Thread: Coilovers / Spring Rates - Need Advice!

I'd go with a 400# spring, they ride about the same as Eibachs. As for struts go with Konis, Bilsteins, something nice like these. As for a revalve it is $180 a piece for Konis.

Originally Posted by matt5112

That site is wrong.

Bilstein does not sell B8's for the W body.

They sell comfort and heavy duty valving B6's.

B8 is designed for lowering springs, typically work well with the H&R springs. Namely they have a slightly shorter rod, say 20-40 mm.

If you're serious about Bilstein coilovers, fill out this form: Fat Cat Motorsports - Consultation form, new monotube suspension, shocks and coilovers

But note it's going to cost you $50 for consultation, and the coilovers will be somewhere around 2500. Maybe.

I bought KYB Sports for my car, I really hate them. I'm contemplating going that route, at least for the front.

The other option would be to buy a set of bilsteins, and have them valved by a local shop, and put them together yourself.

Also bilstein offers revalving and shortening of the rod.

Expect to pay 70-150 for valving per shock, 50-80/per for shortening IIRC.

Thanks for all the very helpful info. I'll be sure to do more research on these routes before I commit to something. This Pontiac will go lower eventually!

Originally Posted by Sandman

I'd go with a 400# spring, they ride about the same as Eibachs. As for struts go with Konis, Bilsteins, something nice like these. As for a revalve it is $180 a piece for Konis.

How does a 400# coilover spring ride like 200# lowering spring? Is it because the coilover spring is skinnier?

It's because of the diameter of the spring 5' coils like the oes factory equipped don't need the same amount of strength rating as 2.5 inch coils do. The less area of spring the more lb/in rating

Originally Posted by 91parkave

It's because of the diameter of the spring 5' coils like the oes factory equipped don't need the same amount of strength rating as 2.5 inch coils do. The less area of spring the more lb/in rating

Hmm. I'm starting to understand this better.

It's all in the shape of the spring. I don't understand it to much either.

Originally Posted by Sandman

It's all in the shape of the spring. I don't understand it to much either.

Yeah, I was really confused becase my b+g front spring rate is 170-180ish, and I thought a 300# spring would be more than enough for going down another half inch. I thought everyone was crazy about going 350-500# stiff.

Wait what are you guys claiming?

That double the spring rate rides the same because of the shape?

Sway bars add a lot more spring rate than you'd think: Automotive suspension engineering - Sway bar spring rate formula

All spring rate does is prevent weight transfer.

Sway bars have the unfortunate effect of reducing traction on the axle by lifting the inside wheel.

So one might think it'd be ideal to go all spring rate, less sway bar. You'll want to make sure your struts are up to the task.

Here's an example, it makes up for half of the wheel rate: http://forums.nasioc.com/forums/show....php?t=1279944

Originally Posted by carcrobatics

How does a 400# coilover spring ride like 200# lowering spring? Is it because the coilover spring is skinnier?

Eibachs are also progressive. that makes a difference

OP--I have coil overs on the front only on my 03 GTP. I got a kit directly from HT Motorsport. I used KYB excel g 339015 struts as they are designated 'special handling package' replacement for GM FE4 (& they're about 1/2 price of AGX). It's been a year and I love the struts. My DD gets lots use and abuse, especially from BAD roads. I started with 350#, and just couldn't handle it. Then tried 275#, and they were set as high as possible and I still only had about 1-1 1/2 finger gap. They were comfortable, but just too soft. Now I have 300#, and I am sticking with them--as long as I live in Chicago (when ever I road trip--I understand why people go stuffer). Very happy with ride and handling. I have about 1 1/2 fingers clear in front w/ zero pogo, and lots of room to go lower. In Cali, you probably enjoy great roads, so 350# is probably a good place to start. IMHO, I imagine 400# being quite stiff, more than most would want for a DD. If you get springs from HTM, you can choose in 25# increments, and not much difference in feel stepping only 1 rate--maybe this is where the AGX are worth the money--depending on how aggressive you want to be, 325#-400#, then dial AGX up or down to suit you taste/need. Good luck!

Originally Posted by Mr D

OP--I have coil overs on the front only on my 03 GTP. I got a kit directly from HT Motorsport. I used KYB excel g 339015 struts as they are designated 'special handling package' replacement for GM FE4 (& they're about 1/2 price of AGX). It's been a year and I love the struts. My DD gets lots use and abuse, especially from BAD roads. I started with 350#, and just couldn't handle it. Then tried 275#, and they were set as high as possible and I still only had about 1-1 1/2 finger gap. They were comfortable, but just too soft. Now I have 300#, and I am sticking with them--as long as I live in Chicago (when ever I road trip--I understand why people go stuffer). Very happy with ride and handling. I have about 1 1/2 fingers clear in front w/ zero pogo, and lots of room to go lower. In Cali, you probably enjoy great roads, so 350# is probably a good place to start. IMHO, I imagine 400# being quite stiff, more than most would want for a DD. If you get springs from HTM, you can choose in 25# increments, and not much difference in feel stepping only 1 rate--maybe this is where the AGX are worth the money--depending on how aggressive you want to be, 325#-400#, then dial AGX up or down to suit you taste/need. Good luck!

Thank you very much for the information! Richard from HTM is going to set me up with KYB AGX's paired with a 400# spring to start out with, we'll see how that goes soon enough!

Originally Posted by carcrobatics

Thank you very much for the information! Richard from HTM is going to set me up with KYB AGX's paired with a 400# spring to start out with, we'll see how that goes soon enough!

For the money though you might wana consider going diy coilover route

People judge ride comfort differently. I've got 500# spring and I think they ride just fine. Then again FL has great roads compared to other places I've been to.

Originally Posted by Sandman

People judge ride comfort differently. I've got 500# spring and I think they ride just fine. Then again FL has great roads compared to other places I've been to.

My friend who has a Mazda3 hatchback runs 10k springs upfront and 8k at the rear. I love the ride of his car.

What is that in lbs/in? I have no idea how the metric ratings would feel.

Originally Posted by Sandman

People judge ride comfort differently. I've got 500# spring and I think they ride just fine. Then again FL has great roads compared to other places I've been to.

I believe it! Im going to order some 500# springs. 350# is way to soft for these boats...

My god I just stepped up to 450# 10' springs but same ride height as the 12' 350# rides way better.

I did about the same thing. I'm not sure if it's the springs length or the rate...\

I went from a 12" 400# to 10" 500#

hmmm maybe ill get some 10" 450#......