IanM

Hey guys,
After a bit of spirited driving this weekend, I've come to the definite conclusion that this winter's project will be to overhaul my suspension. I presently have a stock M030 Koni setup and 28mm/22mm adjustable Weltmeister swaybars. Around high speed sweeping corners, my back end lifts up and wants to oversteer, and the whole car feels "floaty" and unsettled (especially when trail-braking, or lifting off throttle mid-corner).

I'm thinking of going to either 250# or 300# front springs. I'm leaning towards the 300's, but I'd like to get some feedback from those who've "been there done that". I don't want too harsh a ride, but I'm also looking for a noticeable improvement over my current setup. I'd like to do some DE's, track days, and a little AutoX in the future.

Okay, so what rear torsion bar goes with the 250's and 300 fronts? 28mm solids? Would I need 29mm's with 300's?

Regarding the Koni yellows. Would they need revalving to be used with either of these spring combinations? Or is it just a matter of stiffening up the damping a bit? I might look at replacing my rear shocks with new ones, but I'd like to know if I can just stick with the same Koni yellows, or if I need to revalve for the stiffer springs?

Skip - I'd very much appreciate your input regarding these questions. You also once mentioned to me that when the t-bars are being replaced, I might consider Racer's Edge Delrin outer bushings and Weltmeister Poly-Graphite inner bushings. Is this a highly recommended upgrade for mostly stock cars like mine? How would that affect both ride quality and handling?

Thanks!!

ian

Really the difference between 250 and 300 lbs is not going to make or break the ride quaility of the car. The valving of the shock will determine that.

On my old 951 I had 300 lbs up front and coil overs in the back, and when I dialed the ledas to full hard the car was very very stiff. But If I went to full soft it was just as compliant as a stock suspension, ok maybe a little more bumpy, but not much.

The new setup (not in the car yet, come on UPS hurry up) is 450 lbs in front, I'll let you know how they feel, but after riding in Dave Salama cars I know that I can handle the 450 lbs, he has 500 in front and the ride is not too harsh. But then again we all have different thresholds at which we are willing to drive.

TaboII

Ok My .02

I have just completed the front suspension upgrade to the 88 turbo setup along with the Weltmeister 250 AutoX pings on Sach stock touring struts. The ride diff is extremely noticeable “Stiff” and the cornering improvement in incredible! Like I was on rails. The rear does lift with only the stock turbo sway and springs as well as wants to get loose. So this winter I plan on correcting this. I don’t have experience with 300lbs springs in the front but I wouldn’t recommend it for a street/AutoX car, it would be uncomfortable IMHO.

DanD

I started with stock 86 springs. Very soft, confortable..

I moved to MO30 front and rear. Ride quality decreased, felt most bumps. Koni Yellows

I have 400# coilovers on front with 300# plus 25.5 torsion bars on rear. Still the same Koni Yellows on front. Surprizingly, the ride didn't deteriorate much. It's still quite confortable at highway speeds. It tends to bounce around on poor city streets. 100mile trips in racing seats still don't wear out this old body. <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />

Skip

Hi Ian - welcome back!

If you're willing to do the T-bars, I'd recommend the jump to 300# (or even 350#). Keeping the 25.5 t-bars and going to 250# front is an option, but with the power you put down, and the complaints you have, it seems a T-bar upgrade is really needed. General rule I go by is: 250-300 = 28 rear, 300-350 = 29 rear, 350-400 = 30mm rear, and so on. If you plan on keeping the car plump (no weight reduction), I suggest the higher t-bar (i.e. 300 = 29 rear, instead of 28 rear). 350# starts to get into a gray area for overall comfort - *most* folks consider 400# too harsh for street use (I agree, and this is what I have - though, my car is just barely street worthy)

Regarding your specific suspension: Because you are starting with M030 struts, you are a candidate for front revalve trade-ins (8742-1007S - made double-adjustable for bump and rebound, custom valving for rates up to ~600#, which predicates starting rate ~300#). The standard rear Koni sport is an okay match, but consider the Koni 3012 coil-over race shock as the best match (can be run with or without helper spring... so, another option is to leave the 25.5 t-bars, index them, and match a helper spring to the 3012). If you are confident that your Konis are in good shape, it is entirely possible to leave them as-is, and simply add the appropriate spring hardware to the front (perch adaptor, spring, hat)

Regarding the bushings - Since last we talked, RE has finished Delrin bushings for both the inner and outer spring plate areas. Disregarding the slightly increased cost over Weltmeister, this really is the best overall setup to ensure crisp handling in that area (and, Delrin is not prone to squeaks - as Welt Poly-Graphite is... a major consideration for street cars).

