Sway bars vs spring rates.

[Retoropak]

I am ready to upgrade suspension in my m10t e21.

I have a billy sports with bavauto springs right now.

My plan is to use a1 sleeves and do the coilover conversion and revalve the billys.


I know the spring rates alone were discussed multiple times however there was not a lot of discussion on swaybars vs spring rates.

Would it be better to run more spring without the rear sway and stock front?
Or maybe go with less spring and more swaybar?

Thanks




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[autox320]

I am ready to upgrade suspension in my m10t e21.

I have a billy sports with bavauto springs right now.

My plan is to use a1 sleeves and do the coilover conversion and revalve the billys.

I know the spring rates alone were discussed multiple times however there was not a lot of discussion on swaybars vs spring rates.

Would it be better to run more spring without the rear sway and stock front?
Or maybe go with less spring and more swaybar?

Thanks
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I went all the way down this road. I used the GC basic kit with 4 springs of choice and sleeves. Had several different springs testing it out. The billys can handle up to 400 lb springs for a couple seasons, but you'll eventually yes want to revalve. Definitely trim the bumpstops on the front inserts. These are inside by knocking off the bottom silver cap edge with a screw driver. Trim to a single knuckle and tap the cap back on.

I ended liking 350 lb springs up front with stock sway bar. Rear 400 lb springs with no bar. This was with an LSD rear end to btw. Had the larger ST (suspension techniques) bars at first then when adding coil overs they just didn't work as well. A lot has to do with the front end design being part of the bar. Yes it keeps it flatter handling but it's binding. Also if ride height is too low in the front you'll contact the control arms to the subframe giving infinite rate ie terrible push.

Rear ST bar was ok but it too binds since the ends and how they line up with the adjuster hole you choose. The bind there caused the car to have to much rear steer cause again infinite rate when binding. If change the link style to a heim could probably use it.

Bars should be considered as fine tuning suspension after the spring rates are right. Too much front bar just adds more spring etc.

Food for thought.

[Retoropak]

I went all the way down this road. I used the GC basic kit with 4 springs of choice and sleeves. Had several different springs testing it out. The billys can handle up to 400 lb springs for a couple seasons, but you'll eventually yes want to revalve. Definitely trim the bumpstops on the front inserts. These are inside by knocking off the bottom silver cap edge with a screw driver. Trim to a single knuckle and tap the cap back on.

I ended liking 350 lb springs up front with stock sway bar. Rear 400 lb springs with no bar. ........

Food for thought.

Awesome. I was waiting for you to chime in. I knew you had some experience dialing in e21 suspension.


Do you remember what spring lengths and sleeve lengths you were using?





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[autox320]

I've actually forgot, but can measure them for you when back to the garage. Cause it's the ones on my build

[autox320]

Awesome. I was waiting for you to chime in. I knew you had some experience dialing in e21 suspension.


Do you remember what spring lengths and sleeve lengths you were using?





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hey man,
7" springs and 4" sleeves at all four corners

[Retoropak]

hey man,
7" springs and 4" sleeves at all four corners

Awesome.

Time to order some parts



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[sonomaGTLN2]

Here's something I posted in another thread a few years ago...this setup has suited me well with Turbo M42 up front and auto crossing on BFG G-force staggered tires.

I use GC coilovers and camber plates with 300#F/350#R on Bilstein sports. Anything over 400 and it was too much for the Billie sports, IMO. With staggered tire setup, I leave the rear iS swaybar attached (stock 320i front sway), but with same width tires I leave it detached. I've taken the car on 500 mile trips and while it's not riding like a Cadillac it's at least bearable, even with a fixed back Momo seat. I have beaten Evo's, Mustangs, and M3's (with the help of my turbo setup of course!) with this suspension setup.

It's amazing how much even the puny iS rear sway can do to the tail happiness. It was literally the difference between being able to drift my car controllably on non-staggered Falken Azenis to being neutral to the point of where I wanted a little more oversteer!

[OLD MAN]

We have ended up at the other end of the spectrum with our M20 track car.

Car is used mostly for auto-x with LOTS of quick tight turns.

We have -
GTI front Bilstein sports up front re valved for 550lb springs and 550lb springs = no push ever and hardly ever any over steer. As Judy said the front sway bar is also part of the front control arm positioning design and needs to flex inside the lower control arm where it goes through it. So we do not run polyurethane bushing in the arms. I have made medium rubber washers 3/8" thick and have one in the front of the arm on the sway bar and one in the rear. These help limit the control arms front to rear movement on the sway bar and do not bind up as much as the polyurethane bushings do, this binding adds to the spring rate of the front bar to much for me. Up front we run a S T big sway bar.

