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If you plan on keeping the suspension stock-ish, a good cost effective upgrade is to install a later rear sway bar.
It's stiffer which will reduce the amount of understeer you have.
In truth though, the biggest change you can make is wheels and tires. The amount of grip you get per $ compared to swapping to a bespoke suspension is worth it as a first step.
It also reduces braking distances as the tires are more apt to resisting lock up. Something the early 928s are in dire need of with the factory brake setup.
If you plan on keeping the suspension stock-ish, a good cost effective upgrade is to install a later rear sway bar.
It's stiffer which will reduce the amount of understeer you have.
In truth though, the biggest change you can make is wheels and tires. The amount of grip you get per $ compared to swapping to a bespoke suspension is worth it as a first step.
It also reduces braking distances as the tires are more apt to resisting lock up. Something the early 928s are in dire need of with the factory brake setup.
What is the optimal tire to run on 16” phone dials? I want to keep the appearance accurate but realize this will result in taller side walls. I’m sure there are a bunch of options here too.
What is the optimal tire to run on 16” phone dials? I want to keep the appearance accurate but realize this will result in taller side walls. I’m sure there are a bunch of options here too.
IMHO, wheel width * 25.4 * 1.2 should be the widest tire on any wheel, without compromising how the tire then starts to come around the wheel in cornering, and then LOSING footprint. The best part of the tire, is where it is supported directly by the wheel, without the sidewall wanting to push it in or pull it up if too large of a tire, starts to shift around a lot.
What is the optimal tire to run on 16” phone dials? I want to keep the appearance accurate but realize this will result in taller side walls. I’m sure there are a bunch of options here too.
I personally went for Michelin Pilot Sport 4S on my 85. So much stickier than what the cars came with.
If you can get wider tires on the front it would be ideal. Going from a 7 inch width to 8 inch made a massive difference on my other 2 928s.
My 2 cents on S3's: 86.5, almost wholly refurbished, and an 85 that was "refreshed". My goal was STOCK to STOCK + ride quality and handling.
86.5: Rear suspension including the Weissach Bushings, front and rear swaybar bushes, front and rear wheel bearings, new axles, new steering rack, etc....Front Upper and Lower control arms were not replaced. Koni Reds over stock 5" springs and adjusters.
85: This car will be painted so I replaced the rear wheel bearings, swaybar bushings, steering rack, etc.... The Front Upper and lower are serviceable but will be replaced when painted. Koni Reds over 2.5" 500# rear and 350# Front Hyperco springs with Coleman Lower perches and Adjusters. The 85 had 112k Miles and the adjusters were destroyed.
Both sets were adjusted to 1 turn (1.75 approx max) front and 1.5 turns (2.25 approx max) rear. I compressed and TIMED the full release and made minor adjustments to get them as close to even as possible. Both cars are set as close to factory ride height as possible.
Both Cars have the HAN'S OTT LINKS installed. The 86.5 was driven about 5000 miles after refresh without them. (more below)
The 85 is a bit firmer ride than the 86.5. I attribute that to smaller and new springs vs. the OEM. It's most noticeable over SUDDEN compression, like an expansion joint or sharp hit.
Both cars are compliant over a "WHOOP" (Or as I call them, the "Texas DOT Jumps")...the car will lift and settle over the crest and trough in one motion and settle with no drama. As a good suspension should.
The 85 has COLEMAN RACING Adjusters and is much easier to adjust since they're new and the threads are larger. They also have a newer style adjustment ring. If you're a slave to "it has to look stock," this isn't for you, but good luck finding stock adjusters.
Both cars were riding on springs basically before being fixed. If you're on BLUE BOGES, they're DEAD...there isn't a chance in hell your 35-year-old shocks are good even if they look clean (And I'll even include the rear wheel bearings....3 cars all of them were "Marrakas" when removed...40k, 112K and 170K) TRUST ME and everyone else on this. The BIGGEST improvement to ride will be to swap in new cartridges...regardless of brand. When I was doing mine, the REAR BOGES weren't easily available even if you wanted them. I went with KONI REDS for that reason.
