FIX ILEAN (she leans too much)

[BigIke]

Guy my 91 leans to the left (drivers side) hard. I've read that the C4's lean but this looks silly to me. Measurements are

- front right - 27" - After backing off castle nut 26-9/16"
- rear right - 28-5/8" - After backing off castle nut 28-3/8"
- front left - 26-1/2"
- rear left - 27-1/4"

I backed the castle nut off the right rear (high side) about 1/2", until it was flush with the bolt, and it lowered the rear about half that much, and lowered the front 1/8th or so.

The rear mounts look to be in good condition. Is this a rear spring fix usually or both? Think i can get a longer bolt for the front?

Pics with the castle nut backed out... at night, give day pics tomorrow if needed.

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https://scontent-a-ord.xx.fbcdn.net/hphotos-xpa1/v/t1.0-9/10616162_967745339905462_346732781556494488_n.jpg? oh=740987cfceab413976b468ed98d15675&oe=54B0C2AC

[Blue Flame Restorations]

Check your rear spring extremely well. It my be delaminating and be fractured. Also, spring bolts should be tightened at the same length.

[We Gone]

That's more of a lean than I have seen. Not sure what castle nut you are referring to on the front I don't know of any way to ajust the front without removing the spring.

If I'm not mistaken you would need to tighten the nut to raise the car longer bolts lower. I would do some more investigating as to why it sits that much out of level.

Check the rear spring for de-lamination or splitting on the low side would be the first thing to check. I'm sure others will post up also as to what may be the issues.

[mike100]

While my car did not have that much lean, I did flip the spring around 180 degrees to see if it was due to fatigue on one side...nope- it would appear to be batwing bushing sag or similar.

(I did adjust the preload on the spring bolts to level it out some)

[randy ransome]

I've been told it can also be something in the front of your car causing it, or a combination of front and back.

My 95 leans and I haven't been able to solve it.

Good luck

:proud:

[BigIke]

Regarding the Front Castle Nut..

I was talking about backing off the right rear castle nut and seeing it lower the right front 5/16, and the back 1/4... Looks like the rear is jacking the front up... Might Just put a longer bolt in the rear and see what it does. Make sure that it doesn't jack up the camber.

[We Gone]

BigIke, I understand now yes adjusting the rear will effect the front. Be sure when you are checking the body levels your doing so on a level surface. Also to do this correctly there are points on the frame to make these measurements at you can't go just by measuring to body panels. These points and measurements are listed in the FSM.

[BigIke]

No matter where it is parked, you can maybe get your hand in the left side (driver); on the right side, you can put your whole arm in there! LOL Maybe i'll get off my tail and jack it up tomorrow :)

[5ABI VT]

Im wondering if it could be dried up control arm bushings possibly? something not letting it settle

[Dynomite]

Is it the Front or Rear Suspension causing this. I would jack it up on center (Front) and see if it still leans. Then jack up the center (Rear) and see if it still leans. Once you determine which is the cause, Drive the High Side Tire (Front or Rear) on blocks to see if you can do some twisting back into shape.

It might also release some twisting stress loosening the C-Frame Bolts on the level. I would NOT release the C-Frame bolts with one (Front or Rear - Left or Right) wheel on blocks. Make sure the Transmission is back in alignment with the chassis after loosening the C-Frame Bolts.

Loosen the Hard Top just in case there is some twisting when you do some checking.

Just a thought :p

[Paul Workman]

A very interesting topic! LEAN is a common enough occurrence with these cars to warrant a TECH article. A teensy bit to a major list, seems MOST have a little. I myself have dealt with it on my 95, and now I've got a wee bit on the Z. A comprehensive article would be oh so good. Brett????:happy1: (JK...sorta)

IF someone(s) want to PM me with the nuts and bolts (so to speak) of a process for leveling these cars, I will be more than happy to write it up (about all I can contribute to this topic, unfortunately).

Any volunteers??

[Karl]

I am about 1/2" higher on the passenger side. Seems like coil overs are the cure.

I personally hate that!

[We Gone]

My 93 has 1/4 inch difference, higher on the right. The 91 was the same but I made an adjustment to the rear spring bolts (I have the longer bolts with the nylon lock nut) I had to tighten the left up about an inch to get it level.

I'm sure this may upset the cars stability in some way due to the torsional twist on the frame and I may not leave it.

Note: All measurements were done to body panels and not to the FSM trim height locations.

