1971 Suspension suggestion

[stcan]

Hi,

Would like to get some recommendations for my 71 911.
Stock 71 narrow body
2.7 Twinplug Mag case
Deep 6 x 15" wheel all around
Avon 185-70/15 all around
KW front and rear adjustable shock with 19mm raised spindle
Rebel Racing front and rear teflon bushing
Elepant Racing adjustable spring plate

Car will be mostly for spirited street use.

Would like some recommendation for front and rear torsion bar

Also the front and rear sway bar

[PeteKz]

Lots of discussions on this in parallel threads. Take a look at those. Bill V has posted many charts of what different size t-bars and sway bars do to oversteer/understeer.

You already have some significant changes with the Rebel bushings and KW shocks. I suggest that you change the T-bars first, then see how it handles, then add or change the sway bars. For T-bar size, my experience with my car (see below) suggests that you use either 20/26 or 21/27 bars. 20/26 will give a little more compliant ride than 21/27, but a little more lean in corners. HOWEVER, the shock settings will make much more difference in ride than the T-bars, so be sure to experiment with those settings.

Alignment: DOn't over look this. For spirited street driving, you should start about -1 degree camber at the front and rear, then adjust from there depending on your preferences. Corner balancing is important too.

Ride height: Bill also has posted diagrams of the front McPherson strut geometry, and explained why you don't want to lower the car too much. Your car, like mine, sits pretty high visually, even at the lower end of the Porsche specs. However with the KW struts with raised spindles, the front of yours should be lower by the amount of the raise and have a noticeable forward rake down.

Do you have a 19mm spindle raised? How does that work with your 6x15 wheels?

[nickelplated5s]

I'm assuming you didn't go coil over? If not it's sort of a strange mix of bushings first and then T Bar choice. 'Spirited' to me means fast with sight lines, sedate with traffic. With what you've got I'd go 27mm and a light sway. 28/16 works for me in a SWB, stiff though.

[Bill Verburg]

Originally Posted by stcan

Hi,

Would like to get some recommendations for my 71 911.
Stock 71 narrow body
2.7 Twinplug Mag case
Deep 6 x 15" wheel all around
Avon 185-70/15 all around
KW front and rear adjustable shock with 19mm raised spindle
Rebel Racing front and rear teflon bushing
Elepant Racing adjustable spring plate

Car will be mostly for spirited street use.

Would like some recommendation for front and rear torsion bar

Also the front and rear sway bar

why 6s?,
7s even w/ the same 185 tires are a much grippier way to go

what's the ride height going to be?
stock w/ those tires would be b = ~200mm, normally if the spindles are raised 19mm the ride height should go to b = ~180mm, but you could go another 10-20mm lower w/o too much ill effect, though the steering is getting ratty w/o some compensation, at least an 11.5mm rack spacer should be used.

I'd leave the sways stock and just do t-bars

the t-bar effect is going to be a function of the corner weights, what works nicely for a 2600# car will be harsh and stiff on a 2000# car.

In general you really want to run the lightest springs that minimize suspension geometry changes due to chassis roll, secondarily reduced roll is more comfortable for the driver.

besides weight , speed is another factor affecting chassis roll, As you drive the car now is roll at an uncomfortable level?

[stcan]

The car is not complete yet so I won't know how it feel.
19mm raised spindle will fit not fit the 15" wheel properly without machining out part of the A-arm I think.

I went with Deep 6" for look. I initially was going to use the later 7" x15"

I will be using bumpsteer kit, so I the ride height will be lower than stock

Stock Sway is 15 front 15 rear I think. I was thinking of doing the adjustable RSR 19.3mm but that might be too stiff. They don't make anything smaller than 19.3 for the RSR look

The car should be around 2300-2400lbs I think.

[stcan]

some pictures

[stcan]

[Bill Verburg]

Originally Posted by stcan

The car is not complete yet so I won't know how it feel.
19mm raised spindle will fit not fit the 15" wheel properly without machining out part of the A-arm I think.