The 2nd biggest improvement is the HANS OTT LINKS. They increase the torsional rigidity of the stock sway bar and are adjustable. The estimates are 50% higher per OTT's original ones. "seat of the pants" confirms they are much better at controlling sway. Sway bars do not significantly affect straight-line comfort but dramatically improve cornering. Uprating to LARGER Swaybars can be an issue with the OEM mounting points (Do your own research on RENNLIST), but for STOCK + these are the easiest ways to get better cornering if you can find a set.
Summary:
If you have stock suspension, it's likely SHOT. Replacing it will be an improvement.
Decide what your goals are. Do you want a race car? Or "like new" stock experience?
I have 7 after-market suspensions on different cars and bikes, from "out of the box" OEM replacements to custom-made ones just for my application. The cost is dramatically different, and so are the results. There is a value proposition with a "kit" but a compromise. Let the seat of your pants and your wallet be your guide.
Coil Overs will always beat the snot out of struts. If you don't care about originality and want adjustability and tuning, this is the way to go. Again...get out your wallet.
Koni vs. Bilsien: I don't have personal experience with Bilstien. A friend just installed some on an 86.5, and I will get to drive that at some point. But the Bilstiens have a Lower Perch, so you don't have to "make your own" like you would with the KONI. I'd consider that on a car I was upgrading suspension as a PLUS and if I were buying today, I'd likely try the Bilstiens just to try them and because you can use your stock springs. I like the KONI RED and if you have functional stock adjusters, they work fine. If not, you're going to have to change the entire spring setup up, and it's a LEGO KIT, but still works. Min 85 rides stiffer than my stock 86.5...not "worse" but stiffer. Over time? who knows...but the OEM spring weights are likely softer? The smaller springs and changes are making it stiffer on the 85? I"'m sure someone will have an "Opinion" on here...(WINK)...but they're both better than they were and very good.
If you want a "race car," you must pay racecar prices. If you want a TUNED suspension, there are people here who can provide one for you. I'm sure they're all going to serve you well. If you're going to DIY and/or you want it BONE STOCK that's the easy one.
I have an 83 on deck for restoration. I'd likely just put BOGES on it if they are available. If not, then the condition of the adjusters will determine what I replace them with.
My 2 cents,
Dundertaker
Last edited by Dundertaker; 11-17-2023 at 10:55 AM.
All I can say is I spent A LOT OF TIME researching this issue over the years here and then a lot before I purchased this bunch (and just look at this thread KONI's are hard or as soft as a down pillow)
you simply can't beat the looks or functionality of that shock/collar combo especially if I get the bright lime springs
My 2 cents on S3's: 86.5, almost wholly refurbished, and an 85 that was "refreshed". My goal was STOCK to STOCK + ride quality and handling.
86.5: Rear suspension including the Weissach Bushings, front and rear swaybar bushes, front and rear wheel bearings, new axles, new steering rack, etc....Front Upper and Lower control arms were not replaced. Koni Reds over stock 5" springs and adjusters.
85: This car will be painted so I replaced the rear wheel bearings, swaybar bushings, steering rack, etc.... The Front Upper and lower are serviceable but will be replaced when painted. Koni Reds over 2.5" 500# rear and 350# Front Hyperco springs with Coleman Lower perches and Adjusters. The 85 had 112k Miles and the adjusters were destroyed.
Both sets were adjusted to 1 turn (1.75 approx max) front and 1.5 turns (2.25 approx max) rear. I compressed and TIMED the full release and made minor adjustments to get them as close to even as possible. Both cars are set as close to factory ride height as possible.
Both Cars have the HAN'S OTT LINKS installed. The 86.5 was driven about 5000 miles after refresh without them. (more below)
The 85 is a bit firmer ride than the 86.5. I attribute that to smaller and new springs vs. the OEM. It's most noticeable over SUDDEN compression, like an expansion joint or sharp hit.
Both cars are compliant over a "WHOOP" (Or as I call them, the "Texas DOT Jumps")...the car will lift and settle over the crest and trough in one motion and settle with no drama. As a good suspension should.