[USAZR1]

Our 94 was a little higher on the right front before I installed the VB&P adjustable spring. With its threaded adjusters on each side,ride height on either side is easy to change & fine-tune. I also installed a pair of 11" long 14mm rear spring bolts that I purchased at my local Fastenal store,for $24/pair.
Presently have the front ride height at 26 1/2" and the rear at 27".

[batchman]

With the stock setup (ie no front C5 style adjusters) if you lower the right rear you will primarily raise the left front - adjustment works in an "X".

HTH,
- Jeff

[BigIke]

Well... I believe the issue is in the back; when i lowered the back the front lowered substantially. I went to Fastenall today in Conroe and thought I needed a 9" bolt, they only had 8" and 10".

Anyone know how long the stock bolts are? If the 10" will work I'll go back tomorrow and buy it.

I know this is not the FIX, however, I think this will get me by and stop being so lopsided, mine leans a lot.

[Blue Flame Restorations]

I believe you are only fixing a symptom of the real issue by experimenting with bolts. The lean is there for a reason.

Check that rear spring, especially at each of the center mounting area. There is a good chance that the spring is fractured and failing, which could lead to an unsafe condition.

Food for thought.

[BigIke]

I absolutely get that, but i don't see/feel any issues externally..

https://scontent-b-ord.xx.fbcdn.net/hphotos-xpf1/v/t1.0-9/10446348_937409322939064_5627477676066614578_n.jpg ?oh=ca0c05ed89334e8af695d914c647c23f&oe=5473E7A0

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[Blue Flame Restorations]

You may have to un-mount the spring to get a full inspection. You only have bushings and the spring itself that would cause this condition. Other than these items, you would have to have a suspension component failure happening.

Not sure if an internal rear shock failure would cause your condition.

[John Boothby]

I had my rear torsion bar links and bushings replaced and it seemed to have leveled the rear.

[WVZR-1]

I believe if I thought I had a "lean" I'd use the chassis trim dimensions in FSM section 3 as a guide and do my measurements based on those reference points. I'd do it this way if I felt I had a "straight & level" floor. The dimensions for J & K depending on year are going to be 180mm + to 190mm +. I'd cut a gage using maybe 2" PVC conduit 175mm long and then measure from the rocker to the gage and add that for a dimension. I believe it easier to measure from the rocker to the gage vs. trying to measure to the floor. You could use a metric ruler maybe 150mm long. If you measure 9mm to the gage then you would have a 184mm dimension.

To do Z and D in the FSM I believe I'd start with a 40mm gage and measure again to the gage. For Z & D I'd use the front control arm bolt and in the rear the camber bolt centers.

Use the FSM dimensions only as a guide, make sure the tire pressures are equal and if you wanted to get real testy put a live body or weight in the drivers seat.

I have never measured a C4 this way but I've done others in this fashion. Don't be concerned with matching the FSM dimensions, your just trying to establish the status of the chassis.

With so many different wheel/tire combinations dimensions will vary widely but you would like equal/similar side to side relationship at all points.

If these dimensions are far from equal/similar then you've got potential issues and maybe it would be wise to hang some gages to confirm some dimensions in the FSM using section 10-3.

If you've a really lowered car adjust the height of the PVC gages.

Anyone know how long the stock bolts are? If the 10" will work I'll go back tomorrow and buy it.



Rear spring bolts are 192.5mm long on '90 MY cars and for '91+ cars I believe they're 225mm long. I'm quite sure that's an "under head dimension". The bolts are M14 X 2.0. Factory bolts should have likely 30mm of thread.

"BATCHMAN" (Jeff) is correct when mentioning that tampering with right rear should affect left front, left rear would affect right front.

[We Gone]

Stock bolts 9 and 1/4 overall and 8 and 1/2 to the cotter key hole.

http://imageshack.com/a/img537/5202/Zlwomw.jpg

[BigIke]

What I didn't do was measure right vs left (post castle nut adjustment), however, I did measure right side before/after lowering the castle nut and saw a visible and measurable difference. There wasn't a visual difference on the left (low) side...

I'll got back to Fastenall tomorrow and get the 10" bolt, maybe an 11" also and play with it. If i see any issues while i'm under there i'll address them properly.

Thanks y'all

[Vette Guy]

Before you go too far, try isolating the front and rear suspensions.... i.e., jack up the front equally and see if the lean to one side remains..... or jack up the rear from the diff and see if your problem is in the front.

