First 911 Suspension Configuration
 

Alright guys...I figure I might as well start somewhere as there is so much conversation on this topic that even I get overwhelmed reading it all.....but here's what I'm thinking for my first attempt at a little street/DE/AX machine that will keep the wife happy in the passenger seat and daddy happy in the driver seat through the turns and on 300 mile road runs.

1983 SC coupe (all original...parts look good...but are old...garage queen that needs driving!)

Front:
Bilstein Struts (Original) with new HD (B6) inserts
OEM rubber bushings all around including new sway bar (20-mm) bushings
21mm torsion bar (still deciding on plugged and plated vs solid....help me out)
OEM ball joints and strut mounts
Strut Brace (not sure needed....thinking single removable)
Turbo tie rods (already done this last weekend)
Steering rack spacers (already done last weekend)
Euromeister 17 fuch rep wheels
Michelin Pilot SS 215/45 17s

Rear:
Bilstein Sports (B8)
Oem bushings all around including (sway bar 18mm) bushings
28 mm torsion bar (still deciding on plugged and plated vs solid...help me out)
Euromeister 17 fuch rep wheels
Michelin Pilot SS 245/40 17s

Would love to hear what you guys think for an initial go at this thing!

I'm working on my first setup for installation this winter too. Going very similar to you, except Rennline HD rubber strut mounts. Curious to hear why you are going B8 Bilsteins in the back and B6 in the front, as opposed to keeping them uniform.

I think the B8 up front would be too much and based on the torsion bar configuration I'm trying out that's what ER recommended. Are you thinking B6 (HD) all the way around?

That's what I have been thinking, but going 21/27 on TB. Now I'm questioning the B6 in back. I rode in a 911 with all B6 and was impressed with the ride. Plenty stiff, but had enough forgiveness for the street.

I just worry if I was to go 21/27 I wouldn't notice enough of a difference from stock and with HDs in the back I think it would have a very stock ride. But again I am mostly just guessing and going off Word of Mouth.

Out of curiosity what made you choose the rennline HD strut mounts over the ER mounts

I just finished this whole project. Pretty much to the letter. I have been on one drive since I got it back from corner balance,align and ride height. It feels like a new car, squeaks and rattles have been greatly reduced, and it just feels tight and solid. Happy to help anyway I can.

Hd up front, sport in the rear
Turbo tie rods
Ball joints
Elephant racing upper strut bushings
New Torsion bars and bushings front and rear
Sway bar bushings front and rear
Adjustable drop links in the rear

What TB combo did you end up using?

Bilstein B8 is a shorter shock than B6, these are not available for 911 according to the Bilstein catalogs that I've seen

All 911/930 shocks are B6, there are different versions available
Series aka HD these are the green ones
Sport these are yellow
Race
Rally

the difference between Series(HD) and Sport is the valving, HD front is 150/110 rear 195/151, Sport front is 160/161 rear is 220/180. The others have different valving and threaded cases for coil over springs

series part # left strut is 35-001270, right strut is 35-001287, inserts are 34-050019, rears are 24-001694

sport part # left strut is 35-003885, right strut is 35-003892, inserts are 34-050507, rears are 24-009751

It's common to use hd front and sport rear, I've tried all 3 ways(hd-hd, sport-sport, hd-sport) I like hd-sport w/ or w/o digressive valving

rubber bushs for street use for sure

t-b's are a trade off stock SC is 19/23mm w/ wheel rates 152/107
some common upgrades that are close to the same balance as oe w/ wheel rates and delta(more +r is less understeer/more-r is more understeer) from oe are
20/25 187/149 +38r
20/26 187/174 +13r
20/27 187/202 -15r

21/27 227/202 +25r
21/28 227/234 -7r

22/28 273/234 +39r
22/29 273/269 +4r

you can go further but the rates become untenable for other than track or smooth street use.

The closer to the top in the above list the softer the ride, i'd tend to 20/26 or 21/27 and some stiffer sways as the main thing I don't like about stock is the amount of body sway when hustling through the corners.