The 85 has COLEMAN RACING Adjusters and is much easier to adjust since they're new and the threads are larger. They also have a newer style adjustment ring. If you're a slave to "it has to look stock," this isn't for you, but good luck finding stock adjusters.
Both cars were riding on springs basically before being fixed. If you're on BLUE BOGES, they're DEAD...there isn't a chance in hell your 35-year-old shocks are good even if they look clean (And I'll even include the rear wheel bearings....3 cars all of them were "Marrakas" when removed...40k, 112K and 170K) TRUST ME and everyone else on this. The BIGGEST improvement to ride will be to swap in new cartridges...regardless of brand. When I was doing mine, the REAR BOGES weren't easily available even if you wanted them. I went with KONI REDS for that reason.
The 2nd biggest improvement is the HANS OTT LINKS. They increase the torsional rigidity of the stock sway bar and are adjustable. The estimates are 50% higher per OTT's original ones. "seat of the pants" confirms they are much better at controlling sway. Sway bars do not significantly affect straight-line comfort but dramatically improve cornering. Uprating to LARGER Swaybars can be an issue with the OEM mounting points (Do your own research on RENNLIST), but for STOCK + these are the easiest ways to get better cornering if you can find a set.
Summary:
If you have stock suspension, it's likely SHOT. Replacing it will be an improvement.
Decide what your goals are. Do you want a race car? Or "like new" stock experience?
I have 7 after-market suspensions on different cars and bikes, from "out of the box" OEM replacements to custom-made ones just for my application. The cost is dramatically different, and so are the results. There is a value proposition with a "kit" but a compromise. Let the seat of your pants and your wallet be your guide.
Coil Overs will always beat the snot out of struts. If you don't care about originality and want adjustability and tuning, this is the way to go. Again...get out your wallet.
Koni vs. Bilsien: I don't have personal experience with Bilstien. A friend just installed some on an 86.5, and I will get to drive that at some point. But the Bilstiens have a Lower Perch, so you don't have to "make your own" like you would with the KONI. I'd consider that on a car I was upgrading suspension as a PLUS and if I were buying today, I'd likely try the Bilstiens just to try them and because you can use your stock springs. I like the KONI RED and if you have functional stock adjusters, they work fine. If not, you're going to have to change the entire spring setup up, and it's a LEGO KIT, but still works. Min 85 rides stiffer than my stock 86.5...not "worse" but stiffer. Over time? who knows...but the OEM spring weights are likely softer? The smaller springs and changes are making it stiffer on the 85? I"'m sure someone will have an "Opinion" on here...(WINK)...but they're both better than they were and very good.
If you want a "race car," you must pay racecar prices. If you want a TUNED suspension, there are people here who can provide one for you. I'm sure they're all going to serve you well. If you're going to DIY and/or you want it BONE STOCK that's the easy one.
I have an 83 on deck for restoration. I'd likely just put BOGES on it if they are available. If not, then the condition of the adjusters will determine what I replace them with.
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
Two questions that must be asked, especially appropriate in a thread, like this:
1. Has anyone here actually dynoed or paid to have dynoed any of the shocks discussed here?
2. And if so, did you spend the time with a genuine suspension engineer to learn what the dyno results actually mean and how they affect both the spring and the vehicle?
And one important point, which I've highlighted in bold/red:
All of the "replacement" shocks discussed here are valved to "control" a stock 928 spring. That is what they are designed and made to do!!!
Shocks like the Red Boge and Bilstein are adequate to control the 10% stiffer springs, found on the club sport 928's, but that is right at the limits of those shocks.
A replacement Boge or Koni....good for a stock spring. Beyond that, the compression valving is inadequate for anything stiffer. (Yes, if the car is sitting near or travels easily into the 140mm ride height range, the bump stop will made up for some of the inadequacies of the shock compression. However running around on the bump stops is an absurd approach to making a car properly handle. The front bump stop will very quickly turn a 200 pound spring into a 1,000 pound spring.
