Why are Bilstein Sports so ROUGH!?

[six2midnight]

Ok update on my project.

Background. Car had Bil sports with GE engineering (group buy here) coilovers with 450/650 springs respectively. My thoughts...I hated them. way too bouncy and rough ride. I have had bil sports on all my e30s and they have all been rough. This is why I created this thread and this is what I did.

- I bought e30 koni SA shocks for rear
- I bought 92 VW corrado koni SA shocks for front (because im on coilovers with a spring that is only 6" long I wanted to use a shorted shock housing. Bil sports blow in about 6 months in coilovers because its not meant for that).

Replaced the rears first and went for a ride. (I did not adjust them at all. I believe factory setting is full soft). Note I also put in brand new Rear shock mounts. Went for a ride. with the konis in back and bil sports up front. Immediately noticed a difference. way softer damped, and even took out a lot of the rattles I had in my car. was very please, but ride still sucked.

Next replaced the bils up front with the VW corrado shocks (these are what GC uses on their coilovers, at least what I was told when I called GC (yes GC does do a custom valve, but its pretty close)).

Went for a ride with the setting on completely soft. Honestly....rode a little better but still jarring on these roads in Greenville SC. I was a bit disappointed. I then cranked the rebound in front 1 turn (50%). This helped out immensely. Def recommend turning up the rebound a little if your KONIs are still jarring at full soft. I think this is because of the 450lb springs up front. They are too stiff.

So with all the konis, its better but not nearly where I want it for a comfortable driver. I suppose its ok if I just took it out on the weekends in the mountains, but I want to drive this during the week to save some gas.

SOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

My next step....well I started researching a little more about suspension and crunching numbers. I then started looking into natural frequency of the springs (nerd alert). OEM automakers try to make the natural frequency of the springs come in at about 1.5Hz for a comfortable ride. Some sports cars get up to 1.9-2.2Hz, which is getting into the jarring territory. Race cars then go 2.5-4Hz...but they are on a race track and need it.

I crunched some numbers and got the ball park figs, and found out the 450lb springs up front are coming in at around 2.3Hz for my e30 (OUCH!), and the 650lb springs in back at around 1.9Hz.

So if my experiment is correct, the front springs need to get OUT of there. Way too harsh of a ride for a daily driver.

I am going to be ordering 300lb springs, which should give me a natural frequency of 1.9Hz. This is still a little harsher than OEM 1.6 but will match my rear. I also cant go completely soft 1.6Hz, because im lowered and id probably be smashing everything.

**note I am running coilovers with 2.5" diameter springs on all 4 corners.**

[LJ851]

^ How much suspension up travel do you have at the ride height you are running? 300 lb is softer than H&R race....


I have run H&R races with koni SA (stock length strut housings) for years and there definitely is not enough up travel available for a good ride on roughish pavement.

[six2midnight]

Well from what I read, H&R Race are 315lbs in the front...so 300lbs is probably negligible. Plus I cant find a 2.5" coil spring that is 315lbs. They usually run in 50lb increments. Also remember H&R race are H&Rs most aggressive spring. H&R sport is only 180, and stock is around 110.

I was looking more at getting the natural frequency of the spring correct, not the rate. Im using whatever rate gives me the best frequency. This isn't a race car, its a street car. I have a e30 race car too that is set up for track use.

I also have coilovers so I can adjust my perch up and down. right now there are 5" springs up front (I know super short), which is why the perch is cranked almost all the way up.

Im ordering eibach 7" coil springs in 300lbs.

I have not measured up travel, but its plenty since, my shock is probably compressed more than it should be since im lowered. Ive also never had a problem with the spring popping out of the upper top mounts, like if it was too loose.

[TrentW]

So how are you guys tightening the strut gland nut? I found the special socket, but also considering using a pipe wrench.

[nando]

pipe wrench always worked just fine for me.

[six2midnight]

Agreed. 24" pipe wrench from harbor freight is the best tool

[jeffnhiscars]

I'm fond of my 18" aluminum pipe wrench for this. Weighs 1/3 of the steel version and does the same job.

[TrentW]

Round metal spacers go under the strut nut?

White plastic washer sits on top of strut nut if using bumpstop?

Use non-sport bumpstops?

Cut down bumpstops?

What is this "pre-adjustment" I read about?

(I like pictures) ;)

[nando]

put the spacers at the bottom of the strut tube. make sure the gland nut holds the struts tightly without them moving.

[TrentW]

Thanks Nando.

Pre-adjustment is for rears so that's done.

You guys running bumpstops? Thinking I may run without. Car is never driven in rain and stored winters, avoid potholes, so what's the point?

[Luke_M]

My next step....well I started researching a little more about suspension and crunching numbers. I then started looking into natural frequency of the springs (nerd alert). OEM automakers try to make the natural frequency of the springs come in at about 1.5Hz for a comfortable ride. Some sports cars get up to 1.9-2.2Hz, which is getting into the jarring territory. Race cars then go 2.5-4Hz...but they are on a race track and need it.

I crunched some numbers and got the ball park figs, and found out the 450lb springs up front are coming in at around 2.3Hz for my e30 (OUCH!), and the 650lb springs in back at around 1.9Hz.

So if my experiment is correct, the front springs need to get OUT of there. Way too harsh of a ride for a daily driver.

I am going to be ordering 300lb springs, which should give me a natural frequency of 1.9Hz. This is still a little harsher than OEM 1.6 but will match my rear. I also cant go completely soft 1.6Hz, because im lowered and id probably be smashing everything.

**note I am running coilovers with 2.5" diameter springs on all 4 corners.**

I have read that to get an even more comfortable ride you should strive for a frequency that is approx 10-20% higher in the rear compared to the fronts. 1.9Hz in the front and 2.1Hz in the rear for instance. The basic idea is that the rears had to "catch up" to the fronts since the fronts see the bump first. I've thought about experimenting with this since I was not pleased with my 440/650 GC setup comfort wise. Here are a couple of videos discussing the same thing.

https://www.youtube.com/watch?v=ZR0W0XyxN_Q

https://www.youtube.com/watch?v=KpTN8Viau-I

However, I recently raised the car quite a bit and have noticed that it's much much better. I did get new tires the very next day after I raised her but it's the same old falken 615k's and I did not notice much improvement last time I got new tires. It's taken a lot of the rattle and harshness out. Still not perfect but I have 17" wheels and fairly stiff springs. I'm in love with my suspension again :)

I'm still interested in getting a better frequency and maybe controlling roll more with roll bars. Maybe some 16" wheels would help as well. It all adds up in the end.

[nando]

Thanks Nando.

Pre-adjustment is for rears so that's done.

You guys running bumpstops? Thinking I may run without. Car is never driven in rain and stored winters, avoid potholes, so what's the point?

Run them up front. Ive never ran them in the rear, haven't had an issue and i ran them like that for almost 15 years.. Prretty sure i will have coil bind before they bottom out anyway.

[TrentW]

Use the sport bump stops?

[itsonlygeorge]

What's the frequency, Kenneth?!


Sent from the woods of Maine.

[TrentW]

Can someone tell me wtf is going on?

I wanted to assemble struts today, but the gland nut won't fit with the inserts. Car is an "is" so I ordered the non-sport part # cause I knew the Bilstein style won't fit. Filled with 2 tbls ATF and slid in the Koni insert, put spacer on top of insert-but this happened. Do I need the other hex style gland nut?



Even with the spacer removed, the nut won't thread far enough in.