Modern trailing arms for the 914?, 986 carriers/calipers/e-brake, more adjustability, more tire? Options

[Eric_Shea]

We could play with it if you want...

[mskala]

7.5"x16 ET38 wheels, minimal spacers different on each side. Normal trailing arms.
Hoosier 205/45/16 which of course runs wider than numbers would suggest.
Does not hit the brake line or arm. Fenders were yanked a bit and folded. Inner
wheel well rubs first, before you would rub brake line or trailing arm.

[horizontally-opposed]

If I had my new shop set up I would build a gig and narrow a couple. One of you guys should take this on for Pete. Couldn't take but a couple days of messing around to make a couple.

Thanks, Rick—but I am actually interested in something for more than me.

Our 914s have always lived in the shadow of the 911 when it comes to suspension upgrades, being "lucky" to benefit from parts developed for the front of the 911 and even luckier if a matching rear damper/spring was available. I get the idea that there wasn't enough market to justify the developments we've seen for 911s in years past, especially when 914s were $5000-30,000 cars, but I have to wonder if there isn't now?

How many people have made jigs to narrow two trailing arms (I've found several independent jobs in my research) and/or slice off the wheel carrier to weld up a 911 e-brake to gain access to better/lighter calipers? And you're still dealing with a 50yo arm that might need to be repainted, etc. And maybe reinforced, too—though there are two schools on that. How much does all that labor add up to?

Might be cool nice to see something developed that addresses all that, takes any of the three available bushing types up front, accepts a 911 e-brake, can accept different calipers via adapters (914, 930, 986), and maybe offers some adjustment with 2-3 mounting points for the rear damper. Won't be cheap, but people are spending real money on 914s these days. I know of someone who might be willing to fund such a thing if it's done to a high level—and that would leave a cool product on the market. Or maybe we can figure out a group buy. I've been cooking through another idea that might drop serious weight off the back of the 914, and might not be insane in lieu of what some are spending or will eventually spend in this area of the car. I know an F1 contractor who might be cajoled into helping with the billet aluminum (or?) sections, but we also have some very smart cats here.

Yes, I'm definitely thinking out loud—and taking some hits for it—but that's all good.

(IMG:style_emoticons/default/beerchug.gif)

7.5"x16 ET38 wheels, minimal spacers different on each side. Normal trailing arms.
Hoosier 205/45/16 which of course runs wider than numbers would suggest.
Does not hit the brake line or arm. Fenders were yanked a bit and folded. Inner
wheel well rubs first, before you would rub brake line or trailing arm.

Thanks for this, and very cool to see. I've seen people sneak 16x7 Fuchs in (both 951 and maybe 911 too?), but not these—as they appear to have a bit of lip on them. 205/45R16 definitely seems to help, too. @sixnotfour is running custom 16x7.5 Fuchs also, I think, but they're flat-faced with the added width on the back iirc. Like a 16-inch 911R wheel.

As you note, actual tire widths ≠ tire sizes. When I ran 205/60R15 A-008Rs, I had the same point of interference as you and no interference at the brake line/trailing arm. I went on to drop down to 205/55R15 BFGs and, later, Yokos, and had no issues. 185/70 and 195/65 have all been fine, but no surprise there. Test fit with the 215/60R15 Pirelli P6000 shows brake line clearance is a bigger problem than inner fender clearance—so pulling the fender and spacing the wheel further out will help the inner fender more than the brake line, and I'd love to minimize that fender pull…

We could play with it if you want...

Was hoping you might chime in, as one of very few logical vendors for trick 914 trailing arms. (IMG:style_emoticons/default/sunglasses.gif)

Would be great to compare notes and do some thinking…

[mskala]

Thanks for this, and very cool to see. I've seen people sneak 16x7 Fuchs in (both 951 and maybe 911 too?), but not these—as they appear to have a bit of lip on them. 205/45R16 definitely seems to help, too. @sixnotfour is running custom 16x7.5 Fuchs also, I think, but they're flat-faced with the added width on the back iirc. Like a 16-inch 911R wheel.