Note that currently there appears to be a nationwide shortage of 20 and 21mm front Sanders plugged & plated t-bars. The Sway-Aways do seem to be available. I'd wait.

Strut brace isn't generally necessary for street use but won't hurt

t-tie rods are nice, wheel & tire choice is fine for street use

I went with sway a way 21 F and 28 R solid.

I would suggest you call Chuck at Elephant and lay out your plans and follow his recommendations very closely. I did, and between him and Steve W. I got a car that corners like a squirrel on crack and is scary stable at totally stupid speeds. I am using monoballs, on all corners, Sander 21/27 TBs, Rebel Racing semi solids on all 4 corners, Elephant Re-valved shocks, turbo tie rods, quick steering rack, D-Zug X-strut brace, and whole bunch of other stuff. Remember race car suspension may not be the best choice for the street and the super cross grade bumps. I actually can't remember if the suspension is stiffer than stock, but I can say the handling is an order of magnitude better. Just because it isn't riding like a buckboard, doesn't mean it isn't working well.

If you plan on doing the inserts up front your self buy this tool to remove and install the new roll pins.

https://www.amazon.com/dp/B008M22GJ6/ref=cm_cr_ryp_prd_ttl_sol_0

Bill....thanks for the info...great stuff as always! In looking at your table though, wouldn't stiffening up the car in the rear tend to make it oversteer a bit more. For instance....I have the following info from Sway Away using relative rates, RR (relative rate; a function of wheel rate/spring rate). Below is a table for front and rear with percent increase from stock according to my math:

19mm.....320......stock
20mm.....401......25.3% increase
21mm.....488......52.5% increase
22mm.....588......83.8% increase

24mm....703.......stock
25mm....828.......17.8% increase
26mm....968.......37.7% increase
27mm....1126.....60.2% increase
28mm....1303.....85.3% increase

21/27.....in terms of % increase from stock this would increase stiffness 8% more in the rear than the front which would seem to provide more oversteer. In your post....this seems to match your +r creating more oversteer.

21/28....in terms of % increase from stock this would increase stiffness 33% more in the rear from the front which would seem to provide even more oversteer. In your post you have this as a -r and thus creating more understeer?

Is this the case in real world.....I only ask because I definitely don't want to add understeer to the car....I really think I want the car to slightly oversteer for my driving if possible.

I've liked a lot of the Rennline stuff I've ordered so far. I like the idea of "stock rubber +25% firmer", which is the metric they state.

yeah, not enough coffee this AM, I wrote it backwards

compared to stock SC
21/27 is 25 lbs/in more front ie more under
21/28 is 7lb/in more rear ie less under

the %'s aren't useful it's either the actual lb/in difference in wheel rate or more esoterically the ride frequency
ride frequency delta oe is .723hz
21/27 is .707
21/28 is .586

As far as final tune getting it in the ball [park w/ t-bars and wheels and tires then fine tuning w/ adjustable sways is the way to go.

If you definitely want less under(most do) get t-bars that are a little stiffer in back like the 21/28 or 20/27 or 23/31 then tweak w/ adjustable sways.

your wheel and tire choice will up the absolute grip but keep balance neutral

The only other thing to do to tweak the ride is go for lighter wheels

Yeah...I would love to do that....definitely something to put pennies in the cookie jar for later!

Bill, will 20/27 still offer fairly responsive turning, or would you suggest 21/28? I will be driving the car by myself 60% of the time, but need to make sure the wife enjoys it on long road trips.

By using your chart, am I to assume more understeer in my potential set-up of 22/28's? The original plan was to go 22/29's but then backed down to 28's.

Car 78 911SC Targa with any hopes of starting re-assembly soon

The rest of the project:
22/28's ER QC r-bars/plates
ER PB front n rear,
Up-sized Carrera sways
Sport rear
Jury still out on Sport/HF for front
Rack spacers
T tie rods
Rebuilt rack
Rebuilt brakes(PBM)





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22/28 imho. No point doing it twice. It seems to be the compromise of choice over the years. If you get serious about the track 23/33!