I went with Deep 6" for look. I initially was going to use the later 7" x15"

I will be using bumpsteer kit, so I the ride height will be lower than stock

Stock Sway is 15 front 15 rear I think. I was thinking of doing the adjustable RSR 19.3mm but that might be too stiff. They don't make anything smaller than 19.3 for the RSR look

The car should be around 2300-2400lbs I think.

ok, looks like you have addressed the usual issues

I'd want 7s if it were mine

raised spindle fit fit issue is troubling, there have certainly been enough reports of a poor fit but also others w/ no issues at +19mm, I guess you'll have to see

for street use even on later heavier cars 21/27 is pretty hard core, on mine I went w/ 20/26, w/ 20/18 new style sways

so at most I'd say 20/26 which raises roll rate by ~70 lb/ft/deg front and 140lb-ft/deg rear

this reduces roll under steer a bit more than 20/24 or 20/25 and a bit less than 20/27

if roll isn't an issue, then you could also leave the fronts alone and go 24 or 25 rear, the bigger rear also reduces understeer, the bigger the less understeer.

[stcan]

so 20/26 or 20/25?

Leave the swaybar at stock 15/15 or better to go with Adjustable RSR sway 19.3/19.3? (They only make those in 19.3mm and 22mm

[Bill Verburg]

Originally Posted by stcan

so 20/26 or 20/25?

Leave the swaybar at stock 15/15 or better to go with Adjustable RSR sway 19.3/19.3? (They only make those in 19.3mm and 22mm

20/25 is very close to stock balance, 20/26 is a little less under i.e. a little more aggressive, Those shocks should be able to take away what little sting there may be.

Those sways are nice but probably overkill for street use, You can always put them on full soft, only downside is weight and cost.

[AFB24911S]

I have an RS rear sway bar, the stock front sway bar, 21mm front torsion bars and 27mm rear torsion bars with Elephant Racing poly bronze bushings all around. I love the car exactly as it is. I had it corner balanced and aligned by a race shop; worth every penny.

The most important part of my suspension system was the digressively-valved, matched & calibrated shocks from ER: after 500 miles of bedding in, they were absolutely perfect. They offer compliance over bumps and taut handling in corners. Expensive, but stupendous. They were paired to each other and adjusted for my torsion bar choices.

Regardless of how stiff you choose to go on the torsion bars, I strongly recommend that you have your shocks matched to each other and tuned to match your torsion bars.

https://www.elephantracing.com/porsche/911/component-services-for-911/shock-services-and-testing/?srsltid=AfmBOorzEvLw7JEhuZ417Fna6XAN34fyZhl9X9quV EomNYck9qJokYBu

[nickelplated5s]

You've boxed yourself into a corner what with assembling everything with the Delrin/Teflon. Go drive it as is and make your decision for your driving style. Lighter TB's=heavier sways and vice versa. Lighter for street, heavier for track on the TB's. Counterintuitive but I've actually seen cars at AX lifting on the outside at speed. 26 TB's, don't know the sways.

Re the spindles. There are other discussions about problems with 19mm. At a guess is without a jig 19 could be +/- a few mm. Personally I would have speced 16 for your 15" rims. I'm lucky, my 16"s with fancy brakes are no problem. No raised spindles but it handles flat.

[PeteKz]

stcan: FYI, my car weighs 2330 lbs.

Bill V: When I put the Rebel bushings in my car, I calculated the difference in spring rates with the OE rubber bushings versus the low-friction Rebel bushings. The increased rate from twisting the rubber bushings was about as much as going up 1mm in T-bar size with the Rebel bushings. Thus, 20/26 T-bars with rubber bushings is about the same rate as 21/27 with the Rebel bushings.

[chrismorse]

On my dad's 74, one mount was torn/fatigued, the other had been cut off. I went with the Wevo mounts, then went with Tarrett adjustable 22s, F&R, 21/27 bars in "sport/HD" rubber. I think the Elephant adjustable spring plates are going to make the cornerweighting a lot easier.