As you note, actual tire widths ≠ tire sizes. When I ran 205/60R15 A-008Rs, I had the same point of interference as you and no interference at the brake line/trailing arm. I went on to drop down to 205/55R15 BFGs and, later, Yokos, and had no issues. 185/70 and 195/65 have all been fine, but no surprise there. Test fit with the 215/60R15 Pirelli P6000 shows brake line clearance is a bigger problem than inner fender clearance—so pulling the fender and spacing the wheel further out will help the inner fender more than the brake line, and I'd love to minimize that fender pull…

Slight error with the pic, it was taken earlier with Kumho V710 215/40/16, which I
measured as 8.5" section width. Hoosier was wider than this.

[mepstein]

185/70 front & 215/60R15 rear was standard for a 1973 Carrera RS

So one of Porsche's most iconic cars made due with relatively narrow rubber and a 914 could be said to be lighter and better balanced.

Is it just about getting the wider tire on the car. Better handling. Both?

One thing that was suggested to me to improve the ride and handling on our cars was better custom valved shocks. The most common shock upgrade to Bilsteins just uses a 30+ year old design.

We all just tend to throw a lot of "upgraded part" on our cars without really testing how they work together, sometimes assuming a stiffer ride will be a high performance ride.

[horizontally-opposed]

185/70 front & 215/60R15 rear was standard for a 1973 Carrera RS

So one of Porsche's most iconic cars made due with relatively narrow rubber and a 914 could be said to be lighter and better balanced.

Is it just about getting the wider tire on the car. Better handling. Both?

One thing that was suggested to me to improve the ride and handling on our cars was better custom valved shocks. The most common shock upgrade to Bilsteins just uses a 30+ year old design.

We all just tend to throw a lot of "upgraded part" on our cars without really testing how they work together, sometimes assuming a stiffer ride will be a high performance ride.

We're on the same wavelength, and agree with much of the above—but would go further, and less far. (IMG:style_emoticons/default/smile.gif)

I've been testing factory and aftermarket Porsches on road and track since 1997. Long ago lost count of how many cars, track days, and road tests. Along the way, the cars that hit the sweet spot and were "soul connected" were the ones that stood out. They were often less is more, such as a 986 2.5 that was just plain more fun to drive than a 993 Turbo. Or the 987.2 Boxster Spyder, which was far more than the sum of its parts—and probably quicker over the road in the hands of more drivers than a contemporary GT3. And, dare I say it, more fun despite a merely wonderful engine instead of that insane Mezger.

There are a lot of other examples, but the 914 stands tall in this regard—and that goes for virtually any good 914.

The standouts from the Porsche aftermarket are even fewer and further between. Most go for more more more, and the experience isn't any better. And, I'd argue, the driver often ends up less confident, extracts less out of the car, and has less fun. Which is perhaps what you're getting at. I can probably count on 2-3 hands the number of truly brilliant aftermarket Porsches I've tried—they've been rare, and sometimes come from unexpected shops or individuals. One line usually tied them together: Those who carried out the mods were methodical, planned their ideas out carefully, and saw everything as a system. Again, what I think you're getting at.

When it comes to our 914s, a lot of people go for big engines, big brakes, and 16- or 17-inch rubber with 205-225 (or larger…) front tires and 225-265 (or larger…) rear tires. And some 914 hot rods do benefit from that despite relatively modest weight gains vs much less modest power gains. Others end up fast but distinctly un-fun or even scary to drive.

In terms of power, my 914 is making a modest 169 hp at the wheels, so maybe 190-200 hp at the flywheel (insert favorite "conversion/guestimation" here). Target achieved. The 1973 RS 2.7 was rated at 210 hp, and wasn't all that much heavier unless it was a full-boat RST. (One thing to remember re: 914 tire sizes: Wider road/consumer tires weren't widely available on Porsches before the RS 2.7, and were pretty rare in general. Up to 1973, a 185/70R15 was a wider performance tire, and something of a gold standard. Then the 215/60 arrived—and Porsche staggered the tire sizes on a lot of their cars, including even the most modest 2.5-liter early Boxsters.) Porsche used that same 185/215 or 195/215 wheel/tire package on 911s from the 260-hp early 930 through to the 230~ hp 1988 911—in other words, a wide variety of 911s with 180-260 hp and weights both below and above the 914. 16s with wider tires were available as an option or standard on some models (Turbo 3.3, SC, Carrera, SC/RS, Turbo Look, 1989 Carrera, etc). I'd say the 185/215 and later 195/215 has breadth, and we know that tire package met Weissach's performance standards. And the right tires of today in those sizes are better than tires of the same size back then. Much better.

