Suspension upgrade plan feedback requested

[r55forme]

My 1987 Coupe has the original suspension, worn tie rods, deformed rubber bushings and basically ready for a front and rear rebuild. I'd like to upgrade at the same time, but having done this before, I want to try and strike a magical balance between a great handling car but still keep it comfortable enough over bumps and rougher road my wife will still ride in it and not bounce us around. I've made that mistake before, and already own one care she won't ride in, so hoping to keep this more balanced.

I want the car to be tight, flat, and predictable. Maximum smiling while driving is the goal.

CURRENT SETUP

• BIlstein Yellow Sport front struts, Bilstein green rear shocks (new to go on)
• 16x7 & 16x8 wheels with RE17RS (205/55/16, 225/50/16)
• Ride height fender-ground is ~25.5
• Everything else is stock and all the bushings are worn and planning to replace

PROPOSED PLAN

• Lower ride height from 25.5 fender to ground to 25 or 24.75 (don't want to go too low and only do minor fender rolling with the 16x7)
• Keep stock swaybars, replace bushings
• Keep stock spring plates and recondition
• Rebuild Control Arms, use Rebel RSR front bushings
• Replace rubber strut bushings with Monoball from Rebel
• Raise Spindles? (if so by how much?* 20mm not sure how much I need from lowering)
• If raising Spindles, weld on adjustable bump steer kit?* Or just simple one that raises the steering rack or replaces the tie rod ends?
• Turbo tie rods
• Lemforder ball joints
• RSR Rear Spring Plate bushings
• RSR Sealed Monoballs
• Replace hardware

QUESTIONS/FEEDBACK

• Should I raise spindles, and by how much?
• Torsion bars: 20/26 or 21/27? Want to avoid making the car too harsh
• Bump steer recommendations: steering rack spacer, tie rod end, or weld on adjustable
• Keep Stock swaybars ?Would rather get good response from torsion bars than transmit too much of big bumps with large swaybars
• What else should I be considering?

Thank you in advance as I learn how to build this for the first time. I do plan on doing the work myself so any must have tools for the job also appreciated.

MJ

[ericwitte]

I would not go with monoballs up front unless it’s a track car. New stock rubber is likely fine. Invest in better shocks or have these digressively valved. Time and labor (even your own) are more expensive than parts, might as well upgrade to a more modern shock/strut that accomplishes the goals you are looking to achieve.
Bill V.’s posts are likely the best resource as to what works -


Sent from my iPhone using Tapatalk

[PeteKz]

I'll have to get back to this tomorrow. Your plan looks good to me for a street car, except do not use monoballs or the RSR spring plate bushings. Stick to the OE rubber bushings for the suspension.

Raise spindles: 19mm is safe for 16" wheels. More than that and you will have to measure carefully, and may run into parts rubbing the inside of the wheel.

Agree with your plan to increase T-bars instead of thicker sway bars for a street car.

What's your budget?

[wi54545]

I just went thru this last spring. I went with elephant racing mostly.

KW variant 3 struts and shocks with 19mm raised spindles.
21mm hollow ER quick change front torsion, 28mm hollow QC rear
All ER control arm bushings.
ER strut mount rubber bushings
ER Rubber rear torsion bushings
ER quick change adjustable spring plates
ER sport banana arm bushings
Lemf. Ball joints
New wheel bearings
Eibach sways front and rear.
Rebel racing bump steer kit.

After all that, I added Euromeister 17x7 and 17x9 fuch replicas in 215/45/17 245/40 rear.

Fender height is 24.625 front, 24.25 rear.

The car is amazing now. Feels so confident and flat. Not too harsh at all (I have the KW v3s on default setting) and could get them even smoother with changing the settings. No NVH. Went with the 21/28 combo to have a neutral to slight oversteer bias. No a/c, pmo carbs and RSR style amber tinware. Also Ssi and m&k. So I took quite a bit of weight out of rear. Can dial the rest with the KW v3s. Car is simply amazing and almost feels modern…. It wasn’t cheap doing this though. I did all the work minus alignment.

[silverlock]

Agree with PeteKz on most of it + I run a very similar setup after crawling these forums (Bill V; Pete; etc) and talking to friends in the air-cooled rally community.

My take:

• Keep rubber/HD rubber bushings for compliance.
• General thesis on t-bars is to go 21/26 sans-AC and 21/27 with AC.
• Koni Sport if you keep stock spindles; KW v3 otherwise. More softly damped shocks go well with firmer t-bars for the street.
• I cannot exaggerate enough how much the RSR adj bump steer kit improved handling on a lot of the sketchy-but-fun backroads I drive. Car is about 24.5” / 25” and so not slammed but low enough that the kit made sense. I just wasn’t ready for how much of an improvement it would be vs before. Didn’t expect we could dial so much of it out.

