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Another vote for coilovers and "tuned suspension"

D

DET17

Reformed SAABaholic
Joined
Nov 1, 2009
Location
NW Georgia
Time for some testimony.

For the previous 10 years, I've run several lowering spring systems on my 940 sedan. The first rendition was IPD blue "sport springs" matched with Bils HD; this arrangement gave the car a sporty stance for sure, but underwhelmed on handling and suspension manners. The second rendition was B&G Progressive lowering springs matched with KONI Sports. This setup slightly outperformed the original in lateral handling but was worse mannered when encountering road disturbances.

The best, is definitely the last:




After resisting for nearly 10 years, I finally upgraded to coilovers from Kaplhenke Racing, with "old man" rates of 250F / 175R lb/in. My KONI Sports were retained and the rebound both front and rear have been set to the minimum. I did a fair bit of research on TB and elsewhere, and the 7/9 series KONI Sport fronts need spring rates in the range of 250 to 325 lb/in to be properly "tuned".

With an hour long test drive yesterday, WOW am I impressed!. Every road disturbance is met with a once & done response from the suspension..... just as the factory Engineers designed the system. I never realized just how poorly those lowering springs worked with the dampers that I chose, but I sure do now.

An eye opener for me a couple years back, was when I restored my 92 745T wagon to factory wagon springs and mated with the BILS HD which were already on the car, the difference from the previous lowering springs (removed) was amazing. That old wagon was the best mannered 7/9 series I had ever driven. To me, this was validation that the BILS HD were specifically designed to be mated with factory springs. They nailed it.

This testament is probably a yawner for the suspension sages on TB...... but I'm intending it for newbies who are considering suspension work and who are attempting to improve handling while NOT destroying road manners for traveling over disturbances.

Save your nickels, save your dimes, until you can afford a proper coilover arrangement. Then do your research to ensure the spring rates are a match to the dampers that you will run. The assembly of springs & dampers is a engineered SYSTEM........ not something to be haphazardly thrown together for the "stance".

There, I feel better now ;-)
 
and for those wondering about the stance:



My front Eibach XT barrel springs are 12 inch length; the rears are 13inch length. My goal was not lowering the sedan, but improving performance handling & suspension manners. Both coilovers are set for the lowest height possible (pictured above), so if you desire more lowering you will need the 10 inch front Eibachs and the 11 inch rears.
 
Last edited:
DET17 said:
B&G Progressive lowering springs matched with KONI Sports.

After resisting for nearly 10 years, I finally upgraded to coilovers from Kaplhenke Racing, with "old man" rates of 250F / 175R lb/in. My KONI Sports were retained and the rebound both front and rear have been set to the minimum.
Click to expand...

Thanks for the review, but sorry, there's some perspective missing.
Can you tell us what the rates were for the B&G springs?
And what settings were the Koni Sports set at with those springs?
Thanks, Dave B
 
dbarton said:
Thanks for the review, but sorry, there's some perspective missing.
Can you tell us what the rates were for the B&G springs?
And what settings were the Koni Sports set at with those springs?
Thanks, Dave B
Click to expand...

Dave, I never could find rate information for the B&G's. I bought them used from another TBer. About the only thing I could find online stated they would lower the vehicle ~ 45mm I believe.

KONI Sport damper rebound was/is set to the minimum settings front and rear. I tried the B&Gs with them set on #2, but it did not help the manners at all (from memory, I think they only have 3 settings for rebound). A few months back, a Euro initiated thread posted right here disclosed the factory specs for those dampers on compression/rebound.
 
DET17 said:
Dave, I never could find rate information for the B&G's. I bought them used from another TBer. About the only thing I could find online stated they would lower the vehicle ~ 45mm I believe.

A few months back, a Euro initiated thread posted right here disclosed the factory specs for those dampers on compression/rebound.
Click to expand...

Nope! I emailed Koni support and got the rates.

http://forums.turbobricks.com/showthread.php?t=356594

Honestly not so sure how useful these are without a shock dyno plot.

I think the wire diameter on the B&G springs (a copy of dealer option springs from back in the day, as far as I can tell) comes in at 14.7mm in the front and 12mm in the rear, but obviously is a progressive rate, losing up to 2(?) active coils as the suspension compresses. Progressive springs are often difficult to set up a damper around for this reason as your damping ratio changes during suspension action.

If the wire diameter I have is right the spring rates go from 143-230 in the front and 124-238 in the rear at the spring, or 140-225 front and 185-335 in the rear.
 
DET17 said:
7/9 series KONI Sport fronts need spring rates in the range of 250 to 325 lb/in to be properly "tuned".
Click to expand...

Ok, so then maybe we can surmise the weird progressive spring rates were just not compatible with a proper tune for Koni Sports.

Question: For highway cruising, does it feel like the new springs are noticeably stiffer that the old B&G's?
Dave
 
Just because some lowering springs have "dead coils" doesn't mean in end use they are actually progressive, They usually just do that to pass TUV inspection which frown on having loose springs when lowering the car.

Testing the spring in the stroke that is used in the vehicle is the best way to know for sure if its a linear or progressive rate spring.

Mikep would be the best to give us answers about this.
 
I like the graphing that we were able to do in the past for that reason. I am not able to do that now, so any checks i do are limited to my scale. If i get a load cell i can do a little better testing at home, but i’m hoping to have access to the computer testing again some day.

I haven’t seen these b+g springs, but if the stackable wire coils are almost touching when unloaded, they’re just placeholders, like you say.
 
mikep said:
I haven’t seen these b+g springs, but if the stackable wire coils are almost touching when unloaded, they’re just placeholders, like you say.
Click to expand...

KONI sports at full extension, with B&G's installed. Don't think I ever took a pic of them in the front with the sedan suspension "loaded".



Free length comparison, B&Gs vs. Eibach XT:

 
Those aren?t progressive. They look softer, since the overall diameter is large, same free coil count, similar wire size.
Side note, when i measure wire size i measure painted thickness i find a chip in the paint (or make one at the end) to compare. If it?s say, .010? thinner without that chip, i subtract .020? from the full paint measurement. I like to do the math even if i measure them on my scale and/or the spring rig, and i compare several online calculators. I haven?t done the long math in a while, but i might. It?s fun to find errors.
 
Hi DET17,

you stated "This testament is probably a yawner for the suspension sages on TB...... but I'm intending it for newbies who are considering suspension work and who are attempting to improve handling while NOT destroying road manners for traveling over disturbances."

and that's a nice gesture, so concerning I'm a suspension newbie can you provide us with a part list from the 2 pictures of your starting post?

You did the struts yourself as I can see but what parts are in the tower etc. and did everything came from Ben?

Also do you stil have the luxe steer attached as seen in a later picture.

Cuz I stil only have this :(

coilover-3.jpg


Thanks in advance,

Chilm.
 
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