My humble narrow-body 914 drove really well with 185-205 tires at all four corners when it had 80hp. I didn't need the 205s due to power, to be sure, but the chassis sure could put 205s to good use at high and low speeds. Perhaps more importantly, I just liked the car that way.

Fwiw, I was talked into Bilstein HDs by a number of people I respect during my last suspension rebuild. About the only thing we got right was sticking with rubber suspension bushings and the same spring rates. I vastly preferred my previous Koni reds to the HDs, and see no reason to reinvent the 914's torsion bar/coil-over concept or move to exotic and/or remote-reservoir dampers. I might convert my Koni reds to double adjustable, but I might not. Zero desire to go to higher spring rate up front, and will likely keep my fairly soft rear springs. Might go up 20-40lb. We'll see. There are other upgrades that are pretty interesting—such as Tangerine's strut top mount for lowered cars (been eyeing that one), raised spindles (should have done that last time), better bump-steer solutions, etc. Little stuff that can make a big difference. There is some big stuff out there, too, such as Elephant or ERP's A-arm replacements, but I am not sure these are right for a street car—especially at the front end.

On the other hand, trailing arms in modern materials and lighter brakes might offer a chance at serious weight loss (total, unsprung, and rotational). Steel trailing arms were cheap and strong. Heavy, too. Steel brake calipers and one-piece rear rotors were, as well. Better rear arms, alloy calipers, and maybe even two-piece rear rotors—if the right disc can be sourced and the e-brake can be figured out—might drop significant weight. No, it won't be cheap, but I suspect an Avon 215/60R15 on a 911R replica wheel on a lightweight arm with a lighter brake setup—along with a well thought-out front end—might end up less expensive than adding M471 or custom flares, the usual suspension/brake upgrades, and repainting the car. And for those of us who like the narrow-body look…

[Chris914n6]

~21.5 lbs as seen. Scale might not be 100% accurate.

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611908166.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611908166.2.jpg)

[mepstein]

~21.5 lbs as seen. Scale might not be 100% accurate.

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611908166.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611908166.2.jpg)

So without the hub, bearing, bracket and shaft, fifteen-ish, maybe?

[horizontally-opposed]

Thanks Chris!

A little lighter than I expected, but they certainly aren't light. There may be 30 to 50+ pounds in unsprung/rotational mass to be shed between the 914's steel arms, steel calipers, and one-piece steel rotors x2 while adding a number of technical upsides.

Question is how light they can be made, and for how much.

Next question is what the $ might look vs against narrowed/reinforced/e-braked/rebuilt arms. Or flares + paint. And then how many orders would it take for a vendor to step up? The concept is easy. The execution is well outside my ability, and likely prohibitive as a one-off, but it would be a great piece to have on the shelf while assembling parts for the next suspension redo…

[horizontally-opposed]

~21.5 lbs as seen. Scale might not be 100% accurate.

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611908166.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611908166.2.jpg)

So without the hub, bearing, bracket and shaft, fifteen-ish, maybe?

Not much to be done with the wheel bearing, but the shaft and hub might be a place to apply better materials. Maybe also set up for four or five lug wheels.

Anyway, suspect your guess is within a pound or two.

[mepstein]

~21.5 lbs as seen. Scale might not be 100% accurate.

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611908166.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611908166.2.jpg)

So without the hub, bearing, bracket and shaft, fifteen-ish, maybe?

Not much to be done with the wheel bearing, but the shaft and hub might be a place to apply better materials. Maybe also set up for four or five lug wheels.

Anyway, suspect your guess is within a pound or two.

Largest, easiest chunk of weight would be aluminum calipers. Eric did a run but I don't think there was ever a huge demand. I think it was the price that held people back.