Otherwise, in my 2550lb 3.2SS SC w/o AC (and heat backdate), I run: HD rubber spring plate & trailing arm bushings, RSR spherical a-arm bushings (no noticeable NVH issues), Koni Sport clocked in 1/2 from soft, 21/26 t-bars, Turbo tie rods & 24/25 Eibach sway bars.

I actually really like the big sway bars and did them before I refreshed the shocks, upgraded the t-bars & did bushings, and don’t find them to introduce any compliance issues. I have to drive out of NYC to get to fun roads and (as before) regularly drive some patchy twisties, and so a car that doesn’t roll but can eat bumps mid-corner is key.

[Otter74]

My car is lowered about like Matt’s and it’s got lots of bump steer. Since the car has always been like this I’ve just treated it as normal but I admit that I do think hard about bump steer correction. If you’re redoing your whole suspension I’d strongly recommend it.

I personally prefer soft springing for compliance, plenty of damping and more anti-roll bar if I want to keep roll under control.

[Bill Verburg]

Originally Posted by r55forme

My 1987 Coupe has the original suspension, worn tie rods, deformed rubber bushings and basically ready for a front and rear rebuild. I'd like to upgrade at the same time, but having done this before, I want to try and strike a magical balance between a great handling car but still keep it comfortable enough over bumps and rougher road my wife will still ride in it and not bounce us around. I've made that mistake before, and already own one care she won't ride in, so hoping to keep this more balanced.

I want the car to be tight, flat, and predictable. Maximum smiling while driving is the goal.

CURRENT SETUP

• BIlstein Yellow Sport front struts, Bilstein green rear shocks (new to go on)
• 16x7 & 16x8 wheels with RE17RS (205/55/16, 225/50/16)
• Ride height fender-ground is ~25.5
• Everything else is stock and all the bushings are worn and planning to replace

PROPOSED PLAN

• Lower ride height from 25.5 fender to ground to 25 or 24.75 (don't want to go too low and only do minor fender rolling with the 16x7)
• Keep stock swaybars, replace bushings
• Keep stock spring plates and recondition
• Rebuild Control Arms, use Rebel RSR front bushings
• Replace rubber strut bushings with Monoball from Rebel
• Raise Spindles? (if so by how much?* 20mm not sure how much I need from lowering)
• If raising Spindles, weld on adjustable bump steer kit?* Or just simple one that raises the steering rack or replaces the tie rod ends?
• Turbo tie rods
• Lemforder ball joints
• RSR Rear Spring Plate bushings
• RSR Sealed Monoballs
• Replace hardware

QUESTIONS/FEEDBACK

• Should I raise spindles, and by how much?
• Torsion bars: 20/26 or 21/27? Want to avoid making the car too harsh
• Bump steer recommendations: steering rack spacer, tie rod end, or weld on adjustable
• Keep Stock swaybars ?Would rather get good response from torsion bars than transmit too much of big bumps with large swaybars
• What else should I be considering?

Thank you in advance as I learn how to build this for the first time. I do plan on doing the work myself so any must have tools for the job also appreciated.

MJ

You'll need to measure to be exact but 25 1/2" front fender is roughly 150mm a-b
which means ~40mm lower than stock.

this means you have lost most of the shock compression travel and the steering is out of whack

Rasing the spindles restores some of the travel, but w/ 16s the limit for raising spindles is ~30mm, using a shorter seal gains another ~.75"

to restore steering geometry 2 things are usually necessary
1) raise the steering rack up to ~19mm
2) add adjustable height steering knuckles to the struts

for sporting street us 19/26 or 20/26 t-bars, for a more track oriented cat 20 or 21 front and 27 -30 rear.

for street use sport rubber bushes, for more track-oriented mono-ball or poly bronze bushes.

Bilstein green front and yellow rear is a common setup or green/green, digressive revalve is really nice, In Europe they are starting to offer PSS10 Bilstein which are digressive stock and adjustable, you might want to look into those too

[nickelplated5s]

Go with PeteK and WiFi(5). I've, without pulling invoices, got ER poly A arm bushings and ER rubber elsewhere in the front. ER #2 trailing arm bushings in the rear and ER rubber otherwise. Von #2's in the rear and custom Koni's in the front. I've driven the car with the Von's and like them over my blown Bil's. Motor is out so haven't driven it with the new rear bushings. It did take me some thinking to get my head around BillV's roll center math. Mine does not have raised spindles hence the custom Koni's. It's also about 2.5" lower than yours so no need, that lowered the RC the same amount.

[r55forme]

Thanks all for the good discussion and information. A few more things I didn't include about my car.

