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 |
rick 918-S |
Jan 30 2021, 03:56 PM
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#2
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Hey nice rack! -Celette Group: Members Posts: 20,443 Joined: 30-December 02 From: Now in Superior WI Member No.: 43 Region Association: Northstar Region |
My thought was to see if a 911 arm could be sourced and used as is with an adapter to the suspension ear and mount on the 914 chassis without cutting the car or the arm. My concern is the triangle the 911 arm forms when adding the flat bar may interfere with something. The 914 part does not form a triangle. Likely for a reason.
That 986 hub looks inviting... |
horizontally-opposed |
Jan 31 2021, 11:16 AM
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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 |
My thought was to see if a 911 arm could be sourced and used as is with an adapter to the suspension ear and mount on the 914 chassis without cutting the car or the arm. My concern is the triangle the 911 arm forms when adding the flat bar may interfere with something. The 914 part does not form a triangle. Likely for a reason. That 986 hub looks inviting... (IMG:style_emoticons/default/agree.gif) Suspect the far wider triangle of the two-piece 911 trailing arms is afforded by the narrow transmission ahead of the axle line in a 911—the only way to do that in a 914 would be to reverse the trailing arms in a 914…an idea Porsche thankfully abandoned with its very first mid-engined sports cars in the early 1950s. 914 arm is triangulated, though to a much lesser extent…but that still needs to be considered and replicated. Agree about 911 arm + modded 986 wheel carrier + some form of triangulation (that maybe doubles as a toe-adjust). Not sure it will be lighter if it's going to be cost effective, but it might be stronger, newer, and integrate a 986 e-brake, 986 caliper mounts, and wheel bearings in the bargain. I've never liked the idea of slicing the 914 trailing arm to add the 911 e-brake and caliper mounts. I know a lot of people have done it, and successfully, but I have also seen those conversions go wrong. 986 front calipers, meanwhile, are easy to adapt, and probably the best technical solution for a 914 (modern, light, stiff, cheap, plentiful, available for more and less power thanks to 986S, and set up for a mid-engined car rather than a rear-engined one). Only count against them is they don't look as period or as cool as 930 brakes…but the latter are big $. I can't draw to save my life, but the Rennline outer 911 arms are only $250 a pair, while it seems like a nice pair of 986 carriers with e-brakes run $200-300 a pair. So the challenges will be figuring out mating the 986 carrier to an (existing? 911 outer?) trailing arm, the forward pivot/mount, hub placement, body clearance, and triangulation. Oh, and the stub axle, too. See? "Easy." Had an offline conversation yesterday, and a good engineer to speak with this about was named. I wonder if the 986's "pinch" strut mount can be removed so a trailing arm can be made to attach the carrier and also locate the 914's lower coil-over mount. Attached thumbnail(s) Attached image(s) |
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