I think part of the reason a stock 914 is such a joy to drive is the light, narrow tires. They may not provide ultimate traction but feel light and smooth and let the car "dance" over the road.

"I've been testing factory and aftermarket Porsches on road and track since 1997. Long ago lost count of how many cars, track days, and road tests. Along the way, the cars that hit the sweet spot and were "soul connected" were the ones that stood out. They were often less is more, such as a 986 2.5 that was just plain more fun to drive than a 993 Turbo. Or the 987.2 Boxster Spyder, which was far more than the sum of its parts—and probably quicker over the road in the hands of more drivers than a contemporary GT3. And, dare I say it, more fun despite a merely wonderful engine instead of that insane Mezger.

There are a lot of other examples, but the 914 stands tall in this regard—and that goes for virtually any good 914.

I get this. I've ridden and raced bicycles all my life. I ran a bike shop for 6 years so I rode hundreds of different bikes than just mine.
Most of the bikes I owned were top of the line, great bicycles and did there job well. Two of them were outstanding and I have not been able to duplicate the feel.

So maybe we should be aiming to hit that sweet spot with a 914. I've never driven a 911RS but it seems to get described in that way. So maybe we need to make a 914RS.
A magical riding car that can be duplicated.

[ClayPerrine]

The factory trailing arms were designed with narrow tires and limited grip as the parameters. With 50 years of tire evolution, you can put enough sticky tires on a 914 that will make it exceed 1G lateral loads. The trailing arms were never designed for that kind of load, and are going to start failing from a combination of metal fatigue and age.

An aluminum trailing arm, similar to the 911 one, would be a great investment. If I were doing it, I would incorporate a mounting pad for a monoblock (Boxster) caliper, all the required provisions for the park brake (stop block, bellcrank, altered cable mount, etc..) and new fairly hard durometer rubber bushings.


But it is beyond a hobbyists ability to build a upgraded trailing arm like this.

Someone with some deep pockets would have to build and sell it.

[Superhawk996]

The factory trailing arms were designed with narrow tires and limited grip as the parameters. With 50 years of tire evolution, you can put enough sticky tires on a 914 that will make it exceed 1G lateral loads. The trailing arms were never designed for that kind of load, and are going to start failing from a combination of metal fatigue and age.

An aluminum trailing arm, similar to the 911 one, would be a great investment. If I were doing it, I would incorporate a mounting pad for a monoblock (Boxster) caliper, all the required provisions for the park brake (stop block, bellcrank, altered cable mount, etc..) and new fairly hard durometer rubber bushings.


But it is beyond a hobbyists ability to build a upgraded trailing arm like this.

Someone with some deep pockets would have to build and sell it.

Well said! Doesn't exactly look profitable given a upper bound of ~100,000 vehicles and mabye 22,000 rabid fans (or whatever latest membership is here).

Now consider the number of those that would be willing to spend $$$ to make the "upgrade".

For me a good chunk of the 914 appeal is that it is what it is. Faster, more reliable, great handling cars are all around us in this day and age. Agree a 914 stands tall given its age but again, it is what it is.

[horizontally-opposed]

This one would take a village to get done, but I think it's within the realm of possibility between our contacts and even some of the talent here. And I may have a "cost no object" buyer who might underwrite the most expensive pair (the first ones), as he was already thinking along same lines when I mentioned them. He's getting over Covid, and we were talking cars to keep him distracted. He's got a lot of other stuff, but loves his 914. And if a number of us signed on for a group buy…

Four billet aluminum ends won't be cheap, but they should be doable. Best way would be to incorporate choices such as which of three bushings/bearings up front and ears for 914, 930, or 986 calipers in the rear—leaving it up to the customer to move to 911 e-brake, RSR, or spot calipers. Or no e-brake.

Carbon or lightweight steel blades would probably be the "hard" part—after proper/safe design and FEA, that is.