If I had it to do again, i would have had the Bilstein HDs digressively valved and maybe backed off a bit on the bars. I've got Jongbloed 7 x 15s, (a touch lighter than Fuchs 6 x 15s), Dunlop 205/50-15. 2.8 twin plug, 10.5 c/r, RSR wheel with KEP all alum clutch, Guard LSD, Kosmal's PMO, MS2 EFI, twin EDIS ign, ported, SSIs and Scart Riva single out, Carrera fender oil cooler.
Just waiting for life to give me a little slack, so i can get it on the dyno, then Thunderhill :-) :-) :-)
chris

[Bill Verburg]

Originally Posted by AFB24911S

I have an RS rear sway bar, the stock front sway bar, 21mm front torsion bars and 27mm rear torsion bars with Elephant Racing poly bronze bushings all around. I love the car exactly as it is. I had it corner balanced and aligned by a race shop; worth every penny.

The most important part of my suspension system was the digressively-valved, matched & calibrated shocks from ER: after 500 miles of bedding in, they were absolutely perfect. They offer compliance over bumps and taut handling in corners. Expensive, but stupendous. They were paired to each other and adjusted for my torsion bar choices.

Regardless of how stiff you choose to go on the torsion bars, I strongly recommend that you have your shocks matched to each other and tuned to match your torsion bars.

...

I agree wrt the shocks, I have revalved digressive Bilsteins on both of my cars, The 911 has the Vonn's from Elephant and they are great.

But the O/P has gone a different route w/ the KW's They are a very different animal from the Bilsteins, certainly more comfy but w/ less precise control.

choosing t-bar rates is a 2 edged sword, stiffer leads to better geometry control, if you are going fast enough to need it, but it also entails mechanical grip and ride quality degradation. The question is are you going to be going fast enough for a great enough % of time to take the loss w/ the win.

If the car was being tracked a lot then sure 21/27 or even larger makes a lot of sense

An other thing to consider is that w 4x 6 & 185/70 tires the car starts off w/ a very low level on mechanical grip. Add to that the large sways which can double the wheel rates all by themselves

[Bill Verburg]

Originally Posted by PeteKz

stcan: FYI, my car weighs 2330 lbs.

Bill V: When I put the Rebel bushings in my car, I calculated the difference in spring rates with the OE rubber bushings versus the low-friction Rebel bushings. The increased rate from twisting the rubber bushings was about as much as going up 1mm in T-bar size with the Rebel bushings. Thus, 20/26 T-bars with rubber bushings is about the same rate as 21/27 with the Rebel bushings.

Interesting but also at odd w/ what some very knowledgeable folks say about it
Pay attention to Chris-Seven and Driven 97

I keep an open mind about it but I didn't notice any ride stiffness increase when I installed the Sport rubber bush's in my 911

the all mono-ball suspension in my 993 does move almost frictionlessly and does transmit more high frequency vibration

[stcan]

Thanks for all the suggestions. I think I will go with 20/26 and start with stock 15/15 sway and could do RSR adjustable 19.3/19.3 later, I'm not sure if the softest setting may still be too stiff on 19.3 sway.

I believe the KW V3 are digressively valved from factory with 2 way adjustable to match the desirable spring rate

I agree the raised spindle would have been great if it's 16-17mm, but they only make them 19mm from the factory.

[nickelplated5s]

Back to what I said in my last post, drive it with what you have and then decide. ChrisM's Dad probably had heavy sways or driving style to tear the brackets. I'm running a 16mm at the loosest setting, no problems. ER does give you spec sheets on their shocks but you've got the KW's so just go play with the rig.

[PeteKz]

Bill, I'll have to recheck my calculation, but the OE rubber bushings at the front add more than 30lb/in to the wheel rate. The stock total wheel rate (with 18.8 front T-bars) is around 130lb/in, so close to 25% of the wheel rate comes from the front bushings. What do you have for the wheel rates?

[chrismorse]

Originally Posted by nickelplated5s

Back to what I said in my last post, drive it with what you have and then decide. ChrisM's Dad probably had heavy sways or driving style to tear the brackets. I'm running a 16mm at the loosest setting, no problems. ER does give you spec sheets on their shocks but you've got the KW's so just go play with the rig.

Hi Nick,
Yes, my dad ordered the car with Carrera sways, (20 & 18 mm), BUT, he was a very "calm" driver, almost no Enthusiastic cornering, and no sliding. he probably had 25-30 years of easy driving before he had a rear mount fail. He said the shop recommended removing the rear bar, since he drove it easily.

Do the early and mid year cars have the same mounts??