Good Luck!

Robby

This is a big question for me too- been thinking about for a long time, but things keep getting in the way...

My street Turbo S, stock w/~160K, gets floaty in corners too especially over small expansion joints in curves- then I feel a harsh jolt and it gets disconnected & floaty- not very reassuring. My bushings & shocks are shot- car normally wants to understeer- hard to get it to oversteer- IF I'm trying to that is

I'm debating b/t Koni/Bilstein (K/B)- most I've asked recommend B. I've also been told, even by SOME K people, that K's don't last as long. Not sure- just repeating what I've been told. I've never been in one of these cars w/a decent susp- stock OR modded- wish I could ride in one w/either to get an idea...

Some of the recommendations I've received...

Chris Cervelli: B- 250-300lb/29mm w/Turbo S bushings & 968M030 sways- I told him I wanted to stay ~250- he still recommended 29mm's. I'm a little leary of oversteer- I KNOW he can handle it, but I'm not so sure about me- especially for street...

Skip- didn't really make any definate recommendations, but rather gave me a headache w/the myriad of options out there Seriously, he mentioned things I didn't know existed. He seemed to lean towards 250/28 w/MY K (revalved, made dbl adj)- said I might do just shocks first (maybe w/front springs) to see how the rate feels, BEFORE t-bars. ALL very good advice- I may do that, but I hate to do shocks only, since I'll do the rest eventually anyway, but t-bars are a bitch- I'd HATE to make a bad choice!

Danno: similar, but w/B- said B would have a larger range than K- meaning that while K has more range due to adj, their range at any one adjustment is less than B overall range. Ex: to get K as compliant as B, I'd set them soft- at soft setting, car would be soft for bumps, but wouldn't be as tight or flat on smooth ground and vice versa- at least that's how I understood him- may be wrong. He said B is monotube & K is twin, that mono is slightly more versitile for street apps. Again, I'm not claiming this myself, AND, I MAY be misquoting slightly, so if I'm wrong, please do not jump on him for it...

My mechanic's a B man too and confirms everything Danno said...

I'm not sure how re-valving K would effect things when comparing to B...

I'd love to have some more input on this- I want a nice compliant ride but firm enough to be responsive and hang well. I want a firm everyday car that I can be comfortable in, AND, that females can be comfortable in- I don't want it so firm that girls wont get in it anymore b/c it's "too bumpy" Hey, I don't get enough action to be gambling like that

I want it to feel more like an E36M3- I know it's impossible due to the multi-link susp, stiffer chassis, etc, but I think I could get close- definately make it outhandle stock M3 on smooth roads. I just love the way M3s can transition b/t rough & smooth pavement and handle both so well. I even rode in a friend's w/H&R coil-overs- he had twice the spring rate, harder bushings, etc- BADASS! It was STILL much smoother over bumps than my car and would run circles around it on smooth- of course, M3's could out-handle 951's (even S's) in most situations stock vs stock, were slightly faster to ~145 or so- wherever that short-*** 5th redlined- I think the Turbo S would STILL top out faster even if the M3 had real gearing- who knows- unfortunately, about the only thing you can do to make an M3 accelerate faster is add forced induction, wheras simple chips are enough to make a 951 blow it away...

So, I'm leaning towards 225/27- may be soft, but 27's would allow me to run up to ~275 w/out really needing more rear, and, I can always go 250 - 275 w/out much hassle- IF I want to go higher, I can add helpers- doubt I'll want to do t-bars again. BTW- I'm getting HOLLOW t-bars- not much more and I've been told they have slightly better ride quality- not to mention the slight weight savings, albeit at the wrong end of the car- still deciding on shocks though- might flip a coin- either way, I'll keep the K- send them for re-valving & dbl adj to keep for future projects if necessary...