And a final observation of almost every set-up mentioned in the above text:
Almost everyone here, is addicted/dependent on understeer, which is absolutely the slowest way around any corner, anywhere.
Now, don't misinterpret this; when cruising around, understeer is fine.....you hardly even notice it.
However, anywhere near the limits, you are going to exit stage right or left, depending on which way the road turns, unless you take your foot completely off of the throttle and just hope that works.
Glad it works, for you!
It's an interesting combination of pieces.
Three questions:
What tire/rim are you running? 85 is on S4 Rims and the 86.5 has run stock Manholes and now is on Panamera 18's running 245 rears and 225 Fronts
What is your ride height? Stock 173/180 MM (or as close to it as I can manage) on both cars
I'd be really grateful to know how you made the 2.5" spring to fit into the upper stock spring perch.? SEE PICS BELOW
(We just removed some front 2.5" springs, because the spring moved around in the upper perch, constantly. Very unstable spring location which made the ride height and alignment change over every large bump and every single corner......not to mention very noisy when turning corners. We actually delivered the car, back to the client, this AM. Fortunately, the rear springs were left stock, so we only had to fix the front.)
Greg,
Three questions:
What tire/rim are you running? 85 is on S4 Rims and the 86.5 has run stock Manholes and now is on Panamera 18's running 245 rears and 225 Fronts
What is your ride height? Stock 173/180 MM (or as close to it as I can manage) on both cars
I'd be really grateful to know how you made the 2.5" spring to fit into the upper stock spring perch.? SEE PICS BELOW
Collman makes a cone of aluminum. I used Alodine® to coat it and painted it with HVT Epoxy paint. I didn't want raw aluminum (which is how they come from Coleman). They fit inside the cone perfectly fine. I can share specifics beyond that if needed.
Spring and Cone Assembly Order Assembled (but the adjuster was low so the rod is too proud) You also can't use the plastic rod protector with the 2.5" spring (Disregard the ring on the top...that was just to hold it together temporarily)
Last edited by Dundertaker; 11-17-2023 at 06:58 PM.
Greg,
I don‘t know if the KW setup takes care of the understeer but for sure they dynoed it!
It‘s a complete system of mount , shock and spring engineered by a reputated vendor.
If the car with this suspension drives like a 928 should, I don‘t know.
I think you did the same with the sophisticated system in the powerful GTS and with the modifications on the stock suspensions.
So, it‘s difficult for most of us hobby enthusiasts to take the right choice. You and Jochen and a few others who drive a lot of 928 often can make decisions on a broad database.
So refreshing the old shocks and rubber is a no brainer! Better than new for the new sport tires I can only use try and error and that#s expensive.
What I know is that cheap coilovers from EBay will not do the magic!
Konis and Eibachs I had in my 86.5, on a new Autobahn nothing to complain but very stiff.
[QUOTE=GregBBRD;19114669]Two questions that must be asked, especially appropriate in a thread, like this:
1. Has anyone here actually dynoed or paid to have dynoed any of the shocks discussed here?
2. And if so, did you spend the time with a genuine suspension engineer to learn what the dyno results actually mean and how they affect both the spring and the vehicle?
/QUOTE]
Yes & Yes. I also had them re valved for the heavier springs because my spring choice was just on the edge of the acceptable range for the stock valving. The were re-valved to be the dead center of the range so that I could make spring choices in either direction without having to re valve again as long as I stayed in the range they provided me.
Two questions that must be asked, especially appropriate in a thread, like this:
1. Has anyone here actually dynoed or paid to have dynoed any of the shocks discussed here?
2. And if so, did you spend the time with a genuine suspension engineer to learn what the dyno results actually mean and how they affect both the spring and the vehicle?
/QUOTE]
Yes & Yes. I also had them re valved for the heavier springs because my spring choice was just on the edge of the acceptable range for the stock valving. The were re-valved to be the dead center of the range so that I could make spring choices in either direction without having to re valve again as long as I stayed in the range they provided me.
11-17-2023, 12:10 AM