In the rear we ran E21 Bilstein sports with 325 or 350lb springs with no rear sway bar. I have tested three different bars - but even with the stock E21 sport bar the rear gets to tail happy to drive. We have tried rear springs up to 450lbs and always come back to 300 or 325lb springs in the rear.

We can run 8" or 7" springs - I like the 8" better as they do not drop out of the top hats as much as the 7" ones do.

Now we run Bilstein 2way adjustable race shocks in the rear - still getting them figured out.

AS2- 3.jpg AS2- 11.jpg

Ride height is very important - do not go to low as suspension arm angles are really important to offer all handling. And then there is the problem of bottoming out on the frame.

Video of car in some slaloms

http://public.fotki.com/makofoto/201...-cs/c0088.html

[OLD MAN]

With the rear springs we have found the car is way more driveable and quicker in the corner if the inside front tire in a turn comes up off the ground a LITTLE.

[sonomaGTLN2]

OLD MAN, do you run camber plates in front or slotted subframe in rear?

[Retoropak]

With the rear springs we have found the car is way more driveable and quicker in the corner if the inside front tire in a turn comes up off the ground a LITTLE.

Oh boy those double adjustable billies looks sweet. Do they have the universal struts to match?


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[jaredmac11]

Oldman, is your car an early model? If its an early Did those ST sways go in OK or did you convert to the late control arms?

Eventually (when Im looking for a new project) I'd let to beef up the front sways.

[autox320]

Now we run Bilstein 2way adjustable race shocks in the rear - still getting them figured out.
AS2- 3.jpg AS2- 11.jpg

Daryl; Have a part number for those bad boys? Also what rates are they valved for? Price per shock? thanks

shock eyecandy btw

Just helped a buddy setup his E36 with full race koni setup from GC. Another buddy runs MCS on his spec car E36.

[OLD MAN]

OLD MAN, do you run camber plates in front or slotted subframe in rear?

I have both GC front camber caster plates and slotted rear toe and camber using elliptical washers.

I have also raised the rear subframe up in the car by about 1 1/4" or so. I also cut the suspension mounting points off the rear subframe and made my own that move the mounting points for the suspension up higher by 1/2".

Had to remove rear drive shaft tunnel shielding and parking brake tubes to make room for the front of the diff. Also had to notch the rear cross brace on the body that the rear diff hanger bolts to for the rear of the diff.

room for drive shaft 4.jpg raisedrear2.jpg IMG_3360.jpg

[OLD MAN]

Oh boy those double adjustable billies looks sweet. Do they have the universal struts to match?


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Not that fit into E21 strut assemblies - would have to do some custom fab I think.

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Oldman, is your car an early model? If its an early Did those ST sways go in OK or did you convert to the late control arms?

Eventually (when Im looking for a new project) I'd let to beef up the front sways.

Ours is a later 1979 model, so it has the newer front suspension pieces on it.

[OLD MAN]

Daryl; Have a part number for those bad boys? Also what rates are they valved for? Price per shock? thanks

shock eyecandy btw

Just helped a buddy setup his E36 with full race koni setup from GC. Another buddy runs MCS on his spec car E36.

I have had them valved twice now - both times were included with the price of the shocks. Just had to pay shipping. First time was for 400lb springs and with the 400lb springs the car just did not rotate at all. So had them revalved for 350lb springs. Bilstein Motorsports says they valving is good for springs 75 to 100 lbs each way.

Pt.# is ?? They build the shock to your specs Non-adjustable, single adjustable or double adjustable - so the bill has 4 pt number lines breaking down the parts in my double adjustable shocks.

Shocks are in the AS2 line - mine have a 5" stroke and are 16" extended eye to eye. The length and travel can be had different if wanted.

You want to call and talk to the techs at "thyssenkrupp Bilstein of America" Mooresville, NC for on road shocks.

I looked at Koni for shocks alot bout at $1,300 a piece or so I just could not get them, these Bilsteins were close to $1,000 for the pair.

[m60b30530i]

Front I am running vw billie sports 400lb springs - This is my new setup for the front, last year I ran Koni yellow race inserts with 450lb springs. But I found out that my drivers side strut tube was bent.

Rear is qa1 racing shocks with 325lb springs and no rear sway bar.

[Retoropak]

This is awesome. Great job everybody. I think we should extract and summarize the data from this thread and make it a sticky.

So far it seems that autocross/street spring setups range between 350-450lbs. The front/ rear rates will vary slightly depending on the sway bars, valving and amount of tail happiness that the driver is willing to deal with.


Also it seems that 400lbs is max that the stock valving bilsteins sports will take.

I guess ill start with 350f and 400r no rear swaybar and see where its at.




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[autox320]

Front I am running vw billie sports 400lb springs - This is my new setup for the front, last year I ran Koni yellow race inserts with 450lb springs. But I found out that my drivers side strut tube was bent.