Last thing- bushings- I decided on Turbo S bushings long ago. Cervelli and several others warned against PolyU- noisy & short life. Not sure about Racer's Edge or Delrin, but I thought RE's were spherical bearing(?)- if so, they would make the ride harder & noisier. I HAVE been toying w/the idea of solid front strut bushings though- not sure if they would make the ride much harsher or noisier- any input on that anyone?

Ken D

Lots of great advice, as usual! Another resource to check out is

<a href="http://http://www.davidsims.ukgateway.net/944t/suspension.htm" target="_blank">web page</a>

I found it useful on more than one occasion. HTH!

Robby

Trying to edit some small mistakes- screwed up- sorry...

Ken D

sorry, try this??<a href="http://www.davidsims.ukgateway.net/944t/suspension.htm" target="_blank">davidsims</a>

Randy_J

Thanks Ken - I forgot about that site - really good information on 944 suspension tuning.

M758

[quote]Originally posted by Robby:
<strong>
[snip]
So, I'm leaning towards 225/27- may be soft, but 27's would allow me to run up to ~275 w/out really needing more rear, and, I can always get 250 or 275 springs w/out much hassle- IF I want to go higher, I can add helpers- doubt I'll want to do t-bars again.
</strong><hr></blockquote>

If you are going with 225# fronts then stay with the stock rear t-bars. It is alot easier and with the right sway bar & ride height settings you can keep the right balance. If you want 250# then 28MM bars are good. Remember if you add helpers you still need to re-index the t-bars to get the proper ride height.

You also may only need shocks. On my race car I ran it for a while with 250lbs springs and 28 mm bars and DEAD SHOCKS... Car was fine unless I used the curbs. Then it fell REALLY BAD.. I added 350# springs and Koni Yellows and it was MUCH better I can almost fly off the curbs now. I attribute this to shocks rather than the springs. Proper damping is very importanat to smooth handling. For the pros the springs are cheap and they are all pretty much alike, but the dampers (shocks) are big dollar items since they control transient response.

You can adjust take out some of your current understeer with lower front & higher rear ride height. Do you have understeer on corner entry, corner exit underpower, or mid corner steady state cornering?

BTW... I respect Chris Cervelli a great deal however I feel the 250/28mm is really the way to go. The 250/29 will be either dead neutral or a bit or oversteer depending on weight of the interior. This maybe different due to the sway bars however since I am familier with weltmeister 28/22mm bars. The 968 M030 are 30/19mm?? This would be more understeering bar set-up anyway. Come to think of it his 250/29 might be just right for 968 M030 bars.

IHMO a street car should Neutral to slight understeer since it is safer on the back roads. track car should be Neutal or oversteer since it is faster and you are always ready to correct.

Good Luck

Skip

[quote]Originally posted by Robby:
<strong>Skip- didn't really make any definate recommendations, but rather gave me a headache w/the myriad of options out there <hr></blockquote></strong>

Mention the headache when ordering and receive a coupon for Tylenol I like folks to make their own decisions - If I had my way we'd all have Koni 28's, monsterous springs, and a close personal relationship with a chiropractor

[quote]<strong>said B would have a larger range than K- meaning that while K has more range due to adj, their range at any one adjustment is less than B overall range. Ex: to get K as compliant as B, I'd set them soft- at soft setting, car would be soft for bumps, but wouldn't be as tight or flat on smooth ground and vice versa- at least that's how I understood him- may be wrong. He said B is monotube & K is twin, that mono is slightly more versitile for street apps. <hr></blockquote></strong>

I've heard this comparison many times, and still fail to fully understand the point. I won't debate the comparison, just know that both are great dampers, and both have their strong points.

[quote]<strong>I'm not sure how re-valving K would effect things when comparing to B...<hr></blockquote></strong>

Just a brief note on valving - the point is to match both the spring rate and corner weight of the vehicle to the ideal dynamic ability of the damper. Valving is basically generic for the 944 series, but varies wildly from those built for other applications.