[live free & drive]

Maybe one could get an mechanical engineering grad student to undertake a project using some of the new generative design software and DMSL and print stainless or titanium trailing arms with the highest strength to weight ratios:

https://www.pinterest.jp/pin/541698661419803565/

Maybe not the cheapest, but you might get something pretty wonderous for $1400 per arm (give or take)

Autodesk has a new software out to design these type of organically perfected devices:

http://www.withinlab.com/case-studies/new_index18.php

[rgalla9146]

How's this ?
A single large monoball attached at current outer front trailing arm mount.
A rigid narrow cast or box type trailing arm that extends past the hub
and includes mounts for upper and lower un-equal length rear links.
The links extend inward toward the transmission and attach to a fabricated
hoop forward of the transmission mounts.
The loads are now through three mounts intead of two and are spread over
larger areas.
Full disclosure, I'm not an engineer nor could I plot the geometry.
Can't draw so well either.
Nonsense ?

[Chris914n6]

How's this ?
A single large monoball attached at current outer front trailing arm mount.
A rigid narrow cast or box type trailing arm that extends past the hub
and includes mounts for upper and lower un-equal length rear links.
The links extend inward toward the transmission and attach to a fabricated
hoop forward of the transmission mounts.
The loads are now through three mounts intead of two and are spread over
larger areas.
Full disclosure, I'm not an engineer nor could I plot the geometry.
Can't draw so well either.
Nonsense ?

Typical Subaru rear suspension.

[horizontally-opposed]

Open to all ideas, as this is all about spitballin' at this stage. (IMG:style_emoticons/default/beerchug.gif)

With that said, and pursuant to @mb911's post above, I actually think the suspension concepts of the 914 are pretty good. Sure, multi-link, double A-arm, etc are better when it comes to camber gain, etc—but 914s are plenty fast and able to process bumps even by modern standards. The light weight and long wheelbase definitely help. And, to my mind, the best solution is a part that bolts on—so it's a reversible mod. That broadens the customer base. Cutting the tub is a nonstarter for a lot of folks.

I reached out to an overqualified acquaintance who might be able to help with some early feedback on ballpark weight loss vs rough costs for the first pair of trailing arms (development, setup, creation) and then more in small qty. We'll see if he laughs me out of the room.

Meantime, also reached out to one of the 2-3 techs I would hire to rebuild/narrow/reinforce/five-lug/add 911 e-brakes/repaint/re-bush/re-bearing/etc for what he might charge. Asked him to do so on the basis of one stop, so no procurement on my side. First response: "$2500?" Then, as the scope of the work set in, "Could be more like $5k, with no brakes other than the parking brakes." Remember, this is checkbook math, not DIY—and some won't need to do some of those things, and can subtract accordingly, but checkbook math is the fair comp and I suspect $3500-5500 is a decent guesstimate for rebuilt/modded 50yo steel trailing arms.

[mepstein]

Open to all ideas, as this is all about spitballin' at this stage. (IMG:style_emoticons/default/beerchug.gif)

With that said, and pursuant to @mb911's post above, I actually think the suspension concepts of the 914 are pretty good. Sure, multi-link, double A-arm, etc are better when it comes to camber gain, etc—but 914s are plenty fast and able to process bumps even by modern standards. The light weight and long wheelbase definitely help. And, to my mind, the best solution is a part that bolts on—so it's a reversible mod. That broadens the customer base. Cutting the tub is a nonstarter for a lot of folks.

I reached out to an overqualified acquaintance who might be able to help with some early feedback on ballpark weight loss vs rough costs for the first pair of trailing arms (development, setup, creation) and then more in small qty. We'll see if he laughs me out of the room.

Meantime, also reached out to one of the 2-3 techs I would hire to rebuild/narrow/reinforce/five-lug/add 911 e-brakes/repaint/re-bush/re-bearing/etc for what he might charge. Asked him to do so on the basis of one stop, so no procurement on my side. First response: "$2500?" Then, as the scope of the work set in, "Could be more like $5k, with no brakes other than the parking brakes." Remember, this is checkbook math, not DIY—and some won't need to do some of those things, and can subtract accordingly, but checkbook math is the fair comp and I suspect $3500-5500 is a decent guesstimate for rebuilt/modded 50yo steel trailing arms.

Ben/MB911 might be able to give a good estimate since I think it’s in his wheelhouse
@MB911

[mb911]

I would need you to put things down on paper or a picture.. I am more a picture book kind of guy.. Then I could give a real estimate.