Modern trailing arms for the 914?, 986 carriers/calipers/e-brake, more adjustability, more tire? |
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Modern trailing arms for the 914?, 986 carriers/calipers/e-brake, more adjustability, more tire? |
horizontally-opposed |
Jan 26 2021, 12:21 PM
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#1
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Advanced Member Group: Members Posts: 3,431 Joined: 12-May 04 From: San Francisco Member No.: 2,058 Region Association: None |
I've been reviewing past discussions on these (links below) off and on, having test fit a 215/60R15 Pirelli P6000 on a 911R wheel into both rear fenders of my narrow-body 914. It seems doable, but it's going to take some massaging on the outer fender, custom spacers, and—maybe—narrowed trailing arms. Which got me to thinking about the current state of the 914 trailing arm, which is the same it's been since 1970.
Basically, those heavy, non-adjustable steel trailing arms are one of the very few things on the 914 that hasn't been addressed or evolved by the aftermarket. I'm running PMB-rebuilt trailing arms with PMB-rebuilt calipers, and can redo them again with reinforcements and/or some reshaping, but I wonder how hard would it be to do blade-type trailing arms of similar strength with less weight and/or more adjustment. Could a 911 spring plate, or a triangulated or otherwise reinforced version of it, be adapted? Looking at the basic design of the 914 arm, it doesn't look all that complicated, but I'm no engineer. EDIT: Possible use of a machined 986 wheel carrier, an aluminum casting by Brembo that incorporates the 986 e-brake and 986 four-piston caliper mounts, comes up later—a very interesting idea from @Chris914n6, particularly as the castings are available for $100-200ea used or new from Porsche. Bolting that carrier to a new steel trailing arm with a lower damper mount seems viable to me, but here to learn. The custom work to narrow factory 914 trailing arms looks extensive, but has been done by both @914timo and @sixnotfour as well as, it looks like, Rich Johnson. I could see doing it in the process of moving to 911 e-brakes and 986 2.5 brakes, maybe, but I wonder if a group buy might attract a 914 vendor we all want to support? Relevant threads: http://www.914world.com/bbs2/index.php?sho...p;#entry1247827 http://www.914world.com/bbs2/index.php?sho...ailing&st=0 http://www.914world.com/bbs2/index.php?sho...238144&st=0 http://www.914world.com/bbs2/index.php?sho...234391&st=0 |
mepstein |
Jan 28 2021, 07:33 PM
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#2
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914-6 GT in waiting Group: Members Posts: 19,256 Joined: 19-September 09 From: Landenberg, PA/Wilmington, DE Member No.: 10,825 Region Association: MidAtlantic Region |
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 |
Jan 28 2021, 11:23 PM
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#3
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Advanced Member Group: Members Posts: 3,431 Joined: 12-May 04 From: San Francisco Member No.: 2,058 Region Association: None |
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… |
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