"HIZNHRZ" had this same problem for a long time, he even switched the spring around and finally discovered that the rear lean was a front suspension problem.

Regards,
Mark

[BigIke]

I hear that!

The bolt should show me, but i did get a result moving the right rear castle nut, and seeing the right front lower from 27" to 26.5625 and the rear went from 28.625 to 28.375.

Front diff - .4375
Rear diff - .248

Now this was all takin at the same spot on the fender well, not quite scientific but a result none the less.

Lowering the rear caused the front to drop more that the rear. BOLT TOMORROW :)

When i grow up i want my junk to look like USAZR1's!

PS - Mark LOVE THE HEART OF THE BEAST! Just posted a pic about it on the C4 Facebook page...

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[Vette Guy]

I'm sure you'll have it squared up soon! As for the Heart of the Beast, it's our membership's quarterly publication... I think you'd enjoy it!

Here's a peak at October's cover.....

[batchman]

Given the "X" nature of height/weight you should probably check your front spring for damage. That could be the root cause. Best done on a drive-on lift or ramps - you need to see what's going on with the suspension loaded.

Good luck,
- Jeff

[Karl]

Our 94 was a little higher on the right front before I installed the VB&P adjustable spring. With its threaded adjusters on each side,ride height on either side is easy to change & fine-tune. I also installed a pair of 11" long 14mm rear spring bolts that I purchased at my local Fastenal store,for $24/pair.
Presently have the front ride height at 26 1/2" and the rear at 27".

How do you like the VB&p front adjustable spring? Do you have to remove the wheels to adjust the front?

Any feedback is appreciated.

Thanks!

[USAZR1]

How do you like the VB&p front adjustable spring? Do you have to remove the wheels to adjust the front?
Any feedback is appreciated.
Thanks!


I haven't driven the car very many miles since its installation but so far,I really like it. The spring rate is 950lbs so the front end feels firm and tight.
Adjusting ride height is easy,just take the load off the spring on each side,and turn the threaded rubber bumper/adjuster by hand. VB&P offers three adjuster options: short,medium,or long. I went with the medium length and it seems to be the right choice. There is approximately 2 1/2" of adjustment available either up or down and ours are close to the middle of the range.
Taking the wheels off for adjustment isn't necessary. I didn't do so.

[Karl]

I haven't driven the car very many miles since its installation but so far,I really like it. The spring rate is 950lbs so the front end feels firm and tight.
Adjusting ride height is easy,just take the load off the spring on each side,and turn the threaded rubber bumper/adjuster by hand. VB&P offers three adjuster options: short,medium,or long. I went with the medium length and it seems to be the right choice. There is approximately 2 1/2" of adjustment available either up or down and ours are close to the middle of the range.
Taking the wheels off for adjustment isn't necessary. I didn't do so.

Would you happen to know the factory spring rate?

[USAZR1]

Would you happen to know the factory spring rate?

IIRC,the factory spring rate on my stock 94 spring was 430lbs.

[csavaglio]

Here is the ever helpful C4 suspension chart...

http://www.corvetteactioncenter.com/tech/c4/susp_chart.html

The rates are in n/mm and can be converted to lb/in here...

http://www.convertunits.com/from/pound/inch/to/N/mm

I checked a few of the numbers against the Corvette Specs book, which shows a mix of lb/in and N/mm depending on year and the match using the converter.

Anyhow, stock rates on a '91 ZR-1 is 549 for the front, 228 for the rear. '92 is 431 and 188.

Chris

[gbrtng]

Before you go too far, try isolating the front and rear suspensions.... i.e., jack up the front equally and see if the lean to one side remains..... or jack up the rear from the diff and see if your problem is in the front.

"HIZNHRZ" had this same problem for a long time, he even switched the spring around and finally discovered that the rear lean was a front suspension problem.

Regards,
Mark
Mark is getting close here - I would begin by finding a shop that has four load cell pads so you can check the actual weight on the ground of each wheel. Stock car racers use them to set stagger - you are looking for which end of the vehicle is causing the problem. If both front wheels and both rear wheels are close in load, each end may have to be adjusted. If two diagonal wheels are light, something else might be wrong. It sounds like your vehicle was owned by a heavy fellow who never had a passenger, and the springs on both ends have sagged over the ages. A competent shop with 4 load cells can point you in the right direction before you start throwing parts at it. YMMV, Glenn