Transverse leaf spring question

[secondchance]

In summary, 90-91 had stiffer springs but softer shocks. 92-95s had softer springs with stiffer/faster shocks.

For those who are interested, article w/ link below is very interesting read:
http://www.corvetteactioncenter.com/...fx3/index.html

Site Administrator - If I am breaking the forum rule by the above link, please edit.

[WVZR-1]

Originally Posted by secondchance

In summary, 90-91 had stiffer springs but softer shocks. 92-95s had softer springs with stiffer/faster shocks.

For those who are interested, article w/ link below is very interesting read:
http://www.corvetteactioncenter.com/...fx3/index.html

Site Administrator - If I am breaking the forum rule by the above link, please edit.

It's an interesting read but then you need to consider the source. Halverson - oh well! He publishes what he's paid to publish.

It still doesn't negate the possible + to the increased spring rate. Halverson's #'s for his suspension parts are numbers he was supplied with from production specifications, you don't think there were manufacturing tolerances? A '91 spring is 23 or 24 years old and your ''94 spring is just a couple years younger maybe. If you want to know what the '91 spring actually is "NOW" get it checked! Answers maybe all of your questions.

I believe it's being way "over thought" - had the later spring not had the pedestal type cushion at the control arms you would have had the job "done" and been telling us about the things you really enjoyed about the change.

[Hib Halverson]

Originally Posted by WVZR-1

It's an interesting read but then you need to consider the source. Halverson - oh well! He publishes what he's paid to publish.

Actually, I was not paid for that article on the CAC web site. I decided what was published and am responsible for it's accuracy.

"WVZR-1", if you're aware of any incorrect information in that article, so I can correct any mistakes, please post the errors and your documentation to support them.

But even if I was paid for it–let me ask you "WVZR-1"–in your opinion, how would that impact the credibility of the content?

It still doesn't negate the possible + to the increased spring rate. Halverson's #'s for his suspension parts are numbers he was supplied with from production specifications, you don't think there were manufacturing tolerances?

There were, indeed, "manufacturing tolerances". In fact, the tolerances were so large that, during the earlier C4 years, frustrated with chronic differences in trim heights of cars with the same springs, GM finally divided each spring into three "groups". Then it developed the spring shims one finds on the front and rear spring mounts.

The spring suppliers were required to categorize each spring which met the initial specifications into three groups. Some were right at the specified spring rate, some were a bit below and some were a tiny bit above. The spring group determined the number of shims (ft.) or the location of the shims (rr). This system allowed the assembly plant to have all the cars much closer in trim height and was used for the rest of the C4 production.

Obviously, in the front, the ideal sitch is a car with 2 shims because pulling the shims out lowers the car by about 1/2-in.. In the rear a car with 2 shims above the rear spring is desireable because if you move the shims to below the spring you lower it in the rear by about 1/2-in.

[USAZR1]

VB&P told me they manufacture at least five springs at a time and that every one will have a different rate.

If removing both front shims only drops the front ride height 1/2" and will also lower the spring rate of an already soft spring,I probably should look at other lowering options for our 94.

[mike100]

Originally Posted by USAZR1

VB&P told me they manufacture at least five springs at a time and that every one will have a different rate.

If removing both front shims only drops the front ride height 1/2" and will also lower the spring rate of an already soft spring,I probably should look at other lowering options for our 94.

I consider 1/2" a decent drop. You could try flipping the shims to the outside and try it out without altering the bushing permanently (allowing you to go back). Technically you aren't changing the spring rate...just effectively changing the rate by unspringing it some with the initial tension being softer.

I think you get the idea from the way you replied, but I would offer that the shock stiffness on the front end of a c4 seems more critical to me than the spring- even on the ZR-1.

There seems to be only 5 options on transverse springs (for the front):
1) stock
2) stock bushing with shim(s) removed (less drop)
3) lowering wedge with shims
4) lowering wedge with no shims (slammed -->don't do it- cars is dangerously low and close to bumpstops. Also a gap between spring and frame when car is jacked up).
5) VB&P adjustable spring; this is much lower and even the taller setting is probably well into lowered ride height territory. Advantage is high spring rate for heavy LT5 and you don't need the special GM spring tool or have to remove an A-arm to install because it sits flat at rest (quick and easy install).

[Hib Halverson]

Originally Posted by USAZR1

VB&P told me they manufacture at least five springs at a time and that every one will have a different rate.

If removing both front shims only drops the front ride height 1/2" and will also lower the spring rate of an already soft spring,I probably should look at other lowering options for our 94.

While I lack the equipment to measure spring rates, I suspect that the difference in rates is not great enough to have an appreciable effect on handing but it is enough to have make a differenct in trim height. Also, it's possible that the degree to which the spring is arched may also play into this.

All I know if my 95 came with blue dot springs on both ends so I took all the shims out of the front and, and in the rear, moved all the shims to the bottom and got the car lower but not so low that I lack ride travel.

[USAZR1]

Thanks for the input,Mike & Hib. For starters,I'll probably remove the front shims and install longer bolts in the rear. The new 19" tires are about 3/4" or so taller so that will close up the fender to tire distance a little bit too,when I finally get them installed.

If that doesn't get the ride height where I want it,guess I'll go with the VB&P spring.

[Hib Halverson]

Originally Posted by USAZR1

Thanks for the input,Mike & Hib. For starters,I'll probably remove the front shims and install longer bolts in the rear. The new 19" tires are about 3/4" or so taller so that will close up the fender to tire distance a little bit too,when I finally get them installed.
.

No shims, front, two shims on the bottom for the rear and longer rear spring bolts is the set-up I use, but...

Be careful about lowering the car more than that because you'll run out of ride travel. Once the car's on the bump stops, ride sucks and handling goes away.

Also, be careful about using "fender to tire" distance as a measure of ride height. C4s had terrible build quality as far as body mounting and panel tolerances. That is the car to car variance was large. If you're going to accurately measure trim height, do it the way the Service Manual specifies. That's a lot more accurate.