Rear wheel hop above 35mph

[Oceanzide]

Hi,

I have a 240Z that, when it was being driven (10 yrs ago) had a terrible rear wheel hop/bounce at fwy speeds.  As i recal the wheel was balanced more than once.  I believe it's always the driver-side rear that hops.

If the problem is not the tire/wheel then Must it be half shaft universals? Is it possible the half shaft needs balancing?

BTW: i just got it running today using gas out of a jug.  Tires are all flat; I'm hoping gas tank Isn't full of rust!

Edited August 13, 2017 by Oceanzide
Clarification

[dutchzcarguy]

Sounds like worn shocks to me.. get some new rear shocks, also after ten year those tires have flat spots.. new or good used tires is something i would recommend also..  Normally half shafts are not in need of balancing as far i know..  They should be NO play in them..  check them thoroughly.

About the fuel, install a new fuelfilter, you can see through ..  then you can see if there is some crud in the tank.  Also revise your braking systems would be a good thing... 

[rcb280z]

Worn struts will cause wheel hop. Need to have them checked out. Does the back end sag a lot during acceleration?

[sweatybetty]

switch the "bad" tire to the other side. if it is the tire, the hop will be wherever you put the bad tire

[Chickenman]

You can a have a perfectly balanced " square tire" . It won't roll very smoothly though. Old tires that are sitting flat are a prime candidate for  hidden internal damage.  If they've been sitting flat for any appreciable length of time..... get new tires as others have mentioned.  Go through the whole suspension ( and brakes ) top to bottom. Plan on replacing ALL of the suspension bushings if they are still original. Beware of the Poly kits. They can cause more harm than good, particularly in the Tension Rods and Front lower control arms.

 

[Oceanzide]

Thanks Folks!  I need to get "her" back on the road before I can start testing these ideas.  First the carb-bowl gaskets need replacing (fell to pieces while un-sticking float/valve.)  After addressing/replacing tires and brakes, I'd like to have suspension looked at.  I used to live close to a German mechanic (might have been "Hanz") in West Covina CA, USA - I thought he was very good, but that was 15+ years ago!

Anyway, I'll try to post back if I find the cure for the wheel-hop.

Edited August 13, 2017 by Oceanzide

[Zed Head]

11 hours ago, Oceanzide said:

I have a 240Z that, when it was being driven (10 yrs ago) had a terrible rear wheel hop/bounce at fwy speeds.

...Tires are all flat;

You don't want to use those tires anyway.  They're too old, and they've been sitting flat so they'll have overstressed creased areas.  They'll probably all have a terrible wobble.

I had a flat recently on a 23 year old car, and after putting the original spare on I realized that it had leaked down over the years.  So I inflated it to about 50 lbs, so it would have pressure for another 23 years, and eventually put it back on the back of the car for future flats, after I replaced the flat tire.  The sun came out, the tread delaminated and it exploded, just hanging on the back of the car with no weight on it.  It only had about 20 miles total on it.  You've got age and "being flat" damage on yours.  

[gnosez]

Another cause for wheel hop is a loose or not even threaded on strut gland nut.

I have to take exception to the use of poly as a cause of issues with S30 body cars in any location, including the TC rod box (which is a ZX not a Z issue). I have either poly or metal to metal on my 240s without any issues at all but my concept of a harsh but very responsive ride is more than likely different than other folks. 

Other than the TC rod box non-issue, I would love to hear tales of poly that were not ride comfort related.

 

[Chickenman]

How is snapping TC tension rods a non-issue with Poly?

Plot the curve of the Lower control arm with a suspension program you'll see why Poly has a problem. The lower control arm does not travel straight up and down. It follows an Arc. That cause bind with Poly bushings. Rubber and Monoballs do not. Polly also has issues with Cold flow and "Stiction" .  Poly is not a good material for rotating assembles. Never has been and never will be.  Delrin liners or Teflon liners are far superior, but they can only be used in suspension arms that travel in a straight line, such as a double A-Arm setup. With suspension arms that travel in an arc you should be using Monoballs or rubber. You may not " feel "   or " recognise" the bind, but it's there and is detrimental to handling. 

Sources. Herb Adams, Paul Van Valkenburgh, Fred Puhn  and a host of other  Chassis engineers. 

 

[gnosez]

Snapping which TC rods?  On 240/260/280Zs or ZX?

I am still waiting on an example of poly TC rods causing an issue in an S30 body Z. I ran them for 5 years before switching to the Techno Toy Tuning TC rod version. I believe you have mistaken the issue with ZXs to encompass all Zs.

[Zed Head]

I had one break after using polyurethane on both sides of the mount.  There have been several stories about it over the years that I've been on the Z forums.  You commented in one I posted.  This thread is about a bad rear wheel bounce anyway..

 

[gnosez]

One last front suspension, "poly" question.

And were the poly installed TC bushings installed as per the specifications or just tightened too much? Either way, I know what I did when installing both sides with poly and then drove it hard for over 25,000 miles, I can't comment on what others did.