Does have AC, and will be replacing the stock muffler with M&K.

If I do rubber bushings, which ones are considered harder sport bushings? ER looks like they have a sport durometer for the reason, but only polybronze. Rebel has both HD for front and rear. Just curious what recommendations people have.

Originally Posted by Bill Verburg

to restore steering geometry 2 things are usually necessary
1) raise the steering rack up to ~19mm
2) add adjustable height steering knuckles to the struts

Bill could you say a little more about how to achieve #1 & #2? An adjustable bump steer kit vs the steering rack spacers which only give about 10mm of spacing? Or do you do a combination of both?

So I had not looked into coilovers, so that would significantly increase the cost vs. the Bilstein set I have, but I'm open to that. I could only find the PSS10 for early 911s from Rose Passion in a quick Google. Would investing in coilovers as opposed to getting digressive valving on the Bilstein struts I have make more sense and give me more control to adjust for wife driving vs. more aggressive driving?

Thanks in advance!

MJ

[PeteKz]

I think the others have pretty much covered the bases.

Still the open question: What's your budget? Yeah, I know, "Porsche" and "budget" in the same sentence is an oxymoron, but start somewhere reasonable for you. But, recognize that you will probably go past it as the "slippery slope" and "while you're in there," exert their demonic pull.

If budget is high, go with the KW front with 19mm raised spindles, and KW rears. Not cheap, but you won't have to pay to get the spindles raised. And they are easily adjustable for you to find what works best with the rest of your setup, or if you change your setup. If the budget is more limited, have the spindles on your struts raised and reinforced, and use the Koni Sport (Yellow) adjustable shocks. That's what I use, although I have not had the spindles raised yet, because I keep the suspension near the stock ride height, and they are 3" brake brackets, so I really would have to start over with new struts with 3-1/2' brackets. .

Next, suspension work doesn't have to be done all at once, "while you're in there." Go at it in steps, and see how the changes work. One of my rules of mechanical work is "only change one thing at a time!" That way you better know what the changes did, and you don't confound multiple changes at the same time. Doing the rear bushings and T-bars together makes sense becuase it's a lot of work to disassemble it later to change the bars.

Based on my street driving, I recommend either the 20/26 T-bars, or the 21/27 pair. I have 21/26 right now, and I want to increase the rears to 27 becuase the rear feels slightly squishier than the front and I want them to feel more balanced. Or I might change the front to 20, because I have a light car (weighed 2330 lbs empty). Change the T-bars first and see how the car handles. Play with the shock settings. Change the sway bars last. I find that thicker sway bars makes the car harsher on crappy roads, like I have to deal with in my area.

[Bill Verburg]

Originally Posted by nickelplated5s

Go with PeteK and WiFi(5). I've, without pulling invoices, got ER poly A arm bushings and ER rubber elsewhere in the front. ER #2 trailing arm bushings in the rear and ER rubber otherwise. Von #2's in the rear and custom Koni's in the front. I've driven the car with the Von's and like them over my blown Bil's. Motor is out so haven't driven it with the new rear bushings. It did take me some thinking to get my head around BillV's roll center math. Mine does not have raised spindles hence the custom Koni's. It's also about 2.5" lower than yours so no need, that lowered the RC the same amount.

roll center height is a very simple concept, the lower the roll center the longer the lever arm for the force causing roll.

the higher the arm the shorter the lever arm

Roll center height is determined by CoM(CG) height, strut angle which in a 911 is fixed, scrub radius which only changes when wheel ET is changed and the angle of the front A-arm which varies w/ suspension height, here you see that the lower suspension brings the A-arm more horizontal which lowers the roll center and increases the length of the roll lever arm A from A1 to A2, again the longer the roll lever the more roll for the same force

[Bill Verburg]

Here is a chart showing comparative heights used for various purposes

a - b is wheel center heigh - torsion bar center height, the only way to measure that is useful

[nickelplated5s]

Seriously Bill, thanks again for the input. Right now I'm thinking you should pull together info and get the Mod's to make a sticky.

Mine's sort of an oddball, I'll lose the rear before the front. Let me know what measurements you want and I'll get them. It will be two or three days due to work. Only the front for now as the motor is out. PeteK had me out today measuring throw length for old Bil's and new Von's. Maybe he'll chime in as to why for his LWB versus my SWB...

[PeteKz]

Heh, heh--because I want to know what shocks fit best in what cars, and how much travel is reduced when lowering the cars. I'm a junkie for tech info.

[nickelplated5s]

The Von's have about 2" more travel than the Bil's. Same overall length but the bump stops are shorter. Could have cut them but don't think they ever bottomed.

Back to the OP; if you go coil over rear you will need a brace for the upper mounts.