[quote]<strong>Last thing- bushings- I decided on Turbo S bushings long ago. Cervelli and several others warned against PolyU- noisy & short life. Not sure about Racer's Edge or Delrin, but I thought RE's were spherical bearing(?)- if so, they would make the ride harder & noisier. I HAVE been toying w/the idea of solid front strut bushings though- not sure if they would make the ride much harsher or noisier- any input on that anyone?</strong><hr></blockquote>

First, the 968 caster block is the upgrade to that part of the car... M030 version is inferior. Poly bushings properly installed and lubricated will live a long life, even under race conditions. They do wear out, and in many cases will squeak. Delrin bushings are available for some of the places where Poly was the only alternative (spring plate). Racer's Edge manufactures both Delrin and Metal bushings. Delrin is also now available for the 968 M030 stabilizer set (front and rear). Delrin is not prone to squeaking as the Poly-Graphite is (if you're paying attention, I never say "never" - just too new to tell... but, I believe they will_not squeak - ever... due to the nature of Delrin - similar to Teflon).

Also, rather than refer to the ride as harder, I prefer to think it is more precise. Rubber in the suspension is a compromise. It's deflection is chaotic and progressive, thus hard to control. The ride seeming to be harder is because the tires and dampers are now the only cushion from the rough road below - transmitting more of the feel to the driver. One job of the shock/strut is to dampen the brisk movement of the suspension and attempt to control the frequency and amplitude of road imperfection transmission. The resultant feel tranmitted to the driver depends largely on the speed of the damper valving - which ties right back to the manufacturing battle mentioned earlier. Clearer 1, or 2. 3, or 4.

Skip

IanM

I just dropped the car off at Weissach. I asked them to remove the rear shocks, inspect their condition, and set them to 50% stiff. I'll play with the rebound damping of the front shocks on my own. We'll see how that affects the feel of the car.

This winter I think it'll be 300# front springs and 29mm torsion bars. I'll stick with stock Koni yellows for now.

Skip - you once told me that the Koni yellows theoretically don't need revalving for 250# springs. Well, what about the 300's? If I bump up the damping on the Koni's, should they work well with these springs?

Sorry, just a couple more questions. I understand that Paragon sells the rear Koni yellows for a fairly reasonable price. What about my front M030 Koni coilovers? Are they rebuildable? I know you mentioned the double adjustable Konis I could trade mine in for. Expensive? Do upgraded 300# springs slide right on to my stock front coilovers, or do I have to adapt my M030's to fit different springs? Do the front M030 Koni's have a similar lifespan as the rears, or do they tend to last longer?

Robby

Skip- you do know I was kidding about the "headache" thing I hope(?). Actually, it was meant as more of a compliment, as you had mentioned so many different options... But, you said something about caster blocks- I bought the 968 ones, but haven't installed them- I was referring to the front strut bushing- the big ones that you can see when you open the hood- they are what the strut brace would rest on- maybe I termed it wrong(?)- would it hurt the ride to change those w/spherical bearings or the adjustable mounts?

Thanks,

Skip

[quote]Originally posted by IanM:
<strong>This winter I think it'll be 300# front springs and 29mm torsion bars. I'll stick with stock Koni yellows for now.</strong><hr></blockquote>

Sounds like fun - when can I pencil you into "Skip's Cave of Wonders"?

[quote]<strong>Skip - you once told me that the Koni yellows theoretically don't need revalving for 250# springs. Well, what about the 300's? If I bump up the damping on the Koni's, should they work well with these springs?<hr></blockquote></strong>

The standard Koni Sports are capable to ~400#

[quote]<strong>Sorry, just a couple more questions. I understand that Paragon sells the rear Koni yellows for a fairly reasonable price. What about my front M030 Koni coilovers? Are they rebuildable?<hr></blockquote></strong>

Yes, or [gasp] you can perform the cut-n-drill conversion to 8641-1414S (popular for the sealed strut crowd). I prefer you didn't do this, but rather find a used core set to convert and preserve the M030 struts (or, sell them ). This is the most cost effective solution.

[quote]<strong>I know you mentioned the double adjustable Konis I could trade mine in for. Expensive?<hr></blockquote></strong>

Compared to the Space Shuttle, no. I'll Email you.

[quote]<strong>Do upgraded 300# springs slide right on to my stock front coilovers, or do I have to adapt my M030's to fit different springs?<hr></blockquote></strong>

Yes, and no - you need new upper and lower perches, and new bump rubber.

[quote]<strong>Do the front M030 Koni's have a similar lifespan as the rears, or do they tend to last longer?</strong><hr></blockquote>

Not sure - never really thought about it. I would assume shorter, but have no real data to back that up.

Skip