ride height / spring question

[u3b3rg33k]

Long story short - I have new billy HDs, and 25 year old stock springs.

ALL rear bushings, save the RTABs are new, and I got a 2nd opinion (after buying the AKG RTABs) that told (and showed) me that my RTABs are still serviceable, yet I get wheel hop when it's wet or in a few inches of thick snow. Shocks don't feel blown out (but I don't have a shock dyno, and if I pull the rears out and drive up and down my driveway it feels like a cigar boat on a windy day).
I believe I need new springs (possibly with an HD friendly (slightly higher) rate, and want to maintain my current ride height (measurement pending upon return from work). "Suggestions" that I should lower my car are not welcome, thanks.

I've been searching around, and I've found a thread with a list of spring rates, but not related ride heights. I do not want to drop it due to winter / rallyX use, but I'm under the impression that (at the very least) my tired OE springs are no longer matched to new HD shocks.

if this works:

Rear
6" 2.5ID 500 lb/in GC springs on H&R perches, all the way down.
Bilstein Sports
24.125"

my understanding is that sports are within 10% of HDs, so doubling the rate makes me think that I'm way under sprung.

I don't do much with suspension, other than wish it were better, and replace bits when I know it's broken - so don't be gentle folks.

[jeffnhiscars]

The main difference between HD's and Sports is just the length. There are a range of replacement springs from reputable suppliers that are not "lowering" and would pair up nicely with your HD's.

[jlevie]

Wheel hop is caused by low spring rates and/or too little compression damping by the shocks. I doubt, with new Bilstein HD's on the car that those are to blame. So the most logical cause would be the spring rates of the OE springs which are pretty darn low. Unfortunately for your purposes the springs that have better rates will mostly lower the car. H&R OE Sport springs at 180/380 might be a better choice as compared to OE springs at 106/245 and won't drop the car much. As a point of comparison H&R race springs, which do drop the car a lot have rates of 315/570. Turner J-Stock or coil overs go much higher.

Though costly, a properly configured set of coil overs could keep the ride height and get the needed spring rates.

[u3b3rg33k]

OK, that jives with what I was thinking, so I'm glad to hear similar logic come from someone else.

Internet rumors have told me that old springs often sit lower than new ones, so depending on the actual length of newer springs with a higher rate (like H&R OE), I'm hoping to achieve as little drop as possible.

Coil overs is not something I really want to spend money on right now. If I'm gonna do those, I'm going to want really good ones, and then $$$$$$$...

[bmwguy325is]

As you had in your first post in the quote. I Would get the hardware to run race diameter springs. http://www.vorshlag.com/product_info...3db18f4298dcab IE 2.5 inch springs then you can buy the right hight springs and get some spring pads of varied thickness.

[einstein57]

Or buy the rear coilover setup only. Its not that expensive

[u3b3rg33k]

I was looking at that vorschlag kit. Won't not replacing the front springs to match make the car feel all weird, and under steer like a pig? or something else? what happens when you have that much difference in effective spring rate?

[bmwguy325is]

I was looking at that vorschlag kit. Won't not replacing the front springs to match make the car feel all weird, and under steer like a pig? or something else? what happens when you have that much difference in effective spring rate?

No not if by the a stockish spring rate. Hyperco makes down to a 175 spring so I am sure you can match the rate.

[u3b3rg33k]

But isn't the stock rate borderline too low for HD shocks anyways?
or is that only the case when they've been aged for 25 years?

[u3b3rg33k]

I'm genuinely curious now, what happens if you have stiff rear springs and soft/tired front springs? does the car attempt to kill you?

[akorcovelos]

I've never had mismatched springs like that, but I would guess it would increase understeer.

If you that concerned about ride height you could some H&R sports and shim the bottom of the springs with thicker spring pads.

[E30_fiend]

This is a legitimate question. Before you installed the new shocks, were they by chance laying down for a long period of time before the install?

The reason I ask. I have had an experience once with bilsteins in particular where they were laying BRAND NEW in the trunk of the car they were to be installed on, for about a week before the install. So I installed the new rear shocks along with new IE3's all around. About a week or two later I noticed while driving behind the car that the rear of the car was moving up and down in a very odd manor.

Knowing that the shocks were new, I suspected bad bushings. After the lengthy install of ALL NEW rear bushings, the bounce was still there. I was stumped. So I called bilstein. They informed me that their shocks need to remain vertical for at least 24 hours before installation. Their reasoning was that the oil in the shocks would VERY slowly move past the seals internally which in turn screwed the valving of the shock.

I'm not saying this is your problem. But just because they are new, does NOT mean they should be ruled out as a suspect in your problem.


Taylor

[u3b3rg33k]

I've had them in for about a year or so, and the problem showed up in the last 6 months, so I'm leaning towards that not being the problem.

I've never had mismatched springs like that, but I would guess it would increase understeer.

If you that concerned about ride height you could some H&R sports and shim the bottom of the springs with thicker spring pads.

OE sports are probably the route I'll take, possibly with an extra pad (definitely new pads).

[TobyB]

Springs do sag with age, but the rate in almost all cases stays the same. It's just the
ride height that goes away...

t

[u3b3rg33k]

Might as well bump it with the results -
new springs have solved my wheel hop in the rain issue (can't testify to the effects in the snow yet but I feel it's safe to say that problem has been abated as well).

Car worked fine with new rear springs and old fronts, but something just doesn't feel right (might be the lo-ridah stance?).

Complete, the car sits a little lower, and now my hacked together exhaust scrapes noticeably. I have since ordered headers from korman, and called a fabricator for the rest. It's nice being able to kick the tail out in the rain without feeling like the subframe wants to take a vacation.