Z51 vs FE1, how do I tell the difference? Purchased springs.....

[MarshallDillon]

Last year I purchased what I believed to be a set of standard FE1 springs, front and rear, from a custom shop. My 86 has the Z51. I removed the front spring today, and compared it to my new purchase.
They look identical. There is no number on the purchased front spring, but there is a number on the back spring. It is BM_004236. I cannot read the letter of the underscore. Is this the FE1 spring? Looks the same, feels the same. Jump on it and it resists the same. I hope it is not the same. Help or comments please.

 

[vetteoz]

On the underside of the spring there should be a 3 letter code stamped

That is the definitive spring code for ID purposes

My 86 has the Z51. I removed the front spring today,

If the original '86 Z51 spring that spring should be coded HMZ

there is a number on the back spring. It is BM_ .
I cannot read the letter of the underscore.

The available spring code listings are much disputed but the only year showing with a code starting with "B" is 84
Nearly all '85+ rears codes start with "N"

The base '84 springs were used as the Z51 rear springs for later years so rear would be identical rate to yours

 

[MarshallDillon]

I believe the front spring that I removed today was an HMZ, for sure HM. So, this newly purchased spring may be a spring from another year. Where do I find a chart with spring codes????

 

[boomdriver]

I believe the front spring that I removed today was an HMZ, for sure HM. So, this newly purchased spring may be a spring from another year. Where do I find a chart with spring codes????

Look right here in the knowlege base section. Your front springs are very limited. The differences are between convertables and coupes mostly. The usual difference in Z-51 or base or Z-52 will be rear springs and sway bar type/size/diameter. The range in springs from the rear run from 499-lb/in to around 266 lbs per inch.
I installed a 411(i think it was) and that thing won;t flex with anything less than a cow sitting on the tail....its stiff. Most vettes that were z-51 after '84 were in the 300-400 lb per inch range. 499(in 84) was almost solid and caused a ride like a covered wagon on a washboard. Miserable at best. The stiffer the spring the flatter the arc. The more the arc, the softer and more comfortable.
See the C-4 suspension chart for details. Most rear c4 springs can be interchanged. Fronts, you just don;t get any choices.

 

[Hib Halverson]

The front spring for FE7 (the suspension which goes with Z51) is coded BMB. The rear should be NYU.

 

[MarshallDillon]

Well, that was a lot of work. There must be a lighter spring somewhere. The rear spring for sure did come lighter, somewhere, right? At least I can check the arc to determine stiffness. The front spring I purchased has the identical arc of the one I removed. So, it is identical from what I am reading here. All I wanted to do was to soften the ride up a little. From what I have been reading here on the forum, shocks do not make a big difference. I have KYB's now, which are in good shape and came with the car.

 

[boomdriver]

Well, that was a lot of work. There must be a lighter spring somewhere. The rear spring for sure did come lighter, somewhere, right? At least I can check the arc to determine stiffness. The front spring I purchased has the identical arc of the one I removed. So, it is identical from what I am reading here. All I wanted to do was to soften the ride up a little. From what I have been reading here on the forum, shocks do not make a big difference. I have KYB's now, which are in good shape and came with the car.

I apologize.....I was mistaken about the chart here. It does NOT contain the various spring rates and codes.....just the rates or stiffness in one of a couple methods of labeling.

Below is a copy of the chart that has the codes to match the spring weight/speed. There is a softer rear available...shocks DO have a little to do with it, as they dampen the ride. The first sensation that the road gives you is the shock...the remainder of the suspension action is more what the spring is doing....allowing lots of travel or very little. The flat springs barely move while the big arc moves like an archers bow.

Note the ID of each spring and then note the #per inch.
Then look at that ID over the various years to determine which are compatable with other cars besides your yr model. You will see the same rear on many different yr models. Hope this helps.
here is a link to the chart location. Not sure if that will work....below is part of the chart. I tried to copy/paste but it wants to un-align itself when pasted.
http://f1.grp.yahoofs.com/v1/ABYzTfD6E17-UCQ89HiLviPAZIA9OhCB1hauXNVR3KtIerc6063eQ2jxe1pb6qCtroItY3BU5LY_pqhSakbk/Leaf%20%28fiberglass%29%20Springs%20/C4%20%281984-1996%29%20Corvette%20Composite%20Leaf%20Spring%20-%20data.txt