Rear is qa1 racing shocks with 325lb springs and no rear sway bar.

Part number for the QA1's? Was browsing them too when ordering all the heims etc during the build. I swear I thought Daryl was using QA1 in the rear too? After seeing the billy's a bit confused

- - - Updated - - -

with the 400lb springs the car just did not rotate at all.

I find that odd not wanting to rotate better than 350's especially with a 500 or so on the front. Maybe to do with the geometry front and rear why that works better.

[sonomaGTLN2]

This is awesome. Great job everybody. I think we should extract and summarize the data from this thread and make it a sticky.

So far it seems that autocross/street spring setups range between 350-450lbs. The front/ rear rates will vary slightly depending on the sway bars, valving and amount of tail happiness that the driver is willing to deal with.


Also it seems that 400lbs is max that the stock valving bilsteins sports will take.

I guess ill start with 350f and 400r no rear swaybar and see where its at.

What size tires and brand/model do you plan on running?

[OLD MAN]

What size tires and brand/model do you plan on running?

Use to run Hankook RS2 - 3s and Hankook Z214 70s tire sizes were all 225/40-15 on 7" wide Kosi K1s

Currently running 15x9" rims with Maxxis Victra RC-1 slicks - which take for ever to warm up. tire still 225/40-15 trying stretched tires. Thinking about trying some Hoosiers next.

- - - Updated - - -

I find that odd not wanting to rotate better than 350's especially with a 500 or so on the front. Maybe to do with the geometry front and rear why that works better.

I do not know why - all I know is it turns way better with stiff front spring and softer rears. It is way more predictable this way and we can drive it really hard and not have the rear end come around. And if it does swing out it is recoverable.

I like to tinker with suspension so we have tried a lot of ways and keep coming back to this set up. The picture of the track car below is on the day Adam was the fastest BMW at the San Diego BMW event on Hankook Z214s - but it is the first session on the RS2s and it had just rained and I am driving in this shot....


ALSO: The video I shared above is with the new Bilstein rear shocks and 425lb rear springs, the car looks good but was not. We had to be careful in all the corners as the rear was always feeling on the edge of coming around. We do not have that locked in feeling we have with the 325 or 350lb springs in the rear.

Our car (chassis) is really stiff so the springs and shocks do everything we do not have any natural body flex/give. Car weighs in at 2330lbs with 8 gals of fuel and me in it, I am right at 210lbs. The rear of the car is about 220lbs lighter then the front.

[Retoropak]

What size tires and brand/model do you plan on running?

Kuhmo ecstas v720 205/50/15 and 225/45/15


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[sonomaGTLN2]

Kuhmo ecstas v720 205/50/15 and 225/45/15

Cool, I think you'll find the rearend is more planted with that staggered setup (I am also running 205F/225R on 15x7 and 8 respectively)...it's the whole reason why I added the iS swaybar to mine because I wanted the rear to step out a little (predictably) to help point the car on the exit of higher speed turns. Definitely give feedback to this thread when you drive it hard the first few times!.

I have a little stretch in sidewall on my BFG's, but not much...but I think "gives" a little less when under higher lateral loads which seems firmer to me than the Azenis 195s on E30 iS basketweaves (or it could just be the difference between 14 and 15" wheels).

[Retoropak]

Cool, I think you'll find the rearend is more planted with that staggered setup (I am also running 205F/225R on 15x7 and 8 respectively)...it's the whole reason why I added the iS swaybar to mine because I wanted the rear to step out a little (predictably) to help point the car on the exit of higher speed turns. Definitely give feedback to this thread when you drive it hard the first few times!.

I have a little stretch in sidewall on my BFG's, but not much...but I think "gives" a little less when under higher lateral loads which seems firmer to me than the Azenis 195s on E30 iS basketweaves (or it could just be the difference between 14 and 15" wheels).

I have 8" fronts 9" rears. It is a bit too much stretch. But i will use it this season.

Next summer hopefully i will finish my e36 front suspension swap to go along with my e28 rear.




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[m60b30530i]

Part number for the QA1's? Was browsing them too when ordering all the heims etc during the build. I swear I thought Daryl was using QA1 in the rear too? After seeing the billy's a bit confused

- - - Updated - - -

I find that odd not wanting to rotate better than 350's especially with a 500 or so on the front. Maybe to do with the geometry front and rear why that works better.

https://www.summitracing.com/parts/HAL-DS501

No longer available, QA1 has a new line of shocks. I have run these since 2015, will probably get the Ultra ride coil over shocks when these finally quit. The length I ended up with was 17in fully extended and 11.6in collapsed. This worked well, I modified a set of upper shock mounts to bolt the upper joint in. Now I am running a e30 rear sub frame and actually could use a shorter shock. Or just helper springs to stop the springs from shifting when jacking up the car.