is usually one of the first things to try when trying to improve ride.
I don't think they are adjustable. I think the only instructions were how to install them.
 

· Super Moderator
Joined
·
1,925 Posts
Not quite sure what else to advise you on. The Z33 is a pretty stiff platform, and most suspension mods are usually to stiffen the response and increase feedback and cornering. Depending on where you live, there may be a Z car club you could attend and compare your car's ride stiffness to some of the other members.
 

· Registered
Joined
·
70 Posts
Discussion Starter · #13 ·
Not quite sure what else to advise you on. The Z33 is a pretty stiff platform, and most suspension mods are usually to stiffen the response and increase feedback and cornering. Depending on where you live, there may be a Z car club you could attend and compare your car's ride stiffness to some of the other members.
I don't see many Zs around to try out. Thanks for all the suggestions.
 

· Super Moderator
Joined
·
1,925 Posts
There are plenty of Z car clubs in your neck of the woods. Bluegrass Z Car Club, and Z Car Club of Kentucky are two that come to mind. Getting some firsthand feedback from some of their members might help with your problem.
 

· Registered
Joined
·
8 Posts
Are those Kumhos directional? If so, rotating them side to side is a not recommended.

I just did both front hubs on my '06 Z and mistakenly switched the tires side to side. Road noise was very noticeable, it disappeared after I switched the tires back.
I'm not saying this is a major source of your problem but it might not be helping.
 

· Super Moderator
Joined
·
1,925 Posts
Are those Kumhos directional? If so, rotating them side to side is a not recommended.

I just did both front hubs on my '06 Z and mistakenly switched the tires side to side. Road noise was very noticeable, it disappeared after I switched the tires back.
I'm not saying this is a major source of your problem but it might not be helping.
Good point- some unidirectional tires not only become noisy, but the tread won't shed water effectively if rotating the wrong direction. But in this case, Loomis also reports a rough ride after he changed the shocks on his Z. It may be something that only an up-close inspection will help.
 

· Registered
Joined
·
76 Posts
dkmura is being very nice and helpful.

Me, I'm just gonna say it.

KYB shocks are junk. First tried a set of Gas-A-Just on one of my S30s way back in the 80s. Wow.... Horrific ride and who would have thought shocks would contribute to suspension noise? But they did, particularly over rough roads. Tossed ‘em in favor of Mulhollands (made by Tokico).

Bought another Z33 a few years ago where the seller tried to make "new shocks" a selling feature. KYB Excel-G, supposedly an “OE equivalent”. Those were just horrible. Put on a set of real shocks (Tokico HPs - "Blues" as they were known) and all issues disappeared.

Bottom line: Don't take this personally.... but KYBs are worth about what they cost. Next to nothing (when comparing to Konis or Bilsteins or other known good shocks or COs.) I'm guessing that there's at least an 80% probability that a set of good shocks will fix your problem.

Am I just a disgruntled KYB owner? Yup :LOL:. But honestly, I hate low quality products marketed to be "as good as OEM". I honestly don't see how they're still in business.
 
1 - 19 of 19 Posts
Top