FRONT SPRINGS | REAR SPRINGS
Year RPO N/mm #/inch I.D. GM part | N/mm #/inch I.D. GM part
---- --- ------------ ---- -------- | ------------ ---- --------
1984 FE1 63.5 362 HMZ 14106617 | 72.0 411 BMF 14045705
1984 FE1 66.5 379 HMZ 14106617 | 72.0 411 BMF 14045705
FE7 102.0 521 BMB 14045782 | 87.5 499 BMH 14045786






1985 FE1 54.0 276 HKX HMP 14094458 | 39.9 228 ...?1........ - not microed - NYR ?? RCA
FE7 63.5 362 HMZ 14106617 | 57.2 326 NYU 14080196
FE7 66.5 379 HMZ 14106617 | 57.2 326 NYU 14080196




1986 CPE FE1 51.8 261 HMP 14094458 | 39.9 228 NYR 22112253

FE7 63.5 362 HMZ 14106617 | 57.2 326 NYU 14080196
FE7 66.5 379 HMZ 14106617 | 57.2 326 NYU 14080196
CNV FE1 54.4 278 HMN 14094457 | 39.9 228 RCA 14106787

 

[boomdriver]

Well, that was a lot of work. There must be a lighter spring somewhere. The rear spring for sure did come lighter, somewhere, right? At least I can check the arc to determine stiffness. The front spring I purchased has the identical arc of the one I removed. So, it is identical from what I am reading here. All I wanted to do was to soften the ride up a little. From what I have been reading here on the forum, shocks do not make a big difference. I have KYB's now, which are in good shape and came with the car.

Also, watch your shims carefully in the center mount rear spring...each spring has a different shim requirement. Those little aluminum 2 bolt mounts break, real easy...so the shim(s) have to be near a perfect fit. Those can be found at vette stores and flea-bay. Inexpensive but necessary.

 

[Hib Halverson]

If you want to "soften" the ride, you need to do two things
1) Install base level springs
2) Install the shocks that go with the base suspension
3) Replace the Z51 front lower control arms with arms from a base car.

Also, the earlier discussion about spring shims is somewhat inaccurate. Spring shims for C4s were not specific to springs. They were used to set trim height. In the front, shims are not required, thus, if you want the front lower, just take out all the shims.

In the rear, the shims must all be installed but you can vary the locations of the shims to control trim height. For example, if you want the rear lower, you move shims from the top to below the spring.

 

[boomdriver]

If you want to "soften" the ride, you need to do two things
1) Install base level springs
2) Install the shocks that go with the base suspension
3) Replace the Z51 front lower control arms with arms from a base car.

Also, the earlier discussion about spring shims is somewhat inaccurate. Spring shims for C4s were not specific to springs. They were used to set trim height. In the front, shims are not required, thus, if you want the front lower, just take out all the shims.

In the rear, the shims must all be installed but you can vary the locations of the shims to control trim height. For example, if you want the rear lower, you move shims from the top to below the spring.

Ride height was not my concern....rear spring mounting gap was.
There is a chart floating around somewhere that shows how many shims (size in MM) go with each rear spring (over or under,don't matter) since they are all different thickness they all have different requirements for secure mounting at the point of contact. Change to a different spring and I can assure you that different shims will be required to make the fitment correct. Loose mounts have rebound issues, poor return and give a "pounding" sensation to the suspension. A loose spring causes slapping impacts and lots of noise, and eventually leads to a broken spring.

When the brackets are bottomed out on the carrier base, the shims should not be loose enough to move. Tight enough to be solid without having to go more than the 37 lb/ft of torque to cinch the bracket bolts down. The rubber on the spring itself will compress some to absorb maybe 1mm. That rubber is fairly solid, so the shims either over or under the spring should be exact to avoid future problems. Ride height comes 2nd to suspension integrity IMHO.

A spring that is cinched too tight in the mount usually ends up breaking the aluminum mounting bracket when its over-stressed from tightening. The rubber portion of the spring should be snug with the brackets seated fully against the base of the mount. The torque for the mounting bolts is only 37 lb/ft. The point at which the bracket will break from uneven load on shims that are too thick is somewhat less than that...:ugh

I will post that chart if I can find it.

