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Locking Nuts
Currently doing a suspension refresh on my '76 911 Coupe and notice that, through the years, Porsche used a mixture of locking nut options for bolts that are secured with a nut (rather than a threaded hole). For instance, my trailing arms are secured to my spring plates with a regular nut and a Schnoor serrated washer. Whereas in later years (SC/Carrera) it looks like they moved to a longer bolt with a "locking nut", which I presume is the type of nut with an oval end (like on the eccentrics that adjust ride-height). Is there any preference for one over the other? I'm used to using Nylocs - any reason they are not used on these bolts? Another example is the bolt that secures the trailing arm to the chassis.
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10-24-2013, 09:55 AM
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Schleprock
Join Date: Sep 2000
Location: Frankfort IL USA
Posts: 16,639
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The conical/top-lock/deformed thread nuts seem to be preferred due to their higher resistance to loosening. If you do a dry torque test on a conical vs. nyloc, you can see it takes less torque to turn the nyloc.
But I don't think it really matters. These spring plate bolts are torqued rather tight (90 ft-lbs I believe?) and their tightness is being maintained by the stress/stretch in the bolt, not the locking mechanism. Incidentally I was playing with some conical M10x1.5 nuts the other day. I put one on a semi clean stud (head stud that I wire brush cleaned of the threadlock remnants) and it only required ~25 in-lbs to turn. That's only 2 ft-lbs. So the point being is the grip on the bolt by the conical locking is not super duper tight. Actually I replaced all the trailing arm-to-spring plate bolts on my '87. The originals showed a lot of wear/bearing on the shanks so I thought it'd be good to replace them. I didn't want to blow a bunch of money on ordering original M12x1.5 Porsche bolts individually or buying 50 of them from Metric Multistandard. So I bought a box of ten M12 x 1.75 bolts in 10.9 property class from McMaster-Carr. Couldn't find any class 10 nuts in conical so I used nyloc. Has been working just fine, put to the test on the track numerous times!
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Kevin L '86 Carrera "Larry" |
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10-24-2013, 10:11 AM
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As always, thanks Kevin. I found these conical lock nuts in class 10 on Belmetric and was thinking of using them:
https://www.belmetric.com/ntlh12x15-conical-lock-flange-nut-class-10-p-5076.html?cPath=3_54_949 |
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10-24-2013, 10:21 AM
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Schleprock
Join Date: Sep 2000
Location: Frankfort IL USA
Posts: 16,639
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No problem. You ask a lot of questions that i've asked myself before!
Belmetric is a great resource. They have a great selection of nuts & sell good quality stuff. Wish their socket head bolt selection was a little broader though (no 8.8 or 10.9 class bolts). Some unrelated thumbs-up for Belmetric........ I found they have low height M10x1.0 castle nuts for the tie rods. Sort of a hard nut to find. They have great pricing on quality brake line tubing and Cohline tube nuts if you find yourself needing to do brake line fabrication in the future. The cunifer tubing is fantastic stuff.
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Kevin L '86 Carrera "Larry" |
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10-24-2013, 10:31 AM
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I'd think that Nyloc nuts would not be useful for such large fasteners or high torques.
There is an old thread on split ring washers vs. wavy washers on here somewhere, FYI. I don't recall that one is better than the other. |
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10-24-2013, 10:52 AM
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Schleprock
Join Date: Sep 2000
Location: Frankfort IL USA
Posts: 16,639
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I was thinking the same thing about large fasteners or high torques. But then I got to thinking, OK, how big do they make nyloc nuts?
http://www.metricmcc.com/catalog/Ch1/1-133.pdf M48x5 is pretty big! 
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Kevin L '86 Carrera "Larry" |
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10-24-2013, 11:12 AM
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AutoBahned
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huh! - thx for posting that correction
too bad the late, great Jim Sims is no longer around to answer this definitively |
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10-24-2013, 04:59 PM
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