Suspension and tire question

Josies370z

Question for all the suspension guru's out there
So while performing regular maintenance at 60k I noticed small bumps to the outer inner portion on both of my rear tires. Went to go check out tires at my local tire shop and the guy working there said that it was caused by bad shocks (he drives a 350z by the way). I was just wondering if this is possible? I always was under the impression that it was either impact, overinflation, or defective tire related. Just wondering if the shocks need replacing as well???

FYI - car is a 2010 base with oem shocks and springs, mostly driven by my wife as her daily on crappy roads here in Los Angeles lol

DEpointfive0

Post pics

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Boss_302

A little insight, Back in the day when I attended automotive school and front end alignment shop. The instructor discussed tire wear. Showed us a tire with a wavy thread wear which was due to bad or blow out shocks. If you every seen a vehicle on the road and the it has a blown out shock the wheel just bounces up and down and loses contact with the road. Its the weirdest thing and pretty scary when you see it.

Another example isI use to get this floaty feeling in my mustang. it had Koni's in the back with 40k miles on them, and when you did the bounce test it seemed normal, change out the shocks and the floaty feeling was gone. That floaty feeling was due to the wear point in the shock tube.

Now in your case, the shocks are at 60k, and with crappy roads like we have here in NYC. they have taken a beating. They haven't blown out but they have worn a sweet spot in the tube. The wear indication at the outer edge of the thread is from the camber dialed in to the car and the wheel oscillation due to the shock wear point in the tube.

By the way I have a 370z and after 30k I trashed the factory shocks and installed a Nismo S-tune suspension. The handling was like night and day. Just the new shocks alone will make the car handle better, and if you are going to stick with factory, I would upgrade to the shocks that come on the Nismo, they are made by Tocki which is a well know performance shock manufacture.

Josies370z

I will try to get pictures up by tomorrow........the bounce test on the car is fine but i agree to the level of strain on them since the roads here are horrible, i might just bite the bullet and change the entire suspension but trying not to spend on parts (trying to buy a house) and not change them if that wasn't the issue....the bumps are mostly on the inner portion, i did not really see any wear on the outer......thanks for all the info!!

Boss_302

You should hook up with the facebook group - 370z parts for sale- this guy Christopher Spann posted 2016 370z Nismo Stock Suspension (springs and shocks) & Stock Camber Arms for sale
$450 plus shipping, roughly 13,000 miles on it. good luck

DEpointfive0

While I agree to mayyyybe buy his setup, his pricing is INSANE

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Josies370z

ok sounds good i will look into the group buy, thanks for the info

Sensei Kreese

How difficult is it to change the shocks on your own? I'm not a mechanic but I changed out the air intake from stock to long tube. I'm assuming I'd have to buy 2 stands after getting the car up off the ground. Is this an easy project or something worth taking to a mechanic with new shocks in hand? I'm at 80K miles with original shocks so it's time.

MaysEffect

You may have already bit the bullet on doing this.

But in either case, if you have the tools to do it, its a rather straight forward and relatively simple task to do. Having a lift makes it about 50% easier, but not necessary at all.

There are several tutorials and install videos online of doing it on stands in a garage, very few horror stories. Buying the tools necessary is equal too if not less than paying someone else to do it. And most of the cost comes from a good torque wrench and jack. If you buy the run of the mill harbor freight stuff you can get everything you need for under 500 bucks, which is the typical cost for a "professional" install, give or take $100.

The rear is significantly easier than the front as the damper and spring are divorced. The key to a easier install is to preload the lower control arm by using your jack under it and then loosen the bolts.
Before removing either the spring or shock, remove the ASB endlinks from either the control arm or ASB, this will reduce the amount of pressure from the opposing wheel.

Again probably already solved, but that amount of mileage does not warrant a change in dampers without internal damage. In the case of what Boss_302 suggested, this would not warrant tire bubbles or damaged sidewalls either. In most cases it would be from under-inflation (dropping below 30psi) or over inflation while hitting a bump at the right angle to pinch the sidewall or indent it. Bubbled on the inner sidewall usually comes from over-inflation and a bump hard enough to displace enough air to blow the sidewall out.

Without pictures it's all guess work.

Deteriorated piston seals and worn inner tube lining would increase oil flow. As Boss302 stated it would allow the tire to oscillate more and cause vibrations, but this would in almost all cases not increase the chances of tire deformations. This would come from either a compressed shim stack or blockage in oil flow, which is a increase in pressure. This mostly comes from the damper bottoming out and denting the piston shaft, jamming the seals and nuts securing the shim stack. The increased resistance would promote a harsher ride and reduce the ability of the tire absorbing and deflecting road shock. As a result, the tire sidewall is doing the job of the damper. Odds are if the damper is damaged, its from the damper bottoming out and pinching the flow of oil. Over time excess blow by will cause the ride to get softer and less controllable, but this will take a very long time, or extremely wavy and bumpy roads. And you'd have to hit every major bump.

This is all an assumption that the damper is actually damaged. Although it may compress without oil squirting out or making noises. A sign of damage is if you feel any sort of click or swift bump in any point of the compression and rebound when compressing it by hand. I'm going to say that this is not from damaged dampers considering you said both tires. I'm more inclined to believe this is solely tire related problem.

The s-tune(nismo) damper and the base model damper literally have the same valve and shim stack design, they differ in the fact the nismo version has a slightly smaller bumpstop and different spring rate and length. Buying the shocks without the springs would be no different than buying the base variant. An unnecessary increase in cost if any difference in price.

p.s - sorry for errors, i didn't proof read.