 

[MarshallDillon]

All extremely interesting. The springs I purchased are both front and back "BMA". The front spring that came out is HLA I think. Damn, I wish I would write stuff down. I'm damn near 56 and I can't remember a thing. I can type, though.......

 

[MarshallDillon]

If you want to "soften" the ride, you need to do two things
1) Install base level springs
2) Install the shocks that go with the base suspension
3) Replace the Z51 front lower control arms with arms from a base car.

Also, the earlier discussion about spring shims is somewhat inaccurate. Spring shims for C4s were not specific to springs. They were used to set trim height. In the front, shims are not required, thus, if you want the front lower, just take out all the shims.

In the rear, the shims must all be installed but you can vary the locations of the shims to control trim height. For example, if you want the rear lower, you move shims from the top to below the spring.

Can I fit the base spring into my current lower control arm? If not, then not. I am willing to source the whole thing if I can find it. I would think that if a recycler can supply me with springs, he/she should be able to sell me the lower control arms as well. Then it would be a matter of getting a compelmentary shock, and I know you guys would point me in the correct direction.

 

[MarshallDillon]

I apologize.....I was mistaken about the chart here. It does NOT contain the various spring rates and codes.....just the rates or stiffness in one of a couple methods of labeling.

Below is a copy of the chart that has the codes to match the spring weight/speed. There is a softer rear available...shocks DO have a little to do with it, as they dampen the ride. The first sensation that the road gives you is the shock...the remainder of the suspension action is more what the spring is doing....allowing lots of travel or very little. The flat springs barely move while the big arc moves like an archers bow.

Note the ID of each spring and then note the #per inch.
Then look at that ID over the various years to determine which are compatable with other cars besides your yr model. You will see the same rear on many different yr models. Hope this helps.
here is a link to the chart location. Not sure if that will work....below is part of the chart. I tried to copy/paste but it wants to un-align itself when pasted.
http://f1.grp.yahoofs.com/v1/ABYzTf...96) Corvette Composite Leaf Spring - data.txt

FRONT SPRINGS | REAR SPRINGS
Year RPO N/mm #/inch I.D. GM part | N/mm #/inch I.D. GM part
---- --- ------------ ---- -------- | ------------ ---- --------
1984 FE1 63.5 362 HMZ 14106617 | 72.0 411 BMF 14045705
1984 FE1 66.5 379 HMZ 14106617 | 72.0 411 BMF 14045705
FE7 102.0 521 BMB 14045782 | 87.5 499 BMH 14045786






1985 FE1 54.0 276 HKX HMP 14094458 | 39.9 228 ...?1........ - not microed - NYR ?? RCA
FE7 63.5 362 HMZ 14106617 | 57.2 326 NYU 14080196
FE7 66.5 379 HMZ 14106617 | 57.2 326 NYU 14080196




1986 CPE FE1 51.8 261 HMP 14094458 | 39.9 228 NYR 22112253

FE7 63.5 362 HMZ 14106617 | 57.2 326 NYU 14080196
FE7 66.5 379 HMZ 14106617 | 57.2 326 NYU 14080196
CNV FE1 54.4 278 HMN 14094457 | 39.9 228 RCA 14106787

Can't get that link to work with Google, but that link is one I agree I need. I am making headway thanks to the good people here.

 

[vetteoz]

Can I fit the base spring into my current lower control arm? If not, then not. I am willing to source the whole thing if I can find it..

Yes.
Only the bushings were different
Only a front spring from '84 -'87 will fit
A rear spring from any C4 will fit your car.
FWIW, just swapping out the big Z51 front sway bar makes a big differences to ride quality

 

[MarshallDillon]

Yes.
Only the bushings were different
Only a front spring from '84 -'87 will fit
A rear spring from any C4 will fit your car.
FWIW, just swapping out the big Z51 front sway bar makes a big differences to ride quality

Ok, I understand that the base 84 became later years Z51, so I need a base spring from an 85-87. I just betcha that if I find that, I can find a smaller/less stiff front sway bar as well. Thanks to all the great posters here, progress is being made!

 

[MarshallDillon]

Well, I reread the option codes under the console storage compartment. It says quite clearly, "Z52". This is the base suspension I guess. So, in my age-addled brain, I confused Z51 with Z52. Here is my front spring number:

HLA 009491

So there it is. That is the base suspension, right?