[LJ851]

Originally Posted by nickelplated5s

The Von's have about 2" more travel than the Bil's. Same overall length but the bump stops are shorter. Could have cut them but don't think they ever bottomed.

Back to the OP; if you go coil over rear you will need a brace for the upper mounts.

Is that extra 2 inches available on the car ? It seems the strut housing would still hit the upper strut mount at the same ride height unless the Von housing is shortened as well.

[nickelplated5s]

I suppose I should have given the detail I sent Pete yesterday. 5" total travel with the Bils'. 7" with the Von's. With the 28mm T bars I never bottomed out the Bil's. In other words I won't and have not bottomed the Von's either.

[Bill Verburg]

Originally Posted by r55forme

Thanks all for the good discussion and information. A few more things I didn't include about my car.

Does have AC, and will be replacing the stock muffler with M&K.

If I do rubber bushings, which ones are considered harder sport bushings? ER looks like they have a sport durometer for the reason, but only polybronze. Rebel has both HD for front and rear. Just curious what recommendations people have.



Bill could you say a little more about how to achieve #1 & #2? An adjustable bump steer kit vs the steering rack spacers which only give about 10mm of spacing? Or do you do a combination of both?

So I had not looked into coilovers, so that would significantly increase the cost vs. the Bilstein set I have, but I'm open to that. I could only find the PSS10 for early 911s from Rose Passion in a quick Google. Would investing in coilovers as opposed to getting digressive valving on the Bilstein struts I have make more sense and give me more control to adjust for wife driving vs. more aggressive driving?

Thanks in advance!

MJ

You could use the o/s ends in the link you posted but the preferred method is this

which connects to stock turbo tie rods

You don't need coil overs The PSS10 Billsteins are apparently just hd or sport somewhat modified to be adjustable

a concern is that the Spidle may not be able to be raised as far or even at all, there are a lot of unknowns w/ these new items

leaving coil overs out
the basic decision is twin tube or mono tube
twin tubes will have more travel deteriorate more from heat and hard usage and generally be more comfortable

mono-tubes will be more sporting and offer better control

upside down monotubes like Bilstein offer additional unsprung weight savings over regulars like MCS

The best for sporing use will be MCs which can be spec'd precisely for your use in terms of length, spindle height and angle etc. and are digressive stock and adjustable stock

Billsteins would need to be modified, I had my done by Bilstein San Diego, but they no longer offer this service, but Elephant does, they can also add the adjustable height steering knuckle and shorter seals.

for twin tubes many like Koni or KW, Konis spindles can only be raised 19mm but they are adjustable kw can be ordered w/ 19mm raised spindle and are also adjustable

I'd highly recommend Elephants sport rubber bushes

The thing about t-bars is that they are a 2-edged sword, you want them stiff enough to control roll and hence wheel geometry but as they get stiffer, they also limit mechanical grip.

[r55forme]

Perfect, thank you Bill and others. This is helpful and I feel we're narrowing in. Tonight I will get my current ride height calculations F/R so I know where we're starting from.

Bushings: HD rubber for everything (control arms, trailing arms, strut mounts)
Tbars: 20/26 seems to be consensus for neutral to slight under steer, even though my car is a bit heavier
Spindle height: 19mm regardless of which direction I go to stay safe with the 16" wheels
Racing Bump Steer Kit: weld on bracket

I also like the step by step approach of upgrading, and could always go stiffer later on the Tbars and/or swaybars if needed. The rest of the parts are just worn and need replacing. Just looking at the bushing deformation, tie rods, worn struts and the suboptimal geometry setup I am definitely wanting to get it all done right.

I was most concerned with dialing in the dampers and making the best choice there the first time around. I was resisting the budget conversation because coilovers would double the budget.

I have the stock Bilsteins, so I need to decide if I stick with those and get them modified to raise the spindles, put shorter seals, digressively valve them and weld the bump steer bracket on. Once I'm done with that, I'm already in for about $2000 on the Bilsteins that I have. So would the KW coilovers be that much better to spend the additional $2500. From what people have said, if I can afford that I won't regret it. The Vons look to be another $1000 over the KW for $5800ish.

So helping me spend more money or stick with the Bilsteins and modify them to suit is where I'm not sure how to decide. It sounds like there are other costs with coilovers where I need to box the control arms and the upper strut mounts.

Thanks! I am reading and re-reading the discussion and starting to catch up

[nickelplated5s]

Originally Posted by Bill Verburg

The thing about t-bars is that they are a 2-edged sword, you want them stiff enough to control roll and hence wheel geometry but as they get stiffer, they also limit mechanical grip.

That's why my partially blown Bil let me take a test corner faster than the Von2's. Granted, I was 112.5% faster than the posted speed.